It sounds very well like it could be the decompression device. It works by propping the exhuast valve open at very low speeds(kicking speeds) this helps bleed off compression. On that bike it uses a centrifugal device. It needs to be checked for proper action.
BUt, thats a guess. I would do as already suggested. Find an expert. MAny problems found early will cost MUCH less. The top end on that bike is easy to inpsect with out major dissassembly.
You need to do this regulary.
1.) CHange oil and filter a bunch.
2.) Listen and check valves clearances a lot.
3.) clean air filter A lot.
4.) lube chain a lot.
This bike is very reliable. As long as its not over revved/over heated with wrong gearing or somehting. OR the oil isn't changed frequently there shouldn't be many problems.
NOw you need to check.
1.) valve clearnace.
2.) Auto decompression operation.
3.) cam lobes for wear.
4.) cam followers for wear.
5.) condition of cam chain/tensioner.
This bike is very expensive to repair if you have cam journal failure(but shouldn't have to with maintenance). The cam doesn't use a sleeve style bearing. The head itself is machined to carry the cam. Mess up the cam journals mess up the 500 dollar head and 100 cam cover.
IF you need parts over night or some thing to a shop. Let me know. I might have some in stock. Tuesday at the soonest now.