1932 Coventry eagle Silent supreme

[ramwing7]

Does anyone know the stud size for the carburetor studs on a 1932 Coventry Eagle Silent Supreme with the proprietary Coventry engine?
 Mine are in pretty nasty shape. 
I've tried to replace with a 1/4" x 26 tpi BSC on one end and 1/4" x 20 tpi on the other and that's a no go.

This thing is going to be a bear to revive.   

[R]

You don't have the old studs to work off  ?
A thread gauge is near indispensable for this.

What happens when you try these sizes ?
They nearly have to be bsw or bsc   in 1/4".

Some marques (in the 1920s) were famous for 'developing' their own sizes.
Douglas for example used some 27 tpi.
But that was more the 1920s.

[ramwing7]

Nope, but I have one ordered. 

[geoff.godwin]

If 1/4in bsc is too slack try 9/32 bsf  .It is still 26tpi and just a 32nd bigger . I have used this size to repair a fair few 1/4 bsf  ,also 26tpi . the tricky bit is getting hold of good 9/32 taps and dies Geoff

[33d6]

Why even bother to start unless you have basic trade skills to do the job. Elderly orphan two-strokes such as this are possibly the most awkward restoration prospects. Equivalent four-strokes are simple in comparison. As the necessary 1932 Owners Handbook and Spare Parts List is available for free on the New Zealand Barnstormers site I'd look through it very carefully before I started driving myself barmy with that engine. You may think it better to fit the alternative 250cc Villiers engine Cov Eagle used that year in the same machine.

Just a thought.

[R]

You may think it better to fit the alternative 250cc Villiers engine Cov Eagle used that year in the same machine.
Just a thought.

While this might be a 'simple' solution, it entails shock horror gasp FINDING another engine, and PAYING for another engine. !!
And also ditching the original engine. Shock horror gasp again, etc etc.

And if all ?  that is missing is a couple of manifold studs, then this sounds to be well in hand.
Maybe ?

Vintage motorcycle chaps are well known for being a stubborn tenacious lot, so look forward to progress reports.
Cheers !

[Rex]

. the tricky bit is getting hold of good 9/32 taps and dies Geoff

I don't suppose fasteners in such an odd-ball size are that common either..

[geoff.godwin]

Back in the day Namrick had some of them .Geoff

[R]

I don't suppose fasteners in such an odd-ball size are that common either..

I know its not quite the same thing, but the local Norton bolts supplier makes a small range of bolts etc in slightly oversize sizes,
to suit various Norton fasteners that are well known for causing such problems.
Particularly the 26tpi drain plugs into alloy castings, and the front fork stay bolts - also 26 tpi into alloy.

I've deployed a few of these, and they easily 'fix' such problems.  Very solidly and permanently
Note - may not be interchangeable with stock items
(But then neither are 9/32" )....