To change or not to change (Pistons and Rings)

Jon Betts

When should the ring and or piston be changed on a stock CR125? A guy at track last week blew a stock TM motor(looked like the ring gave out) and when I asked him when he last changed the ring or piston he said never, same one since new with about 20 gallons of gas through it. This seems a bit too long! I have 3 hours (4 gallons) on a stock CR125 and have a 3 day event coming up should I change the ring and or piston now?

Thanks JB

S. Clark · Joined: 18 Jul 2001 Posts: 32

maintenence never hurts.

Steve Clark

As a rookie, with a TM, I would be interested in knowing about the life of a ring and or piston. I know that some will change rings and pistons for every event but what would be a minimum.

A friend of mine had the ring let go, on a TM, and it took a chunk out of the wall. Ouch. I would like to avoid that. He was not running with any kind of a gauge. Would that have helped to warn him of an impending failure. Doesn't seem like it would have helped since the kart was running fine, next thing there was a puff of white smoke and the race day was done.

Michael Polizzi · Joined: 18 Jul 2001 Posts: 1565

Jon

the more often you change the ring the longer you will get out of your pistons. I am not sure about the TM's but on my Kawasaki I change the ring after two race weekends. At $11 a pop thats cheeper than Blowing up your motor. I am getting about 4 hours out of a piston. This is on a fully modified KX125.

As for the piston, Take off your exhaust and look up the port at the piston. If you see a polished surface just below the ring (about 1/8 to 3/32 wide) Its time to change the piston. This indicates the piston is rocking in the bore.

As always check with your engine builder.

Michael Polizzi 69n
Full Bore Karting

[ July 31, 2001: Message edited by: Michael Polizzi ]

Steve Clark

quote:
Originally posted by Gary Kozuma:
I have a buddy that recently stuck a ring on a TM as well. Is that a common issue? I don't believe I've ever stuck a ring before on the Honda.

Gary K.

Gary,

How often do you change pistons and rings? I would have to check how many races my friend's TM ring had before it let go.

Dale Fagg · Joined: 30 Jul 2001 Posts: 4

Gary,

I am on my second season with a 98TM, and I change my piston, ring, wrist-pin, and upper bearing every 7-8 hours according to the Mychron run time. Keep in mind that my motor is stock with 10-1/2cc head volumn. After 7-8 hours the piston and ring still appear to be OK, although I beleive any longer would be risky. My TM cylinder needed re-plated when I bought it, and I was told the TM factory plating was prone to failure on the early motors. After I had it re-plated I had a ring break and redamage the cylinder. I was told to make sure I chamfered the port edges after I had it re-plated the second time, and since then have had no problems

Dale