sorry guys...but what exactly does that mean? how do i go about doing that? is it necessary?

 

Rejetting is changing the carb./fueling set-up on the bike: fuel/air mix screw, needles, and jets. It's just the way the bike determines how much fuel to flow depending on set-up, throttle input, etc. A mechanic will know how to handle it. However, you should not have to rejet after a slip-on. It will probably help w/power, throttle response, and the power curve, but it won't be necessary. I didn't rejet after my full exhaust and it was more than serviceable. It just depends on what you want from the bike, and how much you want to spend.

Good luck.

 

I agree with cls, when you add a slip on pipe, you are increasing the amount of air going into the air fuel mixture that goes into the engine. When you do this, it's agood idea to richen out your air fuel mixture by adding more fuel. This is accomplished by rejetting the carbs on the bike. No offense, if you are not experienced in working on bikes, don't attempt a rejet as you can seriously screw up your motor if you don't know what to do. Rejetting will give you slighty more power (probably not a noticeable gain). I had a Suzuki DRZ that I placed a Two Bros. pipe on. After placement, the bike would let out a string of backfires during decceleration-it sounded like a machine gun( a sign that the bike was running too lean and needed to be rejetted). So I rejetted with a Dynojet jet kit and everything was fine. I only rejetted due to the popping on deccel. I personally would leave the bike alone unless you are experiencing some major deccel popping issues. If you want to rejet, go with a dynojet jet kit and have a qualified mechanic do it for you.

 

I agree with 50 on that one.

 

was gonna make a new post on this but i used the search function!!! w00t!

anyway, for clarification sake, if i add a slip on, not a full exhaust i dont have to rejet my carb. looking at an Area P slip on but didnt want to if i had to take it to a dealer and have it re-jetted.

 

do it run a few hundred miles then pull your spark plugs. If your plugs are white or a light grey, your running lean and need more fuel in there. If they are a light brown your good to go.

 

I am going to rejet for the same reasons above. DynoJet kit is about $75 depending on where you look. My friend and mechanic said he'd do the job for $120. He has rejetted my 2 former ZRX1200R's and a 2002 Suzuki SV650S for me in the past. I ride the 250R really hard (very high RPM's), so I want it to run "perfect." If you ride the bike below the 9-10,000 rpm range or lower....leave it as is and enjoy the noise of the bolt on cannister.

BTW, if you ride the 250R for it's gas mileage alone...don't do anything to it. As it is I'm only getting 40-45 miles per gallon and once it's rejetted it will more than likely get less.

 

In a lot of cases jet kits are sold merely to add to the profits of the sellers. Increased fuel consumption costs the rider even more and persuades him that the jets were needed. Usually it just means that the new jets are too big and the motor is running rich. This isn't good for it and does nothing for performance.

Don't change jets until you've either done a plug chop (and know how to read the plugs) or paid for some dyno time with an exhaust gas analyser. If you chop, chop at various points through the throttle range. Start with selecting the correct main jet for full throttle (not necessarilly peak revs) operation and work down, matching jets and settings to the main.

A slip on should not normally require any change to the jets at any point in the rev range. Neither should a full system in most cases, although it should be checked. Changes to the inlet side of the motor, or to it's internals, usually will.

Rob

 

FAQ on jetting

 

I like that FAQ in terms of the 'how to', but it very much expects the rider to tell whether the jetting is correct from the 'feel' of the bike. Ideally selection and tuning should be made on a dyno with an ega, but failing that a plug chop is much better than a perceived feel.

Rob