Have 350 dirt bike kick start was ok left bike shed for a while used kickstart ok but next time it appears jammed wont move tried rocking in gear to free up but no go. Do you have an idea as to what might jam this and can I access this trough side plate or will motor need to come out. Thanking you in anticipation Stoney

Assuming the engine will turn over, the ratcheting assembly on the kick starter may be worn. Remove the kick start lever and then the side cover, (place a pan under the bike to catch any oil). The kick starter is basically just a gear and a spring; the gear will in some manner engage the flywheel, (sometimes indirectly). Make sure there is nothing obvious wrong such as broken teeth or debris lodged in the mechanism.

The other possibility if the engine does not move when rolled is the timing chain may have jumped teeth on the cam sprocket. To get to this remove the gas tank, remove all but the rear engine mounting bolts, remove the valve cover. To check remove the fly wheel cover set the piston to Top Dead center, (TDC) on the compression stroke and make sure the mark on the cam sprocket is at the top of the sprocket and not off set.

Good luck.