Author Topic: Wristpin too long??????  (Read 823 times)

Offline jachenbach

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Wristpin too long??????
« on: 12.05. 2015 23:42 »
Started assembling the top end for the Golden Road Super Star. New Hepolite piston kits (std bore), newly sleeved cylinders. Piston to cylinder clearance? Check, good. Ring end gap? A bit tight, filed for .008" clearance. Installed right piston on rod, all good. Left piston, what the hell????? Wristpin doesn't go in far enough to install circlip. Looks like its up against circlip on the other side. Warm it up, remove wristpin and measure wristpin length and distance between circlip grooves. Not a great measurement, but wristpin looks to be about .010" too long! Make sure everything is clean (again), oil wristpin, heat piston, try to install (not on engine). Yup, the wristpin is too long, by just an rch more than the width of the circlip groove.
  So............. Anyone have an idea what kind of tolerance I should allow for? I'm guessing this is not real critical, but I've never had to do this before.
  Also, a while back, someone had a sleeve slip down. Seems to me it would be easy enough to drill and tap a hole in the cylinder skirt, dimple the liner, install a grub screw and grind it flush. The case mouth would prevent the grub screw backing out and the liner couldn't move. Worth doing or is this too rare a failure mode to worry about? Got these cylinders already sleeved with a truckload of parts, so don't have any idea who did the work.

Offline wilko

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Re: Wristpin too long??????
« Reply #1 on: 13.05. 2015 00:21 »
Just get it ground down to length.

Offline cyclobutch

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Re: Wristpin too long??????
« Reply #2 on: 13.05. 2015 13:02 »
Yeah – But I think the question here is what should that length actually really be? Same as the one on the others side you might presume. If you have confidence that that one is really right, maybe it is short by the 10 thou that this one is long? Or maybe send it back to the supplier for a replacement.
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Offline Derby Rob

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Re: Wristpin too long??????
« Reply #3 on: 13.05. 2015 19:26 »
only looked at this post because i had never heard of a "wrist pin" .....now i know
61 BSA A7,yamaha rd500 ,suzuki ts250er,suzuki x7,1958 francis barnett cruiser 80

Offline cyclobutch

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Re: Wristpin too long??????
« Reply #4 on: 13.05. 2015 22:32 »
Indeed - 'gudgeon' to you and I.
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Offline jachenbach

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Re: Wristpin too long??????
« Reply #5 on: 14.05. 2015 03:30 »
Oops, sorry. English bike, guess I should use English terminology. Yes, gudgeon pin. And I'll use my spanners to assemble it (we call them wrenches in the USA).  *smile*

Offline wardleybob

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Re: Wristpin too long??????
« Reply #6 on: 14.05. 2015 19:37 »
Hi I would send them back hepolit is now wassells !

Online Triton Thrasher

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Re: Wristpin too long??????
« Reply #7 on: 14.05. 2015 19:49 »
They've sent you a wrong pin.

They're not supposed to be too long!

What does the seller say?

Offline jachenbach

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Re: Wristpin too long??????
« Reply #8 on: 15.05. 2015 03:12 »
I got these with the truckload of parts from which I'm assembling bikes. They were probably bought by the previous owner about 25 or 30 years ago. The box says $28.95 and contained 2 pistons with rings, circlips and wristpins (sorry, gudgeon pins). I'm going to take it in to work and try to turn it down on a lathe. If the cutters won't cut it, I'll use a grinder.

Online duTch

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Re: Wristpin too long??????
« Reply #9 on: 15.05. 2015 04:38 »

use the grinder with it spinning in the lathe- steady steady like
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
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Online Triton Thrasher

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Re: Wristpin too long??????
« Reply #10 on: 15.05. 2015 06:45 »
Those will be British Hepolite then.

Put a chamfer on the end of the shortened pin, same as original.  Not tapered inside, are they?

Offline cyclobutch

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Re: Wristpin too long??????
« Reply #11 on: 15.05. 2015 08:52 »
Yes, it will surely need to be ground - I don't think a cutter will touch it. Best to take the one from the other side as a pattern for size I guess.
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Offline chaterlea25

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Re: Wristpin too long??????
« Reply #12 on: 15.05. 2015 10:13 »
Hi All,
The pins will machine down in a lathe if the correct tool inserts are used
I chamfered a couple recently without trouble
I scored a box of tips for very hard materials on fleabay for €20 inc post
I was able to machine down a bearing outer diamater with them *eek*

HTH
John
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Offline edboy

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Re: Wristpin too long??????
« Reply #13 on: 15.05. 2015 10:34 »
could it be an a65 gudgeon pin?. i would use an old a10 one as they very rarely wear unless corroded.

Offline jachenbach

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Re: Wristpin too long??????
« Reply #14 on: 15.05. 2015 13:10 »
Darn it , edboy, why didn't I think of that????? More than likely have others, I'll have to look. Hate it when I miss the obvious.