Author Topic: oversize crank pins  (Read 127 times)

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Dale Ice

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on: August 05, 2022, 04:48:33 pm
After a year and half, I looked at the crank assembly that I removed from a 2001 motor. It had the variable timing feature of a loose timing side flywheel. I got it all apart and found that a PO had installed an aluminum roller bearing in the aluminum rod. That's when something went wrong, I suppose. Somehow the hole for the crank pin got enlarged. Perhaps the fellow thought that the nut would hold it all together...wrong thinking. I don't see any damage to the flywheel bore. I'm wondering if an oversize crank pin would make it right...I see oversize pins are available in the UK...being in Calif., I'd like to find some stateside...Has anyone fitted an oversize pin and have advice as to the installation? What kind of interference fit should I shoot for? The motor had obviously had a valve job and cylinder work...so it should be salvageable...


AzCal Retred

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Reply #1 on: August 05, 2022, 05:29:22 pm
" I see oversize pins are available in the UK...being in Calif., I'd like to find some stateside "

This is very much a specialty piece right in the very guts of the engine, probably under $75 USD delivered to your door. 4+ hours of machine shop time are very likely a lot more money than that. An entire straight & balanced roller big end crank is only about $600 from Price Part and you can just start reassembling. No points awarded for adding difficulty or delay! ;D ;D ;D

https://accessories.hitchcocksmotorcycles.com/1196
PART No. 140921;CRANKPIN, OVERSIZE; £38.00

https://www.pricepartmotorcycles.co.uk/ourshop/prod_2986111-144693sx-needle-crankshaft-500cc.htmlhttps://www.pricepartmotorcycles.co.uk/ourshop/cat_314445-Crankshaft-Bearings-Connecting-Rods.html

A trifecta of Pre-Unit Bullets: a Red Deluxe 500, a Green Standard 500, and a Black ES 350.


tooseevee

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Reply #2 on: August 06, 2022, 03:01:56 pm
" I see oversize pins are available in the UK...being in Calif., I'd like to find some stateside "

This is very much a specialty piece right in the very guts of the engine, probably under $75 USD delivered to your door. 4+ hours of machine shop time are very likely a lot more money than that. An entire straight & balanced roller big end crank is only about $600 from Price Part and you can just start reassembling. No points awarded for adding difficulty or delay! ;D ;D ;D

https://accessories.hitchcocksmotorcycles.com/1196
PART No. 140921;CRANKPIN, OVERSIZE; £38.00

https://www.pricepartmotorcycles.co.uk/ourshop/prod_2986111-144693sx-needle-crankshaft-500cc.htmlhttps://www.pricepartmotorcycles.co.uk/ourshop/cat_314445-Crankshaft-Bearings-Connecting-Rods.html

           That's a beautiful piece, but it again points out what I've noticed lo, these many years & that is that Hitchcocks certainly can't be accused of being overly verbose in their item descriptions. Many, like this one, have no description at all; no who, what, when or where at all.

           But I still love Hitchcocks. They're every bit as good for Enfields as S&S has been for harley for many, many years. AND they sponsor this site where we're talking right now. There is an incredible amount of Value here! 
« Last Edit: August 06, 2022, 03:08:02 pm by tooseevee »
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richard211

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Reply #3 on: August 06, 2022, 04:50:22 pm
An oversized crankpin might not always work. From memory the dimension of the standard size crank pin where it fits into the flywheel is 25.5mm and the first oversize crank pin dimension is around 25.65mm.

 I think it's better to weld the hole on the flywheel and rebore it so a standard pin can be installed. Usually what happens is the hole become oval when the crank pin slips as it loosens up. So it may not always be possible to have the oversize crank pin to fit.


AzCal Retred

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Reply #4 on: August 06, 2022, 07:11:20 pm
Sounds like a known good, already functional unit from Price Part might be the best option rather than trying to find a machine shop that could actually do the repair. If you had your own machine shop and were already well versed in this, you'd likely be related to Grumbern...
A trifecta of Pre-Unit Bullets: a Red Deluxe 500, a Green Standard 500, and a Black ES 350.