@MIGHTYMAN That was a restriction on the RE models. To be honest the RE's always seemed simpler to derestrict.

The obvious ones were the exhaust pipe, YAIS (not convinced that's performance lol), Green Black Wire powervalve.

Older Models were reed switch, some had restrictive pipes,

Yeah no worries that what the forums here for.

Firstly carbs don't just fail so don't panic.

In order for the carb to be professionally setup they would be running your bike on a dyno. Failing that they would be doing runs up and down the street until it 'felt' right.

The best thing you could do is set the carb back up as standard as Yamaha spent many hours researching jetting so you don't have to. Unless of course there is a reason why you should be runnning it.differently.

If the plugs are fouled then it is more likely to be over oiling via the pump. Either the pump isn't setup properly or its broken. Despite this is should still run

If it's not the oil pump then it may very well be the crank shaft seals. Or rather seal located inside the clutch cover.

I would always replace the pair and its a crank case split job to fit. At which points it is always worth doing the main bearings and gearbox bearings.

Obviously if this seal is gone iit will draw in oil from the gearbox.

Easy way to check is to see how much oil is inside the gearbox. Although this would be very worse case scenario. Should just rule that out until we've investigated further first.