Oil is leaking from behind my front sprocket have any advise?

indications are that it is very possible that you have fixed the leak
the only extra thing that you have have to do is use a sealer under the collar but if the nut tension is correct it may be satisfactory

I would replace the seal AND the shim also if the shim appears faulty.

What model is it? If you are fairly good with the spanners you can remove the sprocket and often replace the seal from the outside.Drain the oil and prise out the damaged seal carefully and fit replacement using a socket as a drift, carefully tapping it into the recess. This should stop the leak. Replace sprocket, fill up with correct amount and type of oil for your specific machine and away you go.

If you lean the bike over to the right , no oil will come out while you change the seal. If any did come out it would be quite slow. This seal and bearing will have a pressurized oil feed

There are several things behind the inner primary case that could be leaking. There is a seal behind the inner primary where the transmission mainshaft goes into the primary. This seal sometimes starts to leak. Also, there are seals in the transmission in that area. The final drive gear seal is the big seal right behind the front final drive belt pulley. Somethimes this pulley wears on the splines of the final drive gear and it loses tension on the "quad seal" on the final drive gearshaft.

You'll nee some special tools to get to this area. You'll need sockets to fit the compensator sprocket nut and the clucth nut. You'll need an airwrench, a primary locking bar, and a torque wrench that will pull 150-165 ft. lbs. torque in forward direction, 68-80 ft. lbs. LEFT-HANDED on the clutch nut, a primary locking bar, a final drive sprocket locking device, a mainshaft nut removal tool, and some seal pullers and installers. Good Luck.

where is leaking oil from....behind the front sprocket??

if so your chain is TOO tight

if this is your problem, replace the output shaft seal and check drive line for abnormal wear before readjusting chain tension.

Trans output shaft seal that is behind the front sprocket is bad and need replaced.

you're problemme is the counter shaft seal is leaking....this is the seal right behind the front sprocket....i tough there is also a inner o-ring on that model that you shall have to change...thank you for leaving good feedback.

im not sure but i race hare scrambles to i usually just put a little high temp grease on it and it stops wear.