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Size of AMC rear sprocket bolts?

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Size of AMC rear sprocket bolts?

Post  rob spence on Wed Apr 04, 2018 5:49 pm

Anyone know the thread etc? Plus are they bolts only or do they have nuts on the rear side too? My hub seems to be threaded.

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sprocket bolts

Post  piston 197 on Wed Apr 04, 2018 6:41 pm

They are a special bolt with a reduced hexagon head size, the mounting flange is threaded, but there is also a lock nut on the inside, they cannot easily be replaced with hex head bolts as the heads foul the brake plate unless the head is shortened, this reduces the depth of the socket and is not a good thing, not quite sure what thread they are, but presume they are 1/4 x 26TPI cycle, but 1/4 x 26 TPI BSF is close, but wrong thread angle, Cycle is 60 Deg. and BSF is 55 Deg so the BSF will do the job, just not as well !
I have seen on trials bikes where the holes in the sprocket have been countersunk and countersunk cap screws have been used sucessfully instead of hex head bolts, then there is no chance of the heads fouling the brake plate
JH
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Re: Size of AMC rear sprocket bolts?

Post  paulfb96 on Wed Apr 04, 2018 6:48 pm

Villiers Services list these bolts, 1/4 cycle x 3/4 long with a reduced hex head.
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Re: Size of AMC rear sprocket bolts?

Post  rob spence on Wed Apr 04, 2018 6:51 pm

Thanks all, who knew there was so much in a sprocket bolt!

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Re: Size of AMC rear sprocket bolts?

Post  rob spence on Wed Apr 04, 2018 6:55 pm

My new rear sprocket is marked 428, I'm presuming the gearbox sprocket (its original) is 428 too, is this the case?

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chai size

Post  piston 197 on Wed Apr 04, 2018 7:03 pm

428 is 12.7mm x 7.75mm the equivalent of 1/2" x .305 , so yes should be ok if used with a 428 chain
JH
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Re: Size of AMC rear sprocket bolts?

Post  rob spence on Wed Apr 04, 2018 7:31 pm

Thanks.

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Sprocket

Post  kerabo on Wed Apr 04, 2018 8:07 pm

I am pretty certain as John said they are BSF X 1/4"

I found some countersunk screws with Allen key hex on eBay in stainless.

Ken
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not BSF

Post  piston 197 on Thu Apr 05, 2018 5:47 am

No not BSF, they are cycle, but BSF will do the job
JH
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Sprocket

Post  kerabo on Thu Apr 05, 2018 7:36 am

If I am wrong about the thread they will have to be the correct ones as I am sure the hub is threaded and the outer nut just locks it?

Regards Ken
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Re: Size of AMC rear sprocket bolts?

Post  rob spence on Thu Apr 05, 2018 10:19 am

Just ordered some from villiers services. They have just had a batch made up.

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Re: Size of AMC rear sprocket bolts?

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