This is my first post and I am new here today
So - Hi all, now here is my story-
I have a 2000 Polaris sportsman 500 that I shattered the piston in, the way I did was out on the lake ice fishing, had the choke half open, and I was hauling more than I was suppose to and I didn't let it warm up at all, so my bad I learned my lesson!!
So I pulled out the motor, tore the motor completely apart, replaced nothing but the piston and rings had the cylinder bored .020 thou. over, got it all back together and installed back in the quad. Tried starting it up and got it to fire once there was a big popping sound little smoke, looked down and it blew the carburetor clean off the hose, so I hooked the hose back up and gave her another go, same thing??? This happened many times before I decided to get on the computer and look for an answer, well needless to say, I couldn’t find one so now I am here,WTheck did I do wrong??
I talked to a guy that said that I could have put the piston in backwards, is this true?? Or was he f'in with me?? Because now that I think of it I know the dots on the piston are on the opposite side they are suppose to be on because I was in a hurry and by the time I noticed it I didn't think it would matter I mean its round and it travels up and down, could this really be the problem?
I made sure when I put the engine back together I aligned the dots on the gears on the crank, when I put the timing chain back on the 2 bright links where aligned at TDC with the chain sprocket that is attached to the cam, and the single bright link was aligned with mark on the motor housing all this stuff right by the book accept the piston, you cant really get this stuff wrong everything is keyed or pinned in place.

 

yes u can put a piston in backwards, some pistons have recessed spots in the dome so the valves don't hit it, i can't remember if the 500 pistons did or not, definitely would flip the piston around if i were u and take a good look at ur valves make sure they're not bent or broke

 

thanks-Kcaves will do.
I remember the piston haveing a recessed center sectionon on the top of it.

 

I was able to get the motor pulled out last night (I think in record time about 35min.) then tore into it and sure enough I had the piston in wrong the dots are supposed to go towards the timing chain and i had them facing the opposite direction so after my new gaskets come in I will put it back together. and see if that works. thanks for the help, Kcaves.

 

Wooooo, woooooo, wooooo, lets slow down a bit.

IMHO you need to solvent check the valves before you put it back together again or you may need a 3rd set of gaskets!!!

If that piston even touched those valves the valve is done. Solvent check the valves and if they are good, then put it back together and go have fun!!!

 

Doctorturbo- as soon as I find out what a solvent check is I will do it...thanks for the info.

 

Sorry, didn't mean to leave you hanging.

A solvent check is about as simple as it gets. Just set the cylinder head on a workbench. Make sure the valves you want checked are on the heal of the cam. (They are closed)

Now put the port on the up side and pour some solvent (thinner, gasoline, diesel, anything really) into the port.

Now look on the underside and see if any solvent is leaking out between the valve and the valve seat. If there is, you "might" have some trash under the valve.

Orrrrrrrrrrrrrrr you might have a bent valve.

About the only way to find out is take the head apart and look at the seat and valve. Wipe every thing clean and solvent check again. If it still leaks you more than likely have a valve problem.

Anyway, it's a great check and the reason I like it................It's FREE!!!

Good luck and let us know what you find.

 

polaris 500 motor

 

Doctorturbo - I really appreciate the help, thanks a lot you have been helpful. I don’t have time to work on it this week (I have Joint custody of my children, week on week off they get my attention for the week). So I'll be in touch next week and tell how things work out, thanks again

 

bigcam400- I like your thinking!! I would like to fix the one i have.