Exhaust and jets

Hello all. Looking at changing out my mufflers (looking for a lower rumble) and have a chance to get my hands on a pair of Harley mufflers and inquiring if that would also in tale re-jetting the carbs. If re-jetting is necessary where would someone find an inexpensive jet kit?

 

any change in exhaust flow would require at least some carb tuning. if the Harley mufflers provide similar flow restriction to the stock mufflers, you shouldn't have to mess with the carbs much. if they're "free-flowing", you'll probably have to replace the main jets.

You don't necessarily have to get a whole jet kit (such as Dynojet) to compensate for free-flowing exhaust.

chacal posted a good tidbit on jetting here: http://www.xjbikes.com/Forums/viewtopic/t=8911/start=15.html

be warned, however.. that every bike is a bit different, and more than likely you'll end up having to experiment with different size jets to get the proper mixture.

you may also have to adjust the idle mixture, which is pretty hard to do "by ear", and can be accomplished easier with a colortune plug.

in general, it's a can of worms that should only be opened if you think you have the time/resources to get it done correctly.

 

There is people on here that didnt rejet at all when going with different pipes or a free flow pipe...They just did some real good carb tuning

 

other than sync and float levels (which should be dead on), the only thing that can be "tuned" on our carbs is the idle mixture, which provides fuel at idle and just off-idle. you can also shim the needles a bit to make the mixture richer for mid-range RPM's. However... at wide-open throttle, your bike feeds almost exclusively off the main jets, and no amount of "tuning" will correct for that.. so if you remove enough restriction off the exhaust, you will be running leaner when you get up in the high RPM's. Lean mixture means hotter-running engine, which is bad news.

replace the spark plugs at the same time as you replace the exhaust (or any other flow-related components). that way you can check if you're running too lean by looking at the plug insulators. if they remain white after some riding, you're running too lean. if they get a nice tan color to them, you're probably ok.

just my 2c..