polaris slt780

[roy meinzer]

I have a polaris slt780 that was running fine in very weedy conditions and shortly after this after running fine it quit and would not turn over. After letting it sit for about an hour it would start OK, then after about 2 minutes would quit and not crank again. This problem happens every time now, it stops running and will not crank immediately, till cool down. I am thinking cooling, as if it was oil starved it would have blown up. I have rebuilt carbs on these and replaced starters but don't know where to start with cooling problems, any help would be appreciated, Roy

 

[BlueFishCrisis]

Re: polaris slt780

If the motor was overheating, you should be getting a warning light on your MFD and RPMs will be limited to 4000 or so. Check the cooling inlet screen for any blockage. It is located on the Starboard side of the interior of the jet pump.

Sounds fuel related. Do you get any pressure release when you open the gas cap? It is possible that your check valves for letting air into the tank are clogged, causing a negative pressure build up in the tank and starving the motor of fuel. Is your shut off valve in good working order? If it is clogged, fuel will not be able to get to the motor. Check to see that your fuel water separator is filling and stays filled (under the front hood storage bin).

Could also be electrical - If the fuel checks above don't help, it is possible that the electrical stator is failing when it heats up......

 

[roy meinzer]

Re: polaris slt780

Thanks for the reply. I question the fuel related issue, would this cause the engine not turn over after it shuts down?? Nothing by the jet pump inlet, and never showed any overheat warning, not sure it has an indicator on the instrument panel?.

 

[Froeman]

Re: polaris slt780

Agree with bluefish about the heating warning. But if you are worried about overheating, have you run the machine out of the water on a garden hose to flush out the cooling system?

 

[roy meinzer]

Re: polaris slt780

I have not, however have read many posts about the dangers of doing this improperly, I think doing this should answer my questions weather it is a cooling or fuel problem??? Any advice on proper flushing hose hook up running?

 

[BlueFishCrisis]

Re: polaris slt780

Connect hose, start motor, turn water on no more than 1/2 or so, turn water off, stop motor. The cooling is an open system. If you start the hose before the motor, you can fill up the cooling system and backfeed into the motor itself.

If you connect the hose at the water rail, you will back flush the motor and potentially clean out any debris that might be in there, but the motor will not appear to cool "evenly" the source will be at the PTO, and therefore will run much cooler than the CEN and MAG. If you connect at the water pickup hose by the pump tunnel, You will cool more evenly, but will loose the "back flush" feature...

 

[BlueFishCrisis]

Re: polaris slt780

Thanks for the reply. I question the fuel related issue, would this cause the engine not turn over after it shuts down??

Please define "turn over". Are you referring to the starter spinning the motor, or the ignition and starting of the engine in normal operation.

If it means ignition, than yes, a vacuum locked fuel system will not allow fuel to flow to the carbs. After time, minutes possibly, the system will loose its vacuum and will start back up, until you use enough fuel to reintroduce the vacuum condition.

If it means spinning the motor with the starter, then no. This is an electrical issue likely caused by a loose connection, a dying starter, or a faulty starter solenoid for example....

 

[roy meinzer]

Re: polaris slt780

It does not or will not crank at all, like it is seized up, with plugs in or out, it doesn't crank

 

[shagy959]

Re: polaris slt780

was running fine in very weedy conditions and shortly after this after running fine it quit and would not turn over
if you was running in weeds i would check the impeller shaft area see whats up there

 

[BlueFishCrisis]

Re: polaris slt780

Lots of things to check...

Does it click when you push the start button? If not, the solenoid may be bad, battery dead, or you may have fried a stator wire.
Do you hear the starter spin? If the starter spins and the motor will not turn over, the bendix has likely failed.
Can you manually turn the motor by spinning the drive coupler shroud or removing it to expose the drive coupler? If not, then the jet pump or motor may be seized. Remove the jet pump and try to spin the motor manually again. If the motor won't spin, time to tear into the top end and see what happened.

 

[roy meinzer]

Re: polaris slt780

It will start fine initially, will crank over all day long till it starts, but after running for 5 or so minutes it seizes up, then will start again without a problem after a while

 

[shagy959]

Re: polaris slt780

what is the compression on each hole i would take a guess may have one bad cylinder will start up cold but when heats up will lock up check each hole 125 is the normal each hole

 

[roy meinzer]

Re: polaris slt780

OK, I will check and get back, thanks

 

[BlueFishCrisis]

Re: polaris slt780

The Fuji 780s should be reading around 140 psi.

 

[roy meinzer]

Re: polaris slt780

Compression test was good, 130+ in all cyl

 

[BlueFishCrisis]

Re: polaris slt780

Did you try back flushing the motor from the water rail? Have you checked individual cylinder temperatures when it "quits" to see if one is quite a bit hotter than the others? Since the temp sensor is on the water rail, it is possible that only 1 of the cylinders is getting quite a bit hotter than the others, causing it to expand and seize. This can also happen when the cylinder runs extremely lean, which is why I mentioned fuel issues. What does your piston wash look like? Have you performed any plug chops at full throttle to look at how the cylinders are running? Ride at WOT then pull the lanyard to kill the motor (this must be done in the water). Take the plugs out with a plug wrench, and look at the insulators. White / light gray is Lean, chocolate brown is good, dark brown / black & sooty is rich.....

 

[roy meinzer]

Re: polaris slt780

I have not tried the flush, I have read different versions that say if not done correctly can cause germ, if you have correct procedure(detailed)I want to try this. I have not taken the head covers off yet to check out pistons or cyl walls

 

[Noltz]

Re: polaris slt780

When it quits, does it stop dead no warning? Or does is bog down and die out?

I'm trying to determine if this is a mechanical seize-up for some reason, or if there's an electrical failure (or lockout from overheating?) that's causing to not turn over.

 

[BlueFishCrisis]

Re: polaris slt780

When it quits, does it stop dead no warning? Or does is bog down and die out?

I'm trying to determine if this is a mechanical seize-up for some reason, or if there's an electrical failure (or lockout from overheating?) that's causing to not turn over.

It is not any type of safeguard/lockout, as these skis do not contain such a feature.

 

[BlueFishCrisis]

Re: polaris slt780

I have not tried the flush, I have read different versions that say if not done correctly can cause germ, if you have correct procedure(detailed)I want to try this. I have not taken the head covers off yet to check out pistons or cyl walls

You will need a flush kit or hose attachment that you can find on ebay. Other than that, the only real procedure is to start the motor, then turn on the water and flush, shut the water off, then stop the motor. If you start the water first, you may fill up the system, flood the engine, and cause issues.