Dommi timing cover bolt specifics please

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

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.

Quite right David and if Jason isn't bothered about originality then allen heads will be right first time.

...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!

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

The orriginal screws had fibre washers under the heads.