can you get a different size needle from keihin??

[cals400ex]

i am looking for a different size needle that will go in my 400ex. i want to stay keihin and not dynojet. i want the taper to be a little different. i didn't know if i would be able to find something like this or not.

[terko440]

You should be able to. I did the same thing for my FCR carb. They are known to have a flat spot around 1/4 throttle. The needle took care of it. Good luck.

[airtime]

look at sudco.com they list every needle and jet avalable for a keihin

[Colby@C&DRacing]

Yes you can get different needles for that carb. We sell all the carb parts you will ever need:)

[cals400ex]

colby, or any one else, i have a little hesitation when i am barely on the throttle. this means that my needle is too large and a thinner one is needed. i don't know if the needles come in different widths and tapers or what?? also, i don't have a clue on what one(s) i would need. the stock needle is a B44A. i am not sure what these #'s and letters mean. my modifications are:

x-6, stage 2, ross 10.8 with cosmetic (thinner gaskets), sparks rev box, and a modded airbox lid.

so i have a few questions and any advice would be great:
1. do the needles come in different widths and tapers? if so, how would you go about and pick what you would need? i don't mind buying a couple if that is what it will take to get it tuned in. my opinion on the stock needle is that with my mods i need a thinner needle. i don't have a clue on the taper. also, i think the 4th notch is to rich unless it is in the dead beat of winter. on the 4th notch of the needle it will spudder very lightly when i am barely on the throttle in the hotter months.

2. can you explain what these #'s and letters stand for or what they mean?

3. does a cam and piston change jetting? this is a debatable topic from what i read. the valves are open longer so i would think it would but i am not sure. by adding a cam and piston, how many sizes do you normally go up on the mainjet if you go up any?

thanks

[JOEX]

Good questions:) I have been wondering the same things myself.
#3 probably deserves a thread of it's own.:p

Joe

[cals400ex]

anyone have suggestions?

[CC Rider]

Ya , I have been wondering some of the same things too! I have wanted to get a fcr 39 , but cant handle the initial hesitation that they are known for and that i have experienced first hand because my freind has one and it does it too! If all this could be explained I might be more eager to pick up one of those "race carb only" thingies!!

:D

[Colby@C&DRacing]

Well here goes please excuse my spelling in advance when I start explaining things in length I think much faster than I can type:)

#1
Yes the needle come in different tapers. They all start out at the top as the same diameter ( when I say all I mean for each carb. example all needles for the fcr carb are the same diameter at the top) they just taper at different rates meaing a richer needle starts small at the bottom of the tip and does not get as thick as it goes up as a leaner needle the thinner taper allows more fuel to pass by. A leaner needle has a fatter taper that lets less fuel pass by.

#2
The numbers on the needle coraspond to a chart the shows which needle in richer or leaner. The #'s are not really a measure per say just a number to look up on a chart. Most of the time the stock needle has enough adjustment to get the job done I only change the needle if I have the clip all the way to the top or the bottom and still need to go more. If you feel that you need a setting halfway between the clips in a needle I have very tiny shims that act as a half a clip for fine tuning a needle

#3
Yes a piston and cam will change the jetting on a bike. Higher compression creates more heat which requires more fuel to keep from preigniting fuel. A cam allow will not effect the jetting as much as piston but it is still very important to check it anyway. Anyone that has put in a high compression piston and cam and says his jetting is the same was either way rich in the first place or is run lean now. There is no true rule of thumb as to how much you need to go up in jet sizes but I start with 4or 5 sizes larger. ( if it was good before at a 155 I start with 165 or 168) this also depends on how much you increased the compression and which cam you used. Also to bee note if you just put in a new piston to freshen up the motor with out upping the compression then the jetting will be the same as before.

If anyone has more questions let me know:)

[AndrewRRR]

Very good post colby!
I didn't know anybody had shims for half clips.

[cals400ex]

very helpful!!
i still am a little confused, so here are a few more:

i don't understand if the needles come in different tapers and widths. for example, can you get two different needles that have the same taper with different widths or different tapers with the same widths? also, do you sell these? i have read the jetting article on your website and it seems as if i would need a needle with a thinner diameter.

also, i did not realize that a cam and piston would change jetting that much. i was running a 158 before i put in my 10.8:1 ross piston, cosmetic gaskets, and stage 2 cam. i am now running a 160 main. i might need to go up on the main then. i should be fine on my pilot since i am running a 45. thanks for suggestions

[AndrewRRR]

Jetting isn't something that is set in stone or can be calculated. You pretty much need to know how to read plugs, learn to feel how your bike is running, and go from there when it comes to jetting. Your bike and another that has the exact same setup may take suprisingly different jets to run best. There are so many factors involved it's something you have to do in person with the quad.
As for the needles, it would probably be best explained with a diagram or two. Anybody good with paintbrush or have a CAD program?

[Colby@C&DRacing]

Needle for the same carb come in different tapers not widths. as far as your jetting Andrew is right it is not set in stone two bike set up the same can use different jet sizes. The old plug reading method is not as useful as it once waws due to the unleaded fuel it is very hard to get a good plug reading. I alway just jet way up until it is positive that the bike it to rich and then work my way down.
Cal your pilot is just fine.