QuestionHello, I've had a 1986 YX600 yamaha sitting for a while, indoors, and I noticed you answered a bunch of questions about this bike. Everything seems to be in working order, I made sure I cleaned up the carbs and the tank although everything was properly drained before it sat. It has one of those digital ignition systems, and the plugs spark up fine when I pull them out of the cylinders. My bike will not start, fuel delivery is ok, but it won't turn over. It backfires occassionally and it's absolutely explosive. Do you think it might be a valve sticking? Or maybe ignition timing? Can it be a wiring problem? If you have any ideas, let me know. I'd like to have it running before spring. Thank you very much in advance.
Pasta1nc@yahoo.com
AnswerHi John,
It's tuff to diagnose the problem from the description.
I suspect the carburetors need more thoroughly cleaned, synchronized, and maybe tuned to restore proper performance.
A fouled plug may cause backfiring. The carbs may be fouling the plugs.
Check cylinder compression to determine the condition of the engine. Follow with a leak-down test if compression reading vary or are out of service limits. If valves or other parts are a problem, you'll find out.
Learn about reading the spark plugs. Visit www.ngk.com and click the Spark Plug 4-1-1 link. Navigate the menu links to learn more. The plugs can indicate carb and igniton problems.
I'll send some tech files to your email. Free email servers such as Hotmail and Yahoo do not receive these large tech files very well.
Respectfully,
Mark Shively
