Cranks, idles, runs..... Part II

OK, thanks for all the posts from the first part. Tried ALL the suggestions and this is what I got now. Cranked it up, when it died, immeadiately unscrewed the drain bowl, and low and behold, it was empty. Waited for a minute until fuel was back in the bowl, took the gas cap totally off, recranked, died again and same thing, no fuel in the bowl. Took the gas line off the carb, it was barely draining. Fuel filter was still clean. Took the fuel valve off, and it was full of crap. Turns out, there is a rubber gasket between the two threads and it has seen better days. This is still the original valve. Cleaned it with carb cleaner. Then ran it for awhile. Didn't die. Well, not then, took it for a test run, same thing, it started dying out on me again. But this time, it looks like the fuel filter doesn't even get half full of fuel. It did that when I reassembled it and ran for about 10 minutes. I thought the filter should be full of fuel???????????????? Order a new valve at the local Yamaha dealer, 20 bucks, not bad. You think this IS the problem? When I let it sit, the carb does NOT overflow. It CAN'T be the float or needle valve, could it????????

The fuel tank was trashed, cleaned it with acid and got rid of the crud, should I break down and coat it, or will the filter suffice?

One more thing, when it did run good for about ten minutes, it started getting a little faster after each run. I mean, first, it hit about 15-20. Then about 20-25, every once it awhile, it would "catch" I mean, accelerate like crazy, then start bogging down again. Original jets, Mikuni carb. Jets too big? Did have a new air filter on it. Ideas??? Suggestions???

thanks in advance.......

Re: Cranks, idles, runs..... Part II

Sounds to me like you've still got some crap in your tank and it's plugging everything up. Zip tie a plastic gas can to your rear carrier and run a fuel line from it to your engine, clean out the carb really good again and see if it runs better like that. If it does, you didn't rinse your tank out well enough. Your carb should not overflow, if it does somethings wrong with the float and needle valve.

Re: Cranks, idles, runs..... Part II

Ron Brown /


I think you have answered most of your own questions here.

Did you test fuel flow again after it died again?

When you acid cleaned the tank, did you remove the petcock and seal the hole with duct tape or leave it on? This would not be good for the petcock.

If you have a good in-line filter, your carb should still be fine. Don't worry about bubbles in the filter, gas does not flow fast enough to wash them out.

As for your performance gains, your mixture was most likely leaning out from the bad fuel flow. 2 strokes always run their best just before they sieze from a lean mixture. : (

You will not be able to check the mixture correctly until your fuel is flowing ok.

Yes, your float and needle are probably ok although it is possible for the fuel level to be off without leaking.


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