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Tom_Krause

probable timing problem...need help

2 posts in this topic

At Millville this weekend my YZF400 was running poor for first 2 laps of practice then after starting to rev high with the throttle off, I hit the kill switch. When trying to restart, I hit TDC, pulled the compression release to get past TDC a bit and then tried to kick it throuhg and it would only kick through 2 or 3 inches until the kickstarted wouldn't budge without again pulling the comp-release. No matter what I try, I can't get it to kick through. When I pull in the c-release the whole time, it kicks through easily over and over but as soon as I release the comp-release and try the normal starting procedure, it binds up. I don't try to kick it hard in fear of breaking/bending something. Any pointers or predictions. Thanks for any advice.

By the way, I adjusted the valve clearance last week and swear I had the clearance in spec and the timing correct but I'll check tonight.

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When you adjusted the valves, did you have to changes any shims? Is there a chance you could have swapped cams during the reinstallation? I mean, could the intake now be the exhaust cam and vice versa? I can only think of about two possibilites from your description. Either compression is preventing the engine from being kicked through, or the cams are in some sort of a bind and since they are connected via the chain to the crank, the engine won't sping normally. The second scenario doesn't seem correct because you can spin the engine easily by holding the compression release open. So, that leaves compression resistance. It seems probable that there is some sort of problem with valve timing or clearance. If you start from scratch as if you were going to check the valve lash again, you might discover the problem. While you are at it, you might consider checking the cam gears to make sure one hasn't started slipping. I'd like to know what you find.

Just thought of something to try. Remove the timing plug and see if you are actually getting to TDC with compression. What I'm getting at is that as you are using the kickstarter to find TDC of the compression stroke, you might have a timing problem that makes you think that you have reached TDC when you might not have. If you take the valve cover back off, you watch the cam postions as you crank the engine over slowly. This would give you a chance to observe if the cam gear(s) are slipping or not. Hope this helps.

[This message has been edited by Boit (edited 08-20-2001).]

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