hi everyone, i'm new to this forum.


So i have a moded 400ex with 440 big bore kit,piped,k&n filter with lid off and a 39mm fcr carb. As i said in the title, i have probs with my carb,(actually two) .I don't know alot in carb jetting (pilot,air screw,needle...???) but with my mods, they told me to put in a 170-173 main jet. I had no probs with that ,the plug is light brown. But i still have the same problems,they are when i decide to accelerate rapidly from a stop, it just bogs down for a half sec and then the power comes up. the second problem on my quad is on the top speed. When i'm speeding in 4th or 5th gear and then let go the gas a bit ( 3/4) , then it bugs again for a split second, thos making my front end come down...o and i have no idea of what altitude i am and i dont really know where are the pilots on my keihin carb. But i managed to find the air screw, witch is really hard to turn because of the electric starter motor just under the carb.


(p.s, in the forums on this site, they talked about a pilot size 25 on a 440ex, is that the right size for me?)

Annyway ,thx alot for your help,

I'll stay tuned for your posts.

bye

 

ummm...so whats your question besides the "ps?" [img]i/expressions/face-icon-small-smile.gif[/img]

 

hmmm well, i'd like to know how i could adjust my carb....like pilot size or fuel mixture so my quad will run better[img]i/expressions/face-icon-small-smile.gif[/img]

wep thats it!

 

I have the fcr39 on a 440, also. I think I have a 38 pilot. The bogging under acceleration, at the bottom of the range is most likely a lean condition. Take out the pilot jet, and see what it is. Try going up a size or 2 and see if it improves. The pilot is in the bowl by the main jet. You have to remove the bowl to get the pilot jet.


I had alot of problems trting to get it dialed in. I was trying to sell the carb, and a guy conviced me to keep jetting. I am glad I stuck with it, because that quad runs awsome now.

 

So i'm lean in jetting ? you mean with the main jet or just the pilot ?, can a pilot be lean ? also, i know wheres the fuel/air mixture screw is, should i play with that 2 or just leave it like that ?

thx again

 

ooo ok ok, i see now

so i just need to take out the pilot and find another pilot that is a size bigger.
I don't know what keihin put in my carb but ill try what you said tractorpacker[img]i/expressions/face-icon-small-tongue.gif[/img]

now its getting clearer in my mind,


but again, is it absolutely necessary to adjust my fuel/air screw ??? or it's not important?
I'm asking this question because,like i said in my first post, it is very difficult to adjust that screw because of the tight space under my carb.

so then thx all for helping me.

 

the air/fuel screw makes really finite adjustments. that may help with idle. But i don't think you really need to adjust it, just step up a size or two on your pilot jet which is what effects the low end grunt. Its hould fix the bogging problem. Also what is your needle clip set at?

 

I'd really like to answer your question but i don't really know where is the needle clip.[img]i/expressions/face-icon-small-blush.gif[/img]

So then i'll just do the followings...

1: stop not knowing carb parts like the needle,pilot,etc by just opening the damn carb and looking for my self
2: ask my friend what does a needle and pilot do and what they look like
3: write down the pilot size and needle size i already have in my carb
4: go buy some pilots and needles sizes bigger
5: put all that together and see if it helps my bogging

You must be asking urself 'why didn't he tried all that before posting?!!'
well, before posting i didn't know anything about carb adjusting and thought i was ok with my main jetting, witch was the basic stuf.
now that you've all told me about needles and pilots, i think i can do the rest myself[img]i/expressions/face-icon-small-smile.gif[/img]

I'd really like to thank everybody for helping me on that.
If i still have probs after all that, well, i'll just post again !!

So then...... i think i have work to do [img]i/expressions/face-icon-small-tongue.gif[/img]

chow

 

You should find a tuning guide for the FCR carbs. Factory Pro has a good one on their website and so does SUDCO, it will tell/show you the names of the parts, what they do, and how to go about adjusting them. As for the pilot jet, start with the fuel screw (the one on the bottom of the carb that you might not be able to get at w/ the carb on the engine) turning it out will make it richer in the low/mid range, if the screw is out more than 2 turns you must get a larger pilot jet and turn the screw back to 1 to1 1/2 turns. If the screw is in more than 1 turn, you need a smaller pilot jet, and must back the screw back out. You could also try moving the accelerator pump rod out to the second hole where it mounts onto the throttle linkage (where the cable goes), this will delay the pump a little bit, it may help, or may make it wose. Find a guide, they aren't complicated carbs, you just need a little guidance.

 

arg, sorry guys, but it's snowing now at my cottage,so i just can't jet my carb.

I'll wait till spring to continue all this.

I think i'll put on my old stock carb for winter, cause it has a choke on it !

thank you all for your great info and helping me,i appreciate it.


until next time.