Piston Pin Clip Position?

[hodakamax]

Which way is recommended for the pin clip for the Wiseco piston? I had a clip get loose after installing as shown in the first picture. On the last assembly I did it as shown on picture two with no problem. I've gotten recommendations for both ways. Any opinions?

Max

[thrownchain]

I find it doesn't matter that much as long as the clip is fully seated in the groove.

[MTrat]

As I recall, the Kawasaki G31M instructions were to place the open ends on the top or bottom to reduce inertial flex at high RPM.

[hodakamax]

Hmmm, My thinking on putting the ends near the opening was to optimize the amount of contact between the clip and the groove. On the other hand it appears that bridging the gap would reduce the chance of one of the ends from getting to the opening which is the only way it could leave the groove. I dunno, that's why I'm asking. Having the clip opening at the bottom and far from the piston opening appears the way to go, unlike the first time I assembled it.

Max

[thrownchain]

The only one I've ever had pop out wasn't seated in the groove. Assemble it whatever way makes you comfortable.

[ossa95d]

I also had a G31M back in the day and remember the instructions to have the open ends of the clip on the top or the bottom. The thinking was that if the gap was at 3 or 9 o'clock, the reciprocating action of the piston at 10,000 rpm could close the gap and the clip could become unseated in the groove. Ever since then I have put the gap at the bottom thinking that the impulses on the downward stroke are more violent than the upward stroke and would tend to keep the clip better seated in that position. Probably doesn't make a difference in the real world but I have never had one pop out.

[squid on a 300]

Max
I ALWAYS put the open end of the clip at either 6 o'clock or 12 o'clock depending on the location of the cut out area of the piston pin. I have been told that the inertia of the piston and pin hitting the top and the bottom of the stroke could compress the clip slightly. With the opening at the top or the bottom the inertia would actually forceably retain the clip in the grove as opposed to possibly compressing it and compromising the seating of it if the opening was in the 3 or 9 o'clock position...made sense to me so that is how i have always installed them...as the cut out on your piston is at the 10 o'clock position i would put the opening of the clip at the 6 o'clock position

[MTrat]

Some pin clips have a tang on them. It isn't a bad idea to shorten the tang as much as is practical for your piston.

[hodakamax]

Thanks Gang. I've always done it the recommended way with the tang shortened and pointed up or down to keep the tang from flexing. The Wiseco has no tang and I originally thought that more clip contact with the groove as in picture one would be better. Like I said above and as everyone else seems to agree that the opening should be at the bottom as in picture two. Perhaps the clip wasn't fully seated in the original installation but it certainly appeared to be. I'll probably never know for sure but I'm ready to assemble again and I'll be hoping the incident was a fluke rather than my incompetence. Weird for sure in that it seems highly unlikely that the clip could get out of the groove in any position.

Thanks again all for your interest!

Max

PS--Here's a quick sketch showing how the bevel on the pin should keep pushing the clip further in groove. I started to shorten the pin for more clearance but you would also have to re-bevel it also. After re-doing Ed's experiment on expansion clearances with a forged rather than a cast piston it appears the clearances would increase even faster with the forged piston. If the clip can be fully seated during assembly all should be well. (I hope!)