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Discussion Starter #1
I recently performed a top end motor job to include new rings and pistons. After running the engine for the first time, the number
3 cylinder base gasket blew and water leaked into the cylinder. My question is why did the gasket seal fail?
 

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Possible causes include: the head is warped from whatever caused the problem in the first palce = usually overheating (did you check the head for warp). Old gasket - did you use a new gasket and use the correct sealant? Engine overheating - may be what caused problem in first place? Improperly installed head - were the bolts tightend in the proper pattern and torqued to spec? Did you check the compression before running the engine to see if you were within spec?
 

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Discussion Starter #3
I appreciate your reply. The original problem was water in the number 3 cylinder which maybe was caused by a faulty exhaust gasket at the catalytic converter. The head was checked when we tore down the engine. The gasket that I was refering to is between the crank case and the cylinder which I mentioned in my original post. Have a good day and thanks for your time.
 

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Sorry, I didn't fully read your first post. For the base gasket, my best guess would be that you somehow pinched the gasket on one side. Did you use a torque wrench and pattern the bolt tightening? Some of these gaskets have to have the exact right torque. Bolts too loose is obvious, but many times they will leak if they are too tight on one corner. Was this a new cylinder?

Another thought is that the gasket may have been installed backwards.
 

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Thanks for your reply. I agree with your statement about the cylinder base gasket. I believe the gasket must have been punched and the cylinders were not torqued properly. I appreciate your help in this matter. This is the first 2-stroke Waverunner I have ever owned and have learned much about it since I bought it. I had the base gaskets replaced with Yamaha brand factory gaskets.
 
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