Squish band on a road racer

I haven't read the entire thread and you may already know this, so no offense meant. When we switched from OEM cast pistons to Wossner forged pistons, on a Honda RS125, you needed to be much more careful warming up the engine, prior to leaving the pits and putting a load on the engine. If you didn't, it was easy to cold seize.

I don't have my notes, so going off memory, but I tried to at least hit 40C before letting him ride away and preferred 50C if we had enough time. For our setup we wanted around 60C on the track. On hot days, even with all tape removed it would get hotter, which didn't hurt the motor, but would take away performance.

Also, we would check to make sure the ring was not getting pinched at the end of each day. If so, you can take a triangular whetstone around the ring land, lightly hit it with scotch bright and put it back together. We tried to get about 300 miles out of a piston. On OEM I often could get over 400 miles.

 

yes sir, every time with forged pistons. The thinner parts of the skirt will grow faster than the cylinder.

 

Looking at my old cylinder, I absolutely was not warming it up well enough before going out and ripping. I plan to treat this motor build better. I also need to get a good bore gauge so I can verify clearances before assembly.

 

Yea, it is amazing how much of a difference that will make. Unfortunately, you annoy all the 4 stroke guys in the pits, who wonder why that idiot keeps blipping it trying to get heat into the motor.

 

I need to talk Chicken Hawk into making me a small warmer I can wrap around the cylinder to bring it up to temp while the big warmers work the tires.