ts250 - fixing air leak with tin foil

For as long as I have owned the bike it has had an air leak causing it to run lean at termpature and at high rpms. This issue has plagued me for years. I actually rebuilt the entire motor because I thought some seals were bad.

I finally know what was wrong the whole time and have fixed it. It wasn't seals. It wasn't a warped head. It wasn't the carb. It was leaking at the junction of the exhaust pipe to the head.

I fired up the bike recently to give it another shot for troubleshooting only to hear the exhaust sounding louder than usual. I verfied that air was coming out at the head rather than all going into the exhaust pipe. After thinking about it for a second I realized that with a 2 stroke, this is the quickest way to get clean unmetered air into the cylinder. It would push air out around the exhaust on the upstroke then pull in air into the cylinder on the downstroke. I finally knew what was wrong!

To be fair to my prior self, I recognized that the exhaust leaked so I bought OEM Suzuki exhaust gaskets at a pretty good expense for this bike. Even with those new gaskets, the leak remained, though it lessened. Fast forward to today and I just removed those lightly used OEM gaskets since they weren't getting the job done anyways. A quick search online revealed a better way to seal the exhaust was to use some copper RTV and a bunch of layers of tin foil. The aluminum foil takes up most of the gap and the RTV provides the final seal and keeps things in place.

I am happy to report I have put on about 200 miles and have not had overheating due to lean running.

I wish the OEM exhaust gaskets were a better fit, or that the exhaust attached to the head in a more meaningful way than just a single spring. Either of those might have kept me from parking the bike for years.

Regardless, the problem is fixed and I won't soon forget that lesson.


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OEM gasket is crap
Maybe 10 layers of tin foil
all sealed up, no leaks

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