Backfiring!

[F0ul_Oli]

I understand the point about making the bike run better is more efficient and so in theory, its using less fuel .. but ...
Modern engines are so efficient that the old tricks to make them more efficent have already been made at the factory.

Practically speaking, if you have more power available, you are going to use it, even if you don't give it more throttle, you will be using more fuel!!

[oldboyonrgv]

I agree, but these engines are strangled by emission laws, as supplied by MZ they run very lean and are painfully restricted (remember MZ designed the airbox and exhaust to meet the restriction laws and they dont have the rescources of Yamaha to develop inlet/exhaust which both meet the emissions and flow freely). So by doing the mods you are allowing the engine to breathe as Yamaha designed it, I also agree that you are in charge of the throttle !, after I de-restrcited mine I noticed that it was more economic when cruising around but less so when running hard, but I didn't notice a huge reduction in economy all round, I must confess I don't generally worry about MPG as long as the thing runs right.

[F0ul_Oli]

I think you hit the nail on the head there - its enviromental concerns which mess up the engineering these days!
I just swapped my exhaust last night for a nice carbon fibre one - even if it doesn't do anything to the power, just the reduction in weight will make a world of difference to the bike!