FCR41 Nightmare!

[zukicyw101]

I have an 89 dominator 650 motor (in a chopper/bobber frame). I just rebuilt it boring it to a 675cc, hot cam stage 1, performance rod and a kicker setup off of an old xr600. At the same time I installed an FCR41 and can not get this thing to run. It does have an airfilter simler to a pod filter and some pretty open pipes so I anticipated having to richen it up some but this thing is running super lean. It also has trouble idling even though I have the idel screw all the way maxed out. There is some obvious education on my part as this is the first flatslide I've owned. I've tried the following with no positive result:

50 slow jet

Multiple adjustments on air screw

OCEMR needle on 3rd, 4th, 5th, etc clip

170 main all the way up to a 230

Got JD tuning guide and figured out I needed to try different needles.

48 slow jet

Air screw 3/4 turns out

FMS 2 turns out

OCFHR needle on the 6th clip

230 main

= LEAN!

55 slow jet

Air screw 3/4 turns out

FMS 2 turns out

OCFHP needle on the 7th clip

230 main

= LEAN!

I've been pulling the plug after each run to see how it is and is super white. I don't dare ride it more than a mile or so in fear that I'll burn this motor up (again). It doesn't pull like it should. My best result was when I drilled out the slow jet to a 1.016mm (#60 drill) 170 main with the OCEMR on the 5th clip. Ran rich as hell at the bottom but pulled like a tractor and had no issue bringing the front wheel up. Plug looked pretty good but thats obviously a crazy size slow jet. That's when I tried the other setups above. I've checked for any vacuum or intake boot leaks and came up with nothing. I'm seriously struggling with this one and any help would be great! I'm sure I'm missing a bunch of info so ask all the questions you need to to help problem solve. Thanks

[heart_of_darkness]

What carb adapter? Can you try a different FCR, or try that carb in some other bike?

[zukicyw101]

I bought the kit from pro cycle so the adapter that came with it matches an xr650l. I don't have another fcr but I do have the stock cv carb.

[Horri]

Is the hotstart button in it's hole on the side of the carb??/

 

Is the choke button in its hole on the side of the carb??

 

If either are missing you will not get the jetting right. When I made the mistake of no hotstart in the FCR the carb ended up

being jetted the same as the stock XR600 carb I had in it previously at 165/65. With the hotstart correctly in its place I am now

at 160/45 in the FCR.,,,NCVT needle,,Clip 2 down from blunt , leak 45..starter 68 . Fuel screw 2 turns out.Your jetting sounds way out of whack.

I also have no idea what the OCEMR or any other needle starting with O are in relation to the NCVT,,NCVR needles,,DotCom probably does,,I don't.

Edited May 4, 2014 by Horri

[mastera210]

Like Horri said hot start plunger must be closed. Mine was driving me nuts was wanting big pilot found out was missing the slow jet? the one that is in the intake side of carb. Also the slide plate was upside down!

[jjast]

First we need to find out If it is a FCR"slant" or a FCR-MX, how many screws/bolts holding on the bowl? 3=Slant 4=FCR-MX, I am thinking that since you got it from ProCycle that it is the Slant,

If I were you I would run the SLOW AIR JET just cracked open. run the 48 pilot, fuel screw 1.5 turns out,170 main.

It's still probably not going to run right with the OCEMR needle so most importantly get a rich NEEDLE.

my bike runs crappy lean on the bottom (and crappy throughout) with the OCEMR needle.I'm running a needle I got from Yamaha NCVQ , I'll bet the needle will clean things up, I am giving you advice on what you have on hand (except the needle) and this probably wont put you spot on for jetting and you'll need to go from there but I bet the bike would at least be ride-able.

I'm still playing with my jetting (Slant carb, tuning with a wide band O2).

that SLOW AIR JET can change the AFR by 2 points or more throughout the throttle range up to full throttle and it's pretty sensitive.

according to the "calibration chart" the SLOW AIR JET drops off before half throttle but my hands on and O2 reading say otherwise.

Edited May 4, 2014 by jjast

[zukicyw101]

Horri & mastera210,

This is a slant (3 screw on the bowl) not an mx. I checked all the "blank" holes and castings on the carb thinking it was missing something but everything is closed. Also the "OC" are standard Keihin aftermarket needles. Using the OCEMR as the starting point and keeping all the jetting the same JD's tuning guide shows that the OCFHR is slightly leaner at 0 - 1/8 throttle and more rich from 1/4 throttle up from the OCEMR. The OCFHP is slightly richer at 0 - 1/8 throttle and more richer from 1/4 throttle up from the OCEMR.

jjast,

Stock it came with the setting you recommended (except a 50 instead of a 48) and it was super lean and wouldn't even idle. That's why I started drilling the slow jet to richen up the bottom end.

[zukicyw101]

The latest run was:

55 slow jet

Air screw 2 turns out

FMS 1 turn out

OCFHP needle on the 7th clip

185 main

It idled ok but would stall randomly. I restarted it without hitting the throttle and it would start back up. I did this for over 5min and then pulled the plug. Not bad, looked kinda lean but still wouldn't idle correctly. I took it for a run (less than 2miles) keeping it at 1/4 throttle 98% of the time. Pulled the plug and it was VERY white!

[jjast]

jjast,

Stock it came with the setting you recommended (except a 50 instead of a 48) and it was super lean and wouldn't even idle. That's why I started drilling the slow jet to richen up the bottom end.

 

you missed the second most important part of my reply, to turn in the air screw, no more then a half turn out at first, humor me and try it.

start going out from there in small increments to help compensate for the big main jet (If you don't want to put in the 170), I still say also get that needle but if you find a combination that works great I will gladly eat my words and try your combination.

I bet If you turn in the air screw your bike is going to run rich.

[D0T-C0M]

Such a modded engine it would be best to install an wideband o2 sensor and gauge.   $200 well spent instead of the guess work of plug reading.

[zukicyw101]

jjast,

I had my air screw only 3/4 out on most of the setups but it wouldn't idle. It was too rich like you said. I have a 45, 48, 50 & 55 slow jet I can mess around with to find that sweet spot. Are you suggesting that I run a smaller slow jet and turn my air screw in to compensate for the smaller slow jet? If I don't it won't idle. That being said, with a 55 SJ and 2 turns out it actually idles but stalls randomly. BUT it is super lean when riding it at 1/4 throttle. If I turn the air screw in to rich'n up the 1/4 throttle zone, won't i be too rich at idle?

This is all great conversation and I apologize for so many questions. Trying to learn.

I did order a NCVQ needle to give it a try. Can't hurt at this point!! Haha

[zukicyw101]

D0T-C0M,

I've thought about it(I might wear out the head thanking the damn plug out so many times! Haha). I'm running 2 individual long header pipes. Would it be accurate if I had it in one pipe or would I have to weld 2 in?? Also, even If I did get the A/F ratio I'm still kinda in the same spot trying to feed this thing more fuel.?? I swear I'm missing something simple.....

[jjast]

jjast,

I had my air screw only 3/4 out on most of the setups but it wouldn't idle. It was too rich like you said. I have a 45, 48, 50 & 55 slow jet I can mess around with to find that sweet spot. Are you suggesting that I run a smaller slow jet and turn my air screw in to compensate for the smaller slow jet? If I don't it won't idle. That being said, with a 55 SJ and 2 turns out it actually idles but stalls randomly. BUT it is super lean when riding it at 1/4 throttle. If I turn the air screw in to rich'n up the 1/4 throttle zone, won't i be too rich at idle?

This is all great conversation and I apologize for so many questions. Trying to learn.

I did order a NCVQ needle to give it a try. Can't hurt at this point!! Haha

 

Well, Like I said I'm still playing with my jetting on this carb so I don't have the perfect solution, my biggest hurtle is the lean spot right off idle...

the closest I got my bike to running just the way I wanted, it had wacky settings but If I remember right this is what they where:

152 main

42 pilot

fuel screw .25

air screw just cracked open maybe up to .5

NCVQ clip on top notch

and it was running rich on idle but that damn lean spot off of idle...I'm still trying the best combo to get rid of it.

 

right now I am running:

152 main

50 pilot

air screw 1.5 (I think? I can't remember if I turned it in while out on the road?)

fuel screw .25

NCVQ clip on top notch

rich on idle and the lean spot is way more prominent...and irritating.

besides the lean spot right off idle the AFR is pretty linear, dropping the NCVQ all the way down cleaned up all my other rich and lean spots throughout the rest of the throttle.

 

A friend of mine thinks the solution is to raise my needle to the 5 or 6th from the top, then drop my pilot jet to a 42 in hopes of "getting on the needle" faster to try to get rid of the lean spot...but I'll still need to contend with the rich idle also.

I'll try it when I get inspired to mess with the carb some more.

 

D0T-C0M,

. I'm running 2 individual long header pipes. Would it be accurate if I had it in one pipe or would I have to weld 2 in?? Also, even If I did get the A/F ratio I'm still kinda in the same spot trying to feed this thing more fuel.?? I swear I'm missing something simple.....

Since it's still one cylinder you can get away with running one O2,

If you are missing something simple then so am I !!!

I've done a lot of research and reading, every time I ask one of the carb "experts" they give me parameters I set everything to spec and the bike runs like pure crap on a cracker...so, I'm just going to keep experimenting until I find what works.

[zukicyw101]

I'll definitely try some of those settings (or close to) when my needle comes in this week. I also thought I was getting too much air (if that's even possible) with my open air filter but I have seen these carbs on other bikes running velocity stacks so there goes that solution. I did tape of most of my filter anyway but it didn't help.

On to the next experiment......

Haha

[zukicyw101]

Also, has anybody tried changing the air pilot jet(I think that's what it's called). Mine came with a 200 and I see everybody pretty much leave it alone. I wonder is that would effect the mixture up to a certain point??

Just a thought.

[ThumpNRed]

My engine is similar to yours. I ride at 2000 to 6000 feet altitude. I copied Dot.Com's jetting mix and my bike runs great. The NCVT needle works great... why did you chose an NCVQ?

[Horri]

Think he runs an older type of FCR Red..(slant) .I'd have to agree about Dots jetting. I recently put in the NCVT needle

and went down on the pilot from a 45 to a 42,,starts first kick from cold..I've also gone up in main from a 160 to a 162..Haven't tested

the higher speed running as yet but it's now at least not running as rich in the bottom..plug was black,,too rich the 45..I could see the excess

gas/fumes coming out the muffler in certain atmospheric conditions..My carb is also not an FCR-MX..simple FCR from a Kwaka 450..Having

to actually buy an FCR-MX to do the mod is not correct in my opinion,,any FCR apart from these slants seems to be fine. Lack of knowhow/info

about how to set up the slant FCRs seems to be the problem..I know people have run them on 600s previously..variables into play.

 

and no I didn't mess with any air/pilot jet,,whatever was in the carb stayed in it when I purchased it..Main /Pilot/Leak got changed,,rest as is.

Where is this 200 jet you talk of..Is it inside the rear end of the carb where the airbox attaches.???

Edited May 6, 2014 by Horri

[zukicyw101]

ThumpNRed,

I picked the NCVQ because I am lean from 1/8 to 3/4 throttle from what I can tell by the 9000 plug readings taken on this bike, haha!

I'm havering a hell of a time getting it idle consistently and I've done a lot of "tuning/trying" at 1/4 throttle(super white plug!!). So I've read that the NCV needles help the 1/4 throttle range and a picked a NCVQ because the NCVN is back ordered, haha. But seriously I'm hoping the Q will help rich'n up the 1/4 to 3/4 range. I've already tried 2 other "OC" style needles that are richer than the stock OCEMR that came in it. Didn't help.

Horri,

Correct. The 200 jet I'm asking about is the one under the "bell adaptor" closest to the air box. Speaking of that, remember I'm running an open style tube and filter with 1.5" long drag pipes. This is probably adding to my issue. Basically I completely uncorked this motor allowing it to breath but now can't seem to feed it enough fuel to make it run the way it should.

I will say that BEFORE I found the adjustable screw(I'm guessing slow air screw) next to the "200 jet" I was asking about. And before I did any other tuning, I drill the slow jet out to about a 101 jet size, OCEMR on the 5th clip and that's when it pulled like a tractor. Ripped the front wheel right off the ground! Didn't idle worth a crap but the plug actually resembled a brown color for once and it gave me a sneak peak of the torque it'll have. Soooo, that being said I assumed it needed more fuel (I did put a 50 slow jet back in). And here I am today.....still lean. Haha

[jjast]

Also, has anybody tried changing the air pilot jet(I think that's what it's called). Mine came with a 200 and I see everybody pretty much leave it alone. I wonder is that would effect the mixture up to a certain point??

Just a thought.

 

That jet is referred to as the main air jet, according to the calibration chart it slowly comes on starting at about 1/4 tapers up until about 7/8 where it makes a big effect from 7/8 to full but If you want to use it for carb tuning count on it really only making a difference 7/8 to full throttle, (I haven't experimented with this jet so I don't have hands on of what it effects).

[ThumpNRed]

Not sure where you are sourcing your needles, but the NCV needles are OE from Honda and Yamaha (perhaps others as well). When I got one from Yamaha (Honda was back ordered), I think I found them in the WR450 fiche. Surprisingly enough prices vary WILDLY for the same parts between one OEM and the other.