it sounds like a possible right side crank seal failure, lots of smelly white smoke and an engine choking on the stuff
Check your gearbox oil level...is it decreasing?
Does it smell of fuel?
try adjusting the mixture screw, note where it is first so you can return to that point. I would guess it's clockwise to lean and anti clock to richen on this bike
Try this Alan
Put the bike in 1st gear and push it backwards to tension the top run of chain, hold the tensioner down off the chain, and adjust for 50mm slack in chain, both wheels on the ground mind.
Actually the books says 40-50mm of slack
yeah I know it was but if I had a penny for every time you have related 'crank seal' to 'hard to start'... I'd have at least 10p by now
mines on order BTW
If its running perfect as it is I'm baffled as to why you want to throw money away on a dyno...Its got a filter aleady and buying another will be wasting more money IMO
If you want to play safe just put the next size jet in and enjoy it for what it is they are great little bikes.
The black oily stuff is normal on these it's just unburned two stroke oil, mine used to do it too
The difficulty may well be removing the float bowl screws, sometimes they will need a sharp rap with a lightweight hammer, and always use the correct philips driver.
I've got a drift X170 and the auto exposure is rubbish, try record something in bright sunny conditions and you have nothing but blackness! is it me?
whats this like in bright sunshine then...i'm sure mines ok on dull days?
Wel it does sound like it could be the choke then armfaw...I'm not familiar with it though so sorry I cant help further...best get the carb checked out