F: Frame Burman Repair/Mods

[vibrac]

I think every burman box I have had the 'pleasure' of owning needed the lower bolt adjuster threads opening out with a larger corser thread
Engineering wise a good idea but counter intuitive in the period when most gearbox cross securing bolts slid back and forth.

 

[chankly bore]

A repair I have done successfully is to accurately tap out to 7/16" B.S.F. and Loctite in a threaded section bearing the correct inner thread, 5/16" x 26 t.p.i., also doming and turning off the first 1/4" of thread on the bolts.

 

[vibrac]

26tpi is a silly thread to put in an alloy casting I cannot guess what the Burman guys were thinking last time I did it I seem to remember I used 3/8 whit
Still I suppose it was a good price for an off the shelf gearbox and there wasn't a lot of choice back then.

 

[chankly bore]

Correct, I use brass or steel for the inserts. You can do the same for the 3/8" thread on Twin primary adjustment after re-tapping 1/4" B.S.P.