A note on piston circlips

[il_10]

After destroying my last top end when a piston circlip came lose and chewed into the jug and piston, I started trying to figure out why and came to a possible conclusion.

I haven't noticed any mention of circlip position on the piston on this forum, and didn't think about it before, but it's apparently standard practice to place the circlip opening at either 12 o'clock or 6 o'clock.
If it's in sideways, at high RPMs it can flutter, compress, and jump out of its groove.
Since our circlips have the added mass of the inside prongs that allow you to get purchase with pliers or what have you, that makes even more sense.

So before you lose a top end and have to dig chunks out of the crank case, check those circlips!

 

[MotorBicycleRacing]

After destroying my last top end when a piston circlip came lose and chewed into the jug and piston, I started trying to figure out why and came to a possible conclusion.

I haven't noticed any mention of circlip position on the piston on this forum, and didn't think about it before, but it's apparently standard practice to place the circlip opening at either 12 o'clock or 6 o'clock.
If it's in sideways, at high RPMs it can flutter, compress, and jump out of its groove.
Since our circlips have the added mass of the inside prongs that allow you to get purchase with pliers or what have you, that makes even more sense.

So before you lose a top end and have to dig chunks out of the crank case, check those circlips!

Here's a real world test for you.

Install the clip at either 12 o'clock or 6 o'clock.

Run the motor for a while then tear the motor down to see what position the clips end up in?

 

[Kioshk]

Here's a real world test for you.

Install the clip at either 12 o'clock or 6 o'clock.

Run the motor for a while then tear the motor down to see what position the clips end up in?

Even a broken clock is right twice a day.

 

[2door]

Even a broken clock is right twice a day.

And a flat tire is only flat on the bottom.

Tom

 

[Kioshk]

And a flat tire is only flat on the bottom.

Tom

Sounds like my ex-wife!

 

[Goat Herder]

I had a fun time with piston clips when I first got started on these motors. Seams there are two differant style clips out as well.. http://motorbicycling.com/showthread.php?t=6307

 

[maniac57]

Position is not nearly as important as correct installation. Be sure the clip is fully seated in the groove and is not bent or damaged.
There is very little danger of inertia throwing it out of place at the kind of rpm's these engines are capable of...but it's easy to THINK it's seated if you're not careful.