jetting hard on engine?

[fiveohoss]

ok...i have a couple questions. i recently became the owner of my first quad, an 03 400 ex...bone stock except for a K & N air filter and no baffles in the exhaust. now...it came with a K & N jet kit but the guy never put it on. i've heard these 400ex quads are hard to break and very reliable. so my question is, how rough will a jet kit be on my motor? will i start running into problems or is this a very minor upgrade and shouldn't put any more stress on my quad than it can handle? also, how strongly do you recommend me putting a pipe on it if i do decide to jet it?

[iamsickofitall]

Originally posted by fiveohoss
ok...i have a couple questions. i recently became the owner of my first quad, an 03 400 ex...bone stock except for a K & N air filter and no baffles in the exhaust. now...it came with a K & N jet kit but the guy never put it on. i've heard these 400ex quads are hard to break and very reliable. so my question is, how rough will a jet kit be on my motor? will i start running into problems or is this a very minor upgrade and shouldn't put any more stress on my quad than it can handle? also, how strongly do you recommend me putting a pipe on it if i do decide to jet it?

jetting is done to stop mods from being hard on the the motor. the reason you need to jet for mods is because your mods allow the motor to move more air, which means that you need to add more fuel into the mix to keep your air/fuel ratio in check. an unjetted or underjetted carb/motor will be running lean due to lack of necessary fuel. an overjetted carb/motor will run rich due to more fuel being added to the mix than is necessary.

you should not need to jet for a K&N filter. if you do add that exhaust, it will be necessary to jet.

idk about that statement not jetting for a K&N because they flow way more than the stock filter.

[drew416ex]

Any stock engine should be jetted according to location because there is no way the factory can jet something properly that is running in say colorado that was made in california.

[iamsickofitall]

Originally posted by FoxHondaRider
idk about that statement not jetting for a K&N because they flow way more than the stock filter.

I was just basing that off my personal experience with my quad and the fact that Ohio's elevation is within a couple hundred feet of anywhere I ride.

I bought mine bone stock except for a K&N filter. Just after I got it, I tossed in a new plug, blasted WOT and did a plug chop and everything looked perfect.

I also always hear everyone saying that the K&N's flow so much more air but haven't seen any flow bench testing or something similar. Anyone have any links?

[jrsmith_80]

Adding just a K&N is pointless unless you have some way of letting all of the excess air that you have taken in, out. I have been around for quite some time and I would not worry about rejetting just for the K&N. If you add exhaust later on the you will have to rejet the carb.

i would rejet for just a k&n simply because you ARE letting in more air...which makes the mixture lean and we all know what lean does...

[HondaRaceReady]

Rejet whenever you change the bikes engine or anything that effects the engine.