2013 Grizzly 450 problems

[BadLuckPete]

Hey, guys!
I bought a 2013 Grizzly 450 and I've had nothing but problems with it. When I bought it, it only had 440 miles on it. After riding it for about 3 to 4 hours, It started blowing smoke and burning oil. I took the top half of the engine apart and found that it had already been bored-out and had an aftermarket piston/rings. When I removed the piston, I found that the connecting rod had a lot of play and that the piston rings were very worn-out. I measured the cylinder with a telescopic bore gauge and it seemed perfect. Yes, I measured across the bore one way and then again 90 degrees to the first measurement; I also measured it at the top, middle, and bottom of the cylinder.

I took it to a mechanic and had him replace the crankshaft and the piston/rings. I put a Wiseco piston in it. He also lapped the valves and replaced the valve seals. When I got the bike back, I took it to my hunting lease in Alabama and rode it for about 5 to 6 hours. It used up half the oil, which I filled back up, and shortly after that, it started blowing smoke again.

Then, I took the bike to a different mechanic. That second guy said that he was 100% sure that the oil was coming from the valves, so I had him replace the valves, guides, seals, and the springs - all OEM Yamaha. That second guy - a moron that was recommended by a neighbor of mine - was 100% wrong. When I got the bike back, it was still burning oil, sputtering, and had no power at all.

I took the top half of the engine apart, again, and found that the new piston rings were already worn-out and the skirts on the piston we're pretty scuffed-up.

That's 2 sets of pistons/rings that have been worn-out in very little time. The only thing that makes sense to me now, is that when the cylinder was bored out - before I bought this headache - it wasn't bored out square to the base of the cylinder, that the bore of the cylinder is not inline with the travel of the piston. Does that make any sense to you guys? Can you think of any other reasons why this engine keeps wearing pistons and rings out so quickly?

Thanks, Pete

[Timmi]

I'd replace the top end with factory parts, James can get what you need.

[BadLuckPete]

We're sending the cylinder out to get re-sleeved, bored out, and hopefully nikasil plated. We're sending a brand new Wiseco piston with the cylinder so they can make the cylinder to match the piston. The mechanic used to race offshore boats and he has a good connection with Mercury Marine; they used to build his racing engines.

Replacing the whole top end with OEM parts is definitely a good idea and an option that I seriously considered. The only reason I didn't decide to do that, is the cost. I've already spent more money on this ATV than if I would have gone to the dealership and bought a brand new one... with plenty of extras.

Have you guys heard of similar problems with bored-out cylinders? Has anyone ever heard of a cylinder being bored-out out of square to the cylinder base?