Dynojet if it already runs smooth?

[shaggyfrog]

This is in regards to my friends '04 400ex. He has already put on a procircuit t4 slip on. It runs smooth and everything. There is no backfire at all. He has a dynojet jet kit still in the box, but should he put it in if it already runs smooth? Or is there still some advantages of putting it in regardless?

[sprtrx300ex]

By adding an exhaust system to his bike he is changing the bikes air/fuel ratio. Technically to get the full benifits from the pipe, you need to rejet, especially if he is running no air box lid.

[shaggyfrog]

right now the airbox lid is on. would it be better to take it off? even in dusty conditions?

[Rip_Tear]

first he needs to get more gas to the cylinder. If he takes his spark plug out he will probaly notice that is it white, meaning he is getting too much air and not enough gas in. He'll have to up the jet size and try to get a plug that is a brownish colour.

[JPhonda]

ok i also have a question about the dyno jet kit. I have a white bothers slip on exhaust and a moose racing air filter. now do i have to install the whole kit or can i just install the main jet only and be fine with running that.

[Rip_Tear]

just the main jet should be fine.

[JPhonda]

ok thanks because i really didnt care for taking out the whole carb and all.

[coryatver]

It is not that hard to take out at all.. It is a lot easier than you think. Also I wouldn't just change the main with the dyno jet kit. You need to follow there directions closely or it might run like crap. Besides why even get the whole expensive kit for one main jet.

[JOEX]

From what i've read if you use the Dynojet main you need to use the Dynojet needle, the taper of the needle and jet is different than the stock needle and jet.

It may or may not run fine with just the jet change:ermm:

[shaggyfrog]

so in other words, if he's going to get a UNI or K&N and put on there, then he should definately wait til then to go through the trouble of putting the jet kit in? because if we put it in now with his stock filter on, the air fuel mix would be different when he added an aftermarket filter? is this right?

[JPhonda]

yes this is right. but iam pretty sure that just an air filter alone isnt going to do that much to your settings. you might use have a do a little bit of tuning, but not have to rejet the whole thing over again. But if you are going to take off your air box lid then you are prob going to have to rejet the whole carb again.

[shaggyfrog]

Thanks guys. The help here is great! :D