I could not start this atv so I did a compreeion test and it had 30 psi. I know now that it needed the top end rebuilt. I broke the top end down and I can see heavy scarring on the sides of the piston so now I know why it would not start. I guess my question is how did this scarring happen? Did it not get the oil it needed or what? I just dont want to put a new top end in if this is going to happen again. IS THERE SOMETHING ELS I NEED TO CHECK. There is no side to side movement on the piston rod so what els can I check. How do I know its getting the oil it needs.

 

To make sure this thing doesn't wreck all your hard work, you could pre-mix your gas for awhile. Put something in there like 40-1 or 50-1, that way you know that its getting oil. Keep an eye on the amount of smoke coming out of the tail pipe. If its way too much, as in killing all the mosquitoes, you may want to lean out the oil a little. Do this for awhile and watch the level of the oil resivoir. It should be going down, although slowly as these bikes use very little while they're going. If its going down, you know that its working and you should be able to stop pre-mixing.

 

youll need to get the cylinder measured so you know how much to have it bored, then buy the correct oversize Wiseco piston and rings and have it bored to it.

 

thanks evey one for you help I will do everything you told me. Looks like I half to go to a 73.50 1.50mm pistion. I will keep you guys updated.

 

sounds like it had a seizure of some sort. you should be able to see if the oil pump is working. make sure the seals are good as well so it didn't suck air causing it as well. just a couple of thoughts.

 

I hear alot about crank seals, maybe I should go ahead and change them out to. Im not sure how, is it a major job? I took a look at a print and I think you just pull the pull start cover and one is behind there and the other you pull the belt cover but not sure what els there you have to pull to get to the seal or do I have it all wrong?

 

how can you check the oil pump to see if its working?