FCR 41mm Carb Xr650r Recommended Jets and Settings

[Brent Norris]

I finally found a deal on an FCR 41 carb for the XR650R. 

To my knowledge its the older slant body FCR.

2000 xr650r

most riding closer to sea level elevation 

looking for any install tips/kits but more importantly the correct jets and settings and where to get the jet /carb kit. 

Thanks!

[drewbug]

I have an FCR41 on my 650L. With it all desmogged, new pipe and header, etc. it runs well on 170/60 at sea level.

[notoriousE-R-I-C]

Daaaamn a 60??? At Sea level??
Post a pic of your plug!!!

[Brent Norris]

2 hours ago, drewbug said:

I have an FCR41 on my 650L. With it all desmogged, new pipe and header, etc. it runs well on 170/60 at sea level.

Thanks drewbug!

[Brent Norris]

1 hour ago, notoriousE-R-I-C said:

Daaaamn a 60??? At Sea level??
Post a pic of your plug!!!

Do you have some recommendations notoriuseric? 

Thanks

[notoriousE-R-I-C]

Well, theres no point in recommendations if your conditions are different. But sea level San Diego. I have two xr600r's. One stock bore with an fcr41, NO airbox(pod filter) xl headers, crf250r muffs,45 pilot.

The other a 628 hi comp with webcam and stock airbox, xl headers, powercore 4 muff. Fcr39. 45 pilot.

45 worked well on both a/f setups. Notice no difference on the overbored hi comp. But I was 160m with pod filter and 155m with stock box/Uni filter.

So I know its a bigger bore and a different motor. I just think 60 sounds high. Im curious what your plug looks like. Know how to do plug chops?

+28cc required nothing richer, whats another 22? Its how much more it breathes that cause more need. If its breathing more (more air) than it needs to drink more (more fuel) So maybe you got an in/ex system that BREATHES!

What are your in and ex?

If you have a couple extra plugs and a few jets between 60 and 45...do some plug chops.

I just think your bike would feel like the boxed bike felt with the 160. Thats why I went to 155.

But there are many factors along with elevation.

If it works awesome. Im not hatin. Its just a surprise to me. Very interested in what your plug looks like

Edit: ohh thats right the 60 is on a 650l...same motor. Yes displacement is different but me boring up 97-100mm demanded no changes

 

[drewbug]

I was pretty surprised myself. When I picked it up from the dyno shop, they said they couldn't remember the jets they ended up putting in. I was curious, but just cracked the carb yesterday because the pig was coated in clay after a fun ride.

I should have taken pics but I didn't. Sorry, but I swear that's what's in there.

Maybe it's not comparable to the jets on the stock carb?

[drewbug]

I'll pull the plug and post a pic when I get a chance.

[notoriousE-R-I-C]

Thank you drewbug! If it feels good it feels good. And Im talking about an fcr41 on an xr6 and an fcr39 on an xr628. I havent ridden a stock CV carb in years.
If it works fine it works fine. I was surprised at a sea level 60p.
Sounds like youre loving it. And if you gotta shop to do it, you probably dont have other jets to try. Its easy to switch jets, as you said you can do that. (Without carb removal)
How the plug looks will tell if its rich. Black and sooty

[Guest]

I wrote this last week on XR650R riders group on Facebook.

This post is about me installing a FCR Mx 39 carb on my 650R.
A couple nights ago I decided to commit and do the install of a Keihin FCR Mx 39 from a 2008 KTM 450xc-w on my 650R. I already had the carb so I set it up like I have several FCRs in the past on other bikes.
I have a FCR on my 650L with Dotcom from ThumperTalks jetting. It runs awesome. I used the NCVT needle he recommends for the 650L in this carb I put on my 650R.
I did a lot of research on FCR jetting on the 650R. What I found was a bunch of incomplete forum threads. Not to many people replied to someone else's jetting suggestions to let them know if it worked or not. The best info I got was from on here so I am posting what I did and my end results.
The first thing I did was disassemble it and clean it. Then I got a Noss adapter. I let it set for a few days after I siliconed it to the carb body. Make sure the air holes are clear if you use silicone to attach it. I always put a R&D Power bowel with the adjustable leak jet on my FCRs It's expensive but I know it works. I use the R&D remote pilot adjuster also.
I Put in a 48 pilot jet, a 175 main jet, the NCVT needle in the 3rd clip from the top to start with. I clamped it in my vise and made sure the accelerator squirt was good. It missed the slide and I adjusted the leak jet to a squirt of about 1/2 second.
I already knew I would have to heat up my IMS 4.6 to make room but before I did that I fit the carb to see where I was. I took an air hammer and put a dent in the header where the ac pump was hitting and ground about 1/2 of the 8mm cam chain adjuster bolt off to let it come as far forward as I could. This was as close as I was going to get it to level. It was now time to start fitting the tank. I'm just going to tell you this is not fun. I probably had the tank on and off 6 times but I got it. It has clearance and I am using both pull and push cables. The KTM cables are perfect length for my ProTaper woods high and 2" risers.
One thing I did that I have not read anywhere else was to trim the 2 thick rubbers on the left side of the rubber tank support and move them to the right super gluing them in place. This moves the tank over almost another 1/4". I also rerouted my wires to the right side so the tank would move over more.
I am very happy with the way I was able to fit this carb. I know it's a pain in the arse but I really like these carburetors. For me it was worth it.
Now for the fun. After getting off work this evening I was able to ride it. It took a few kicks to fire it up and I had the idle adjustment to low but I got it warmed up and set the pilot. It ended up at 2 turns out. I'm good with that. I readjusted my idle and took off. Putting this FCR on completely eliminated the hesitation or dead spot from idle I had before. It pulled better and It has a little better top end and is a smoother transition to that arm jerking torque we all love from these bikes. I love it. I just made a really fun bike super fun.
I messed with the pilot adjustment some more and settled on 2 turns out. After a 40 mile ride with a few stops just to see if it liked to start with this new setup and it did. Key off, Kick through 3 times, Key on, Get to TDC, Kick like you mean it and it starts 1st or 2nd kick. I did the same procedure dead cold with no choke with the same result.
I checked the plug color when it cooled off and it looked great. I am staying with what I have in it and will ride the crap out of it.
This is what I have.
Sea level -700ft today it was 75deg, 93 octane pump gas.
Stock engine completely uncorked, Stock head pipe, Pro Circuit T4 with spark arrestor, bat wing in air box, TwinAir filter with OE back fire screen, XRs only air box cover mod.
175 main jet
48 pilot jet.
Pilot screw 2 turns out
NCVT needle 3rd clip from the top
Leak jet adjusted to 1.5 turns out

[Brent Norris]

22 minutes ago, TwinSparXR said:

I wrote this last week on XR650R riders group on Facebook.

This post is about me installing a FCR Mx 39 carb on my 650R.
A couple nights ago I decided to commit and do the install of a Keihin FCR Mx 39 from a 2008 KTM 450xc-w on my 650R. I already had the carb so I set it up like I have several FCRs in the past on other bikes.
I have a FCR on my 650L with Dotcom from ThumperTalks jetting. It runs awesome. I used the NCVT needle he recommends for the 650L in this carb I put on my 650R.
I did a lot of research on FCR jetting on the 650R. What I found was a bunch of incomplete forum threads. Not to many people replied to someone else's jetting suggestions to let them know if it worked or not. The best info I got was from on here so I am posting what I did and my end results.
The first thing I did was disassemble it and clean it. Then I got a Noss adapter. I let it set for a few days after I siliconed it to the carb body. Make sure the air holes are clear if you use silicone to attach it. I always put a R&D Power bowel with the adjustable leak jet on my FCRs It's expensive but I know it works. I use the R&D remote pilot adjuster also.
I Put in a 48 pilot jet, a 175 main jet, the NCVT needle in the 3rd clip from the top to start with. I clamped it in my vise and made sure the accelerator squirt was good. It missed the slide and I adjusted the leak jet to a squirt of about 1/2 second.
I already knew I would have to heat up my IMS 4.6 to make room but before I did that I fit the carb to see where I was. I took an air hammer and put a dent in the header where the ac pump was hitting and ground about 1/2 of the 8mm cam chain adjuster bolt off to let it come as far forward as I could. This was as close as I was going to get it to level. It was now time to start fitting the tank. I'm just going to tell you this is not fun. I probably had the tank on and off 6 times but I got it. It has clearance and I am using both pull and push cables. The KTM cables are perfect length for my ProTaper woods high and 2" risers.
One thing I did that I have not read anywhere else was to trim the 2 thick rubbers on the left side of the rubber tank support and move them to the right super gluing them in place. This moves the tank over almost another 1/4". I also rerouted my wires to the right side so the tank would move over more.
I am very happy with the way I was able to fit this carb. I know it's a pain in the arse but I really like these carburetors. For me it was worth it.
Now for the fun. After getting off work this evening I was able to ride it. It took a few kicks to fire it up and I had the idle adjustment to low but I got it warmed up and set the pilot. It ended up at 2 turns out. I'm good with that. I readjusted my idle and took off. Putting this FCR on completely eliminated the hesitation or dead spot from idle I had before. It pulled better and It has a little better top end and is a smoother transition to that arm jerking torque we all love from these bikes. I love it. I just made a really fun bike super fun.
I messed with the pilot adjustment some more and settled on 2 turns out. After a 40 mile ride with a few stops just to see if it liked to start with this new setup and it did. Key off, Kick through 3 times, Key on, Get to TDC, Kick like you mean it and it starts 1st or 2nd kick. I did the same procedure dead cold with no choke with the same result.
I checked the plug color when it cooled off and it looked great. I am staying with what I have in it and will ride the crap out of it.
This is what I have.
Sea level -700ft today it was 75deg, 93 octane pump gas.
Stock engine completely uncorked, Stock head pipe, Pro Circuit T4 with spark arrestor, bat wing in air box, TwinAir filter with OE back fire screen, XRs only air box cover mod.
175 main jet
48 pilot jet.
Pilot screw 2 turns out
NCVT needle 3rd clip from the top
Leak jet adjusted to 1.5 turns out

Thanks! 

How would you think this could differ (if at all) with the 41mm FCR?

where would any of you recommend ordering jet kits? 

[Guest]

7 minutes ago, Brent Norris said:

Thanks! 

How would you think this could differ (if at all) with the 41mm FCR?

where would any of you recommend ordering jet kits? 

I think on my bike if I had the 41 I would've ended up with the same jets.

It seems like some bikes are different even with practicly the same setup, your bike might be diferent than mine, thats why I put in the post exacly what I have done to my bike, elevation etc.

The NCVT needle I used is a Yamaha part. not sure of the part #

I already had the jets so I'm not sure where the best place to get them would be. A good bike shop that has a decent mechanic should have a selection of Keihen jets on hand. Otherwise the internet.

 

[Brent Norris]

Thanks again everyone! 

[notoriousE-R-I-C]

Thanks! 
How would you think this could differ (if at all) with the 41mm FCR?
where would any of you recommend ordering jet kits? 

I have a 41 and a 39 and theres no difference.
Dont order a jet kit. Just get a specific jet. Go to any bike shop. Theyll have kehein jets. I just feel a jet kit wont be as specific as getting the # pilot you need, the # main you need, the # leak you need, and a NCVT needle.
I have both a few part #s, but yamaha had it in store for less than Honda did. Hold up lemme look
16203-MEN-731. At Honda
5TA-14916-VT-00. At Yamaha
16187-0216. At Kawi

[drewbug]

Daaaamn a 60??? At Sea level??
Post a pic of your plug!!!

Okay, it's been a while, but plug pic here. What do you think?

[notoriousE-R-I-C]

Looks fine/ next to lean actually. If it were me, I'd richen up. 62. And feel it. Look at the plug again. I was just surprised cause I have a stock, 97mm, xr600r, and a 100mm, 628. Both sea level with 45 pilots. The 97mm has the 41. The 100mm has an fcr39. But it took the same pilot.
Whatever. You know what feels good.

[drewbug]

Thanks for the feedback. Headed to Montana next month to ride the Selway. Any suggestions on jets for the trip?

[notoriousE-R-I-C]

From sea level to Montana? Even the lowest place there is 1000ft above sea level. Then up to 10,000ft. So I have no idea. Ive never been to Montana. But I know youll need to go leaner. Ride with that 60 first and feel it. But Id get a couple leaner pilot jets to have and play with.
Maybe someone will chime in with Montana jetting.