9.8 Compression Question

[Dchapp123]

Hello New on the site,

I just purchased a NSF 9.8 A3 Nissan 4 Stroke Motor. Everything seems to be fine but wanted to check compression during serviceing. 60psi on both cylinders. I have looked online and cannot find anywhere if this is acceptable. Is there compression relief to assist in pull start to cause lower number . Thanks for any input.

 

[ahicks]

Was the throttle held wide open for your compression checks? If not, that can/will certainly affect your readings.

60psi is considered not so good, with a good chance something is seriously wrong.

 

[Dchapp123]

Yes throttle was wide open. Runs great on water took it out 6 times already. I'll try different gauge tomorrow.

 

[Dchapp123]

What psi should I be looking for?

 

[pvanv]

The decompressor is engaged during cranking by hand. Above 500 RPM, the compression should be 128 psi.

 

[Dchapp123]

Ok first gauge was not good. Talked with manufacturer this morning. The 2012 8 and 9.8 does not have decompressor. So I borrowed a friend's compression tester that is used on a weekly basis and I have 135psi on both cylinders. The manufacturer told ideal is 128psi and being a used motor anything around 100psi is acceptable. Thanks for the Response guys.