A buddy of mine is having a hell of a time with this bike. It was bad luck that started it all. While mudding one day the bike started to make a noise and smoke. He stopped to check it out and found the little breather hose that goes in the top of the crank case had come off and it allowed all the mud sand and water to enter his engine. He disassembled it had the cylinder bored and new piston and rings installed. He drove it for another 100 miles and it started the same thing again. Spoke to a honda tech and he said more then likely we didn't get all the sand out of the base of the engine and that once the bike got heated up the sand came loose. So we completely disassembled it again and washed and rinced it really well this time. We put it back together,oh ya had to bore it out again and install new piston rings. We reassembled it and it is working good except for there was a distant knock or noise. So we pulled the cylinder off again. We had two different engine shops measure the allowable tolerence on the piston thinking it was piston slap and we also measured it ourselves and the measurement was 3mm that is well with in the tolerance. A new bike is 2.5mm. So we were looking things over trying to find the noise maker when we noticed that there is play between the connecting rod and the wristpin. We were told there should be no play. This was a new wrist pin. It looks like the connecting rod is worn. Any suggestions guys? He is pretty pissed at the whole thing

 

Only two ways to go on this one.
#1 Get and install a new rod.
#2 Bush the rod.
The choice is up to your buddy.