Why do Jetkits cost $50. What do they include? Aren't you basically changing the main jet to compensate for high flow air filters and pipes? So couldn't I just buy a larger main jet from my dealer for $4, or am I missing something?

Also, at an altitude of 4,500', what size jets should I experiment with if I run with a K&N air filter, no airbox lid, and top end oriented pipe. This is for a 300ex.
Thanks,
Jeff

Here was my recent experience in installing a Dyno-Jet kit on a '00 400EX. Included in the kit were several main jet sizes--as the kit included "Stage 1" and "Stage 2" jetting. Also was included a new needle. Probably one of the most influential parts of the entire kit. You're spot on about only spending a few bucks on a different main jet, but I feel that the new needle provides some worthy benefits in power and throttle response. The kit was spot-on about what jets to run with what mod's. That was a nice suprise. I would reccomend buying the entire kit as it does give you some room to grow(more mods down the road), it's pretty much spot-on out of the box(as directions are followed), also, it is included with in-depth instructions and VERY handy tuning info(even for the pro's), and it provided a nice boost to that EX. Worthy of the $50 in my opinion.

Can't you buy the needle from the dealer to?

00 400ex
86 200sx

www.geocities.com/cory_14/

When I put my dynoJet kit on I measured the needles and it looked like to me that the needles where the same size

I don't believe you can get different taper for a given carb from a dealer
may be able to go direct through carb manufacturer
but you would need to know what size needle you wanted
my advise is to by the kit.

get the 4 buck jet and btw i think you can get the needle from dyno jet not sure though

I just bought the larger jet size for $5 and adjusted the needle clip. With my 400Ex I run with a 152 main jet (2 larger than stock) and raised the needle by lowering the clip 1 notch (I think, I can’t remember exaclty how many notches). I use a K&N filter and precharger with the lid off and a White Brothers e-series pipe with 18 disks (for high end). I usually only ride below sea level (Glamis) and it runs great. I’m thinking about raising the needle a little more and see if it helps any. With these minor mods idle is not affected much so you don’t need to worry about the pilot jet or as stated below “slow jet”.

The stock needle is perfectly atequit, until you get into big bore kits in which case you would actually need to replace the entire carb. Buy some spare clips though, because they bend easily. People always forget about raising the needle when they say “don’t forget to re-jet the carb”.

As far as what jet to use with which mods: I called White Brothers directly and told them which mods I had and they recommended a starting point. So call you pipe manufacturer and they should know. The norm for this standard mod (filter, pipe and no lid) is between 2 & 4 sizes larger than stock main jet.

As far as altitude adjustment: Find out from Honda what the correct jetting should be for stock and then adjust from their for the mods. You will probably end up right back where you started. Lean it out for altitude and then richen it back up for the mods.

I pulled this from Off-Road.com’s atv site:

OFF IDLE TO 1/4 THROTTLE.....The SLOW JET and SLOW AIR JET are the most effective in this range. When you want a richer mixture in this range use a larger SLOW JET or a smaller SLOW AIR JET. The opposite holds true for a leaner mixture.

1/4 TO 3/4 THROTTLE.....The jet NEEDLE is the most effective in this range. Raising the NEEDLE (by lowering the clip) will richen the mixture. Lowering the NEEDLE will lean the mixture.

WIDE OPEN THROTTLE.....Changing the MAIN JET effects this range the most. Select the size which offers the best performance at wide open, then install a MAIN JET one size larger for engine durability.

Damn! 4:30am and I can still think! :)
Sorry for the length but this is a very important subject.
Hope this helps.

Save $46.00 and just get the main jet. I got a new air filter and complete exhaust system and the only thing I had to get was a 150 main jet, no new needle or nothing. For the extra 5.00, I have a beast!!!

i have a 300ex,iput a KnN power kit in it,stock exh.the directions (stage1) called for 114 jet and 3 turns out on air screw.i ran the machine and it didnt feel right,my buddy has the same machine but all stock,i use that for comparing.mine felt sluggish.my stock jet is a 122 i heard dyno has thier own #s,but i measured the holes 120-122-124 they go up in size perfect. so i went to a 124 that helped at top end low was still sluggish,then i went to the needles the dyno needle is short and fat compard to stock is longer.so i put stock needle back in semms to run great except it seems to me a little lean,spark plug is a little white.i would realy appreciate any feed back.

Atvdad36,
You said you put the stock needle back in but did not say if you adjusted the clip. Did you adjust the clip to richen 1/4 to 3/4 throttle? If not, try that. Read my post above if you didn’t already.