Gearbox adjuster top bolt

'68 750: Ugh. After finishing primary chain tensioning, the top gearbox nut stripped when trying to torque to 70 ft/lbs. It looks like inner primary case needs to come off to replace this bolt, is this correct?

Also, this is the second time that I've needed to adjust the primary chain in the last 5 yrs./~15,000 miles, both times to loosen it just a bit. That frequency doesn't seem alarming to me, but I seem to remember reading somewhere that a tightening primary chain is predictive of gearbox death? I have no idea if it is the original layshaft bearing or not.

Happy Fathers' Day, dads.

Brendan Shannon

Might need to install one of these. More necessary for a belt drive alignment, but might help yours hold proper tension too. Just a thought....

Commandos can have a tendency to tighten up the primary chain, the back chain pulls the gearbox back because of all the clearance between the bolts in the normal side gearbox adjuster & boltholes in the gear box. Even when done up tight, the gearbox can still shift in the cradle until it meets the bolts.

Hi Brendan,
To answer your question, no the inner primary case does not have to be removed in order to change the top transmisson mount bolt. Provided your bike has the stock (well, mostly stock) nut and bolt configuration as shown in the photo provided by Snorton74.

GB

I thought Snorton was showing a double-sided adjuster. My adjuster is on the timing side of the cradle, and the gearbox bolt inserts from the primary side. As I look at it more closely, the inner primary cover will foul the top bolt, so it looks like the cover will have to come off. (picture posted below)
As a side note, the part number for the 68 gearbox bolt differs from the later 750's, and according to the OldBritts site is 9/16 x 20 (presumably CEI). The later bolt is listed as 9/16 x 18 (UNF). The nut fit a 7/8 SAE socket so maybe there was a UNF nut on a cycle thread bolt. The adjuster itself seems to be cycle thread.
Brendan

I doubt if you would get an 18 TPI nut onto a 20TPI stud, without
a/ wrecking the nut
b/ wrecking the stud
c/ having arms on steroids

Probably all three.
cheers
wakeup

The early gearbox top fixing bolt 14367 is indeed a 1/2-20 CEI.

Dave
69S