Exhaust Questions

Hi all,

I had my bike dyno'd the other day and found that it is running very rich throughout the entire rev range. I am running a standard filter / airbox configuration and I have Micron race headers with a Scorpion road legal exhaust so i'm guessing that the carbs have been re-jetted to richen the mixture... in order to lean it out a bit I was thinking about a free - flowing exhaust and k&n filter, would this have the desired effect?

Also how does fitting a race can (unbaffled) affect the rideability and power as i've heard that it can increase peak hp but at the cost of some low down torque / power.

Any advice would be a big help.

Chris

Originally Posted by UKStreetFighter

Also how does fitting a race can (unbaffled) affect the rideability and power as i've heard that it can increase peak hp but at the cost of some low down torque / power.

Im no mechanic by any means but i do have a VIPER race can fitted and have ridden with the stock one for a while too,
with mine starting of as baffless it feels ( or what i can only describe as ) very free at the back end, kind of like the pressure wasnt there but the bike was more responsive on the throttle in higher revs, but i had to up my idle speed on it and i found it was a little sluggish in the low range, but if you drop clutch at 3000 RPM and give it the beans thats normally enough to rocket you off with your front wheel skimming the floor.

I now need my throttle balancing tho, and dyno'd in for max performance

[rictus01]

Generally speaking you need to have the jets filter and exhaust in balance, filters come in three main flavours, standard (or replacement for standard), slightly freer flowing and race (as in BMC terms road/race & race RS)

using the above as a guide, your jets may have been setup for the headers and perhaps a full micro system at some point in the past and used a race or race RS air filter then (probably removed when the bike was sold), in which case a race or race RS filter would be required to balance out the mixture ( although I'm not sure how restrictive you road legal can will be, as I'd suspect the race version was also removed before sale, so you'd need a race on of those).

Jet's require stripping the carbs to change so were probably left as were the headers, the standard air filter and end can aren't suited to them as you have it now.

you could find out the jet size and then change the rest to suit it or perhaps the best way would be to fit a set of standard jets as they should work fine with what you already have.

Cheers Mark.

If you still have a stock air filter in there with an exhaust I would start by removing the airfilter or replacing it with a free flowing one before you go messing with the jets. It could just be that it is set up for the airfilter and some cheapo kept it when it was sold to you. So if you don't have a decent filter I'd start there before diving into the mechanical stuff.