fcr adjustment please help

[neals03400]

i have a 03 400 ex with hetrick pipe 11:1 piston stage 2 hot cam ported head and just installed a 39 fcr carb. it hesitates when you accelerate hard. were should i adjust to fix this.

[lilpoppy]

I have had it for a while and I havn't been able to get rid of the hesitation when you go wide open throttle from a stand still. I have talked to many people including engine builders and they say this is normal but a few people on here clain that they have been able to get rid of this but they don't have any explanation as to how to actually get rid of it. As long as it doesn't do it during normal riding it might be something that you have to learn to live with. I have gotten used to it and even found way to get around it without it stalling at all. Basically I just give it a few quick revs before I punch it and it seems to be fine.

[hondaracer31]

Have you guys tried adjusting the accelerator pump? On mine I got rid of the bog. Everybody assumes that when it bogs it isn't getting ENOUGH fuel, but on mine I found it was getting TOO MUCH fuel! The accelerator pump was basically flooding it as soon as I hit the throttle. I leaned out the pilot one size and it fixed it.
Try disconnecting the rod that activates the pump and see if it still does it. If not then you know it's getting too much fuel.

Hope that helps!

[lilpoppy]

I will give that a shot but I know absolutley nothing about carbs. I dont know where the accelerator pump is and I have no idea what it looks like. Where is it located?

[hondaracer31]

On the right side of the carb. On the wheel where the throttle cable hooks to there is a rod with some bends in it that goes into a little rubber boot on the right side of the float bowl. Just pull the little cotter pin out on the inside of the wheel then pull the rod out of the wheel and try it then. If you ride it like that be sure to pull the rod out of the boot! There is nothing holding it in there. (I don't want you to lose it!) If the bog is gone hook everything back up and try a leaner pilot jet.

[lilpoppy]

Ok thanks I will give that a shot.

[Mxbubs]

Originally posted by neals03400
i have a 03 400 ex with hetrick pipe 11:1 piston stage 2 hot cam ported head and just installed a 39 fcr carb. it hesitates when you accelerate hard. were should i adjust to fix this.

This is from www.motoman393.thumpertalk.com.

It worked wonders for my carb.

__________________________________________________ _

BK Carb Mod Info/Procedure

Info:
This accel pump mod is ONLY for the 00'-02' YZ426, 01'-02' YZ/WR250F and 00'-02' WR400/426) this WILL NOT work on 98-99 YZ400's and 99 WR400's. When this mod is done correctly is will make your bike run and start better. It also will give quicker throttle response and eliminate the bog off the bottom. Your jetting will most likely need to be richened up since this mod shortens the duration of gas sprayed (from 1.7 secs stock to .3 secs)

The Procedure that Brian Kinney gave me:


Brian Kinney is Tim Ferry's Factory mechanic (and the originator of the BK mod) and these were his instructions...To limit the accel pump spray length you must drill and tap the pump cam stop and install a 4mm screw/spring combo. That will contact the pump cam. A hex socket bolt works well approx. 25mm long. Remove the subframe so you can look down the throat of the carb and with a stopwatch time the length of the pump spray when you stab the throttle. I usually click the stopwatch at exactly the same time I turn the throttle and click it again when I see it stop. It may seem weird but it works! Also you need to adjust the pump timing screw so that it does not hit the slide when it is raising. The timing is close when the spray just misses the slide. Then set the duration of the spray to .3 seconds with the adjustment screw you just installed. This may sound comlicated but is the only way to get rid of the pesky bog off the bottom.
Helpful Tips from me:

You dont have to use a 4mm bolt I used a 6-32 1" long flat head screwdriver bolt. I also used a spring out of a pen that you write with. My stock pump timing was around 4.5 secs and now it is around .35 secs (maybe that was why is flooded easy and was sometimes hard to start when hot?) Also when drilling put a piece of metal (like a hacksaw blade) inbetween where the drill bit will poke through and the black pump thingamajig LOL. The squirt of the gas was also off on my bike...it should spray gas so that it just clears the slide...but mine sprayed when the slide was about halfway up the stroke!

Just by starting up the bike I could literally "feel" the difference, it felt like the snap of a 250 2 stroke and didnt have any bog whatsoever! You will really be amazed by what $4 does to the performance of this bike! The jetting I ended up with: 168 main, 42 pilot (1 3/4 turns out), needle in middle position.

[Mxbubs]

BK MOD

[lilpoppy]

I will check that out but it sounds kinda confusing. I don't know the names of all the internal parts of a carb so I guess that is why I'm so confused.

[400exRacerX]

I got the fuel screw from C&D racing and it worked wonders for my fcr39mm. I still have a slight bog when cracking the throttle from idle to wide open. I cant get rid of it, otherwises my carb runs smooth.

[Hoodeye3]

So you have tried this on your 400ex Bubs, and It worked for you?
If so what differences did you notice?

[400exRacerX]

Mxbubs fcr is different than ours and hes got a yz426.

[Mxbubs]

Im not sure, you'll have to do some research.

All I know is my carb is the 2000 model FCR. It should be the same. Read the above info, it tells you what year's fcr this will work with.

Better yet, email Yamaha mechanic Brian Kinney.

No, I lost his email, you can search google and find him Im sure.

[neals03400]

i fixed the hesitation by playing with the fuel screw and the air screw under the intake manifold. u need to leave the 2 screws out of the intake and adjust the air screw first and then adjust the fuel screw. i dont know if the adjustments are correct but it runs great with no hesitation at all.

[lilpoppy]

I'm not really sure what two screws under the intake manifold you are talking about.

[shamisc]

He's talking about the 2 screws that hold the bell housing on the air filter side. There is an air adjustment screw in there.

[lilpoppy]

I still dont know which screws you guys are talking about. They only two screws I can find are two little gold ones and one is right next to the float bowl and the other is kinda off to the side and under the float bowl. Are those them or am I looking in the wrong place?

[lilpoppy]

Well i tried those two gold screwd and those werent it so odviously i have not idea where to look.

[hondaracer31]

You're looking in the wrong place....On the back of the carb where the boot from the airbox clamps on. If you take the boot of and bend it out of the way there are 2 holes in the carb, at the very edge on the bottom inside the carb. The hole on the left is the "main air jet". THIS IS NOT AN ADJUSTING SCREW!!!! However, the hole on the right has a screw in it which adjusts the air mixture, turning it in makes it richer (less air) and turning it out makes it leaner (more air). You can adjust it without taking anything apart by taking a small flat screwdriver and grinding it down till it will fit in the hole without binding.
Good luck!

[hondaracer31]

The other screw is the fuel mixture screw. It is on the bottom of the carb right in front of the plug you take out to get to the main jet. This screw adjusts fuel, turning it in makes it leaner (less fuel) and turning it out makes it richer (more fuel). The two screws affect different RPM ranges but only below 1/2 throttle.

[lilpoppy]

Ok thanks I deffinatly have a better idea where it is at now.

[bmw500hp]

Very informative post bubs! :)

[JabberJaw]

Originally posted by lilpoppy
I still dont know which screws you guys are talking about. They only two screws I can find are two little gold ones and one is right next to the float bowl and the other is kinda off to the side and under the float bowl. Are those them or am I looking in the wrong place?

All this talk of screwing, float bowel, gold ones, two screws and looking at your Avitar... I'm kinda dizzy.

[Extremeracer167]

lilpoppy,
i dont think they are talkin about the same carb. Cause on my FCR 39mm i dont have those screws.

[lilpoppy]

I think I know what they are talking about. I had myne apart but i had to put it back together real quick so i didnt have a chance to look but there are two little holes right at the intake of the carb and I'm guessing if i look inside those i will see a screw. I'm gonna check it out tomorrow. and I will let you know.

[MIKE400EX]

If someone can tell me how to post a .htm file on here I've got a good article on how to adjust the FCR's. It's got pictures, every format I try removes them. The website that it came from is no longer available.

[Extremeracer167]

man someone tell this guy how to do that, this article could come in use for me for the race. If not, can u e-mail it to me at yota1524@hotmail.com thanks, it would ALOT!!

[MIKE400EX]

Extremeracer167 >>> You've got mail! Tell me if it works.

[shamisc]

SEND IT TO ME TOO MIKE 400EX! It's always good to have info!!! THANKS. :eek2: :cool: shamisc@yahoo.com

[Hoodeye3]

Ditto! I would really appreciate it Mike Ive searched the web on FCRs and I have only been able to find marginal info on them.
hoodeye3@msn.com Thanks J.

[Extremeracer167]

well i cant get the pictures to work, but onc ei get time to read over it thoroughly im sure it will help. The piece on the fuel mixture screw i think is gonna be the ticket. Thanks ALOT MIKE!!!!:D

[lilpoppy]

E-mail it to me to if you have a chance please.

[MIKE400EX]

LILPOPPY What's your email address?

[lilpoppy]

oh ya that would help huh. lilpoppy23@yahoo.com
thanks.

[Doibugu2]

Mike, I know this is old but if you still have it that would be great.

Dberry@corp.phoenixintl.com

[jimboatv]

Hey If you Guys go to www.ducatitech.com/2v/img/fcr_graphs you can get some detailed information on FCR carbs.

[Quadzilla]

Here is the fix for the older style FCR carbs with the external (rod, etc not covered) accel pump. Simply go down to your local hobby shop and pick up a pack of 3/32 rc car wheel collars (I paid $1.59 for them, yes under 2 bucks!). Disassemble the accel pump (mentioned ealier in this thread). Mount the wheel collar on the accel pump rod between the accordian boot and the lever and insert and tighten the lockdown screw supplied w the wheel collars. This will limit the range of motion on the accel pump rod and is adjustable by moving the collar up or down the rod. After reinstalling your carb, look in the carb when you open the throttle up all the way to see how long the accel pump squirts gas for. It should be less than one second vs the 3 - 5 seconds that it is standard. If it's still longer than that, adjust the collar to make it shorter. THIS WILL FIX YOUR BOG PROB!!!

[Quadzilla]

Pic of the older style FCR with the external accel pump (not behind a plastic housing. The mod that I described above is the fix for these style FCR's....

http://www.exriders.com/vbb/attachment.php?s=&postid=493839

[moto93]

Originally posted by Quadzilla
Here is the fix for the older style FCR carbs with the external (rod, etc not covered) accel pump. Simply go down to your local hobby shop and pick up a pack of 3/32 rc car wheel collars (I paid $1.59 for them, yes under 2 bucks!). Disassemble the accel pump (mentioned ealier in this thread). Mount the wheel collar on the accel pump rod between the accordian boot and the lever and insert and tighten the lockdown screw supplied w the wheel collars. This will limit the range of motion on the accel pump rod and is adjustable by moving the collar up or down the rod. After reinstalling your carb, look in the carb when you open the throttle up all the way to see how long the accel pump squirts gas for. It should be less than one second vs the 3 - 5 seconds that it is standard. If it's still longer than that, adjust the collar to make it shorter. THIS WILL FIX YOUR BOG PROB!!!

So the collar will fit under the boot?

[Quadzilla]

On the pic, the carb is upside-down, so if you go by the pic, it would be below the accordian boot. It you are holding the carb right side up, the collar will go on the rod above the accordian boot. While you are doing all of this, it's a good idea to put some clear RTV Silicone (permitex makes some sold in most auto supply stores) aorund both ends of the accordian boot to prevent dirt from getting into your accelerator pump.

[hondafreestyler]

Mike if you could ... if you still have ... plz email me that information ..

hondafreestyler@hotmail.com


Also ... im not totally sure what kinda fcr 39mm carb I have ... old or new ... I can't post pics ... can I email someone a pic and they could post them for me? and help me out?!!?!

[dork]

on the early 39's, the accel. pumps have a tendency to rust up under the rubber boot and stop working all together, so its definitely a good idea to clean it out and seal the boot with RTV like Quadzilla said.

if the right side of the carb looks like this,http://www.msnusers.com/fcr39s/shoebox.msnw?action=ShowPhoto&PhotoID=2[/IMG] then you have the 1st design and the RC collar mod will work.

[cals400ex]

Originally posted by Quadzilla
Here is the fix for the older style FCR carbs with the external (rod, etc not covered) accel pump. Simply go down to your local hobby shop and pick up a pack of 3/32 rc car wheel collars (I paid $1.59 for them, yes under 2 bucks!). Disassemble the accel pump (mentioned ealier in this thread). Mount the wheel collar on the accel pump rod between the accordian boot and the lever and insert and tighten the lockdown screw supplied w the wheel collars. This will limit the range of motion on the accel pump rod and is adjustable by moving the collar up or down the rod. After reinstalling your carb, look in the carb when you open the throttle up all the way to see how long the accel pump squirts gas for. It should be less than one second vs the 3 - 5 seconds that it is standard. If it's still longer than that, adjust the collar to make it shorter. THIS WILL FIX YOUR BOG PROB!!!


you have any pics with this mod done? i am not sure what the 3/32 wheel collars look like.

[Quadzilla]

Correction, the collar goes under the accordian boot on the rod about .6mm above the carb housing. For pics of this go here:

Click Me (http://www.husaberg.org/modules.php?set_albumName=album57&op=modload&name=Gallery&file=index&include=view_album.php)

[cals400ex]

Originally posted by Quadzilla
Correction, the collar goes under the accordian boot on the rod about .6mm above the carb housing. For pics of this go here:

Click Me (http://www.husaberg.org/modules.php?set_albumName=album57&op=modload&name=Gallery&file=index&include=view_album.php)


i am not sure what a block connector is?? is that the part i need to buy from a hobby shop?

also, do you use the skrews to tighten the conector down so it says about .6mm above the carb housing?? when you say carb housing, you mean the the connector doesn't go into the carb at all but around .6mm away from hitting the carb?? thanks for the help, as you can tell i don't have a clue. :p

[moto93]

Originally posted by Quadzilla
Correction, the collar goes under the accordian boot on the rod about .6mm above the carb housing.

That's where I was thinking it went, I didn't see how it would do anything above the boot. Thanks for clearing that up.

[Quadzilla]

Originally posted by cals400ex
i am not sure what a block connector is?? is that the part i need to buy from a hobby shop?

also, do you use the skrews to tighten the conector down so it says about .6mm above the carb housing?? when you say carb housing, you mean the the connector doesn't go into the carb at all but around .6mm away from hitting the carb?? thanks for the help, as you can tell i don't have a clue. :p

You can use a block connector from radio shack or a 3/32 wheel collar from a Hobby Shop or Hobby Web Site. Under $2 for the part plus another couple bucks to whip it if you get it from a web site. Well worth the price of under $5 for a bog fix!!! :-)

[Doibugu2]

Alright, I finally got to ride my quad a bit this past weekend and think I have the bog.

But mine seems to come on when I'm in like 2nd gear going prettly slow, then stab the throttle. It bogs really bad, I let off the throttle and then get right back on and its fine.

Is that what you guys have. I don't seem to have the bog in first gear though.

[Quadzilla]

The motor can rev up faster in first. The bog will be more pronounced in upper gears when whacking the throttle open from down low. The BK (on 40mm FCR's) and the Taffy (on 39mm and 41mm FCR's) mods will fix this. Thumpertalk.com is a good source for how to do it. This thread has most of the needed info if you take the time to read the whole thing...

[TC426EX]

I just wanna say this was a great thread!! It really helped me get my FCR running mint the way its supposed to!

[EPDP99]

Ok, I know this is old but if someone has that e-mail about adjusting these carbs that would be excellent. EPDP99@aol.com is my e-mail address. Also does anyone know where i can get a manual for 41mm FCR. I bought one used and have know idea on this. I found this thread by searching and this is the best one with info so dont tell me to do a search. I am also looking to put in the white bros fuel adjustment screw so I dont have to take the carb off to adjust it. also i would like the manual before i try the accelerator pump adjustment thing. I know there is a aftermarket thing that screws onto the bottom of the accelrator pump to fix this problem, would this be a better route to take??

[EPDP99]

here is the link for the bolt on fix i was talking about:

http://www.mxsouth.com/factoryrd/fac11p-38li.htm

Let me know what you think.

[EPDP99]

bump

[dork]

the p-38 is just a redesigned accelerator pump cover that has a higher pump stop machined into it to reduce the squirt duration. you could do the same thing with washers, put them under the pump diaphragm. or you could use the RC car wheel collars like some members here have done on the pump shaft above the bowl.

i welded a small nut onto the arm that rests against the plastic pump arm and threaded in a screw with a spring(like an idle screw) that pushes against the pump arm. this way you can adjust the squirt duration infinitely to dial it in. it works great. you can even turn off the pump with the screw so nobody can flood it out if they're playing with the throttle(kids) or whatever. most of the aftermarket fcr's have a 3-5 sec spray. you only need like .5-1.5 seconds.

the reason its so long is because these carbs were originally designed for superbikes with 4 carbs and one carb was built with an accelerator pump to feed the other 3, so it needed a healthy squirt.