85 hp compression

[kbh121956]

1987 Force 85hp with 120 psi at WOT on all three. Is this too low to run well? Thanks.

 

[Nordin]

From factory the compression was 140-150 PSI.
120 and pretty equal on all, not more then 10-15% in difference are acceptable.
The value depends on how good compression tester you are using.
But 120 PSI is good enough to run with.

 

[kbh121956]

Thanks, Nordin, I did try another gauge and came up with the same numbers. All three were even.

 

[jerryjerry05]

120 is acceptable as long as it's on all 3.
What kind of tester? How many revs to take the reading?
As many as 10 for the right results.
Harbor Freight gauges give bad results.

 

[kbh121956]

120 is acceptable as long as it's on all 3.
What kind of tester? How many revs to take the reading?
As many as 10 for the right results.
Harbor Freight gauges give bad results.

Thanks Jerry, I used 2 different gauges, and both read the same. About 3 to 5 revs per cylinder.

 

[jerryjerry05]

Does it start?
My twin 1988/85's had 145# when new.
When I sold them almost 30 years later they still had 145#
IF??? it's running?? run it.

You can try adding a bit of oil in the cyl. and if that raises the # then the rings might need replaced???

 

[airshot]

If the cylinders are dry from sitting for a period of time, the compression will be low...

 

[Jiggz]

As Jerry mentioned with 120# across all three, that motor is still good to go and can still run. I would surmise it is not running hence you took the compression. If you can post the steps you took for troubleshooting, then the group can focus on the remaining steps to take.

 

[jerryjerry05]

Setting for some time shouldn't really affect the comp readings.
Get a Snap On or Mac tool comp tester and try again.

 

[racerone]

What is your motor doing / not doing ?