FCR XR650L Sudco pumper carb

[toofast1000]

Im a stout fellow 6' tall weighing in at a modest 250lbs. Even with the lean flat spot I was able to lift the front with a simple 1st gear throttle roll on. That was NEVER possible with the CV.

One of the things I didnt like about the XR650L was when riding in the woods I would have to think more about how I was going to get over that log. In the past on other bikes I would burn up to it wack the throttle and over I went. I think the instant power will bolster my confidence in the woods.

I just wish honda would see the sucess they have had with the XRL line and update some of the technology. The trend is toward fuel injection and the XRL is stuck with a CV carb:bonk:

I regret not being able to find one used. I bought two off Ebay and had to return both before decided to just bite the bullet and go new.

Additionally Sudco although responsive to my questions could take the feedback which they have received and put out a better package.

BTW the jetting recomendations posted here thus far have been so close to perfect that extensive trial and error testing has been minimized. An AF guage is a must though IMHO.

[D0T-C0M]

WOW. I just read this entire thread and suddenly don't believe I would ever part with the trusty CV carb on my XRL.

Best of luck guys. I know the effort will eventually pay off, but dialing in a hotrod carburetor sounds like a HUGE lesson in patience and perseverance. My easily frustrated self would have already taken that thing out back and thrown it into the next zip code. ?

Also this thread is long as it is because there was some good dialog between the posters. Bottom line if someone just slaps in the jetting I recommended in this thread you might have to take your carb apart maybe twice max to fine tune the PJ and/or needle clip and/or MJ for your altitude and temperature. I've already went through all the tedious work of dialing my carb in perfectly so you don't have to start from scratch.

[Itchykawa]

The FCR swap is definitely not for you if you do not have the patience but the end result is definitely worth it IMO.

Agree. And make no mistake about it - I admire you gifted tuners. ? I'm just a parts changer.

[jjast]

I didn't disappear, I was just sidetracked with other projects, so just to be clear it doesn't take months to tune one of these carbs, someone could do it in a day if they had the jets on hand,I just do things differently I guess...and in keeping with that theme...last night I swapped out my 55 pilot with a 42 and swapped out my main 155 with a 150 and haven't had a chance to start it up yet mainly because It was almost midnight when I got done and didn't want to wake people up,

I swapped out my needle last week (tried the "Q" needle first rather then the "R") and went for a short ride (about 6mi) not far enough to get a proper O2 reading but from what I saw the numbers where looking promising,

[jjast]

with the different "Q" needle enriching throughout I ended up with AFR's 11.9-12 idle,11.4 mid,11.6 WOT,and a big dead spot (lean) right above idle to quarter throttle, (this has been a constant problem area), I suppose that's why they updated the FCR-MX with a throttle valve cutaway to better tune this spot?

I raised the needle 2 slots and need to go test ride it to see what that does.

[toofast1000]

with the different "Q" needle enriching throughout I ended up with AFR's 11.9-12 idle,11.4 mid,11.6 WOT,and a big dead spot (lean) right above idle to quarter throttle, (this has been a constant problem area), I suppose that's why they updated the FCR-MX with a throttle valve cutaway to better tune this spot?

I raised the needle 2 slots and need to go test ride it to see what that does.

Im still in a similar similar situation unfortunatly based on my research the three variables which will eliminate the lean at 1/8th throttle is needle throttle cut out, needle diameter and the Air screw/jet (left side in carb intake) my carb came from sudco with the screw 2+ turns out... I pushed it in to .75 turns out and saw a positive improvement. Im using the ncvr right now but have the ncvq and ncvp on my bench. based on your post is sounds like the ncvq is not the complete solution so I think my next test will be to screw the air air jet in to just shy of seated and switch to the ncvp needle.

[ThumpNRed]

Mine has an NJGR in it and it meters very well.

[zx12r]

Im still in a similar similar situation unfortunatly based on my research the three variables which will eliminate the lean at 1/8th throttle is needle throttle cut out, needle diameter and the Air screw/jet (left side in carb intake) my carb came from sudco with the screw 2+ turns out... I pushed it in to .75 turns out and saw a positive improvement. Im using the ncvr right now but have the ncvq and ncvp on my bench. based on your post is sounds like the ncvq is not the complete solution so I think my next test will be to screw the air air jet in to just shy of seated and switch to the ncvp needle.

You might want to post this in, TT Intake & jetting. There are a few guys over there that really know the FCR very well.

https://www.thumpertalk.com/forum/forumdisplay.php?f=64

[jjast]

You might want to post this in, TT Intake & jetting. There are a few guys over there that really know the FCR very well.

https://www.thumpertalk.com/forum/forumdisplay.php?f=64

I will If I hit a proverbial wall, I'm not out of idea's yet.

[Kenzo]

with the different "Q" needle enriching throughout I ended up with AFR's 11.9-12 idle,11.4 mid,11.6 WOT,and a big dead spot (lean) right above idle to quarter throttle, (this has been a constant problem area), I suppose that's why they updated the FCR-MX with a throttle valve cutaway to better tune this spot?

I raised the needle 2 slots and need to go test ride it to see what that does.

it sounds like the pumper squirt is too short...?

...that's where these carbs have a trade-off.

for offroad riding with a lot of rapid on/off throttle u want about a one second max strong squirt. this is typically achieved with a diaphram with a longer "nipple"(shortens squirt duration) and the "o-ring" mod (strengthens squirt) for the 3rd generation FCR MX. without these adjustments there can be a lean bog from closed throttle to rapid WOT.

for onroad riding u want a longer 2-3 second squirt which is achieved with the shorter diaphram "nipple", different leak jet or the Boysen Quick Shot adjustable leak jet.

?

P.S. I believe some of the "kit carbs" out there may be still be provided w/ the 2nd Gen carb rather than the newest so the way u go about tunning it may be slightly different.

[zx12r]

,and a big dead spot (lean) right above idle to quarter throttle, (this has been a constant problem area),

sounds like you have a ap squirt or ap timing issue, it should squirt 5 feet, not just trickle out. have you tried the o-ring or (taffy mod,for slant body), this fixed my slight bog, when i installed a fast ratio vortex throttle.

[toofast1000]

When I have been testing with the bike warmed up I have the throttle marked with eight positions 0 idle to 8 WOT at position 1-1.5 approx 1/8th throttle I get an AFR of 15 and a cough if I roll past this point to any other postion AFR 12.5 ish. I have recorded the AFR at each throttl number after holding it at that position for several seconds.

I dont understand how the duration of the ap squirt matters when the AFR is off at a steady state condition. Can anyone explain?

[jjast]

it sounds like the pumper squirt is too short...?

?

sounds like you have a ap squirt or ap timing issue,

I'm not even touching the AP variables at this time,all my AFR readings are at a steady throttle where the AP factor is taken out.

I will be re-reading your post when I get to playing with the AP settings tho'

When I have been testing with the bike warmed up I have the throttle marked with eight positions 0 idle to 8 WOT at position 1-1.5 approx 1/8th throttle I get an AFR of 15 and a cough if I roll past this point to any other postion AFR 12.5 ish. I have recorded the AFR at each throttl number after holding it at that position for several seconds.

I dont understand how the duration of the ap squirt matters when the AFR is off at a steady state condition. Can anyone explain?

I am also reading my AFR's the same way you are toofast1000,so hurry up and figure out a solution for that dead spot so I can apply it to my bike because it sounds like you and I are chasing the same demon.

[Kenzo]

I'm not even touching the AP variables at this time,all my AFR readings are at a steady throttle where the AP factor is taken out.

I will be re-reading your post when I get to playing with the AP settings tho'

I am also reading my AFR's the same way you are toofast1000,so hurry up and figure out a solution for that dead spot so I can apply it to my bike because it sounds like you and I are chasing the same demon.?

then is a combination of ur main jet and needle taper...easiest test wud be be to raise ur needle one clip position(on the taper sooner) and see if it getz better...

[jjast]

then is a combination of ur main jet and needle taper...easiest test wud be be to raise ur needle one clip position(on the taper sooner) and see if it getz better...

?

That's the plan, I already raised the needle but have yet to go test ride it.

[_mrp_]

So at this point would this be a good carb for a modded xr600r? Would your jetting suggestions apply? I am definitely not a tuner, but I will be needing a better carb shortly, and would like to be in a good ball park out the gate.

[jjast]

So at this point would this be a good carb for a modded xr600r? Would your jetting suggestions apply? I am definitely not a tuner, but I will be needing a better carb shortly, and would like to be in a good ball park out the gate.

A FCR pumper carb over a stock XR600R carb? yup, that wound be a good upgrade,

I can't help you on the jetting suggestions tho'.

[Kenzo]

So at this point would this be a good carb for a modded xr600r? Would your jetting suggestions apply? I am definitely not a tuner, but I will be needing a better carb shortly, and would like to be in a good ball park out the gate.

sure...just remember these guys on this thread are trying to tune it to respond like FI at all throttle settings.

the FCR MX carbs are relatively easy to "tune" in the ballpark...plenty of used 39mm and 41mm carbs for around $250...then u just have to make the boots work.

I sometimes wonder if the 39mm wud be better han the 41mm on the L...since the 39mm is frequently used on bikes making 45-50Hp and the L is closer to 40Hp...unless ur just look'n for topend.

P.S. I believe the AP squirt also kicks in at other throttle positions when rolling on besides closed throttle.

[zx12r]

So at this point would this be a good carb for a modded xr600r? Would your jetting suggestions apply? I am definitely not a tuner, but I will be needing a better carb shortly, and would like to be in a good ball park out the gate.

I got my 40mm FCR-MX on ebay off a 04 crf450r, for a good price. It came with a 45pj, 170mj and NCYR needle(I did go down to a mj168). I installed it on my 97 XRL650L with that jetting, and its been running great ever since. Is it perfectly jetted, I'm sure it isn't, but it still works much better than the cv carb. Point being, that even not perfectly jetted, its still a major improvement over the rejetted cv carb. Best mod I've done, she even has a top end hit that it didn't have before.

[jjast]

sure...just remember these guys on this thread are trying to tune it to respond like FI at all throttle settings.

Hahaha, I swear that's not what I'm going after, I just want to kill that dead spot and get the AFR tuned close.