Hitchcocks Forum

Have tried all of the following in pursuit of that little bit extra;

Free flow exhaust supposedly designed for Euro IV C5
K&N air filter
Moved the engine breather from the air filter box and plugged the hole in the box

The exhaust and air filter mods were tried separately and together and in all cases actually reduced performance. Moving the breather did nothing.

The only thing that actually seemed to increase acceleration and responsiveness (not interested in top speed really) was when it rained heavily and the standard air filter got wet! I replaced the air filter and things went back to normal. So I decided to cover 1/2 of the new air filter with electrical tape. Guess what! The extra performance returned.

These things must be tuned so lean that the only way to get any sort of performance increase with the standard ECU is to actually restrict the inlet to richen up the mixture a bit?

I can see why the factory gave up on trying to get a 500 Bullet through the next round of emissions regs after Euro4. The 350 seems to have staggered through for the domestic market but with some extra eco-junk needed.

A.

Maybe a Booster Plug would have the same effect, its purpose is 'up' the temperature to richen the mixture

What really does make a big difference is altitude. The bike pulls up hills much better at sea level than it does where I live at 750 metres. I suppose that with so little horsepower/torque available any small loss is really noticeable.