Super Jet Pitting in rear cylinder

[mike b]

Buddy was riding his all stock sqare and when he stopped he said he thought something was wrong because when he went back to start it the ski sounded like battery was dying. When opened the hood and tightened battery i grabbed the coupler for some reason and was able to turn the motor over by hand. So i knew there was no compression, and when he went to start it just turned over and sounded like there were no spark plugs. Two days after the lake, brought the ski back to my place and there was alot of pitting on the piston and the head. I felt the cylinder walls and all felt smooth except a very little grove in the rear cylinder. Does that need to be bored/honed before putting motor back together. Looking like he needs and new piston and rings for the rear. Anything else? Take apart case and check main bearings and such? What could have caused this? will post up pics soon..

 

[Scraggly]

i would tear down and look for a bearing failure

 

[550headache]

Maybe lose a c clip. Tear it down and find the cause

 

[mike b]

 

[mike b]

The pitting and damage is only in the rear cylinder. The front piston and cylinder looks to have no pitting, scoring, or markings on the wall. Looks to have normal carbon too?

Now would this cause the engine to not run. My friend and i were riding for an hour that day. went to take a break, then it wouldn't fire back up... WHY?

 

[Scraggly]

The pitting and damage is only in the rear cylinder. The front piston and cylinder looks to have no pitting, scoring, or markings on the wall. Looks to have normal carbon too?

Now would this cause the engine to not run. My friend and i were riding for an hour that day. went to take a break, then it wouldn't fire back up... WHY?

thats no deto, theres some metal in there somewhere. wrist pin bearing, crank bearing........ take it all down and find it. may even need some cases depending how bad the lower damage is.

 

[mike b]

yeah dissembling as we speak. Why would this cause the ski not to run. I didn't have a tester but seemed to have good compression when i turned the motor over

 

[Scraggly]

might have been a reed. i broke one once and it ran only at wide open wouldnt idle. or could have been the jet ski gods trying to save you more damage

 

[jri93]

yea x2 on the reed. my motor was running weird and wouldent fire back up after i turned it off. pulled the motor apart and i too had pitting on the rear cylinder only. not nearly as bad as that though, any way i ended up having badly broken reeds. Not sure about the lack of compression though, that is weird. that damage seemes more like it was caused by metal. check the reed cages and make sure non of the little screws fell out lol.

 

[mike b]

yea x2 on the reed. my motor was running weird and wouldent fire back up after i turned it off. pulled the motor apart and i too had pitting on the rear cylinder only. not nearly as bad as that though, any way i ended up having badly broken reeds. Not sure about the lack of compression though, that is weird. that damage seemes more like it was caused by metal. check the reed cages and make sure non of the little screws fell out lol.

Thats funny you talk about metal pieces. I found a broken piece of metal and a washer in the reeds but none of the reeds look messed up in the cage. Finally broke the cases and looking at motor. Will link a video up later for some help from you guys cuz idk what im looking for. It all looks good to me in the case. The cylinder has a mark the either will need to be honed or small bore. Piston looks like it caught the ring or something.

 

[Scraggly]

Damn man did one of your flame arrestors bolts or something get down the carb? I would be super curious where those came from. And if you haven't split the cases yet make sure and remove the flywheel and stator before you do. Check the rods for any up and down movement an pull the pistons and check wrist pin bearings and cages. To me just from the pics looks like a needle bearing from either the wrist pin or crank rod bearing, but its hard to say for sure in pics especially if you are finding random washers in the case.

 

[mike b]

Well washer was in reed cage but never went into motor so i doubt that had anything to do with it (although it could have if it went into the cage). pistons seemed in good shape, minus the bad one. Its really weird. Everything seems to be fine except that cylinder and piston. Maybe it just caught an edge and thats it?