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Carburator - Seems to get dirty quickly?

Posted By: Rocky Baker

Carburator - Seems to get dirty quickly? - 04/19/19 02:53 AM

Hey everyone,

So I picked up a broken down 1992 XT225 last summer for peanuts and put lots of time, money and energy into it to get it running again. I have been running it since last summer and it is still being used however, it seems to be having much more trouble starting and the carb is apparently getting dirty very quickly, if that makes any sense?

So here are the symptoms. After cleaning the carburator and putting it back together, the bike runs like brand new. After about 50km, it seems to start lacking power (will not lift the front wheel anymore, cannot hold speeds above 80-85km/h). If I take the carb out and clean it again, it runs like new again for another 50km before starting to lose power once more.

Before you start offering answers to my problem, here is a list of things that I have done on the bike recently which can be eliminated as part of the problem:
- Clarke plastic tank (no rust anymore)
- Rebuilt top end (not the pistons or rings anymore)
- Carb rebuild kit with a new side cover (not cracked anymore)
- New intake boot from carb to motor (not cracked/leaking anymore)

When I take the carb apart, the smaller diaphragm that's under the side cover doesnt seem to slide in and out smoothly, like it's hanging up somewhere on the inside tube where the nipple slides in. Is this something I can lube with vaseline before putting back in? Could that in itself even be my problem? How do I fix it?

Judging by everything I'v put into this bike so far, you can imagine I'm getting really sick and tired of having to tinker with it between each ride. But again, I do love this bike when it's running properly. I also definitely don't have the money for a new one. PLEASE SOMEONE TELL ME THERE'S AN EASY FIX!
Posted By: #brer15

Re: Carburator - Seems to get dirty quickly? - 04/19/19 09:36 PM

Are you using fresh gas?
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/20/19 04:30 AM

Yes, I put a brand new plastic gas tank and filled it to the top the day of my first ride this year.
Posted By: Newb Rider

Re: Carburator - Seems to get dirty quickly? - 04/20/19 11:13 AM

Have you thoroughly cleaned the airbox and the pipe leading from it to the carb? Is the air filter clean and making a good seal against the airbox door? Is the airbox door itself sealing (there's a rubber seal supposed to be in the lip of the door, dab-off sealer would suffice)
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 04/20/19 08:15 PM

Did you install a fuel filter? What does the carb look like before you clean it? What sort of debris do you find?
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/23/19 05:40 PM

Sorry for not replying right away. The weather here in northern Ontario has been horrible so not much riding opportunities.

I used to have an in-line fuel filter but when I installed the new tank, I removed the filter thinking it might be contributing to my problem. Also, last time I cleaned the carburator I didn't bother taking it apart in order to troubleshoot the problem. All I cleaned was the large intake and exhaust orifices and the fuel lines connected directly to the exterior of the carburator. I didn't see any debris or dirt per say, but IT WORKED! Again, started losing power after 50-60 km.

Am I wrong in thinking that I can now eliminate a fuel issue and concentrate on the air intake system? I believe my next step is to do what Newb suggested and just do a thorough cleaning of the snorkel, airbox and air hose going into the carburator. Please keep the ideas coming if you have any. Thanks for the support as usual!
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/23/19 05:41 PM

Thanks for that idea. Read below for an update and what you suggested will be my next step.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/23/19 07:12 PM

Before i do the intake clean-up i have a question. After taking it all apart and cleaning it well, should I maybe wipe vaseline or something like it on the inside of the snorkel, airbox and intake tube to maybe trap some of that dust on its way in? Is that a bad idea?
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 04/24/19 12:08 PM

It would seem strange to me that a dirty airbox would cause the problem you're having. I'd think the air filter would have to be completely caked with dirt to cause the stalling problem you're having. And if that were the case it, cleaning the carb wouldn't help. A clean, oiled air filter will clean the incoming air just fine. If you're riding where it's extremely dusty, you can add a pre-filter.

When you notice the bike start to lose power, shut the bike off and open the fuel tank. If you get a whoosh of air, the tank vent isn't working and you're slowly pulling a vacuum on the tank which is starving the engine of fuel.

You might also check the breather hose from the crankcase to the airbox. If it's blocked, you could be building up crankcase pressure while riding.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/24/19 12:51 PM

The fuel tank is venting fine through a length of fuel line on the cap and I have often taken the cap off to check the gas before I ride. The crank case hose it also fine and I have a new clean and oiled filter.
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 04/24/19 04:30 PM

You wouldn't notice the whoosh of air when checking before a ride, only after it's been run for a while. It could be venting some, but too slowly to compensate for a period of high speed running. Not sure.

Could also be a stator starting to die as it heats up. Those can be tough to figure out.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/25/19 04:34 AM

THanks again Peejman,

Just to be clear, the bike is not stalling. It idles fine and sounds normal. Also, the fuel tank is venting properly. It's just a simple fuel line coming off the plastic cap that came with the Clarke tank which I can easily blow into and when I stop I hear the air rush out of the tube. Whatever the problem is has to be related to the carb or air/fuel mixture because cleaning the carb solves the problem for about 50 km or so.

More specifically, cleaning the large orifices on each end of the carb fixes the problem without even having to take it apart. I could be wrong but I think that eliminates the crankcase hose or the tank venting.

I did notice something while looking at the airbox just now. After removing the air filter cover, I noticed the front face of the airbox seems to be completely removeable in order to see the front section where the crank vent tube goes in. If there was a leak in that seem between the box itself and that larger cover, could that be the cause of my problem? Would a tiny seperation of the seem be enough for air to bypass the filter and go directly into the carb?
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/25/19 04:43 AM

Sorry for the numerous responses, I had not seen your last reply. I also dont think it can be the stator heating up because those 50km aren't necessarily in one ride. I can park the bike overnight after losing power, try the next day and still have no power until I clean the carb again. I litterally have to clean the carb every 50km or so no matter how many rides that meens.

I will take apart and do a thorough inspection of the whole air intake system this coming friday. I think I will also dap the seams before putting everything back together in order to seal any small openings that could exist. Is using dap (rubber crack sealer, like caulking) a bad idea for any reason I don't know of?

Thanks
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 04/25/19 03:08 PM

Ok... I'm kinda out of ideas at the moment. This is an odd one for sure. Cleaning and sealing the airbox certainly couldn't hurt anything.

I've not heard of an airbox in multiple pieces. Perhaps the older bikes were made that way.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/25/19 05:30 PM

When the air filter cover off your air box, do you not see other smaller screws you can remove? I think it's 1 or 2 small screws in the front and 2 that must me removed from the behind or with a U-curved screwdriver. Do you have a different way of accessing the part of the airbox where the crank case vent tube goes in?

I'm going to work on it now. I will try my best to post pictures of what I meen in the next couple days.
Posted By: #brer15

Re: Carburator - Seems to get dirty quickly? - 04/25/19 08:50 PM

If that little tube on the bottom of the air box is full of oil, it may be worth taking the air box apart in the way you describe for further inspection.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/26/19 12:06 PM

I yesterday I took the time to remove the airbox completely from the bike and take it apart as described in past posts. There are 6 screws keeping the faceplate on the airbox, 2 visible and 4 form behind. Upon removing the faceplate, it became clear that the front portion of the airbox was not properly sealed at all. The inside of that cavity was quite dirty on the wall and in the hose going to the carb.

I could see 2 seperate contrbutions to this problem. The seam between the faceplate and the airbox was not sealed properly. You could tell that there used to be a sealing agent there many year ago but it had deteriorated over time, properly from numerous removals. Also, there is a small tapped hose in the center of the faceplate cover with a function that is unknown to me. Whatever bolt is supposed to go there holding something was never there on my bike and that bolt hole went directly into that cavity.

So i did the dishes, thouroughly cleaned the snorkle, faceplate and airbox completely. I also scrubbed off whatever old glue or sealing agent was left in the seam. After drying it well with paper towels, I applied Dap (acrylic silicone caulking in a small tube) all around the seem of the airbox before re-installing the faceplate. I also filled that small bolt hole with Dap.

The dap has dried over night and the airbox is ready to be re-installed with the air filter and cover going back on afterwards. I will take apart the carburator and give it a good cleaning again (for like the 4th time already this year) put everything back together. If everything goes well, I should be able to get that done at some point today and I'll let you guys know how it goes.

Thanks again everyone! This website is a life saver.
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 04/26/19 12:07 PM

Originally Posted By: Rocky Baker
When the air filter cover off your air box, do you not see other smaller screws you can remove? I think it's 1 or 2 small screws in the front and 2 that must me removed from the behind or with a U-curved screwdriver. Do you have a different way of accessing the part of the airbox where the crank case vent tube goes in?

I'm going to work on it now. I will try my best to post pictures of what I meen in the next couple days.


Now that you mention that, yeah I do think I remember those screws. I recall that mine had some sort of sealer gunk all around the seam that I cleaned off. Looking at the fiche, the air filter cover has an o-ring and there's another o-ring under that cover that's screwed on. I probably just put some grease on it when I put it back together. That's been several years ago.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/26/19 04:59 PM

Okay so the bike is reassembled and it has it's power back after cleaning the carb again. Now if only it can stop pooring rain I'll be able to tell you if my fix worked long term!
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 04/28/19 01:32 AM

Woke up to 4 inches of snow on the ground this morning with the streets all slushy...might have to wait a bit for the conclusion.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 05/02/19 04:57 AM

Well guys I'm glad to say my problem has been SOLVED! Cleaning and sealing the airbox has fixed my problem. I have put on 80km since doing the fix and the bike has the same amount of power as when I first put it back together.

I suspect the main culprit was that bolt hole in the center of the airfox section AFT of the filter. It looks like there's supposed to be a part bolted into that part of the cover, however I'v never had that part that it used to just be an open hole into the airbox section between the filter and carb.

So the carb really was getting dirty quickly after all. It also explained why I would have SO MUCH power immediatly after a carb clean, because my bike was getting much more air and running lean. In the first 10 km or so, I would be able to wheelie in first sitting normaly, without clutching or pulling the bars at all. I thought that was odd....haha. Then it would start to slow down, becoming sluggish and sounding whinney until it couldnt even hold 80kph after about 50km.
Now the power output seems to be more in line with what 15hp is supposed to give you and its staying constant. Quite nice actually...smooth and predictable.

Thanks everyone for your input and Ride On! The XT is a great little bike!
Posted By: Muniac

Re: Carburator - Seems to get dirty quickly? - 05/02/19 03:35 PM

Glad you got things all sorted out. Enjoy the riding.
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 05/02/19 04:18 PM

Good. A short piece of tubing, sealed on one end, is supposed to go on that nipple. It's there to act as as drain should you suck water into the airbox during a deeper than expected creek crossing, or oil should the bike spend much time running while laying on it's side.
Posted By: #brer15

Re: Carburator - Seems to get dirty quickly? - 05/02/19 06:34 PM

^+1
I think of it as more of an inspection tube.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 06/20/19 03:47 AM

So the problem was NOT resolved. It just lasted longer than previous tries. I am not sure what to think anymore. I doubt it's an airbox problem anymore because after taking apart and putting back together many times over.....this thing is CLEAN.

With clean gas coming in from a new plastic gas tank and clean air coming through a very thoroughly cleaned airbox, I'm thinking it must be a carb problem of some sort. I had the fortune of finding a brand new complete carburetor assembly on ebay canada for 42$ and jumped on it. If it's a carb problem like I suspect, it will be gone.

If the problem persists now, I'm at a complete loss...
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 06/20/19 01:29 PM

What kind of fuel line do you have? Gas with ethanol can break down different kinds of tubing which could be adding debris to the carb. Same with the petcock, it could be corroded inside and letting debris in. If you haven't already, install an in-line fuel filter and only use 100% gas.
Posted By: Az4x4

Re: Carburator - Seems to get dirty quickly? - 06/20/19 02:20 PM


I'll second Peejman's inline fuel filter recommendation. Once you have that new carburetor in place make sure the gas supply is filtered before it gets to it and you'll avoid further headaches. It's cheap insurance and easy to install..
Posted By: Muniac

Re: Carburator - Seems to get dirty quickly? - 06/20/19 03:06 PM

Regarding inline fuel filters, avoid the cheap Chinese imports as the plastic will crack in the presence of heat and fuel. Alcohol in the fuel is always a good idea to avoid. Alcohol attracts water, is tough on rubber and oil.
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 07/02/19 07:10 PM

I just got my new carburetor in from Amazon.ca. Delivery was nice and quick as promised. The carb has some very slight differences from the original but it was designed for the same engine and looks much much better than the old one so I'm sure it will work. I'll be posting the results when I get to chance to install it and give it a good try-out through a couple gas tanks.
Posted By: Az4x4

Re: Carburator - Seems to get dirty quickly? - 07/02/19 08:05 PM


Good deal Rocky. Looking forward to learning how the replacement carburetor works for you. Don't forget the inline filter while you're at it. It'll help you avoid future dirty carb headaches..
Posted By: Rocky Baker

Re: Carburator - Seems to get dirty quickly? - 07/29/19 01:04 PM

Hey everyone!
So after 300+ km of testing, I’m glad to say that the XT is running properly and staying that way smile.
The new carb I ordered was for a TTR 225 and not the XT and there are actually some differences between them. When trying to simply put the new carb in there, the bike barely ran, seemed to be much too rich, as if always running with the choke on. It would idle but couldn’t really handle any throttle input whatsoever. Although this new carb had some differences, I’d say 95% of the parts were identical so I went back to the old carb and used the new one to swap parts. I ended up changing the choke cable o-ring and the diaphragm.
So although the new carb didn’t work on its own, the sum of its parts still ended up being a very good deal.

Tractor like 1st gear yet capable of local highway speeds (cruise @indicated 100kph no problem), little thing is great!
Posted By: #brer15

Re: Carburator - Seems to get dirty quickly? - 07/29/19 07:38 PM

Sounds great!
And I always like it when the original poster gives the conclusion to the thread. Well done. wink
Posted By: peejman

Re: Carburator - Seems to get dirty quickly? - 07/29/19 08:12 PM

Glad you got it fixed!
Posted By: Az4x4

Re: Carburator - Seems to get dirty quickly? - 07/29/19 10:27 PM


Nice fix! Well done. Enjoy your bike and keep us posted as the adventure continues..
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