Just realised I was already on the Proven Setups sticky
Couple of further thoughts....
That TBS exhaust seems to play a key role here over the TB, cos the airboxes are identical. Maybe it's to do with 'scavenging' - kind of turbo charging on the cheap one cylinder exhaust 'pulse' from a cross connected header can help to 'pull' the charge thru' another cylinder on it's intake stroke. I suspect the Thunderbike 3 into 1 maybe doing just that.
However, it may be that airbox mods can make up for this when using stock headers & TOR mufflers. Tho', as that rear airbox plenum is a 'tuned' resonant (air) circuit, the characteristics at different revs / throttle will be slightly different again...
All I can say is that my TB pulls like train with a 19t front sprocket (11% higher gearing) & still does 50+ (Imp) mpg - result
Thanks to all the posters who gave me the info to do it !
