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ubu

Pro-X Circlips

12 posts in this topic

Getting ready to install a fresh piston in my 08. Got a Pro-X piston kit and it came with the round wire circlips. The groove looks like the OEM style. I'm wondering if I can use OEM style snap ring type circlips on this piston. Way easier to install:bonk:

I'm looking for experience with this specific piston kit.

And, I do have brand new OEM circlips, I won't be re-using anything.

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You MUST use whatever type of c-clips are supplied with the piston. The round-wire locks are a pain-in-the-arse to remove but are less prone to displacing than the snap-ring type Yamaha has traditionaly used on the YZ.

If you install snap-rings in a piston designed to use round wire locks you will probably lose the pin and trash the cylinder.

Edited by 2grimjim

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I should have known better than to even ask the question. Just had a fit of wishful thinking.

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The problem is the shape of the groove cut in the i.d of the pin bore. With the piston you have, the groove is a radiused cut that conformes with the diameter of the wire-lock. The cut on the OEM Yamaha piston is square, matching the profile of the snap ring. I'm sure you can see what kind of problem this will cause.

I don't really care for either type (round-wire or snap-ring). Spiro-locks are probably the best I've ever seen but seldom used in the motorcycle world.

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The grooves into which the wrist pin retainer rings seat are cut for a particular style of ring, and if they are to stay in place while the the piston is bounce up and down 3 inches 160 times a second, they have to fit the rings precisely. NEVER use a "square" section snap ring in a groove cut for round wire rings under any circumstance. In fact, the best advice is that already given; use only the rings supplied by the piston manufacturer.

Regardless of the ring type, the gap should be placed at the top to reduce the possibility of inertia lifting the ends out of the groove as the piston goes over TDC.

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Yeah I knew better. I started installation that night. The piston is installed with the circlips that it came with, with the gap at top. After flinging the 2nd clip across the shop for the 3rd time, I called it a night. It went in 1st try in the morning. They fit much tighter than even the stock OEM assembly.

With regards to the groove shape, how can you guys tell? To the naked eye, they look the same. I know I'm probably not experienced enough to notice; only dealing with wire-lock clips on my kid's 2-strokes.

1st 4T top end and it's kinda nerve racking.

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The shape of the groove will match the cross section of the retaining ring. Grooves for "Tru-Arc" rings, snap rings with eyes, or other rings made from flat stock and having a rectangular cross section will be cut "square", with vertical sides and a "flat" bottom. Grooves for wire rings will be cut half round, and often shallower.

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The shape of the groove will match the cross section of the retaining ring. Grooves for "Tru-Arc" rings, snap rings with eyes, or other rings made from flat stock and having a rectangular cross section will be cut "square", with vertical sides and a "flat" bottom. Grooves for wire rings will be cut half round, and often shallower.

Maybe my eyesight is bad, or just hoping for an easier assembly, but it's hard to tell the difference in the groove. The deciding factor was the access cutout for removal. And, of course, that the wire clips came packaged with the piston.

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Maybe my eyesight is bad, or just hoping for an easier assembly, but it's hard to tell the difference in the groove. The deciding factor was the access cutout for removal. And, of course, that the wire clips came packaged with the piston.

That's the safest thing you can do.

Even if you have a piston from an aftermarket manufacturer that uses 'Yamaha style' tru-arc (snapring, whatever?) pin retainers, don't assume that they will interchange the OEM Yamaha part. Not all snaprings are the same thickness, and snaprings will usually fit in a groove cut for for spirolock retainers, but will have too much axial clearance.

About the only kind of pin retainer that is foolproof are teflon buttons. But thankfully, I haven't seen those things in quite a while.

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The grooves into which the wrist pin retainer rings seat are cut for a particular style of ring, and if they are to stay in place while the the piston is bounce up and down 3 inches 160 times a second, they have to fit the rings precisely. NEVER use a "square" section snap ring in a groove cut for round wire rings under any circumstance. In fact, the best advice is that already given; use only the rings supplied by the piston manufacturer.

Regardless of the ring type, the gap should be placed at the top to reduce the possibility of inertia lifting the ends out of the groove as the piston goes over TDC.

If I didn't put my circlips in the up position on my recent rebuild should I disassemble and re-do them? All OEM stuff of course.

Edited by FinchFan394

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Why do people make me tell them stuff like this?

To be as safe as you can be, yes, take it apart. But understand that installing them out of their ideal location does not guarantee that they'll come out. It does increase the risk of that, but it doesn't ensure it.

What kind of clips were they?

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OEM. ..they were pointed down, not straight up and down though.

It didn't say anything about it in the manual.

Edited by FinchFan394

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