Hitchcocks Forum

I have a January 1999 500cc Bullet. It has the standard cylinder and Mikcarb carburettor. It can only be used with a conic air filter consisting of metal gaze. A very "free blowing" one. I bought a new circular air filter from our host and it causes misfiring and power loss. That is not due to that particular airfilter. I also have the standard Royal Enfield metal box with cloth (?) air filter, and that causes misfiring too.
With that metal gaze air filter he runs very well. I just wanted to replace it because it does not filter enough dust.
What can this be due to ?

Hi, carb is running rich, how does it run without a filter? Vince

A change from a very ‘free blowing’ filter to a more restrictive filter will reduce the amount of air into the engine and upset the fuel/air ratio making the mixture richer. Less air requires less fuel.

Normally it is necessary to replace one [main] or a number [main and needle] jets to compensate – reduce their size.

If there is only a marginal difference in mixture strength you may be able to compensate for the reduced amount of air by adjusting either the clip on the throttle needle [lift the clip on the needle to weaken the mixture] and/or the pilot air screw setting [screw out to increase air and weaken the mixture].