Carb 787 with 45 psi compression difference?

[seadoodoopartsofcf]

Mag side compression is 185 PSI PTO side is 140 PSI. I double checked with different compression gauge and made sure there wasn't anything getting in the cylinders to increase the readings..anyone run into this and how did the engine run? Thanks, Jim

 

[mikidymac]

You have something wrong and should not run it. There should never be a 45 psi difference between cylinders and perfect for a 951 is 130 psi, a 951 DI, is 135-140 and 787's and smaller should be 150 psi.

 

[seadoodoopartsofcf]

Thanks Mikidymac, Any idea why the compression on the on cylinder is so high? I've compression tested many 2 stroke pwc engines and have never seen readings this high. Guess I'll pop the head off and take a looksie.

 

[mikidymac]

Only thing could be oil, fuel or water unless there’s something mechanical wrong.

You are holding the throttle wide open before and during cranking to disable the fuel pump correct?

 

[seadoodoopartsofcf]

It was tested on my workbench with nothing hooked up and the carbs off.

 

[mikidymac]

Oh, this is a carbed 787? Sorry, it’s even in the title, LOL!

No, then no good reason for one to be so high. Pull the head.