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Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

KTM 250MX Starting Troubles

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

KTM 250MX Starting Troubles

Q: I have a 1986 KTM 250MX and am unable to start it using the kickstarter. I have installed a new spark plug, and the carburetor is clean. The timing is correct, and I’ve installed a new power reed. It will start if it’s pulled behind a four-wheeler. — Clair Raible/Black River, New York

A: Without seeing the bike, I can only guess, but for a 2-stroke, starting troubles that are overcome by pull starting usually point to bad crank seals. Once you have it running, will it idle reasonably, or does it die? That’s another pointer to crank seals. If you can do a pressure test, you should be able to pinpoint the problem easily. If it idles once you have it started, it may be poor compression. Again, a pressure test will give you the answer. See our How-To in the March/April 2015 issue or online. MC