Compression Problem?

I have a 2001 YZ250F I recently purchased and have a problem with the compression. When trying to start the bike, I am allowed to push the kiskstarter all the way through the stroke. I know that on '01 250F's, this should not be the case. To try and help this problem, I put a Wiseco top end kit in it because I thought that my rings may have been going out. While in the engine, we checked all of my valve clearances which were in specs with what Wiseco told us to run. We also set the decompression lever to where it has some play in it. These modications helped slightly, but you can still push the kickstarter through the stroke with one hand. This problem is most noticable when trying to start the bike cold. The bike will not fire. When the bike is hot, the problem seems to correct itself. When hot, the kickstarter will push through but it takes more effort. If it helps, the bike has a DSP pipe and runs a 175 main, 42 pilot, and clip in the #4 position. Weather here is around 50-60 degrees in the day. Thanks for any help you can give me. I just want it to start cold!


Hey dude. Had the same problem. Ended up being carbon build up on the valve seats intake side I think. Do a quick test with the head off upside down with water to see if any leaks through your valve. I had them reseated by my dealer but sounds like I should not have after reading all the posts saying not to.

Good luck!!

This same thing happend to me last sunday at the track. At first i thought it would be the valve clearences but sounds like i also have carbon build up. How much of a job will it be to go remove this carbon? Could there be any other problems with my bike if this is happening, like why there is carbon on my valves. :)

Good question for those in the "know", is carbon build up from your fuel not completely burning up (i.e. a rich condition)? The NGK web-site stated that you have to run your engine between 500 and 850 degrees Celcius to be in self cleaning mode where everything is burned off of the spark plug (i.e. jetting must be just right, not too rich or too lean). I'm thinking that the lean conditions will melt things (bad state!), while rich conditions will cause bogs and leave carbon deposits behind - any thoughts? :)

The gas I am using is BP 100.

AV, are you saying this might be because I am running rich? Last 2 times I rode it was very cold and I had some back fire so i doubt im rich. Does anybody know why i could be having this carbon build up?

I don't know what your problem might be, I'm guessing that it's a rich condition or a bad plug or the wrong type of plug (wrong heat range) or bad gas etc. that can leave unburnt fuel behind causing carbon build ups that look like a rich condition - see the various pictures on NGK's web site, the rich condition at the bottom leaves carbon build up in the plug so why not in the valves also?!

There is a lot to your carb's setup - mixture screw for 0-1/4, needle 0-1/2, pilot/main jets etc. If one of your throttle setting is too rich, e.g. if you have too large a main jet for WFO, you could be too rich if you pin the throttle all the time, yet lean i.e. pop when the slide is closed - I'm guessing, but sounds possible that if the whole throttle range is not tuned correctly you could have problems either way (lean or rich) if you're in that area of the throttle a lot...

Stock jetting and works fine for other locals at the track.

So how does one go about cleaning the valves off?

Hey gang,

I was at the dealer today and I think I've found what we've been looking for:

Yamaha Ring Free Fuel Additive

Usage on back...

Yamaha's web page

Discussion on the Ring Free product...

Do a search on on "Yamaha Ring Free Fuel Additive" and you can read on. Notice other products that Yamaha sells such as the "Octane Improver" and the "Fuel Stabilizer and Conditioner"...

I'm thinking of using this treatment from now on for "Deposit Prevention", especially once I've put the auto decomp e-cam in... Now how will I go about measuring just the right amount per gallon? If you're supposed to use 1 ounce per 15 gallons = 1/15 of an ounce per gallon, how many cc is that? Anyone know the conversion? I've got a brain cramp right now... :)

My dealer charged $9.99 for this 12 oz bottle. RockyMountainMC has it for $8.59


It says it will clean the carb and carb jets. Does this mean you dont have to take the carb off and clean if yourself? Who has used it?

Cleans carb, jets, manifolds, valves, the whole passage! Sounds promising to me! :) Apparently many people have used it on their outboard engines (watercrafts). It's designed for 2 and 4 strokes and seems promising to clean everything for our Fs - especially those darn carbon build ups in the valves! :D

I haven't seen anyone mentioned this on TT, but since others have used it elsewhere I thought I should mention it here to see what everyone thinks... If this stuff works as advertised, we won't need to take anything apart to clean, just run this stuff through every tank and presto - sweet! :D

If you have stored your bike for a while or have clogged jets, you can do the "Deposit Removal" route to clear things up. The parts guy said they use this on bikes that have been stored for a while and need the various fuel passages cleared up. If you have to do the "Deposit Removal" procedures, he recommended changing the oil right afterwards so that any deposits from the rings that fell into the crankcase can be cleared out with the oil change.

So what are your thoughts on the Yamaha Ring Free Fuel Additive product? :)

Come on all you gas, jets, carb, valve gurus - would this stuff help with the stuck valve syndrome? Should we use it or not - can't hurt anything can it? :)

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