I had a smoking problem on my ATV and oil traces in the exhaust. I pulled the head off and the piston had rough spots on the outside like something had dug into it a little. The rings were fine, and the shaft (or jug!?!) that the pistons rises through was ok, no scratches just a little bit of discoloration. The pin that holds the piston on the rod was roughed up and in bad shape. I am looking to bore the jug out and go with an oversized piston. I was told if there was any roughness on the rod where the piston pins goes, or discoloration then i have to replace it. My question or advise im looking for is, can you replace just the piston rod without replacing the whole crankshaft?!?! If so, where would be a good place to find the rod? I believe this was caused by it being ran on oil from the guy i bought it from.

Please respond if you can give me some advise, Thanks guys!!!

 

Yes, you can just replace the wrist pin (goes through the piston and top of piston rod) without replacing the piston rod (goes from the crankshaft to the wrist pin), as long as the piston rod is not worn. If the hole in the top of the rod is worn egg shaped or bigger, replacing just the wrist pin will do no good. To determine if the rod is good without having a new wrist pin or precision measuring instruments will be hard. Is the old wrist pin worn to the point it can't be used to check for slop between it and the rod? If so, you'll have to get a new wrist pin and then check the rod with it. If the rod is worn, that's a bigger job because you'll have to split the case, yadda yadda yadda. Let's hope the rod is fine. If it is, then replacing the piston and pin is an easy DIY job.

 

If the wrist pin is worn then the rod will be worn ... Will probably need a new rod or new crank either way the cases have to be split...