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Engine loss at throttle
#147334
03/20/20 12:34 AM
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Joined: Mar 2020
Posts: 12
Jalake
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A few months back I had run into my bike (a 2007 xt225),suddenly cut out when driving around 35mph, like running out of fuel. Started back up after a few minutes, made it maybe a mile until it happened again, seemed like the more throttle I gave the less power and more it wanted to shut off. I finally got it started and running over the weekend and today, same issue. Tough time starting, battery kept dying from cranking. After about 10-15 attempts it started but then wanted to shut off every time throttle was applied. I've attached a link to a video of the issue. https://drive.google.com/file/d/1KWGCanxKCh0UV218fkzm1NEkiQcl1BZs/view?usp=drivesdkI have checked the resistance of all electrical components and they seem ok, replace spark plug and coil. Removed and cleaned airbox/filter Does this sound like a carb issue? This is my first dirt/Enduro bike, and actually first carb'd bike so I'm at a loss of what to do next
Last edited by Jalake; 03/20/20 12:36 AM. Reason: Added year of bike
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Re: Engine loss at throttle
[Re: Jalake]
#147336
03/20/20 10:27 AM
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Joined: Mar 2020
Posts: 46
nobade
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I'd definitely tear into the carb first, since it won't cost anything but time. I have had bikes do that from dirt in the carb or strange things like a jet falling out or needle clip come off. Certainly worth a look and hopefully it's something simple like that.
Aerial! Ookla! Ride!
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Re: Engine loss at throttle
[Re: Jalake]
#147352
03/21/20 06:31 PM
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Joined: Jun 2013
Posts: 4,160
peejman
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The bike doesn't suddenly cut off when it runs out of fuel. It'll start to burble and throttle response goes away, then it'll chug a few times before it dies. A hard shutoff is usually electrical.
That said, I think you have a big vacuum leak. The really high idle is a symptom of that. Check the intake boot between the carb and cylinder. If it's dry and cracked, it's probably leaking. There's also a vacuum port plug that could be cracked or missing.
If all that is ok, the carb could be clogged up.
This shall pass, be still and know. 2006 XT225, UNI filter, ProTaper bars, MSR handguards, SS front brake line, Shinko 241's.
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Re: Engine loss at throttle
[Re: peejman]
#147354
03/21/20 09:34 PM
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Joined: Mar 2020
Posts: 12
Jalake
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I had removed the entire airbox and inspected as well as the intake boot, all seemed fine.
Started with electrical as I was thinking a possibility of intermittent spark
It is not affected by turning choke on or off, only affected once the throttle pulls the plate in the carb open. (Sorry for not knowing the tech term) I have just removed the carb and found it was a mikuni aftermarket.
My next step is replace with a oem Yamaha carb and see if that works, I have not found anyone having good luck with mikuni in these bikes.
Last edited by Jalake; 03/21/20 09:35 PM. Reason: Typo
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Re: Engine loss at throttle
[Re: peejman]
#147355
03/21/20 09:36 PM
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Joined: Mar 2020
Posts: 12
Jalake
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My theory was a massive dumping of air without a fuel increase to match, now I know nothing about carbs... But that is what I was thinking since it was directly related to throttle position and nothing else
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Re: Engine loss at throttle
[Re: Jalake]
#147366
03/22/20 07:06 AM
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Joined: Oct 2016
Posts: 672
#brer15
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Silver Member
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My next step is replace with a oem Yamaha carb and see if that works, I have not found anyone having good luck with mikuni in these bikes.
Mikuni is the stock carb.
2004 XT225 purchased new in October 2004 0 miles. Current miles over 27,000.
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Re: Engine loss at throttle
[Re: Jalake]
#147383
03/22/20 05:50 PM
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Joined: Jun 2013
Posts: 4,160
peejman
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That's the stock carb.
I still think you have a vacuum leak. Checking for that is fairly easy. Get a can of aerosol carb cleaner, brake cleaner, starting fluid, ... something flammable. Start the bike and squirt small amounts on various places around the intake and the carb itself. If there's a leak, the engine will rev up. If it's a bad leak, it may not slow back down on its own (which is called a hanging idle). Try that and see what you find.
This shall pass, be still and know. 2006 XT225, UNI filter, ProTaper bars, MSR handguards, SS front brake line, Shinko 241's.
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Re: Engine loss at throttle
[Re: peejman]
#147385
03/22/20 07:27 PM
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Joined: Mar 2020
Posts: 12
Jalake
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Since I have the carb out I think I'm going to rebuild it anyway then I will go ahead and try what you suggested.
I could not find any noticable areas with cracks or anything.
A vacuum leak would have to be somewhere between the head and carb correct? Airbox side wouldn't affect much
It does not have this issue every time I run it, and the last time it seemed to clear up after idling for 20 minutes.
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Re: Engine loss at throttle
[Re: Jalake]
#147386
03/22/20 08:00 PM
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Joined: Jan 2004
Posts: 6,620
Muniac
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There's a rubber capped nipple on the carb boot going into the engine. On the top. Check that. As well as the carb boot itself to include the band clamp around the carb. The coaster enrichment cover (black plastic) can have a leak which can be difficult to spot visually. peejman's technique can be used for discovery. On top where the diaphragm is can be another potential vacuum leak. Check the diaphragm and where it seats.
The stock carb will have a choke cable connection, black plastic coaster enrichment cover and black plastic diaphragm cover on top. Good luck.
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Re: Engine loss at throttle
[Re: Jalake]
#147393
03/23/20 12:53 AM
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Joined: Mar 2020
Posts: 17
FloridaMan
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Good luck and keep us posted. I have a recent thread up you can catch my story but at the end of the day needed to have someone work in the bike a bit professionally. Good news now the bike has more longevity and will be great!
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Re: Engine loss at throttle
[Re: Jalake]
#147399
03/23/20 02:32 PM
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Joined: Jun 2013
Posts: 4,160
peejman
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A vacuum leak would have to be somewhere between the head and carb correct? Airbox side wouldn't affect much
It does not have this issue every time I run it, and the last time it seemed to clear up after idling for 20 minutes.
Correct. Idling for 20 minutes? I hope it was cold outside as the bike will get really hot sitting still for that long.
This shall pass, be still and know. 2006 XT225, UNI filter, ProTaper bars, MSR handguards, SS front brake line, Shinko 241's.
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Re: Engine loss at throttle
[Re: Jalake]
#147411
03/25/20 06:25 PM
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Joined: Mar 2020
Posts: 12
Jalake
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Well I have found something! The small black cover with the small diaphragm inside, the one prone to cracking... It was cracked. When applying slight force and snapped in half completely.
Does anyone know where to source a new one? Partzilla does not have it... Or a part number listed.
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Re: Engine loss at throttle
[Re: peejman]
#147414
03/25/20 08:04 PM
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Joined: Mar 2020
Posts: 12
Jalake
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Yes that is it! Thank you!
It had a crack and split in half when I removed it
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Re: Engine loss at throttle
[Re: Jalake]
#147415
03/25/20 08:24 PM
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Joined: Jan 2004
Posts: 6,620
Muniac
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Someone here had reinforced the plastic tube with JB weld on a new part. Seemed like a good idea and might avoid a crack down the road. That part isn't designed very well IMHO.
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Re: Engine loss at throttle
[Re: Muniac]
#147419
03/25/20 09:03 PM
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Joined: Mar 2020
Posts: 12
Jalake
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I found that post, that is what made me think to check that part thoroughly. Well, hoping that and a good carb cleaning/rebuild will sort my issues out.
Side note, does anyone know how many turns out from seated the adjustment screw should be? I've been seeing 3ish but mine was only 1-3/4
Or does it vary bike to bike
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Re: Engine loss at throttle
[Re: Jalake]
#147420
03/25/20 09:12 PM
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Joined: Aug 2008
Posts: 5,072
Az4x4
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Depending on the bike and where its ridden, plus or minus 3 turns is about right for most.
..I'd rather have questions I can't answer, than answers I can't question.. Dr. Phil
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Re: Engine loss at throttle
[Re: Jalake]
#147421
03/25/20 09:14 PM
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Joined: Jan 2004
Posts: 6,620
Muniac
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3 turns will provide a bit richer idle and easier starting. That's a good place to begin and has been reported to work for most bikes. The bike is jetted lean from the factory to compensate for a BIG increase in richness as the carb body heats up. It's right behind the cylinder on an air cooled engine. The seat is delicate so when you bottom the adjustment out, do so carefully. Then back it out 3 turns. That's the nominal setting.
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Re: Engine loss at throttle
[Re: Jalake]
#147434
03/26/20 04:36 PM
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Joined: Mar 2020
Posts: 12
Jalake
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I have reassembled the carb, minus the coasting enrichment cover, the float height (I have to measure in 32nd or 64ths as I don't have something to measure mm) the float was set at 12.5/32nd -which roughly translates to 10mm.
I have moved it to to 18.5/32 or 14.5mm
Also the adjustment screw has been set at 3 turns out from seated. Once the new cover comes in I'll put it back in and see how it works.
Is there any kind of priming process? Or just petcock on and crank it?
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Re: Engine loss at throttle
[Re: Jalake]
#147435
03/26/20 07:52 PM
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Joined: Jan 2004
Posts: 6,620
Muniac
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No special priming is required. When the bowl fills with fuel it's ready to go. At that point you're in the same position as those running their carbs out of fuel. Might need some enrichment (choke knob) to get it to fire. Good idea to replace OEM bowl screws with socket head cap screws (allen key). I think these are 4mmx.7 but not sure about length. Match up at hardware store. 10/8 SS is good with some anti-seize applied. Good luck.
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Re: Engine loss at throttle
[Re: Muniac]
#147437
03/26/20 10:30 PM
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Joined: Mar 2020
Posts: 12
Jalake
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I did replace these as the old ones were in there pretty good, one head stripped out during removal.
Thanks all! Hopefully I can try to get it running over the weekend!
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Re: Engine loss at throttle
[Re: Jalake]
#147440
03/27/20 01:51 PM
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Joined: Jan 2004
Posts: 6,620
Muniac
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That's a really good idea. When the heads strip on the OEM screws it really sucks. Galling is coming between aluminum and SS especially with heat and moisture. Anti-seize compound or synthetic grease is always a good idea on the threads. Who knows, you might be the next mechanic trying to back those screws out in a couple of years. Good luck getting it running. Ride safely.
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Re: Engine loss at throttle
[Re: Jalake]
#147448
03/28/20 07:40 PM
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Joined: Mar 2020
Posts: 12
Jalake
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Well she fired right up and ran for a bit, didn't get to go anywhere besides a few laps in the backyard as we are under stay at home orders. Seems to be running great
I'll try to ride a few times over the next few days to confirm all is well.
Side note, is it beneficial to run with the petcock in off position and burn excess fuel after every ride or only long term storage?
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Re: Engine loss at throttle
[Re: Jalake]
#147449
03/29/20 12:29 AM
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Joined: Jan 2004
Posts: 6,620
Muniac
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Glad it's running. I always run the bike out of fuel after every ride. Good insurance against ethanol attacks. Ride safely.
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Board Upgrade:
Board upgrade to V7.7.3 has been completed on Monday Feb 3rd 2020. Ride safely.
Enjoy the new software!
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