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  1. #1

    Compression checking a fresh rebuild..any need to put oil in the cyl first ?

    Just about to compression check my fresh rebuild and I don't want to damage anything....should I squirt a little oil in each cylinder ? I have not run it yet so there has been no lubrication in the cylinders except for the oil I used to install the new pistons and rings etc.

    Any thing else I need to do before the compression check and starting of a fresh engine that you guys think of please let me know.


  2. #2
    A small amount of oil can't hurt anything but an initial compression check is really just a reference point at best. Your rings won't seal very well even with the oil as the surface of the walls and the rings themselves are purposely kinda rough to necessitate a break in process. Don't be discouraged if you see low numbers across the cyls and even an uneven balance as there could be minor differences in the initial fit between them.

    If you are not pre mix, put some 75:1 mixture of oil and gas for an injected two stroke. If you are pre mix consider even a 30:1 initial tank. A lot of smoke but you want those bearings to get happy as soon as possible. If you are talking four stroke, Ideally, it is a good idea to rotate the engine manually enough to prime and even pump oil throughout the engine prior to hitting the starter. This is tough on a watercraft but if the engine is not installed you should be able to rotate the pto a few times with the plugs out to get the party started in terms of lube.

    Best of luck with the maiden voyage.

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