1987 Yamaha 25

[Brock6135]

Just curios on what the compression should be on my 25? Both cylinders r reading bout 110 give r take a few

[boscoe99]

The only value I have seen from Yamaha for a two stroke is 81 psi, but this is just a reference value. You are well above that.

As important as actual compression is all of the cylinders being reasonably in agreement with one another.

If the motor starts and runs well I suspect that your motor has adequate compression.

[Brock6135]

Thank u it runs fine and isles fine I just had a few local people tell me it should be up around 130 seemed kinda high to me and u can't find it on the net anywhere so thought I would ask

[99yam40]

Most good running small 2 strokes I have measured compression on were 110 to 115 .
But the compression gauge you use can be off, I believe that is the reason they do not list it much

[rodbolt17]

over the years I have seen normal pressures as low as 80 psi and as high as 185 PSI.
just depends on who made it and when.

general rule,3cyl Yamaha excepted,is no more than 10 PSI difference.

[Brock6135]

Thank for the help