good news everyone. I've been playing round with lots of things on the scoot and now it's definitely broken.
Tried to replace the original rollers with new - that was interesting - the thing revs up to top revs super quick but still accelerates like a turd. also after about 40 miles it's died. I can drive it at around 5mph but any faster than that and the revs drop back to very low again.
Am taking it to pieces and putting it back together again but no idea what's causing the above. Anyone?
More annoyingly, this thing is still under warranty. I think it's been derestricted as it does 37mph (when working). That would invalidate the warranty so I'm trying to re-restrict it. I've replaced the original jet, checked the rollers were original, and now I'm looking at the variator boss.
I've got it out and it has no shoulder on it - it's completely smooth and it's 38mm long by 20mm wide - is this definitely a performance boss. ie. do all kymco agility 50s come from the factory with a shouldered boss? If so I think I've found how the bike was derestricted. Now the question is where the heck do I get an original shouldered boss from? Not so easy...
Any help welcome!
UPDATE: I've just taken it apart again and put the original rollers back in, which I think are 6.5g (I fitted 5.5g temporarily as above). Unfortunately I still have this problem with it not wanting to go over 5mph. If I rev it up, it just dies back down immediately with no acceleration, but I can creep up to 5mph if I take it sloooow. Looking at the driven pulley drive face there seems to be a big black ring of black rubber towards the outside of the face which I'm not sure was there before or not. Also just checked the belt and it's 15.7mm wide - below the service replacement limit.
Not sure if whatever I did last week has toasted the belt somehow. Aaargh!
New belt ordered...