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Weird Wrist Pin Bearing Issue

  • Isaac
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Replied by Isaac on topic Weird Wrist Pin Bearing Issue

RT325 wrote: ok ignore most of that above as cant find any record of thrust washers up top but still think its thrusted there so must be the piston sits close to the rod to keep it central to thrust it, but that's not helping is it. How hot did you heat the gudgeon eye of the rod.



I heated it for a minute or two with a propane torch (not MAP gas) it was nowhere near glowing hot. I am usually gentle with these things as I know how a heavy hand can make it much worse. Heating was a last resort. I also checked ot see if there were any burrs on the pin, piston (where the pin slides in) and the small end of the connecting rod. Nothing I could see. I hit the piston holes with a rolled up bit of 800 grit and that seemed to make it slide a bit easier, but it still needed some gentle taps with a rubber mallet and socket to get the pin in.

It was very tight when I removed the pin originally. How does the small end of the connecting rod get out of round if I haven't dropped it or hit it with anything larger than a rubber mallet? I'm going to measure it now.
22 Oct 2019 16:15 #11

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Replied by Isaac on topic Weird Wrist Pin Bearing Issue

RT360Fan wrote: Hammering, heating, neither are good on pistons/rods. I'm assuming since the bottom end was all together you used a torch?


I agree with that. A rubber mallet and socket and a torch were last resorts. The pin has alway been tight since I took it out so I thought it was supposed to be that way. It was not binding when I took it out though
22 Oct 2019 16:17 #12

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Replied by Isaac on topic Weird Wrist Pin Bearing Issue

I finally had some time to work on the PE again.

I measure the small eye of the connecting rod for "out of round" with my micrometer. It was not out of round at all, the same measurements side to side, up and down and at 45%. I measured both sides of the hole.

I then measured the wrist pin. It is not out of round either. Then I lined the wrist pin up against a straight edge and I think I can see a very slight bow to it. Maybe I'm imagining it, but my brother saw it as well. I ordered a new wrist pin just in case.

This would make sense as the bearing (new and old) seem to bind on one part of the rotation, like its tighter in one part than another.

I'll update when that comes in next week.
The following user(s) Liked this Post: Snglsmkr
26 Oct 2019 14:16 #13

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Replied by liferbiker on topic Weird Wrist Pin Bearing Issue

Wow, bent wristpin? Been running nitromathane? I don't think even if it hydraulic'd it'd bend a pin! Roll it on a machine shop "flat stone" with a flashlight behind it, just for grins to be sure.
26 Oct 2019 21:45 #14

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Replied by Isaac on topic Weird Wrist Pin Bearing Issue

I just now remembered I had not updated this forum. Here i what ended up fixing it:

The wrist pin had a slight bow to it. Not sure how that happened or if it was always that way? It would cause the wrist pin bearing to bind as it rolled.

I ordered a new wrist pin and the new bearing I had already slid on to it perfectly. The bike has been up and running for about 8 months and 10+ rides and runs great. I tend to ride these old bikes like they are new ad this bike has really held up.

Ive attached some photos of the bike in action. Thanks again for all the help here!
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25 May 2020 13:35 #15

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Replied by Isaac on topic Weird Wrist Pin Bearing Issue

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25 May 2020 13:43 #16

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25 May 2020 13:53 #17

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25 May 2020 13:55 #18

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