Doing a compression test on Johnson GT150, have a few questions

[Steve88]

I am giong to be doing a compression test on a Johnson GT150 and I have a few questions. The motor will be cold and I read where using a misting oil will help give more accurate readings on a cold engine. What type of oil should I use? Hot battery, all spark plugs removed, misting oil, anything else I should know? Thanks

 

[Timmstng67]

Re: Doing a compression test on Johnson GT150, have a few questions

Hi

Not sure on what type of oil to use, but you will also need to unhook fuel line and hold the carburetors at wide open throttle to get a proper reading.

Tim

 

[JB]

Re: Doing a compression test on Johnson GT150, have a few questions

Misting oil is not necessary, Steve. It might even mask a problem.

Remember that the objective is too see if one or more cylinders are failing to match the rest. As long as the psi are above 90-100psi, they are irrelevant. What matters is the ability of all cylinders to pull the same weight, ie: compress the same psi, within 10-15%.

Plugs out, ignition disabled, hot battery, 5 or more turns per cylinder.

That should do it.