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Dommi timing cover bolt specifics please

Submitted by jason_jordan on Sat, 18/07/2015
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Nortons - General

Hi all

This is a simple one I hope. I am looking to replace the tired cheese head screws securing the timing cover on my 62 Dommi.

Being less than 40 years old (a mere whippersnapper) I still struggle when trying to work out grandad dims and the confusing array of threads.

I can get stainless nuts a bolts through my work for next to nothing so begrudge paying the likes of Norvil £40+ for 12 simple hex head bolts. I just need to be able to identify exactly what I need to order.

Feel free to take the piss as much as you like.

Cheers, J.

Submitted by david_cooper on Sat, 18/07/2015

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Hi JasonI hope someone knows the thread size - but remember they'll need to have small enough heads. Socket screws or cheese head. You won't get hex heads in there - or at least you won't get a spanner in as well. So they are just that little bit 'special' - also being Imperial threads (not metric like the stuff most modern factories use). Also they have at least two (or three) different lengths. So you'll probably have to take them all out to measure them.Regards - David

Submitted by neil_wyatt on Sat, 18/07/2015

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No need to extract the Urine on here Jason, your screws are 1/4 Whitworth and I think, come in two lengths. You can either remove the old ones and measure them from under the head (The length of the thread) and buy the correct lengths or all of them all at 1" 1/4 and cut the shorter ones down.

Put a 1/4 Whitworth nut on the ones you cut down if going down that route to clean off the thread before use.

Be careful if you are changing the gearbox outer cover at the same time. They were 1/4 BSF but so many were re-tapped over the years to W/W.

Submitted by david_cooper on Sun, 19/07/2015

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...and 1/4 Whitworth means that you almost certainly have convenient thread gauges in the house, both to check it and to take to work. It's one of the most widely used threads in the world. Every camera tripod socket uses it!

Submitted by phil_hannam on Sun, 19/07/2015

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Attached drawing of Timing Cover should help to get the screws in the correct position.

Originally there were three separate lengths but most suppliers, such as RGM only provide two. These being p/n 10940 - 1 1/4" & E6980 - 1". The screw threads, on early Dommies, were 1/4" Whit but it is now more likely to be 1/4" UNC as used on the Commando engines. The cheaper versions, for less than £10 a set, generally do not have the short shoulders near the heads in which case a touch of sealant will help to keep oil leaks at bay.

Attachments timing-cover-screws-bmp

 


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