View Full Version : PW80 has no compression
07-25-2006, 04:01 PM
Hello everyone. My son has a PW80 that has no compression. I would like to repair it for as little as possible knowing he will outgrow it very soon. (He is 10) My question is can I just replace the rings on the stock piston and buy some time or should I have it bored and replace the piston too? I have not tore it down to see what size the piston is(if it has been bored before). Thanks for your help! HB PS. This is an 1983 model bike
07-26-2006, 08:32 AM
You can if the piston is in good shape and not worn funny like out of round or damaged. Make sure you clean the ring grooves real good and at least get the cylinder honed and the ports chamfered.As long as the bore isn't worn bad or has deep scratches or is out of round it shouldn't need bored.Pistons for them aren't that much anyways if you do need one.You can get a Wiseco piston and rings with the wrist pin for about $70 from Dennis Kirk www.denniskirk.com (http://www.denniskirk.com) .Or a stock Yamaha one from any dealer or the million or so OEM parts places for Yamaha on the net.Just type in Yamaha OEM parts in search.
You will also have to know what brand the piston is (factory Yamaha or a Wiseco replacement piston) 9 times out of 10 on something like that it will be one from Yamaha but if it has been bored before it could be an aftermarket one like a Wiseco. There is a difference in ring size and thickness for them as I'm told.If you have a Wiseco piston there might be a W on the underside of it where a stock Yamaha one won't have anything on the underside of it as far as I know.If you plan on getting parts from a dealer take the piston and rings along with you.Either way you'll need to get the right rings for it.Lots of aftermarket parts places on the net carry Wiseco rings.
If you need to know anything like torque specs or sizes post back. My 6 year old has a PW80 and I have the book for it someplace.
07-27-2006, 09:43 AM
Thanks, I need to put the piston out now and see where to go. HB
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