need help with knoking in bottom end

[aritab8]

I have a 95 seadoo GTX. I was out ridin 2 weeks ago and when i went to start it up after taking a rest it would not start only wine.When i got home i tore apart my starter to find the armature broke in two. Replaced the armature and it fired up and ran the next weekend but difficult to start, so i rebuilt the carbs, the filters were a little dirty but that did not help.it turns over and i can get it to runn after a few cranks but there's a knock which sounds like the bottom end,and when i rev the engine up the noise goes away.Just wondering if anyone has had this problem before and do i need to do a complete rebuild of engine.

Thanks aritab8

 

[robin savell lloyd]

Give it a compression test. If the compression is low on one cylinder it may be runing out of ballance. :cheers:

 

[aritab8]

checked compression

I checked compression it fine,this one's got me baffled, any other ideas ?

 

[derek]

are you sure it isn't an exhaust system rattle, or a broken motor mount. these guys don't usually have crankshaft knocks. they just loose rpm's over about 15 seconds from full throttle to siezed.

 

[stoltjr]

Give it a compression test. If the compression is low on one cylinder it may be runing out of ballance. :cheers:

by "running out of balance", I assume you mean one cylinder has higher compression than the other. Why would this cause a knock?

I ask because I checked my compression on Friday and it was 150 PSI in each cylinder. Took it to the lake and rode about an hour, then it slowly started to run worse until it died. Brought it home and noticed no smoke from the exhaust, and could not get oil out of the bleeder screw. It appears to be a clogged filter. Anyway, I rechecked compression, and now I have 120 in the rear cyl and 150 in the front, and a low end knock when running. Do they usually just sieze when you lose oil, or will it sometimes cause a rod knock? Or is it that the cylinders don't have the same compression that is causing this knock? Thanks!

BTW, it never siezed the engine, it would still spin over but not start, however it did change my compression readings. After cooling off it will now start, only it now has a "knock".

 

[robin savell lloyd]

I recieved the out of balance info from Dennis he is very good with these engines. 2 cylinder 2 cycles are new to me but I have repaired over 1000 single cylinder 2 cycle engines. I will give you a guess at what may be happening. With 1 cylinder low on compression it may have enough damage to efect it's ability to bring the fuel up though the port on the intake side and may not have a explosion on that cylinder at low rpm with only 120 psi and the other cylinder is working and the engine is ballanced so that when the engine fires it will absorb the shock. If the engine is balanced and it is only runing on 1 cylinder when it is supose to fire on the one that is not fireing and has been balanced to take the shock then the ballance is doing the opposite of what it is supose to do. This is only a guess and I hope that others will respond to correct me. :cheers: