1997 Polaris 900 SL damaging pistons

[natecollins1]

I am working on a 1997 Polaris 900 SL. When the PWC arrived to me it had 0 compression in the #1 cylinder. #2 and #3 had about 130 psi. The piston in #1 had a hole in it, that was pitted away. The pistons in #2 and #3 looked fine w/ no pitting. I installed a new piston kit. I went through the carbs/fuel pumps to see if there was a problem. The fuel pumps seem to be working fine. I do not notice any issues w/ the carbs. I tested the PWC on the lake. I adjusted the low fuel mixture settings all the way out since the PWC was idling rough, and I could get the idle speed to increase by choking the engine. The engine temperature also seemed fine when running it on the lake. I tried to check the timing, but on this particular PWC it is impossible to check due to the fact that the handle bar unit and dash is directly over the hole in the magneto compartment. I was able to use a flashlight and mirror to see a couple of marks on the flywheel while turning the shaft at the other end of the motor. I see a mark when the #1 piston reaches TDC, so I believe that it is set up all right. I would assume that the timing is right since there was no pitting on the #2 or #3 pistons. I tested the trigger and it was in spec.

The customer brought the jet ski back to me the following day saying that it was not running right and was cutting out. I took a look at it today. I had good spark on all cylinders, but no compression in the #2 cylinder. I looked at the top of the piston and it is pitted. I do not see a hole, but the compression indicates that there is a problem. The spark plugs on all 3 cylinders look wet, if not slightly fouled.

Can any one help solve this problem. I plan to put a new piston in the #1 cylinder but want to correct any possible issues before it happens again.

 

[natecollins1]

Re: 1997 Polaris 900 SL damaging pistons

I also checked the oil lines. All 3 are connected. I also turned over the engine when performing the initial work to see if oil was pushing out of all lines.

 

[Jeff Walkowiak]

Re: 1997 Polaris 900 SL damaging pistons

polaris has a history of burning pistons from lean run condition caused by insufficient fuel supply the remedy was to add a second fuel pump,, if it has a second pump already ,, there may be a fuel supply issue with the selector switch or loose fuel lines sucking air