KFX-HMF Jetting

[Tmac23]

I will be installing a HMF slip on muffler on a KFX-400 within the next week or so. I would like to know if I deffinetely need to rejet at all. I would also like to know what jets I should install if I need to at all. I live in Northeast PA around 1200 ft above sea level. We will not be changing the air filter right now so it will remain stock. Any help will be appreciated.

[batgeek]

wait til you get a new airfilter and just rejet once.

[Tmac23]

I'm not sure if we will be adding an air filter any time soon. I have the pipe installed. It sounds good and runs well. No backfires and it seems to be responsive everywhere. I just want to be sure it is ok to run it with the stock jetting without causing any problems. So will it hurt anything to leave the jetting alone and run the HMF slip on?
thanks for the info

[nemesis]

most people dont have problems with just a slip on. Once you get the filter. check yoshi's website for jetting recommedations.

[roostin_dale]

jetting is really a thing of trial-and-error....just buy a jet kit and start testing..

[nemesis]

Originally posted by roostin_dale
jetting is really a thing of trial-and-error....just buy a jet kit and start testing..

True but it is nice to know where to start and then go from there. Start with the yoshi recommendations then go up or down from there.

[LTZ400rider]

try 165 main jet with the air box lid off or snorkel

[450r pimp]

Yes, once you get your aftermarket filter or snorkel you will run around a 165 jet I'd say 160 to 165 tops, but until then you may be able to try around a 148 jet which maybe stock b/c that's what my buddies 400ex was. If it's running fine and you noticed gains you shouldn't have to change it.

[z400ACDC]

The filter will not make that much difference if you leave the lid stock. I have the HMF slipon with a 2x2 hole in the back of the lid and started out with the recomended 170 mikuni main. I went to a 165 and then a 160. I have ran the stock and now a noss adapter with UNI filter with the same jetting. It runs great!