FCR Carb Owners! Jetting Survey...

[skemp]

Just out of curiosity, I'd like to see what everybody's setups are with FCR carbs. This will be a good thread for new FCR owners to check out if they have questions.

- List your mods
- List your jetting:
1. Pilot
2. Fuel Screw
3. Needle
4. Main

Hopefully we can get something together here. :)

[K_Fulk]

I have the 39mm
165 main
50 pilot
EMP needle in the middle, Thanks silverfox:cool:
fuel screw out 4 1/2 turns

[Silverfox@C&DRacing]

Originally posted by K_Fulk
I have the 39mm
165 main
50 pilot
I bought the needle sparks recomends from c&d cant remember what one it is though but i have it in the middle.
fuel screw out 4 1/2 turns

That would be the EMP needle :D
I will have to let Colby post what mine has I haven't done much with my carb I leave that to him although I did change the main jet to a 172 a while back :D

[Bad Habit]

11:1 416
port job
Web Cam
Sparks X6
Open air box
39mmFCR

1000ft elev.

172 main
55 pilot
factory needle-middle clip
3 turns

[AlaskaSpeed]

Originally posted by skemp
Just out of curiosity, I'd like to see what everybody's setups are with FCR carbs. This will be a good thread for new FCR owners to check out if they have questions.

- List your mods
- List your jetting:
1. Pilot
2. Fuel Screw
3. Needle
4. Main

Hopefully we can get something together here. :)

K/N filter, no airbox lid, Sparks X-6 exhaust, cam mod

Pilot-48
Fuel Screw-Zipty Racing fuel screw 1.5 turns out
Needle-YZF dirtbike needle on 6th clip
Main-178

[Colby@C&DRacing]

11:1 416
Hotcam stg2
advanced timing
sparks x6
K&N filter, outerware
no airbox lid


172 main
52 pilot
3 turns out on the fuel air screw
EMR (stock) needle in the stock clip

elevation 2900 ft


Kfulk you might want to try a 52 pilot.

[K_Fulk]

I did but it runs better with a 50. It got rid of the rest of the bog.

[norcalatver]

Just curious, Have any of you with the 170 main jets and above ever dynoed your atv with a sniffer to check your true exhaust gas mixture? When i originally built my 440 in 1999, LRD installed a 160 main jet and it ran awesome. Recently I rebuilt my engine again this time with an FDO 493. I have 12.88:1 compression, full race cam, 39mm FCR, Ct Race exhaust, etc.. I originally installed a 170 main mostly because of what I've read on these posts. Since installing the main I've had the opportunity to have it dynoed with a sniffer. The results were I was running way too rich! By dropping the main to a 160 I gained over 2 h.p. as compared to the 170! And after adding VP Ultimate 4 I gained another 2 h.p. I am at 50 feet elevation here in California. It was well worth the 40 bucks it cost to use the dyno!

[Paul400ex2002]

165 main
50 pilot
EMP Needle (i think, it's the one sparks recommends)
Not sure on the fuel screw

[skemp]

ttt

[norcalatver]

[QUOTE][i]Originally posted by Colby@C&DRacing



172 main
52 pilot
3 turns out on the fuel air screw
EMR (stock) needle in the stock clip

elevation 2900 ft


C&D, how did you figure the 172 main, and 52 pilot at the elevation you are at? I'm just curious because I was blown away when the dyno read how rich I was with a 170 main jet at nearly sea level!

[MIKE400EX]

Norcalatver,
Probably the fact that your 493 is quite a bit bigger than the others that you're questioning the jetting on is the reason why yours needs a smaller jet. All else remaining the same, the more air the motor pumps, the stronger the signal to the carb will be. The better or stronger signal will pull more gas from the same size jet as compared to a similarily setup smaller CC motor. Anything that changes the vacuum signal to the carb, like cam timing, lift, compression, ignition timing, type of exhaust and porting (and carb size itself), etc.., will also affect jetting to some degree. I think Mickey gave the example that he has to jet DOWN when he puts a stock type EX carb on one of his monster 500's.
There's no denying that a dyno is better at tuning than our butts for 99.9999% of riders.

[86atc250r]

Refreshing to hear from someone that actually understands jetting...

So many times, people's school of thought is "bigger engine, more cam, etc - need larger jets to get more fuel"...

[norcalatver]

Mike400Ex, I also posted that my Dyno tuned 440 by LRD only had a 160 main jet at sea level. Is that considered large displacement also? 440 is a smaller jump from 400 than 493 is to 440. My other 400ex has a 10.5:1 piston, T.C. all around cam and only has a 155 main jet. That is per Tom Carlson of T.C. Racing. What main are you running? I guess all I'm trying to do here is factually find out proper jetting technique. I'm just thinking there's a lot more h.p. for those who are jetted so fat!

[thomas]

If you guys run your fuel screw at 2+ turns out you should consider a bigger pilot jet. 1.5 - 2 turns out is the range you should run at. In my Ex I put in a 60 pilot, my KTM runs a 52. I highly recomend doing the BK mod (1-1.5 sec squirttime) before you play too much with pilot and fuel screw. The BK mod will make throttle response more "snappy".
If you encounter backfireing on deceleration, you are also lean on your pilot, turn out your fuel screw until it goes away, and change pilot acordingly. BTW needle will affect your pilot and main jet settings, so make sure you start with the proper needle.

[400exBro]

this is some good info... keep it coming!!!!

anyone have suggustion on a 425, open air box lid, full exhaust porting, 11.1 comp piston at about 980 feet above sea level?? i have a 39mm carb for a 400ex.

[MIKE400EX]

86atc250r
If I havn't gotten it by now I doubt I ever will. My father helped me jet my first "project" in '64 <<<< that's not a typo either! LOL :eek2:

[Hoodeye3]

I also started running my FCR with jetting suggestions off the forum (as a baseline) I purchased mine used so the inital settings were way off. I have now dialed mine down to the following
Main=160
Pilot=50
Needle=EMT (3rd clip down)
and my C&D fuel screw is set at 1 turn out, I need to drop my pilot down to a 48 here because I have minimal adjustment.
These settings are on a 416cc 10.8-1 built motor with pretty much all the normal mods (airbox K&N, CDI, slip-on & stage 2 cam)
I run my machine at an average ALT of 5,000ft . Its good to see that norcalatvers settings are paying dividends!

[JD400exrider]

Mods

416 10.8-1 piston
HRC Cam
Porting
EHS air box lid
CHM slip on with power bomb


Main 168
Pilot 52
Clip In Stock Post. ?
C&D Fuel Screw 2 3/4 -3 turns out
50' elevation (Ride allot at 2000-3000' elevation)

[JD400exrider]

Norcal dave

You also have larger valves on your 493 and your old 440 too. That may be making a difference. I am going to take mine over to CHM and have them dyno it also. That will give a good read for allot of people on here too. :cool:

[skemp]

One reason many owners of 4 strokes are disappointed in the power is that they have very rich jetting. Unlike a 2 stroke, 4 strokes will run quite well over a relatively broad range of fuel supplies. I've taken a guys quad down from a 195 to a 152 main and never seen anybody happier. He put a pipe on it and kept throwing more gas at it until it was literally choked. He thought the motor was cooked. The thing ripped like it should after getting the main down to where it should be.

I know there's more FCR owners out there... :) Good info so far. This will really help those looking for a baseline. Now if we could just teach people to use the search feature. :blah:

[norcalatver]

[QUOTE]Originally posted by skemp
One reason many owners of 4 strokes are disappointed in the power is that they have very rich jetting. Unlike a 2 stroke, 4 strokes will run quite well over a relatively broad range of fuel supplies. I've taken a guys quad down from a 195 to a 152 main and never seen anybody happier. He put a pipe on it and kept throwing more gas at it until it was literally choked. He thought the motor was cooked. The thing ripped like it should after getting the main down to where it should be.

I know there's more FCR owners out there... :) Good info so far. This will really help those looking for a baseline. Now if we could just teach people to use the search feature. :blah: [/

Exactly Skemp! I don't think any one here has done a W.O.T. plug check let alone a dyno run to check for proper jetting.

Jd400EXrider is the person who told me where to dyno my quad. I think he'll be amazed when he finally makes it to the dyno and realizes how much power he is losing due to improper jetting.

[crashinmatt]

my mods include:
426 11:1 wiseco piston
White Brothers "Track" cam
open airbox w/ K&N
and i have a shorty slip-on White Brothers R series

main jet: 175
pilot jet: 55
screw: 2 turns out
needle: it say ocemr on it and it is on the 4th groove from the bottom

i know this jettin is real close to right on, cuz for one it was runnin like a raped ape, and when i tore it down to get the head ported, the whole inside was clean, with a slight brownish to a light tan in color. i could beat many crfs in holeshots (against national "A" riders) locally. now that it is ported, i have the same jettin(not totally done jettin it yet) but the pilot jet and needle position r the same, and the screw a1/4 turn more out. that jettin is only while it was sittin on stand. ill get more tinkerin once i get to ride it.

[pnut420]

If an exaust sniffer is used then the dyno is awesome, but you can get more power onthe dyno by running it a little lean, but running lean n a 440 osnt a great thing to do, I try to stay just a little rich and am going to do plug checks at idle, mid throttle and W.O.T until I get the dyna ingnition and head to the dyno

[skemp]

Thought I'd bring this back up top. :)

[dork]

has anyone put in one of those adjustable pilot air jets from sudco in their fcr?

[JD400exrider]

Originally posted by dork
has anyone put in one of those adjustable pilot air jets from sudco in their fcr?

Never herd of those. Are you sure your not talking about the adjustable fuel screw. I have one of those from C&D and it works great.

[dork]

i'm not talking about the fuel screw. the fcr carb has removable air jets. if you look in the airbox side of the carb you'll see an oval slot at the bottom with two jets recessed in there. those are the air jets and they can be changed. one is for the main jet circuit and the other is for the pilot circuit.

technically, when you change the pilot or main jet, more than 1-2 sizes than stock, you should also change the air jet for the circuit(pilot or main) the same way(up or down). in reality, the pilot air jet is the most noticeable.

there is an adjustable pilot air jet kit that can be turned with a screwdriver as opposed to buying different air jets. that way you can tune the air jet to your pilot. if the pilot is changed without adjusting the air jet, then the pilot circuit fuel curve may be good at 1/8 throttle, and rich at 1/4, or vice versa depending on which way you went. the point is the fuel curve won't be linear which can cause tuning problems. alot of the dirtbike riders have had big gains in low end and response by putting in these kits and playing with the air screw.good fcr info (http://www.factorypro.com/tech/carbkei.html) scroll down the page and there's a pilot-pilot air screw graph that illustrates this

[MIKE400EX]

Dork,
I think that most of the FCR kits sold for EX's, at least those originally sold by Sudco, come with the adjustable pilot air jet. Mine did.

[YLW400]

In what year was that Mike???? :eek: lol

[MIKE400EX]

2002!!! I'm not quite as old as the dirt you ride on - stop rubbin' it in! :mad: j/p

[dork]

I think that most of the FCR kits sold for EX's, at least those originally sold by Sudco, come with the adjustable pilot air jet. Mine did.

thats cool they include it. makes tuning easier. did you ever check your accelerator pump timing and duration? i know that on my yz400 bike the pump squirted for about 4 seconds. i reduced it to about .5 seconds and response is much better, crisper.

[YLW400]

You know I'm just funnin' Mike :D

[pairanutz]

i know the fcr39 is longer than a stock carb-did you guys do any mods to make it fit better -on the front since it doesnt slid in all the way- it just doesnt feel very secure to me -any one else have this problem-the stock one has the notch to hold it from turning -

my carb hits the tank but if i space it up my fender bolts dont line up -

this one has had the bracket tapped so you can use the stock throttle cabel

with 440 kit and k&n airbox lid 55 pilot and 185 main

[skemp]

The FCR39 should fit the stock intake boot just fine. You can put a little oil on the boot to see if it helps slide in a little better. I didn't have any problems.
As for spacing up the gas tank, I just used some pieces of 1/8" thick floor mat on the existing rubber gas tank rests. Plastic still fits just fine.

[pairanutz]

what throttle cabel do you guys run -and if your using stock how are you routing it -mine is getting wore thru from gas tank(i have ims xc tank)i have been told that the extra gas weight is why its doing this-i have it running down the left side of quad because of that metal angle part coming out of carb end

do you guys have bogging problem off jumps or large woops-i have checked float level and it is set properly-installed a dual vent kit and that mixture cabel -still having problems any ideas -thanks chris

[hondafreestyler]

I just got a fcr 39mm ... what is the bk mod?
how much is it?
where do i get it from?

[crashinmatt]

pairanutz - im not sure what cable im usin, but i hear the yfz cable works perfect. as for the boggin, does it do it just when u jump and go through whoops? i know it may sound wrong, but check ur wiring, i had a buddy that when he jumped sometimes, and did stuff his quad would bog or just die. it turned out to be a bare wire by the coil. ut then again it could be something with the carb.

hondafreestyler - the bk mod is basically puttin a stop on the accelerator pump so it doesnt squirt as long. ive heard of this mod on ys426 bike motors, and ones with hard startin and i believe a bog problem. normally the squirt is like 3 to 4 seconds or something, cant remember right off my head. but by doin this, it lessens the squirt to around .5 of a sec to 1 sec. it consists of drillin and tappin a hole on the brace by the accerlerator pump arm, and puttin in a bolt or set screw so that u can adjust the amount of movement the arm allows, and reducin the amount of squirt. i thought this was on www.thumpertalk.com but i cant find it otherwise i would give ya a link.

[hondafreestyler]

sweet thanks bro ...

anyone else have ne more info on this?

[dork]

the fcr's that you guys are using are the 1st design fcr's i thought. they're different than the ones on the 426's and 450's.
.[/quote]http://www.msnusers.com/fcr39s/shoebox.msnw?action=ShowPhoto&PhotoID=1
is your accelerator pump rod and linkage exposed? if so its the 1st design and the specifics of the BK mod on thumpertalk doesn't apply. the theory of reducing the pump duration applies, but the way you do it is different.

[twisted threads]

On my FCR im runing a ....
175 main
50pilot
and stock needle dont know what position the clip is in..I forgot.:D

I do have a little problem with my 440 and I know its a carb problem. I have had my 440 for a few years now and ever since I put my FCR carb on it when ever I do slow wheelies it acts like its running out of fuel or its getting to much fuel...I just spits and spudders. I have tried differend pilots and notting works. I know that my 440 does not run on the bottom as good as it can but after 1/4 throttle watch out and hold on.

The other problem I got is I cant get any idle ajustment out of my carb... Its got to be turned ALL the way in just to get it to BARELY I MEEN BARELY make it idle faster ... it idles fine though.

[K_Fulk]

You ought to try the sparks needle, chances are it will take care of your bottom end problem.

[Quadzilla]

Originally posted by dork
the fcr's that you guys are using are the 1st design fcr's i thought. they're different than the ones on the 426's and 450's.

is your accelerator pump rod and linkage exposed? if so its the 1st design and the specifics of the BK mod on thumpertalk doesn't apply. the theory of reducing the pump duration applies, but the way you do it is different.

I just bought an old FCR 39mm (used, off of a 99 YZ400F). I'd love to know how this one could be adjusted. Anybody know how?