Quad motor rebuild question.

[Degsy]

I am working on a co-worker's 2000 Polaris 250 Trailblazer quad. It needed a new starter or a starter rebuild. When I started working on it I discovered that it had no compression. Long story short, motor out, took it apart and it needs a piston, cylinder bore, crank bearing has a little side play but no up/down play.

Does anyone know what the best thing to do is? I can get the cylinder machined. Is it worth just buying a 1mm over piston/ring kit from wiseco ($80) and boring it 1mm over. Does the head need any work if you go to a piston overbore on these? Anyone know? It's a 2-stroke. I'm hoping to leave the crank bearing alone so as not to have to crack the cases.

Advice?

derek

[UngaWunga]

How many hours on the engine?

If you're in there, and you want it to last, replace or rebuild the crank. Plenty of local shops that can rebuild a single crank for $150. I have no idea what a new crank for that thing'll cost, but it'll probably be around $200.

Bore the cylinder, replace the piston and rings, and call it good for the top end. No need to mess with the head unless its damaged from junk floating around in the combustion chamber.

A little side-to-side play isn't bad, but if you can tilt the rod back and forth a little, then its approaching time to replace it. The bottom end bearings do wear out, and the rod bottom end does wear out and elongate.

Do the job properly so you don't have to do it all over again when the rod lets go.

And make sure to check the ring gap before you put it all together.

[Sheppo]

How many hours on the engine?

If you're in there, and you want it to last, replace or rebuild the crank. Plenty of local shops that can rebuild a single crank for $150. I have no idea what a new crank for that thing'll cost, but it'll probably be around $200.

Bore the cylinder, replace the piston and rings, and call it good for the top end. No need to mess with the head unless its damaged from junk floating around in the combustion chamber.

A little side-to-side play isn't bad, but if you can tilt the rod back and forth a little, then its approaching time to replace it. The bottom end bearings do wear out, and the rod bottom end does wear out and elongate.

Do the job properly so you don't have to do it all over again when the rod lets go.

And make sure to check the ring gap before you put it all together.

+1 and check the crank seals. Polaris bottom ends were notorious for the seals going and letting air in.