For all the FCR39mm carb owners

[400exRacerX]

Hey,

I just ordered a fcr39mm carb today and I was curious on how easy this carb is to tune for my bikes application. Does it come with jets or do I gotta buy them? And did any of you guys have trouble tuning it in?

Thanks, Norm

[Crowdog]

Mine came with several main jets, but the largest was 165. I have a 416 with 10:8 and I ride mostly at 4500 ft. Went with the 165, then jumped up to 172. Don't have any problems that I know of.....

Jon

Norm the only problem I see you having is not being able to handle the power increase your 416's gonna have..:eek: ;) :D

[shockwave67]

Usually right out of the box is close and sometimes nothing has to be adjusted. Duplicate your current needle setting, 3rd or 4th clip,start at 165 main,47-50 pilot, and go above and below with main until happy,Two air screws to play with,one at the bottom of the carb,one behind the intake adapter, to fine tune the idle and thats about it. Ive installed and worked on a dozen or so and they are pretty easy to work on.
Id love to try a 41FCR! Ive heard mixed reviews as to more power.
Later!

[out4sand]

I just had to rejet it a couple of times to find the right jet to make it work for our 400ex, but that was it. Pretty darn easy really and what a power increase! I had a chance to drag race boxcar at Coos Bay over the 4th of July weekend with a good deal of other 400ex. It's pretty crazy how much of a power increase it makes over just a 416 or even a 440 for that matter.

www.out4sand.com

[Tommy 17]

Originally posted by Rico
Norm the only problem I see you having is not being able to handle the power increase your 416's gonna have..:eek: ;) :D

haha i am not happy with u gettin this carb norm... now ur really gonna kick my @$$ at rausch creek!!!!!! haha i wanna ride ur quad next time... u got so much stuff on it!

[Evan]

Alot may depend on the mods you have and the elevation you ride at but for me I found that the 165 was way to lean. I kept bumping it untill it got black then backed off one. I am at a 170 right now I belive. I am not running a lid. The air screw which is on the bottom is at 4.5 turns out I belive. My carb did not come with jets but you can get them from service honda pretty cheap. They are the same as the stock jets. You will like the FCR its alot better than the lectron I think. Its easy to install, just put the cable in the top hole. Is yours coming with a cable? The hardest part about the whole intallation was the little spring that pops off when you are attaching the cable in the housing. It fits like a glove.

[400exRacerX]

Yeah, I got it all from LRD, the carb was $430 and the cable was $26.95. What do you think my best bet is? Bolting it right up with the settings that its on and see how it runs and go from there? Did your carb atleast come with a jet inside it? Well I should be getting it tomorrow because I got 3 day delivery, I'm so siked about the carb. I heard its a real wake up to a modified motor. I been running my 416 with the stock carb for a couple months now and I thought it was fast, its gonna have even more grunt now.

I'll fill all you guys in on the details once I get it bolted on.

Thanks for all your input I appreciate it, Norm

[nakomis0]

$430 + $27....

Man you guys gotta start getting your carbs from Magic Racing.

Thats the price of thier 41mm, and it comes with a cable to fit your stock thumb throttle.

I hate to talk places up, they kinda shafted me when I bent my steering stem on the first ride... but heck they ussually have the best prices on lots of stuff.

..but anyways.. I'm sure your gonna be real happy with that carb, it will really wake that motor up.

I suggest you put some tread sealant on the part that screws on... I forget if its the intake or exhaust part, but you will know what I mean when you see it. And tighten it real good cause it likes to come loose.

It will come with a needle. You probably won't have to mess with any jets except the main. Start off with a 168 main, and go from there. GL

[400exRacerX]

I got the carb today. I was kinda pissed that I spent almost $500 and I had to assemble part of the damn thing. Then I found out the guy from LRD jipped me $42 for a thumb throttle cable. The carb was a joy getting it out of the shrink wrap. Then I assembled it and used locktite on the exhuast portion of the carb. Set the adjustment on the cable and fired it up. It runs great in the low rpms but once it starts to get to the higher rpms its sputters like a mofo. The 165 is in now, I'll try the 170 tomorrow and if the 170 dont work which I dont think it is, I'll have to buy a 175.

I also noticed that it made my quad alot louder and my gas tank is practicaly sitting on top of my carb?

[hetrick425ex]

before it wares a hole in the plastic tank put something between it like a piece of garden hose and you will haev to turn it sideways to make it fit a little better... they dont fit good at all but they sure work! congrads

[NacsRacing400]

Ya they fit really bad. My cousin runs one and the past few races he has had a problem with it popping off because of the gastank hiting it.

[PsychoDave]

put rubber spacers under the gas tank rails(at the rear of the tank).....it will sit up 3/4 of an inch without a problem.....that should clear it .....

[FullBore52]

Thats what I did to mine psycho dave..works fine. Dont turn the carb sideways, it will run fuel out the over flow....atleast mine did!

[400exRacerX]

Were could i get rubber spacers? And how could I get them to stay in?

[PsychoDave]

CUT A PIECE OF HOSE IN HALF AND TAPE IT ON THE FRAME. yOU COULD DOUBLE UP ON THE HOSE TO MAKE IT THICK. uSE ELECTRICAL TAPE SO IT WONT HURT THE TANK. THE RUBBER STRAPS THAT HOLD THE GAS TANK ON SHOULD BE OK WITH THE MOD

[nakomis0]

Can I ask .. What the **** are you guys talking about?

Rubbing on the gas tank? I don't recall mine rubbing. I have had it apart a bunch.

Did you notch out the snorkle like your suppose too? Thats all I can come up with. Maybe you didn't notch that and it sits higher. ... Or maybe it just rubs?:huh

[400exRacerX]

I dont have a snorkel anymore.

[400exRacerX]

I can't seem to get this thing to run right. I have went from a 162 to 165 to 168 to 170. It seems like its running rich because when its at low rpms and I cracked the throttle wide open it just bogs right out. But if I gradually work it to about 2,000 rpms and then crack it wide open when it hits mid rpms there is a huge hesitation and then hits full throttle. It doesnt idle right either, it idles way too low and I have a valve tap when it idles that low.

So it looks like I have alot of tuning to do before I can go riding.

Any tips would be appreciated.

Thanks, Norm

[Tommy 17]

send it to me;)

[slates74]

This is off my friends website. He has a ported 425ex

The carburetor will be changed to a Keihn FCR (Flat CR) 39mm race only model. This is the recommended carb for modified 400s from both LRD Racing and Sparks Racing.

The FCR as jetted by LRD has been dyno tested by them with claims of 3hp gain across the entire power band over the Edelbrock Quicksilver. No comparison data is available against the Lectron 36 or 38mm models or stock carb. The carburetor has been sourced, used, from Tommy Tantillio District 34 expert rider #112. (The carburetor was installed and running unsatisfactorily on Tommy's 425. Tommy installed the LRD recommended main and pilot jets and made the recommended air screw setting. When installed as is on our bike it ran poorly at low and mid range but worked well on the high end. Without time to dial it in it was removed and replaced with the stock unit equipped with a 172 main jet, a 45 pilot jet, and air screw at 1 and 1/4 turns. This report will be updated upon further testing of the FCR). !!!!!UPDATE JULY 30, 2001. After hours of test time we have the FCR to a usable state. We used a 162 main, 50 pilot, air screw of 2 turns, rod clip in center position. We also had to open up the fork adjustment on the actuator arm of the accelerator pump. There is still a slight lag punching the throttle from idle but does not affect racing. After the first race, rider reports significant change in mid to upper power as though we did another motor build up. This was well worth the effort as the flow of the rest of the motor needed the additional intake flow.

[400exRacerX]

Interesting,

Mine runs like crap on low rpms and has a huge gap in the mid rpms also and I got it from LRD.

Thanks alot Sean!

[Evan]

I am not sure what to tell you. What alt are you at? I would suspect your mods are close to mine, at least when I had a 416, I had a 170 in it and it ran a tad rich, 168 was close to perfect but I would rather error on the rich side so I put the 170 in. Then turned the air screw thats on the bottom 4 1/4 turns out so that its slightly rich at a 1/4 throttle I belive. I am not sure what pilot came in it but I didnt change it, most likely a 45. Mine came from Sparks for 450, it also cam with the cable, and was fully assembled. The only thing I can tell you is maybe its not assembled right if this combo that I have isnt even close.

[nakomis0]

You can also call Keihen, I called them once about how many turns on the air screw. I can't remember correctlly but i wanna say it was something like 1 and a 1/4 turns. The guy was real helpful.

[400exRacerX]

Well I am going to mess with it once more today. I have only messed with the main jets so far. I am going to try messing with the mixture screw and maybe the idle screw?

[James70214]

400exracerx
Do you race at all. Theonly race I know of that you did was MT. Morris. Why don't you do any local races?

[400exRacerX]

I havent done to much districts this year because I have been having a ton of problems with my bike latley.

I got it to idle today.

Now the only problem is, it has a huge hesitation in the mid rpm range,, I'd say around 1/2 throttle.

What do you think I should adjust?? The needle or air screw??

Thanks, Norm

needle

[FullBore52]

adjust your air screw if you havent yet. If it was still in the shrinkwrap when you got it, it is probably all the way to one adjustment. Mine was all the way out to make it lean, REAL lean...Cooked a piston lean. So whatever way makes it richer, thats the way to go. Then if that doesnt help it at all, move the clip on the needle down, raising the needle...later man, good luck

[Evan]

All the way in is lean, on most. I belive.

I would try the air screw b4 the needle.

BTW mine doesnt have any problems fitting under the tank, has about a 1/4 inch to spare.

[400exRacerX]

Is the air screw right next to the main jet plug????

I think thats were it is. And my dad says the carb is a pos because you cant adjust the mixture while the quad is running becasue the screw is on the bottom of the carb.... am I right is this were the air screw is located??

Norm

[nakomis0]

Dood call this number. (323)728-5407 (sudco)

I really don't think you wanna mess with that screw to much.

That screw isn't meant to be played with. Stop guessing, call them, in less than 5 min. they will get you somewhat straight. Then just mess with the only jets you should be touching. Pilot, Needle and Main

Good Luck.:macho

[Colby@C&DRacing]

The screw that you are refering to on that carb is a fuel srew not an air screw. It regulates the amount of fuel that pass thru the pilot curcuit were as an air screw controls the amount of air that pass thru that curcuit. The best way to tell the difference between the two is that a fuel screw is on the motor side of the carb and an air screw is on the filter side of the carb. Settings for that carb are pretty close for most people at a 50 pilot, the needle in the center, a 168 main jet and the fuel screw out 2 turns. If you have to go much more out with the screw than that you needle to run a larger pilot jet. As far as the bog that you get when trying to stab the throttle all the way in from idle when the bike is not in gear or with the clutch in will always happen with that carb. The fcr carb opens very quickley and lets in a large amount of air this cause it to lean out the air fuel mixture way to much for just an instent. This should only happen at a no load condition. If this happens when you are riding the bike turn the fual screw out 1/2 turn and that should help.

Sorry for the book but just trying to help I have had alot of tuning time with these carbs

[sieg400ex]

Hey I found this post a little while back. It should help you out because it has a step by step procedure. Sorry its long.

I have similar engine mods as you...416cc JE 10.8 piston, XR400 cam, 39mm FCR, run either a K&N or a UNI filter, but with the stock head pipe and a FMF Powercore Q. My jetting for sea level includes a 52 pilot, needle on the third groove, and a 165 main. With this setup my jetting is dead-on perfect. You should be okay with a 50 pilot depending on your elevation, but I think you're way off with the main jet and needle clip position adjustments.

First of all, you are way lean on the needle. When you raise the clip position on the needle (top position) that's actually the leanest setting for that particular needle. Raising the clip lowers the needle into the needle jet, which allows less fuel to flow past it. Conversely, lowering the clip down on the needle raises the needle in the needle jet, which allows more fuel to flow past it. With the clip on the top position, this is most likely the reason it stumbles and why you have a huge dead spot above 1/8-1/4 throttle. Anyway, if you feel it's running lean between 1/4 and 3/4 throttle, richen that circuit by lowering the clip one notch and see how it performs. With my setup the standard setting for the accelerator pump on the FCR is just fine, and I don't have a stumbling problem at all. Also, given your mods, I'd be surprised if you really need that large of a main.

Here's what I suggest... First, change the clip on the needle back to the 3rd position. Second, if you have a 52 pilot handy, install it. Third, if you changed the spring on the accelerator pump, put the original back on. Install a 170 (or so) main jet. Lightly seat the air screw (the one on the airbox side) and then set it to 2 turns out. Then lightly seat the fuel screw (engine side) and then turn it to 2 1/2 turns out. Now start up the engine and let it fully warm up.

Adjust the fuel screw (engine side) by first turning it out until you notice a decrease in idle speed, and then in until you notice a decrease in idle speed. Note the range between these two points. Find the spot in this range where you get the best off idle response when "slightly" wicking (opening) the throttle. If you end up more than 3 1/2 turns out go a size larger on the pilot, and if you go in less than 1 1/2 turns go a size smaller.

With the needle on the third groove, see how it runs from 1/4 to 3/4 throttle If it feels lean, lower the clip to the 4th position. If it runs too rich on the 4th position, go back to the 3rd position and now look at adjusting the accelerator pump so it pumps quicker. Since I've never had to adjust mine, the only help I can suggest is to call Sudco at 323-728-5407. They've always been helpful when I've called and can probably provide you with instructions/options on how to do this.

Lastly, once you get the 1/4 to 3/4 range dialed in, move to the main jet (3/4 to WOT). The best way I've found to dial in the main is to use a method I call "purposefully over-jetting". Start with a large size main and do a run with the throttle above 3/4 and the engine under load just under the rev limiter--you'll know if you're too rich when the engine blubbers similar to running with the choke on. Also, make sure you can distinguish the difference between the blubbering condition and hitting the rev limiter. Once you know you have too large of a main installed, do a high speed run just under the rev limiter and then do a plug chop by quickly killing the engine and pulling in the clutch at the same time. Coast to a stop, pull the plug, and check the porcelain for a light brown color. Keeping doing these runs and going down in main jet sizes until the blubbering condition goes away and the plug reads light brown--once you get to this point the main is perfect. Also, keep in mind that clean burning fuels will make it very difficult to get a good plug reading. When I jetted mine, I ran a 75/25 mix of 111 octane leaded race fuel to 92 octane premiuim (the lead in the gas will help give you a correct plug reading).

Hope all of this helps...

[400exRacerX]

Wow,,,thanks.....I never thought it was gonna be this complicated.

[TDBRPH]

Currently I am running a JE 10.8:1 87mm piston with XR 400 cam, play porting, 2 inch hole in air box lid, stock headpipe with fmf PC IV slip on..... I am running a 39mm FCR. Upon 1st installation of the exhaust I put in a 52 pilot and a 168 main jet and the bike ran well through the powerband (except for bog when under no load at idle) but had a blubber at the top which didnt appear to be the rev limiter. I then up the main jet to a 170 which improved the situation but didnt solve it completely. No one had a 172 main so I put in a 175 for kicks which I knew was too much and the bike ran well up to 1/2 to 3/4 then it bogs severely. My question is do you think a 172 main will cure the problem or will I have to adjust the needle or air/fuel screw which are things I have never done before. I dont quite understand how the bike is responding b/c I thought the main jet would really only affect 3/4 to WOT. Any tips would be greatly appreciated.

Thanks
Triston

[400exRacerX]

All my problems are over, I finally got the SOB tuned!

I called sudco up twice, the people there are very nice and know what they are talking about. My mid range problem was the needle, I had to lower the clip and raise the needle. And my low range bog was my air screw. The air screw was in way too far.

If you are having problems tuning your fcr too, call sudco and ask for Eric in Tech, hes the man to talk to.

Norm

[TDBRPH]

Newbie carb tuner question. Is it hard to change the needle and clip settings. What is the proper procedure? Are there any on-line diagrams?

Thanks
Triston

[TDBRPH]

BTT

[Giz400ex]

For a person that just got the carb I was wondering your opinion on the carb??? Compare to before and after??

[400exBro]

so norm how does she run?????
if i do the 416 some time, i wana either put the kehin (sp?) 41mm or the sameone you put in....
thanks
Bro

[400exRacerX]

Well to tell you guys the truth I really cant say too much about my power gains yet.

I got it tuned and running good, but only took it up and down my 100ft driveway a couple times hitting 3rd. So I really havent been able to test the power out yet. I meen I did notice a difference in throttle response and pick up, it also seems tto get up and go alot faster. The first thing I noticed is it makes your quad 10 times louder.

I'll get a good ride on it tomorrow and let you guys know.

BTW this carb is by far alot easier to tune than the stocker.

To change the needle setting, take the top cap off the carb (were it says "flat CR"), then look for the allen head screw, unscrew that, tilt the carb so the needle comes out, change the clip setting, drop the needle back in, tighten the allen screw, and put the top of the carb back on,,,,,,,very simple.

Norm

[nakomis0]

Dood, you bike is gonna rip!:blah :D