B31 gearbox pivot stud

[Barriball]

Hi.

While under the B31 draining the oil from the gearbox, I noticed one end of the pivot stud had its nut missing. I took the other off for a pattern but still cant find or be sure of the thread. It looks to be 3/8" UNF. It has a very fine thread. The nut that I took off is quite new so the stud has probably been replaced.

Can anyone help with the thread. I will probably knock the stud out for a pattern. Is there a reason why the other fixing around that area are bolts and not studs? I think its called a pivot stud so does it have a particular function?


Barry.

[idie]

Is it a swinging arm B31 or a rigid or plunger as they are different gearboxes. I would guess you have a swinging arm gearbox. As you adjust the primary chain tension the box moves around the stud which has to be tightened as well as the top one which should be a bolt. The stud should be 3/8 x 26 tpi normally called cycle thread.

[sidewaysid]

Yep 3/8 cycle 26 tpi

[Barriball]

Thanks chaps.

Have a good Christmas.

Barry.