95 sl 750

[gorehead]

I bought ski from freind who had top end rebuilt at a polaris dealer after it had burned a hole in the p.t.o. piston.He ran the sle for one half hour and burned the piston again. I bought it after he had give up I replace piston and cleaned rebuilt carb on just that cylinder I also replaced the fuel pump with a mikuni 3 outlet and ran seperate fuel lines to each carb.I also burned a hole in piston after 15 minutes ski performed just like new then quit.Im afraid to do anything without some suggestions apparently polaris cant repair maybe its time for a new crank or rebuilt engine but would like to know whats causing it before spending all this money

[polaridoo]

Assumming all your carb/fuel issues are solved, how is the crank? Out of phase? How do the spark plugs look?

[gorehead]

All The plugs look fine it only run for15 minutes ran real good the crank i beleve is in phase but it has never been touched freind had complete top end rebuild by polaris before i got seems they would have checked that who knows it just makes no sense seems if the seals were leaking between the cylinders it would burn more then just the pto cyl.From reading some of these threads this isa common problem.

[polaridoo]

Since it appears you have looked at the obvious, I would consider doing a pressure test and check the crank. You would need a serious air leak to cause that cylinder to sieze. Are you getting oil to the cylinders?

[polarisguru]

You only need a very small air leak to cause to piston failure. If the crankshaft is out of index on the PTO cylinder,then every time it rotates 360* it will open up the pto crankseal and draw air. This is why a pressure test does not always work, as most mechanics, do not spin the engine under pressure. If you look at the piston you can also help diagnose wether it is ignition related from detonation, a fuel issue, or oiling issue. Are you premixing your fuel? If so did you richen the engine from the stock specs? Have you checked your ignition timing? Everyone seems to want to just throw a piston in an engine and consider it fixed, without finding out what the real cause of the failure was. Failures are caused a high % of the time from no maintance or improper maintance issues or repair diagnoses. It is most likely not a quality of part or manufacture issue. It is not POLARIS'S fault but maybe the mechanic's or your friend not wanting to spend the $ to make it right and just took a chance on a top end rebuild without fixing the real problem. :D
We see this all the time in the engines that we redo. It is a hard sell sometimes to convince people to do the job right and find the problem first !!!!!

[ September 23, 2003, 12:31 AM: Message edited by: polarisguru ]

[SpikeT]

Re: 95 sl 750

First off Greetings to all.... In reference to "Just throwing a piston in"

Is it possible to just throw a Piston in a '91 SL750 that has a hole the size of a #2 pencil eraser in the #1 cylinder. Knowing that the cylinder leaned out due to a fuel problem? If I Know for sure that this was the cause couldn't I just put a piston kit in it? Another thread on this topic states that the motor is fowled from debris from the piston failure and that a complete rebuild or replacement is in order. I'm willing to rebuild it but can't afford a "crate" motor.

Pardon my stupidity but what does PTO mean?

[Riixxii]

Re: 95 sl 750

PartThingOUT, lol It means power take off dude,like on a tractor duh

[SpikeT]

Re: 95 sl 750

:emoticonl I guess I'm a newbie..... Riixxii set me streight on that.

But what about the other questions?

[Greg2560]

Re: 95 sl 750

i had the same problem on my 95 750. I bought it with a hole in the pto piston. Thought no big deal clean the carbs and but a new piston in. WORNG!!! about 30 min or so here we go 2 cyl 750 not much power. Come to find out after i pulled the motor got it all apart. I was the crank..Put new crank in and it runs like a top now. It does not take much on the crank to slip and mess up the timeing..
hope this helps greg

oh the crank got messed up when the old owner put it in the water with the plug out. And then after getting the water out of the hull trys to start it with the plugs still in the motor...

[SpikeT]

Re: 95 sl 750

Never had a water log issue. But it always had some kind of fuel delivery problem. The boat has never been driven hard, jumped or abused in any way. I can almost ensure that it burned the #1 due to a fuel starvation issue.

Please keep the input comming!!! and mucho thanksamundo!!

SpikeT

[Riixxii]

Re: 95 sl 750

On my '94sl750 i hooked up dual fuel pumps,installed wiseco piston kit,richened pto cyl. another 1/8 turn,rode it for a summer and sold it to a friend of a friend who is still riding every weekend. that was 2001.

[SpikeT]

Re: 95 sl 750

Rixxii,

Did your SL750 ever suffer from a hole in the PTO piston? And another question you can rib me on... Is the PTO the most forward piston? the one i refere to as the #1?

[Riixxii]

Re: 95 sl 750

No more ribbin' man,the only dumb question is the one you should ask but don't. The MAG(magneto,where you develop your ignition) Middle,well duh, and PTO(where your power takes off out of the engine to the driveline) When I picked it up it had the classic aluminum spark plug, 0 compression and a hole in the piston (PTO) side.