engine compression

[jason turner]

hey there. i have a kawasaki 900 stx that im selling(im a seadoo guy) compression is 90 90 80 in the three respective cylinders and it runs good.just wondering if anyone could tell me if those numbers were good or bad and if bad why.im sorry if i offended anyone by asking a kawasaki quetion lol, but you guys have been helpfull with my seadoo problems so i figured id give it a go,thx

 

[johnson2_r]

souds like the 3rd cylinder is loosing compresion all 3 cylinders are suposto be around the same compresion prity shure within 5 psi not to shure about the 10 psi difference maybe someone with some more experience then me will comment.

 

[khriss]

That would be low on all 3 cyl, BUT I am guessing that you used a 'push' in type of compression tool, or used a gauge with a long hose on it (10" or more?) or a combination of the two. 10 PSI difference is a little more than I would want to see, but if you used a push in type it might be user error?
The push in type or long extension hose drastically reduce PSI readings because they increase the combustion chamber volume, reducing the compression ratio. On a 454 Chevy, no big deal, but on these tiny cylinders, it matters a lot.

Khris

 

[jason turner]

thanks ive heard different things about them being 5% or 10% of each other if 10% is ok its pretty close. i think it might be the headgasket

 

[jason turner]

it was a screw in type that a bought today, but it did have a long hose(id say about a foot or so) but i tested my 95 xp limited and it said 130 130 so i thought it was reading fairly accurate

 

[seadoo GTS 1993]

90 90 80 is low, 150 is ideal, down to like 115 is fine... as long as its within 10% of eachother

 

[seadoo GTS 1993]

Unlesss, its different with different engines? I doubt it tho

 

[seadoo GTS 1993]

Kawasaki 2 strokes run 109 psi when brand new and with a non-professional compression gauge, 90psi is fine.

Learned sumthin new today, good info