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Discussion Starter · #1 ·
Have a 660 that is all stock won't start. Carbs are clean checked valves stator spark etc. A little oil in cylinder it will fire right up until oil is gone.Did a leak down test. Engine leaks down 8% or so. Did a compression test reads around 110-115psi. I would think with it that low on compression from the spec of 180psi the motor would leak down more than 8%.

Anyone done a cranking compression test on a stock 660 motor?

Thanks Robert
 

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Discussion Starter · #3 ·
Stock motor with decompression working you would see about 130lbs
I would think that if this is correct that at 115psi it would run. It also makes no sense that at only 8% leakdown it would be real low on comp. But the old oil in the cylinder trick works until its out of oil. This thing is pissing me off!!!:eek:
 

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starting the motor with oil would imply the rings are bad but 8% isn't a bad leak down, sure 3-5% is better but this isn't a fresh engine. Could you hear the leak coming from the exhaust or intake manifolds? or did it sound like it was passing into the crankcase past the rings?
 

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Is the flywheel key sheared? Anyone had the top end apart? Cam chain stretched and cam jumped out of time?
 

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Discussion Starter · #6 ·
starting the motor with oil would imply the rings are bad but 8% isn't a bad leak down, sure 3-5% is better but this isn't a fresh engine. Could you hear the leak coming from the exhaust or intake manifolds? or did it sound like it was passing into the crankcase past the rings?
With only 8% you couldnt really hear where it was going. I would agree that the rings worn sound like the problem. I would just think there would be more leak down.:unsure:
 

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Discussion Starter · #7 ·
starting the motor with oil would imply the rings are bad but 8% isn't a bad leak down, sure 3-5% is better but this isn't a fresh engine. Could you hear the leak coming from the exhaust or intake manifolds? or did it sound like it was passing into the crankcase past the rings?
Is the flywheel key sheared? Anyone had the top end apart? Cam chain stretched and cam jumped out of time?
No had flywheel off to check that. Also checked timing and adjusted valves all is good. I really want to condem the rings but with so little leakdown I dont want to get it apart and find nothing.
 

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No had flywheel off to check that. Also checked timing and adjusted valves all is good. I really want to condem the rings but with so little leakdown I dont want to get it apart and find nothing.
So basically you have fuel, spark, decent compression but no start, clue me in here.................
What happened, did the bike all of a sudden not start, did you just rebuild it...............:)
 

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Discussion Starter · #9 ·
So basically you have fuel, spark, decent compression but no start, clue me in here.................
What happened, did the bike all of a sudden not start, did you just rebuild it...............:)
It was a yard feature before it came to the shop. The story is it wasnt running very well. So he took it to another shop. They took the aftermarket exhaust off it and installed the stock muffler. Then told him the carbs needed jetted cleaned and valves adjusted. He got it back after that and it wouldnt even start. I got it, adjusted the valves. They were out a little. Not tight so it should have ran. Cleaned carbs jetted to stock. Found spark was weak. He had the stock stator for it from before hi output was installed. Tested factory stator it tested fine. Installed factory stator. Still weak spark. Installed coil from my personal 700. Weak spark still. Removed Cdi installed Cdi from a friends bike has Great spark still won't start. Old cdi was a advantage cdi "procom". Bought a cdi from board member for future. Checked compression 110-115psi. Book says 180psi compression at sea level unsure how they get this with a decompression? Leaked motor down only looses 8% shouldnt be enough to cause low compression so at this point its pull it apart and hope to find something. The oil in the cylinder tells me its rings. I have wasted enough time on this thing and don't want to keep going in circles.


Sorry for the book!!!:banghead:
 

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It was a yard feature before it came to the shop. The story is it wasn't running very well. So he took it to another shop. They took the aftermarket exhaust off it and installed the stock muffler. Then told him the carbs needed jetted cleaned and valves adjusted. He got it back after that and it wouldn't even start. I got it, adjusted the valves. They were out a little. Not tight so it should have ran. Cleaned carbs jetted to stock. Found spark was weak. He had the stock stator for it from before hi output was installed. Tested factory stator it tested fine. Installed factory stator. Still weak spark. Installed coil from my personal 700. Weak spark still. Removed Cydia installed Cd from a friends bike has Great spark still won't start. Old cdi was a advantage cdi "procom". Bought a cdi from board member for future. Checked compression 110-115psi. Book says 180psi compression at sea level unsure how they get this with a decompression? Leaked motor down only looses 8% shouldn't be enough to cause low compression so at this point its pull it apart and hope to find something. The oil in the cylinder tells me its rings. I have wasted enough time on this thing and don't want to keep going in circles.


Sorry for the book!!!:banghead:
Read this thread and tell me if there are any similarities..............
http://www.raptorforum.com/forums/showthread.php?t=39381
 

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Discussion Starter · #11 ·
Never pops through the exhaust and doesnt stop starter but ? The only problem with this theory is that its had 2 diffrent stators both with same result. Not saying it couldnt be this but wow. Wish I had a running stock 660 to check cranking compression on!!!

All the thoughts and help is very much appreciated!
 
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