gearbox experience

Hello

my gearbox was making noises in 1st, 2nd, 3rd gear. I put 1000 mls on the bike since rebuilding. I don't ride the bike hard and don't make hard launches. I drive it slowly home for about 10 mls.
I disassembled the box and the 4th gear on the layshaft was missing one tooth. I have no pitting on the gears.
Should i replace all gears or is it a good idea to replace the single one?

Greetings
Marco

Gears should always be replaced in pairs.
So, in your case, replace mainshaft and layshaft 4th gear.

who knows or admits to prior abuses like over tight primary so might want to check shaft straightness as you are 1st report i've come across of 4th teeth lost. 3rd's teeth seem to be the weakest in my case of harsh clutch drops just for fun and games irresponsibly till i kill it or me. My 'feeling' is the tooth lost is not the real fualt but don't know what might of knocked it off by such wimpy careful mature operator, as if that really makes much difference as I'm so so often told again and again.

well, it looks exactly like in my manual, it shows a gear with a broken tooth. Maybe not so unusual.
What the pre-owner have done with the bike is not known, it comes with a lot of parts like aluminum gas tanks, fiberglas fenders, dunston bars.
There is absolutely no history,no titles and taxes for vehicles recorded. Maybe it was imported as a kit bike and was raced :?: In the rear frame loop was a 1/4 inch bar welded in, to support the fiberglas rear end.

Marco

I've had 3 owners of 750's tell me they put more into engine than a couple of new Commandos and used it to beat all comers in sprints by WOT clutch drops in 4th and just hang on till far enough ahead to let off. Amazingly two of them were in righteous chopper hard tail extended fork construction. Both those said end of their joys was loosing control on Gravel crashing after gaining some lead but not from breaking otherwise.

We will see. I have ordered the spare parts from MIck Hemmings. He told me that it is not unusual, chain tension is critical and will stress the 4th gears.
I assemble the gear box and see what happen. I drive defense with my Norton so it shouldn't brake again, i spend to much time to restore it. For the race track i use my 04' Thruxton, it brakes a lot better and it screams with the Norman Hyde muffler and the open race carbs like a Norton :mrgreen:

Thanks a lot for your feedbacks

Greetings Marco