I musta read Z1’s original thread regarding the stock exhaust modification about 10 times before I got the nerve to actually do it. My major concerns were the noise increase and the “ya can’t go back” aspect of the project, but hey with so many rave reviews its gotta be good, right?

Took the plunge this past weekend and have no regrets. IMO the noise increase is minimal and the sound is much better. For those of you who would like to hear my meager attempt to demonstrate the sound difference, check it out:

STOCK EXHAUST
MODIFIED EXHAUST

I have 2 bikes so decided to document the procedure with photos on the 2nd one. The mod is extremely easy so long as everything comes loose. I had some trouble with the screws; tried a screwdriver, then an impact driver, then a Craftsman Screw-out (just ate away more of the head), then finally a Craftsman Power Bolt-out which worked like a charm (quite the handy dandy tool). In fact I went straight to the Bolt-out when I did the second bike...

Before you attempt this mod I highly recommend, err no, I INSIST, you read the thread and accounts originally posted by Z1XT225 et al- he’s the innovator and absolutely deserves the credit here. I just thought I’d do a full description with photos to make it easier for those that follow....
Z1XT225\'s original thread


Tools required:
Drill
Philips head Screwdriver (and/or something to remove a stubborn screw - I suggest a Bolt-out, see above)
Rubber or plastic mallet
Hole saw + extension (I used a 1 ½” but anything less than 2” should do)
Extension magnet
PB Blaster, WD40 or some other penetrating catalyst
Anti seize compound


Access to the screw that holds on the endcap to the exhaust:


Removing the screw with a Bolt-out - drill in reverse:


Spraying around the cap seal with PB Blaster:


A few gentle (or not so gentle) taps...


And out she comes:


continued...

[ July 06, 2006: Message edited by: crash ]

[ July 06, 2006: Message edited by: crash ]

The piece to drill out is about 7 ½” inside the exhaust end:


Hole saw extension end is 7/16 - my drill chuck is 3/8...so jury-rigged it with a 7/16” socket. :rolleyes: Worked ok, but recommend using a drill with a 1/2” chuck...


Drill...


Hole...


And the metal piece:


continued...

Both times I lost the metal piece and had to fish it out with an extension magnet (taped to keep it from catching the side walls). Here with metal shavings from the drilling process:


Start the bike up without the cap in place to blow out excess shavings.

Replace the cap with a new (hex-head) screw with anti-seize compound. The screw on the left shows how much I messed up the head on my first try...


Done!

There are other tips and tricks in the original thread if you get into some difficult situation like not being able to get the dang end cap off. So again I urge you to read Z1’s original thread: Z1XT225\'s original thread

I still have a bit of riding to do to get the full impact of this mod, but my initial impressions are the same as everyone else - wow! Thanks Z1 and all the others before me

Crash,

Very nice job of documentation. I wish I had seen your pictures before I did mine. This will definitely help anyone who is contemplating this mod, and like you said....WOW.

Thanks for the photo "how-to". Just what I need to spur me into action!

BTW - the links to the sound files cause my browser to shut down.

FreeMe - don't know why your browser would crash

If you wanna hear the sound files shoot me an email at kbrame@uplink.net and I'll mail 'em to you.

I will be trying this procedure this weekend and will then share my experience. Without those pic's from crash I would have been lost. I will let all know the out come...

well I also took the plunge and tried this mod!
as per normal the screw was seized and I stripped the head, so I drilled it out and used a self taping bolt with a 10 mm head.
I have not really tried it out yet but we are going on about a 200 + km ride tomorrow so we will see what happens!
I also adjusted my valves with the help of the valve adjusting for dummies post!(funny that was posted just when I was thinking it was time to get them done?)
I also did the carb adjust!(3.5 turns out)
while I had it all apart I cleaned the chain,air filter, and changed the mobile 1 synthetic oil, lubed the cables,kickstand, footpegs, shifter, brake lever,adjusted the chain,and back brake!
it was some day! I managed to get gas in my right eye, dirt in the left eye, cut my hand twice, and tripped over my kids kdx 200.
all in all I did more than what the shop did on the service that cost me $200 canadian!
Thanks too the guys that post all the great information and pictures on this site!
it is greatly appreicated!
Evil69

[ July 08, 2006: Message edited by: evil69 ]

Nice job on documenting this mod Crash. It's nice to see the number of people that have found the same joy that I did in doing this mod.

do you have any idea if it will give a noticable boost in power?

I did this to my bike the other day. Initial test ride did indicate a noticable affect on low end torque. Throttle response is a bit snappier.

-Steve

I bow down to you...thanks for the very clear, and precise run down. I'm almost about to scrap the Pro Circ T4 exhaust and do this first. I just have one huge issue...the screw for the end cap on my '04 is almost stripped could I work around that? Any suggestions?

Thanks.
RoKer

Doh...sorry I didnt read....I got ahead of myself, Trigger happy if you will....I'm goin to tap that Baby out...

Ceez.

I just got a 92 serow for my wife last week and this is the first mod I did to it last night. Definitly an improvement. One thing that might help somebody else out is I used a toggle bolt
to remove the spark arrestor. I slid it in and then used vice grips on the screw head and gave it a good tug. (I had previously beat on it with a rubber mallet and sprayed it down with WD40)

To add my 2 cents. I did this exhaust mod last week. Fence sitter for months as my bike is new and under warranty. Any way, cutting a hole through the muffler as documented by zt & crash makes a BIG BIG difference in performance. I started out by removing the spark arrestor. All that did was increase the decibel level. It's cutting the hole that makes the difference. Tried it with and without the spark arrestor installed. Verdict, leave the spark arrestor in place, the increased noise outweighs any hp increase. Bottom line is with the hole, exhaust sound is deeper (more thumper-like) and there's significant low rpm pull. Didn't do anything to the carb yet.

Now for the problems. I have two hole saws, one that will use a 1/4" socket but it's a small diameter and another that will maximize the hole size but requires a 1/2" socket extender, my 3/8 drive extender wasn't long enough. I chose the larger holesaw which necessitated a nondrill option. With the 1/2" extender all I had to move the hole saw was a socket wrench or air impact wrench. I used the impact wrench which wasn't as easy as a drill. The regular 1/2" socket wrench would have never cut through the metal. Second, the metal didn't stay in the holesaw and fell into the exhaust. I couldn't fish the metal tab out with just a magnet, I had to remove the exhaust to remove the metal tab. Not a problem on a new bike, but something to consider on an older one. Third, removing the spark arrestor. To apply the proper torque on the screws one really needs JIS phillips head drivers. In lieu of JIS screw heads, I used an impact driver I bought at harbor freight for $4.00, part # 93481. It did the job, but then again I have a new bike. If I didn't have an impact driver, I would have stripped the head with a US phillips #2 screwdriver. I replaced the screw with a M6 hex head with phillips backup bolt.

Again, this mod is the most bang for the buck one can do for these bikes.

I finally did the mod today. No problems carrying it out. Took a ride out to that long hill that I normally have to shift down once to keep any speed up. No downshift needed this time! A definite improvement there, but I can't really tell about the low end. Certainly didn't lose anything there though.

I'll have to ride it this way awhile to see if there's any difference in fuel mileage, but for the first hundred miles, it looks like it might be the same or slightly better.

It is louder, but not too loud - certainly not as loud as the kid's YZF250.
Cool!

My Sunday project was the exhaust mod. Of course I stripped the screw on the spark arrestor. Drilled it out and cut the 1.5 inch hole but I cannot retrieve that cut metal. I passed a couple of different magnets and no luck. The bike really runs quite a bit better on the road and on the trails. My question is......do I need to remove my exhaust to retrieve that 1.5 inch metal disk? Can I leave it in? I doubt it can find it's way out of the muffler. Any thoughts and/or opinions gang?

Hey Cajun,

I'm still learning about the XT's, but I would try hard to get that piece out. i would assume it fell down into the pipe and could eventually move around and possibly block off the pipe.

I would take the muffler off and not stop until I had the sawed off hole piece in my hand.

Just my 2 cents worth.

zeke513

cajun,
I agree with Zeke. Get it out. It took me a while to get mine out...I couldn't fish it out from the bottom and had to start the bike up and give it a couple good revs to force the metal piece back up to where I could snag it. I'm surprized you don't hear it rattling around in there.
If you can't get it that way, take the pipe off...

Hi Tom,

Are you sure the piece isn't still inside the hole saw?

Seriously, I'd make damn sure it was out before I did any riding. The stock exhaust has these perforated fins along the insides, and the part could get pinned on them and end up *corking* your exhaust at a time you'd least want it to.

The pipe is easy to remove:

First loosen the front pipe clamp bolt way out.

Then remove the bolt by the side panel.

Then take off the bolt by the rear handle while supporting the pipe so that it does not drop down and put stress on your headpipe.

Now gently rotate the pipe back and forth on the axis of the headpipe while pulling rearward. There is a graphite impregnated gasket separating the head pipe from the exhaust, so it should just slip right off.

Take Care,


Greg

i finally fished out the metal cut out disc by removing the muffler. Didn't take long at all. I did ride around a bit for a few days with it in my muffler. I have to say hats off to Z1 and Crash for the inspiration and the great pics. The difference is really amazing. WOW WOW WOW!!!

Ok, I did this a little over a couple weeks ago, then road the bike a bit. At elevation too. So tonight, to thwart off that spit a sputter at top speeds, I installed a 140 main jet this evening. Now, where the XT wouldn't hold 70mph for an extended period, (55mph cruise was OK), Now it will run 78mph, (120k), at just above sea-level without a complaint. It won't go any faster, but on the level it'll run there. I haven't had it on any hills yet, but I'm figuring that most of what I have available to me -paved, the Lil XT should do better than before. I set the pilot screw to 4 turns out. Idles nicely with good low RPM throttle response. I'm sure that things will be nicer on the dirt too. I'll have to ride some more and keep an eye on the spark plug color.

-Steve

I took a real shortcut.

I used a 10" by 3/8" diameter Nail used for securing 8x8 railroad ties in retaining walls.

I sharpened the point and with a smart blow from a regular 20oz hammer made eight holes around the parameter of the inside diaphram at 12,2,4,6,8, and 10 O'clock positions.
I think this allows the exhaust to exit around the outside of the spark arrestor "guide" vanes.

It took 15 minutes. The engine definitely breathes better at my 5000'msl rides here in NW North Carolina mountains. More power.
Sound is not too loud......just a little heavier "rap" under power.

I used a heavy glove to hold the "nail" in case I missed.............which I did! Ha.

I replaced the scared arrestor screw with an Allen head bolt. Works great.

Good luck.

I guess I lost my post when the Forum was down yesterday.

I took the shortcut route.

I used a sharpened 10" x 3/8" rail road tie nail and punched 8 holes in the parimeter of the inside diaphram.
I think it helped swirl the exhaust past the arrestor "guide vanes"
It took 15 minutes.

Worked great for my 5000' msl North Caroline mountain riding. More power. Just a little louder "rap" at throttle.

I replaced scarred screw with Allen head.

A quick tip...I frequently have need of extensions for hex drive bits like hole saw arbors. If you dont have a bit extension, cut the handle off a cheap nut driver

I keep a couple of cheap china brand nut driver sets around for just such an occasion. You can probably buy a set for about $2. Check the length though.

One of them worked for me with a 1/2" keyless chuck.

You could also use a 1/4" socket extension with the appropriate socket.

i just did this mod on mine. It took me all of 30 minutes and I finished moments before a torrential downpour. I can't wait to try her out. Thanks for all your work and pics.

Sorry to sound redundant but I wont need to rejet would I? Thanks everyone.

C.

You might. I did the Z1 mod and opened up the airbox, and I'm on the verge of being too lean - and I'm operating at 2500'-9000' above sea level (mostly 2500'-3500').

There is a guy on ebay selling a rejet kit for the XT225, but I don't know if it's a good deal. You'll have to run a spark plug check on your own bike to find out if you need it.

Either way, it's worth it!

Before I throw my 2 cents in, Z1, Great Find! and Crash, Excellent documentation! I am also doing this mod on my bike and I hope this helps. Mine is a 2006 which probably made it easier, but when i tried to get the screw out it didn't want to budge, so before I stripped it, I got my pencil torch and heated it up for a good minute or two. I got it to break loose with a decent sized phillips I had, but halfway out it didn't want to move again, so I repeated the process and out it came. Thanks Again you guys and Johnny Q glad you mentioned to leave the spark arrestor in, I was going to cut it out also.

I have just purchased a 2007 xt225 in nw ohio. The spark arrester is welded in place...any input???

Captain,

My 2005 was not welded in. I do not believe yours would be any different. If you look at the underside of the end cap there is a 3/4" opening. Inside that is a phillips screw that holds the spark arrestor in. The spark arrestor and end cap are assembled as one piece. The sooner you get the screw out, the better as they seem to freeze in. I put a 6mm x 1/2" socket head screw with anti-sieze in place of the phillips for ease of future removal. Once you have the spark arrestor out (I used a drift inserted in the 3/4 hole to knock the end cap off) you will see the baffle to be drilled about 6" inside the muffler body. The spark arrestor should be re-installed after the drilling is completed.

I can check at the Yami shop. But all other US models have the screw. I'm running the stock carb with only diverter fins removed.

maybe I was wong about the weld. I see a screw underneth.

Hi Crow,

There is no better bang for the buck mod than the Z1. A small hand impact driver and hammer works really well at removing that spark arrestor screw, because at the same moment the phillips bit is being driven into the head of the screw, it's also turning it. It's good to leave the spark arrestor completely intact for safe and legal off roading, and the exhaust isn't really that much louder, just more growl... and you will be suprised at how much better the bike performs!

Take Care,


Greg

As an addendum:
Unless the offroad terrain is tinder dry, I felt comfortable removing the screen wrap on the arrestor and drilling out every other hole slightly larger on the stinger.
I swear it makes an additional small, but feelable, difference and still basically retains a "spark" arrestor.

As some have read, I simply used a long sharp spike to punch peripheral holes around the inner baffle/diaphram.
I also removed the "swirl" vanes on the arrestor.

The engine breathes so much better at higher altitudes in the 4000' up range I ride in here in Western NC.

Bill O>

My xt has only 400 miles on it but after reading all the hype on the Z1 I to had to try it. I used some small magnets inside the hole saw (Lowes has them in stock) and that retrived most of the metal shavings and the disc. Ended up drilling out the spark arester screw and oversizing one step and installing a allen head bolt. Actually it went very smooth. Will give it the test later this week when it warms up to 45 deg. I would like to thank all that contribute and have Happy and Safe New Year.

I lost the metal insert while doing this and am planning to remove the exhaust. I'm struggling to get the bolts loose - I've tried the t-handle manually and a power drill approach - can someone advise me on the best method? Thank You

Bump... someone out there can advise me -- I know it.

Hi lobo

I am not exactly sure what bolts you are trying to get loose? Are you trying to remove the whole rear portion of the exhaust pipe from the bike? If the bolts are stuck, soak the threads with WD-40, and then use a socket with ratchet to do the deed. I don't know what you are referring to with the power drill approach.

If you can be more specific on what you are asking I'm sure we can help you out.

nice job! anyone know how to or have done similar mod to a 1994 model serow which hasnt got the bolt on the end cap? cheers

mjf1974 -
There is discussion in Z1's original thread regarding solutions to this issue:
Z1's stock exhaust - original thread

and I believe CougarBait wrote up a method for doing the mod on older bikes:
CougarBaits thread

Good luck!

If you want better performance get the FMF or similar pipe. The stock pipe on mine started rusting away in 9months.

Z1,
Thanks for the info on the mod to the exhaust. Had to use an ezout to get that screw out. Other than that, no problem.

I just completed this mod, as well as the pilot jet mod. Both went fairly easily, but I do have a small concern, I'm getting some backfiring on deceleration now. I suspect it's because there is little backpressure in the pipe, but it could also be the pilot since this is when you shut down the throttle.

Anyone else experienced this, and if so, how did you fix it?

thanks,

Matthew

Matthew,
I did the two mods and don't get the backfiring with three turns out on the idle jet screw. I do get a little rumbling sound.

i've been reading on the forum for awhile now, but just purchased my '01 xt and i decided this mod MUST BE DONE!

i wish there were mods like this available for my volkswagens!

major improvement!

next comes mixture screw adjustments!

oh, a quick question too..

in the original post by Z1XT225, there was talk about making rejetting the carb on early xt after this mod (new xts didn't need it)..

how valid is this argument?

i own a '01 xt and would like to know if this rejetting is nessecary. i live in an area of michigan which is at about 600 feet above sea level.

thanks.

My cousin & I did this mod on my '04 XT and it really does sound so much better, and pulls a little harder. I know I go faster too; on the expressway. I want to say 90+ MPH.

I live in NYC and could use all the attention getting sounds and lights possible. Too many boneheads on the road to not think of the safety ramifications of such an upgrade. &&&& Now it sounds like dirt bike...a real dirty bike Making love to my XT never Felt So Good in My Life Before(a write up(how-to)with possible pictures coming soon)

Next will be the detachment of the snorkel, but I have a feeling I will need to re jet. and thats no fun for anybody...kit or no kit.

Z1..I bow down to you... Crash your write up is on point...I want to grow up to be just like you and your photography skillz.

Thanks you two champions of the XT!!!!!~~~~ Drool.

Later Gators.

RideorDie :)))

Yeah, my wife said I had girl's bike and I said "oh, it's a girl alright".

Uh, did I say that outloud?

I decided to mod the exhaust and had a lot of trouble getting the cap off. First I had to use an EZ Out to remove the bolt and then it was another hour of banging and twisting to get the rusted on cap off. My bike is only a 2006 but I assume that the salt spray here makes it rust quickly. When I removed the cap the spark arrestor circled in blue was loose and with a gentle twist it came off. I can't tell if it was spot welded or the ring on the cap served as a compression type fitting. In any event it's quite rusted. I cleaned the cap and repainted it so it looks good. My question is, how important is this spark arrestor/baffle? I haven't drilled the hole in the pipe yet as I was concerned with it getting too loud. Is everyone here running with that internal arrestor/baffle or have some of you removed it? Thanks in advance

Exhaust Baffle

unfreaknbelievable ! ! just Z1'd my 05 XT i bought 3 weeks ago and i only got to put 100 miles on it because of the weather today i Z1'd it it took every bit of 30 minutes and 15 dollars to do i dropped the "restrictive chip" down the pipe when i drilled thru and so i took the three screws out pulled the muffler off and out fell the chippy chip with a little shakey shake i am not by any means a mechanic or cycle junkie this is my first bike in years she's growling like a lion now with an overdose of torque and top end speed im so excited now i was beginning to feel like this was a beginners bike i just couldn't get it to act the way i wanted it to but now i literally have to take it easy the Z1 mod has totally brightened my future in riding this bike i'll prolly keep it for several years to come thx alot fellow riders see ya on the streets!
txtradesman

by the way the spark arrestor screw started to strip little and so i drilled the screw a little bit with a 1/8" bit and then i tapped a small flat headed screwdriver into the slot and it came right out once i got the arrestor out i lightly tapped the wings with a crescent wrench until they bended in against the mesh tube i used a 1-3/4" metal hole saw with a 12" extension to drill the inside out the metal is very thin and it will go thru in about 15-20 secs after that i reassemled the exhaust and off i rode howling at the moon. . . .its so easy even a caveman can do it!

What is the size and TPI of the allen screws you guys are replacing the stock one with?

Also, where can one purchase the parts required to do the Z1 mod.

Core2Quad,

You should be able to find all you need at your local hardware store, Lowes or Home Depot.

Take the original spark arest. screw with you to make certain you get the correct size. I honestly cant remember what size I replaced it with.

This mod is a MUST DO.......

So with the Z1 mode and going with 130 and 42.5 piolet jet, how much more HP do you think I'd get? 3-4HP?

Is it recommended to also replace the jets when doing this mod, and what about the airfilter? Making it breate better I guess is a good idea...

Z1, 135 main / 42.5 pilot, 3 turn mod de-snorkled w/air box vents and a UniFiter. I did all these at one time so I could really see the full benifit. I've never dyno the bike so I couldn't give you and accurate HP, but honestly it will be a completely different toy. You will be very supprised how much you can get out of that hamster wheel.....

If you are going to just do the Z1 I would recomend at least doing the jets and air box mods (De-snorkle, UniFilter).

With more exhaust going out you might as well allow the engine to breath in better giving the proper amount of airflow for the larger jets if that is the route you decide to take.

I was very hesitant myself, but these are all very easy and inexpensive ways really bring your XT to life.......

I bought a 2005 XT225 with 500 miles a couple of months ago. It wouldn't start. After going to a 130/45 jetting (Yamaha dealer couldn't get a 42.5) the starting problem went away. The bike starts good now but it lacked power (65 mph would have been absolute top speed). I did the Z1 mod and top speed immediately went to 75. There's still some roughness once up to speed so I likely still need some carb tuning or something. But this site is absolutely great with so many people who are willing to help.

The muffler end cap screw size you're looking for is 6mm.

Liberia,

Before you start making any carb adjustments try making some changes to your airbox. If you did the Z1 and Jets and you're getting some chocking at higher speeds, it's possible there is just not enough airflow for the larger jets. I would recomend removing the snorkle.

Before you do anything try taking your bike for a ride with the air box cover off and see if you still get the same roughness at higher speeds.

Thanks for the advice. I'll try that tomorrow and give feedback.

And be advised that metric bolts/nuts have two or three thread pitches. . . so, again, take that little bolt to the hardware store with you!

I took the bike out for a run this afternoon. It was pretty cool here (50 degrees or so). The bike ran pretty smoothly but topped out at 70 mph. I then took the air box cover off and tested it again and still topped out at 70 mph. Bike ran about the same. So no sputtering at speed today.

It does seem that I should be getting more than 70 mph with stock gearing. Is using a 45 rather than a 42.5 jet affecting me negatively?

The 45 jet is your pilot and should not hurt your top end performance. Although I would recomend going down one to the 42.5, I think anything more would be a waste.

You can get these things going more than 70mph depending on your load and weight. I can't imagine why you would want to for prolonged amounts of time. This isn't one of the most comfortable bikes at those speeds. I usually find myself around 55 - 60mph when commuting to and from work. The engine sounds real comfortable there.

I figured that having the extra power and speed would mean that at 55-60 I would be easier on the bike. I plan to use it on a 20 mile (each way) commute and would like it to be at less than maximum power. I think 55mph as it sets now would be okay.

On my completely stock 03 XT225(except for Kenda K761 tires) I hit 80mph rather easily and still had some headroom. I think it could go 85mph in the condition its in right now. I weigh about 175 btw.

If your only hitting 70mph after the Z1 mod and larger jets, there id somethhing not right... Air filter? Tire pressure? Chan tension? Are a few simple things that come to mind.

Are we talking about GPS measured top speeds here? The XT speedometer can be very optimistic depending on the front tire size. Rider weight is not such an issue on top speed, aero drag and horsepower are the major determining factors.

Were talking indicated speeds with the same size tire as stock, so it shouldn't be off more than 2-3mph... I'll have to get my GPS out though so I can see what the actual speeds are...

My speeds were indicated as well. I need to check them with a GPS.

I have not shimmed the needle yet so perhaps that is affecting my top speed?

Needle position affects transition from 1/2 to full throttle, and shouldn't influence top speed.

Wow.

Just did the Z1 mod. My bike is totally more powerful. It is louder, but not too much by any means. WAY better throttle response. WAY better acceleration. Higher top speed.

Thanks for the heads up Z1 and thanks for the clear instructions crash...

One question. I got my bike from a guy who worked at a yamaha dealership and when I got it off him I was asking him about the common hard starting issue... He mentioned that he had fixed it. Never had a problem with starting... Do you guys think that my carbs have already been modified?

Let me know!

Thanks,

Sounds like you at least have the 42.5 pilot jet. Every XT that comes in the shop here, my lead tech wastes no time in throwing that 42.5 in the carb. Solves so many issues!

It is easy to go too rich on the XT225. When you are going down the highway and you roll on the throttle at speeds over 60 mph and it actually feels like someone is hitting a kill switch you are too rich on the main. Too lean seems to happen as you feel a stumble when cranking open the thottle at slower speeds.
The XT225 jetting needs can vary given air temperature and altitude.

attempted to do this mod yesterday. stripped the screw that hold the end cap on...drilled it but the bolt extractor broke off in it. that's as far as i got.

Meh that sucks Daddysmut. I replaced my screw with a hi-temp anti-seized ss allen head - as someone here suggested. Its worth doing - slight increase in noise, but I've noticed a difference in power, tho I still need to shim the needle.

My son and I just did this mod. We sprayed the end cap and screw with some penetrating oil the last 2 nights. The screw stripped and I had to drill it enough to use an 'easy out' but it came out right away. I place a short piece of 2x4 against the end cap and hammered all around...the cap basically vibrated itself out after about 10-15 blows. I used a 1.5" hole saw on an extension and made sure to put a small drill bit in the centre of the mandrel. The drill bit extends a ways past the hole saw and the disc that was cut out remained on the bit.

The sound is much improved...a deeper richer sound. Will check performance soon. We also had Kenda 761 tires installed today and plan to swap out front sprocket for a 16T when it comes in.

I guess I am the odd duck here. I hate the sound. Its loud and obnoxious. Basically its a straight pipe with the spark arrestor on the end. A buddy of mine rode it, and I could hear him a mile down the road. So if you like quiet, I would pass on the mod.

You are not alone.

I think it is too loud with the snorkel removed!

You can't even here my 250cc scooter going down the road, I wish the xt was as quiet.

Of course the muffler on my scooter is 5x bigger, that would look silly on the xt, but, some days I am tempted!....

I just did the Mod on my xt250 after reading the many posts about how great it was. The mod itself was easy and took only minutes but now I'm stuck with an obnoxiously loud bike. What can I do to reduce the "tinny/hollow" crack on hard accelerations/decelerations? I have had big bikes with big pipes and I am over it. A thudding xr650 is one thing but a firecracker 250 is another. I have thought about packing some glass around a perforated pipe or other mod but I am unfamiliar with the territory. Any ideas?

Did you remove the spark-arrester too? "Cracking" sounds like you're running very lean; you might try getting things richer.

Other than noise, did you experience a gain in performance?

Alexd

I agree that the full Z1 mod is too loud. Maybe I'm getting to be an old fart but I am getting tired of hearing loud motorcycles. I regret doing the Z1 now but I did tone it down by packing some coarse stainless steel wool in the exhaust. The regular finer steel wool would not last long.

Alexd,
I removed an 1&1/2" disc from the inner baffle and replaced the spark arrester. There is some performance gain but not enough to offset the increase in volume. (for my taste anyway)

Barnone,
how did you pack the wool? Did you just cram some in the tube? I was concerned with fire issues if it were in the line of fire so to speak. I had an idea of welding an extension onto the arrester with a fender washer on the end to create a bit of a diffuser. Any thoughts?

If you haven't already seen SoreToeJohn's illustrated post in another thread showing his solution Greenwater, take a look at it now..

http://www.xt225.com/forums/ubbthreads.php?ubb=showflat&Main=6304&Number=52531#Post52531

I do understand the trade-off between performance and noise, and it is everyone's individual choice of course.

When I first heard about the Z-Mod, I decided to just go 1."
I recall seeing a post from others that over 1" seems not to give any appreciable extra performance...just adds more noise.

Now that you're at 1 1/2" it seems to me that adding steel wool and clamping it with a metal muffler clamp (or screw clamp) might be the way to quiet things to your satisfaction.

Alexd

I'm surprised by the complaints of excess noise with this mod. I did it to a stock xt225 with no air box changes etc and it sounds great.

Due to a request from a fellow board member I've dug up the sound files originally posted on the first page of this thread (I realize the link no longer works)...

If you want the files email me kbrame@uplink.net and I'll send them to you.

Here's a possibly simpler way to do the Z1 mod, one that achieves the same result but saves having to clean metal pieces and debris from the system once the mod is complete.

http://www.xt225.com/forums/ubbthreads.php?ubb=showflat&Main=6352&Number=52923#Post52923

I've dome the muffler part of this along with the snorkel/ filter mod . Now I am waiting for the dealer to call me up and say the carb parts are in. I am a heavy guy at 260lbs but the bit that I gained is a nice bit. I dont think its too loud i can still ride nice and quiet on it. It is louder Thats what one would expect from the mod though. If I have to run through a sound trap I would pull the cap off and wrap it in Fiberglass. On the flip side it is an invisible mod, as opposed to bolting on a aftermarket can where everyone can see that you have done mods. This still looks stock.

Let us know how everything works out.
(This thread's last post was about 2-1/2 years ago)

Alexd

got the carb modified now. Runs pretty good but I live at sea level.
I realize that the thread was 2+ years old but they are still selling and there are lots of these that are still stock without any mods . Mine was a perfect example, being a 03 that was still stock after 18000 kms. I have in the last few weeks added little bits and pieces and been making a good bike better. I have now added a seat pad made from a ensolite sleeping pad(the blue stuff)that makes a huge improvement in comfort while riding.





0

If you're at Sea Level and your float heights are set within specs, you should probably change your main jet from a #125 to a #127.5, with the mods you've made. It might support a #130; it's something for further experiments.

Changing the Philip head screws to Allen head screws on the floatbowl is useful, as is adding a small gas-line filter.

Alexd

I bought a used XT225 and the stock muffler has been drilled with the Z1 mod - but *really* drilled. The hole is about 1.75" - there's barely any plate left. It's pretty loud.

Any idea whether this would be louder or quieter than a FMF Q4?

Hi every I want to do to K1 mod. but I can't get the screw out! I have read that it can be drilled out, but then what? do you use an ease-out, will that work? I also read about using an extration tool but I don't have one.

On another subject I would like remove air box snorkel, can this be done with out destroing it. I have already rejetted the carb.

Thanks Terry

If you're going to be wrenching on a bike that's going in and out of mud, you're going to have a lot of rusty/stiff screws & bolts. This is worth the investment, IMHO:

http://www.craftsman.com/shc/s/p_10155_12602_00952160000P

I personally don't like the "easy-out" style where you drill into the center of the screw and then use a tool to twist it out. I've broken more than one of those. They also wear out quickly.

http://www.amazon.com/Easy-Out-Screw-Ext...howViewpoints=1

In my experience most easy out, or those extractors dont work, just drill it completely off, dead center, and then insert a new allen head (non stainless steel) bolt.

i changed my philps exhaust baffle bolt with a 12.9 grade allen one.

I was gifted a set of the craftsman Bolt - Outs that Jim posted. They sat for a few years, but when I needed to use one, I was pleasantly surprised at how effective it was. I've only used them a few times, but they have worked every time.

I too changed out the exhaust baffle bolt with an allen bolt, and then stripped out the hole a few weeks later. I ended up having a bolt welded into the pipe, works great now, and no fear of stripping that super thin can wall any longer.

I've used both, and presently have an Allen-head replacement screw.

You can easily strip the holding threads with the additional torque available with the Allen. However, the advantage is that you can always get it off, without stripping the head of it, like the stock Philips-head.

I've also used EZ-outs and also just drilled down the middle. EZ-outs are better for broken heads without severely rusted-up, gummed-up threads. If the threads are very bad, drill the broken screw out completely.

(If the EZ-out breaks inside the pilot hole, it's much more trouble drilling the whole mess out!)

Alexd

On the XT225, remove the seat and the air-box cover. The snorkel is held in by the compression of the rubber, and a thin layer of sealer/glue. Work a screwdriver around its edges, and pull it through and out with your fingers and/or a pliers. You can do this without damage to either the snorkel or the air-box, and can put it back again later if you want (which probably will never be done).

Air-box modifications like this cause more changes to AF ratio than exhaust changes, like the Z1 mod...a general principle to keep in mind. Idle is generally not affected.

Alexd

A silly question from a mechanically retarded xt225 user:
-what is the snorkel on the carb look like?
Any pics?

Part #8, called a Duct by Yamaha, on the XT225:

http://www.nielsens.com/fiche_section_de...&fveh=18067

Alexd

Tried having a go at it while I was replacing the air filter, that snorkel is solid as!!
Is there an easier way to pull it out?

It's usually glued in.

I've done it several times using a flat-blade screw driver to break the seal and pry around the entire edge. It probably will come out easier through the air-box, than from the top. But, getting a grip on it from both sides and twisting, will eventually do it.

It won't break and with care you could put it back; I've neve done this though, as I like the effect. You will likely gain power, but you may wish to go up one "'notch" in main jetting.

Alexd

I removed mine, didn't like the sound, and put it back in. Putting it in was harder than removing it, but the bike sounds & performs exactly as it did before.

The increase in power was noticeable. It wasn't the decibels that bothered me; it was the frequency of the sound. It felt like the sound waves went directly inside my helmet. I found it unpleasant. I imagine a different rider & helmet on the same bike wouldn't find it so bad.

Here is a video of my modification. I have recorded sound at every stage of the mod. ENJOY

z1 MOD

private again lol.

fixed sorry about that

Vertical Video Syndrome

Just joking, very good video.

I won't do this mod because local police now has sound meters and anything over 100dB get you a ticket.

Anyway maybe I'm weird but I wish my bike was quieter...

I very much doubt that the Z1 mod (at 1" hole) makes any more noise than a good aftermarket muffler...certainly not 100 db.

Alexd

If you leave off the spark arrestor you will be over your max. But its not that much louder.

I did notice however, once removing the snorkel, when acceleration with a lot of throttle, it creates a deep tone heard by the operator but not those around you. Its like it channels the sound up through the seat not out the side.

Yeah.

Pretty much everybody now leaves the spark-arrestor part alone.

Alexd

Thanks to all for the pics, info and to HeraldJ's video. Performed the mod on my '92 yesterday, screw came out with 2 hammer blows on a hand impact screwdriver. I didn't even pre-soak or heat it up. Pulled out the plug and filings with a magnet. It is amazing how much the arrestor cuts down on the decibels, I was a little nervous my bike was going to be extremely loud when starting up with the cap off to clear out filings. Also upped the jet +5 to 135 and the pilot to 42.5, pilot screw out 2.5 turns. Still need to do Alexd's low speed full throttle trick to test for richness. Mod worked awesome, not much of an increase in noise and now I have to watch the shift from first to second as I've caught myself lifting the front tire off the ground with my normal shifting habits...

You're probably running too rich on the main jet at 135. But, no harm...just look for "burbling" at full throttle.

Alexd
P.S. Whenever you check jets, be sure the day is typical (not rainy) and be sure the engine is THOROUGHLY warmed up. Good gasoline, etc.

I can be a little obsessive about details when working on things, and I was wondering how I was going to get the hole in the baffle in the exact center.

A plastic cap from a vitamin bottle is 1 7/8" in diameter, and with a layer of duct tape around it is just about a perfect fit for the inside of the muffler. The cap even has a little dimple at its center. I drilled a 1/8" hole in the cap, slid it down to the bottom, then slipped a center punch into a socket on the end of an extender to punch a dimple in the steel, and drilled an initial 1/8" pilot hole — right down the middle. Waiting for a step bit to arrive from Amazon on Wednesday.

It's not necessary to be so exact.

Four 1/2" holes or 16 1/4" holes are mathematically the same area, as a single 1" hole.

Alexd

I know — just my OCD kicking in.

Since I ended up with a >6mm hole for the retaining screw, couldn't find a 7mm cap screw, didn't want to go to 8mm, and wanted to stay metric, I used JB Weld to secure a nut inside the muffler:



JB Weld is rated for 450°F, and this area probably never gets above 200°F, there is lots of contact area around the nut, so I'm not worrying about the nut coming loose. I coated the bolt with some anti-seize before screwing it back in.

The hole in the baffle came out as expected:



I found a surprisingly good 3-piece Step Drill Bit Set 4-12/4-20/4-32mm on Amazon for $10.99. Used plenty of WD-40 during the cutting process, and stopped to re-spray every time the WD-40 started to vaporize, keeping the cutting edges nice and cool.