Originally Posted by
MassiveMods
Hey 2fst2c
Ok first thing ill ask you to do is measure the gudgeon pin from the same place on the vernier , you will get a different reading depending on where you measure it from on the claw. the new ones should measure 3.99 mm , now looking at yours in the pic if you had premature wear on the gudgeon ends then that can be the cause of the pin popping out. The front of the piston is where the hole is on the gudgeon , or at least that is how they are assembled, the gudgeon having a lip can by chance catch onto the G Clip if it has movement. so that is possibly why that happened. the question is why did it wear prematurely ?
Can you outline your run in procedure exactly how you did it ?
that will give me bit more of an idea ..
Cheers MM
Mark, I measured it on the end of the pin with the tips of the caliper because the wide part of the caliper is wider than the wear spot. It is worn the amounts shown. You can physically feel it and see it. For break in, I heated the engine to 215. Temp taken at the base of the head. Figured internal temp was around 200. Turned over nice on the box. Ran it at a good idle for 1 tank while keeping the head temp 215-220. Let it cool 30 mins. Heated the motor back up to 215 and fired it up. Leaned it enough to keep it running while doing ovals in the parking lot and keeping the head temp 200-220. Had HD tinfoil on the head. Did this for 4 more tanks cooling down 30 mins between tanks. Tank 6-12, heated as above and removed tinfoil. Leaned out each tank and widened the rpm range and kept engine 215-220 through entire tank and again cooled down between tanks. Tank 13-till broken, heated engine, began tuning on the track. Was about 90% tuned when it stopped. That was just under a gallon. The clip in the 1st piston actually broke. Part of it is still in the groove. The 2nd piston has no clip left. That is the one that had the worn pin and I also believe the pin wear caused the clip to pop. I need to get your addy because I wanted send these into you to look at anyways. Thanks