Diagnose my dead sled

[Craig_S]

1995 Polaris Trail DLX, 488

First time out and it took me about 4 miles. There it died immediatly at about 30 MPH - no sputter. Was able to get it started after choking hard. Went about a mile heading towards home, and it died again. Checked plugs - dry as a bone and pretty black. It was harder to turn over this time, but didn't seem hot at all. Had another episode before getting it home. Now it seems tight, and makes a little grinding noise when cranking it.

Any guesses? Scored? Fried? Just cranky?

Craig

[hanson]

Sounds like you diagnosed it yourself.

I would assume PTO side cylinder scored on you due to it being a fanner. You said it was also first time out, could be either side as a result of dirty carbs and it was leaning out on you.

Put the compression gauge on it or a thumb over the spark plug hole and see which side doesn't have the compression. After that, sounds like a trip to the repair shop.

[ChuckN]

My brother had this happen to him. Rode for a few miles just fine, and died. Got it running, died. He had to pull it home.

He called me to ask what was wrong, and I suspected water in the fuel. He had no isopropyl or Sea Foam, nothing. He drained the bad fuel, and it was in fact water in the gas.

I have seen bad fuel blow pistons on the first ride of the year. I don't know if this happened to you or not, but grinding noises?? Not sounding good...

If you have fuel from last season, get rid of it and go from there.

[Knotwood]

Check compression, should be within 15% of each other, and most likely above 120 pounds. If it is low, with a good flashlight, you might peek at the exhaust side cylinder wall for scratch marks. Check out the transfer ports for areas where bearing retainers, snapped reed valves, or rings may have worked through the engine and snagged. Pull off the exhaust manifold and see if the pistons are scratch free. See if the rings move freely by gently poking them with a screwdriver, see that they are not stuck (don't try to rotate them, they are pinned in place). Sometimes the oil works it's way down the face of the piston and varnishes rings from contacting the cylinder wall, usually blackening the piston. Time to pull off the top end if it is scored. Lack of lubrication seizures typically appear all the way around the piston, lean seizes show up on the hottest part of the piston. Snow scoring happens on the intake side, sometimes breaking off a part of the intake skirt. Find out why it burned down (if it did)- replacing pistons will become a regular thing until the cause is found. If everything seems kosher, it might be a screw under the flywheel, or a pawl inside the recoil came loose.

[Craig_S]

Thanks guys. Here's the scoop. The shafted gear that drives the oil pump busted in half. That stopped the oil flow and scored the cylinders and pistons. The shop is honing the cylinders and the whole works should be done before the weekend. He said he'd seen bunches of these break in the past. Something to check if you're in the engine for something else.

Craig

[hanson]

Was there any mention of excessive rust on this shaft at all?? Since its at the lowest point of the crankcase, I'm just wondering if it happened to rust up on you over the summer and broke because of that.

[Craig_S]

Nope. I looked at the part and it's clean as a whistle. Just snapped in half. It probably falls under the "sucks to be me catagory". Everything I have is in the shop right now!

Craig