Anyone know why randomly my atv has started making a knocking sorta of noise only when accelerating in 2nd gear but runs fine? Runs smooth in all gears just makes a noise when riding in 2nd

 

The one thing I can think of that would only knock in second gear is if a tooth had broken off that particular gear. Looks like you will have to strip the gearbox and find out.

 

If left unfixed could it do serious damage? if so how long do you think it could last before causing worse problems

 

Had a customer with a Honda 250 Recon who lost 5th and said not to bother when he fetched it for service, as he never used 5th anyway. About 12 months later he lost 4th as well, so had me rebuild the engine. A tooth had gone from 5th and it looked like it had eventually found it's way between the teeth of 4th gears and crunched them too.

 

Ah okay if that happens to mine for $300/$400 I'll just replace the engine haha Thanks