The same problem has now happened the last two times my son has ridden his 2006 2-stroke Sportsman 90 and before I start taking things apart I'm hoping someone may be able to give me some insight.


The quad runs perfectly for 15 minutes or so and then all of a sudden a rattling sound will begin and the motor dies. The sound seems to be coming from the flywheel area and is related to engine rpms. The motor will restart with no problem but when you rev it up it dies again. Same thing happens both in neutral and in gear. If I let it sit overnight it runs fine again the next day for 15 minutes or so and then the problem happens again.


When it dies it acts as if the ignition switch was shut off so it seems like it's losing spark. This plus the fact that the rattling sound seems to be coming from the flywheel area indicates an ignition system problem, but maybe someone has experienced the same problem and can point me to exactly what might be going on.

 

Polaris has had their problems with the stator.
Hopefully OPT will chime in.

 

I installed a new stator a couple of years ago when I bought the quad. It does sound like something came loose and is rattling around in there. Strange though that it's only happening when it's hot.

 

When it dies have a spare plug handy that you can slip in the plug cap and check for spark. If it still has spark,then I'd check compression.Should have a minimum of 115 psi according to the specs. The rattling sound could be that old piston slap that all two strokes have when the piston to cylinder clearance is excessive.Marbles in a tin can is what I used to describe this sound.Plus low compression could be the reason it runs for awhile then dies. Once a cylinder heats up,rings can loose their seal against cylinder walls,compression will drop. Once they cool down a little they can run for awhile and do the same thing again. If when you check for spark when it dies,there is no spark,then that's another common problem on these models.The open cover to allow the small fan on the flywheel to cool the stator allows dirt ,water and mud to enter and stators can short out. You might get lucky and pull the stator cover and clean the flywheel and pick up coil face and see if that solves it. If not,stators are cheap on ebay.Stator Fits Polaris ATV Sportsman 90 2001 2002 2003 2004 2005 2006 Magneto | eBay Same for top end kits if compression falls below 115 psi.Polaris Sportsman 90 Cylinder Piston Gasket Top End Kit 2001 2006 | eBay

 

After it dies, it will restart immediately without any trouble so it has spark at low RPMs. It only dies when you rev it up. I'll confirm compression, but I rebuilt the top end a couple of years ago too (along with replacing the stator), just after I bought it. I did a lot of work on it then and it's run great until now. I'm going to take the flywheel off tonight and poke around in there.

 

If you can't find anything that stands out you can do several tests. Resistance test on the stator is one way. Black to White/Red 450 ohms, Black to Black/Red 800 ohms,Blacl to Yellow/Red 0.5 ohms,Black to White 0.6 ohms. Black wire to ground should show 0.
You can also check voltage from the pick up coil wiring.Black/Red to Red should show 34 dcv when cranking engine over. Next make sure all wiring is hooked up,pull the cdi wire leading to the coil. Cranking engine over it should show 130 dcv with a peak out put tester OR 20 dcv with a digital voltmeter. Plus general resistance tests on the ignition coil. Coil tab to to ground 0.2-0.3 ohms. Plug cap to coil tab 8.0-9.3 With plug cap removed,the bare coil wire to coil tab should read 3.0-4.0 ohms.

 

OPT, what does it mean if you get all the correct values on the stator and when you go black to ground and you get a 0.90 instead of a 0? Battery charges fine but I was checking mine the other day and noticed this. Do I have a bad ground or a short some place?

 

Could be just your meter. Touch both leads together and see what it reads.Some may not zero out,but will fluctuate a little back and forth. Black is ground on the youth models and this test of black to ground is to just see if the black wire is intact and zeros out ok to ground,same as touching the leads together. Wouldn't worry about it if it runs ok,charges ok,etc.

 

Hi Bradley. Wondering if you ever figured out what was going on with your Polaris 90 as mine is doing the exact same thing. I hear a rattling noise on the flywheel side of the engine, it dies then will restart almost immediately. Sometimes it will make the noise and sometimes it goes away. Just pulled the flywheel off and I don't see anything obvious other than it's filthy. Going to test the stator, but I don't see why a bad stator would make noise.

Anyway, if you get this please let m know. Thanks!

 

Hi all. Not sure if anyone is reading this, but I pulled the stator off with the gasket and found a bunch of oil sludge around the oil pump gears. I think that's the noise I'm hearing. Why that kills the engine I'm not sure, but I'm going to clean it out and make sure the oil pump is working. The PO had the cable adjusted way out where it was giving it oil all the time so that's probably the reason for the sludge. I also think the stator is bad as the battery keeps draining so I'm going to test that as well.

I will keep posting what I find in case this helps someone in the future.