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Question about Wrist Pins

Posted: Tue Jul 24, 2007 2:56 am
by MrShake
Hello everyone!

Its been quite a while since I posted, my project bike was put on hold as we bought our first house and moved. Now I'm back at it, parts flying through the mail, grease and dirt under the fingernails, all is good.

Currently, the engine is off the bike and on my work bench in peices. I have to replace the camchain since it broke, and while I had the engine apart, I decided to do some work on it. I've replaced the rings on the pistons and they are back in the cylinders. I'm going to be ordering circlips this week, along with a new oil filter bolt and filter. The question is... should I replace the wrist pins. At 13 bucks each, they arn't unreasonable, but I don't want to waste money on a part I don't need. Are there things I can check?

I'm excited to be in the "put it back together" stage of this rebuild. I oughta be riding soon!!

-Adam

Posted: Tue Jul 24, 2007 3:51 am
by Johnj
Adam, umm where to start, circlips are used to keep the wrist pins in the piston and rod so they don't gouge into the cylinder walls. You said you replaced the rings and reassembled the cylinders. So now you need to disassemble the cylinders to remove the old circlips and wrist pins. Now you need to fit the new wrist pin. Does it fit into the bushing on the end of the rod. If it does you need to replace the bushing. Using an inside reemer, reem out the inside diameter of the new bushing until it's like .001 in larger than the wrist pin. I like it when the wrist pin can't be hand pressed into the bushing, but takes little mechanical effort to press in.


Image

Posted: Tue Jul 24, 2007 5:04 am
by MrShake
Maybe i wasn't clear.....

when I took the engine apart, I pulled the circlips and the wristpin, so the pistons are not connected to the rods and are in the cylinders without pins and only 1 of the 2 circlips are in for each cylinder.

If I understand correctly, you think I should replace the wristpins?

Posted: Wed Jul 25, 2007 2:36 am
by Sev
At the very least you need to replace the circlips.

I'd only replace the wrist pins if they were out of spec.

Posted: Wed Jul 25, 2007 3:29 am
by Johnj
Image

I guess I wasn't as clear as I thought. Your wrist pins are most likely fine. If you put them in the rods do they fit or can you wiggle them around. If you can you need to replace the bushing in the small end (circled). You press the new bushing in as you press the old bushing out, then reem it to fit your wrist pin. Always replace the circlips.

Posted: Wed Jul 25, 2007 4:13 am
by MrShake
Yea, circlips are already on the order list.

I put the pins in the rods and I don't feal any play, if there is any its barley noticable. In the pistons themselfs, there is no play.