Bike sat for a week, went to go for a ride and noticed a clunk in the drive line when the bike was rolling with my weight on it (i.e. suspensions compressed, chain tightens), noticed the nut on the output shaft was loose and sprocket was moving so i tightened it, bent the tabs back down and the noise seemed to go away.

Noticed later that while coasting at low speed with the clutch pulled in, and in any gear, i get this faint tap/clunk that is coming from the area where the output shaft and front sprocket are and possibly in the trans. It only starts when i slow down to a certain speed and decreases occurrence as my speed lowers.

I ride 80/20 street and dirt, swapping supermoto wheels for stock when ever i do, been stressing the bike a little more then normal recently trying to keep up with my friend on his ktm 525exc (i know its a useless battle haha)

worried its possibly the output shaft bearing or mabe a damaged trans gear, suggestions ?

 

Thats why my chain slack is loose. Like a mx bike. too tight chain can mess up that area. Hope you find out whats wrong and a fix.

 

yeah I'm usually pretty good about it, not sure of the previous owners treatment of it though. Really hoping i don't have to split the bottom end, i suppose that's an excuse for a BB 351

 

Take your chain off to get a better look. Better yet, remove the sprocket as well. Rotate the output shaft with your fingers. Does it turn easily and smoothly? It is normal for it to take a little force with your fingertips due to viscosity of oil on the shaft & gears, seal, etc. But it should turn smoothly with no binding, or roughness. Also look for shaft delection. There should be almost no up-down/ fore-aft movement. It is ok for a slight in-out movement however. It is likely if the bearing is really worn and loose, you will be leaking oil as well.

That bearing is pretty stout, I have seen it firsthand. I replaced mine, although it did not need it. I already had the cases split, decided to replace all bearings as PO ran it out of oil and seized the top end.