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Discussion Starter #1
First I'd like to introduce myself. Names Dan I'm in Sk Canada. I'm not really a sport bike guy but I love working on bikes, any bike in need really. This one came to me from a guy who loves to ride them but not work on them.
Now the issue. Bike started then died, no restart but doccasionally a little backfire. Compression test starting on the right side 60 60 30 0. I'm thinking a broken timing chain. I haven't pulled anything yet and before I do I'd like some insight from guys wgo have been there. Am I looking at bent valve's maybe cracked pistons for sure? I just did a Yamaha xj750 that had done samething. It'd 4 valves and a piston ruined.
Thx in advance guys. I look forward to playing with this engine either way.
 

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Honestly, the only real way to know, is going to be to just dive in and look. It sounds like it could very well be anything. Could be bad coils, could be an ignition failure, could be plugs, or timing jumped, maybe a bad head gasket. Like I said, without having it in my shop, it could be anyfreakinthing.
 

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Discussion Starter #3
Yeah I sorta figured but thought maybe there was a problem that would be common to these. Had a few min today so pulled the valve cover, and rad, rad hoses and coils. Timing chain on and tight. Cams still in time and ignition timing is good as well as spark from coils. With the bad compression across the whole head and non on one hole I'm still leaning toward bent valves. Tomorrow should tell th tale. Head comes off.
 

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STOP! before you pull the head, do a leakdown test and it'll tell you where that air is going. don't do unnecessary extra work when it may be a simple problem.
 

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That’s Mister Chalet To You ....
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Welcome to the forum. You should post an intro in 'the starting line' per forum guidelines and tell us about yourself, riding experience, bikes you've owned etc.....

And post PICS of that 400 of yours. We don't see those every day.
 

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+1 on a leak down test before you go further. It might give you a better idea of what's wrong and save a some cash in replacement gasket kits
 

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Discussion Starter #7
Problems solved. A good night sleep will do that. It occurred to me I should do wet compression test. Seems he'd washed the cylinder walls. Squirter of oil in all cylinders compression shot up.
Reassembled and it runs like a top.
Thx and I will take care of intro in the appropriate place.
 
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