Hi there! I'm in the process of installing a keihin fcrmx 40mm carb on my xr600. Before I start messing around with the jets... has someone around here done this, and what jetting did you end up with?

Thanks!

at sea level I run
150 main
55 air jet
ac pump is a 50
42 pj
starter Jet 68 (I think it is called starter jet)
Nhfs-5c Needle.

this was done last year and my note is not very good. the 5c could be 5 from the top on the needle clip.  I think i changed the needle for a richer one I would need to pull my carb to find out.

the needle jet can change every thing.
good luck and WATCH THAT PLUG! dont blow your bike up. good luck

http://www.thumperta...highlight=rejet

:thumbsup:I did dyno it to get my main jet right.
its a good mod if done right.
B

bigredpig said:

Thanks guys! I will buy those jets and neede for a starting point!

I'm also in the process of building a (non thumper) turbo bike and I need a wideband lambdasensor for that. So I figured I'm going to use the wideband lambda sensor to check A/F when testing the FCR carb on the xr600.

Yesterday I fitted the FCRMX 40mm pumper carb.... and it went pretty well!
Things I did to make it work:
-It fitted in the main manifold, so no action needed there.
-It hitted the exhaust pipe (dual headers) so I rerouted the top one..
-CRF450 throttle cables and zx6r 00 throttle handle
-Fitted 152 main jet
-45 pilot (already in there)
-Made an adapter between the carb and the air box hose. I used a small piece (20mm) of 56x1mm diameter steel pipe. This fits in the airbox hose. Then I connected the steel pipe and the carb with a small piece of silicon hose and two clamps.

It runs really great! Pulls very strong through all gears and at any rpm.

It starts pretty good too. The only thing is I need to adjust idle when cold and turn it 2-3 turns back when hot... but the old carb also had that problem..

Watch out to turn the throttle when the bike isnt running..  It squirts quite a bit of fluid in there and you might get problems getting her running again..

Some pics:






I'm really happy I did this mod!

for cold start just give it two pumps.  did you bend the top pipe?

bigredpig said:

You mean the exhaust pipe? Yeah, I moved the bend further back by cutting it out and rewelding it. It was hitting the fuel pump at the bottom of the float bowl.

:worthy:yes, Very nice I need to do that.

Ilja said:

You mean you would be happy to cut up a perfectly good exhaust pipe to make a pumper carb fit which you could most likely find another brand of such a Mikuni thats fits and not have to destroy your pipe?

I dont think i could live with myself doing that

jokerflingo said:

I don't see why not.. You almost can't see the welds and it fits just as good as it did. I TIG welded it pretty clean. Does it look so bad in the pictures then? I just moved the bend a bit further back.

As for the different carbs, I got this one pretty cheap. I didn't know it would hit the exhaust pipe... maybe you don't have the problem with the non-dual header pipes. Buying another one from a different brand was not an option.....they are waay too expensive..

Besides, when fitted these carbs rock!

I'm trying to find a hotstart knob right now as I don't want to fit another handle on the steering bar...

arc hot start start levers
this is what i use on my fcr setup
as to jetting it is a little dependent on what is built into the carb allready
some years of the fcrmx have different sized non removable jets which changes everything else

http://shop.thumpert...fault.asp?p=168

http://cgi.ebay.com/...=item35b1ee7b73

check this one out $38. I am happy with mine. one again pipe looks great I will do the same soon.

bigredpig said:

LOL that fleebay lever would mean I would get decompression, clutch and hotstart lever on one hand.

I bought an aftermarket hotstart lever for an crf450. It's gonna be pretty messy on my handlebar....hope I'll find a spot for it..
Roadbookholder, roadbook holder remote, trailtech vector, vector remote controll, decompression, hotstart, dual sport mirror...

For people doing this... I installed a bigger main jet after a while, because it got pretty hot from running WOT. went from 152 to 165. All is fine now.

IIja, did you mod your tank or tilt the carb to get it mounted?

tilted the carb no leaking problem. it has worked good for all this time.B

Cool. Thank you!

I have the exact same carb.  The only difference is I used a NOSS adapter on the airbox side. I think this would eliminate the need to mod the exhaust.  My jetting is calibrated using a wideband o2 sensor.  My jetting is as follows,

Main Jet 158
Pilot Jet (slow jet) 42 2-1/2 turns out
Pilot Air Jet 100
NCVT needle 2nd clip
R&D leak jet just cracked open 1/2 turn (or use a #35 leakjet or just completely block it off).

The jetting bigredpig mentioned is about 10%-30% too rich at 1/8 to 1/2 throttle.  At 1/2 to 3/4 throttle his jetting is close to mine (within 5%) and the WOT is about 5% leaner than mine.  All this to say that I would set the clip position on his needle to the 1st clip on the top and put a 158 MJ and you'll almost be bang on to mine. Should make a huge difference at 0-1/2 throttle where we drive the most!!!

Edited by D0T-C0M, 15 May 2012 - 09:19 AM.

D0T-C0M, on 15 May 2012 - 09:15 AM, said:

All good info and  it can get you close to where you need to be, but
What elevation are you at?
What cam are you running?
is your air box drilled out?
What needle are you running?
I think its imposable for you to tell me I am lean or rich.
you have not put you a wide band o2 on my bike. Now I am not saying my bike perfect but come on you can not jet anyones bike dead on over the net.  B

Edited by bigredpig, 15 May 2012 - 11:41 AM.

bigredpig, on 15 May 2012 - 11:39 AM, said:

Well I was going under the assumption that IIja had a stock bike,  wasn't really looking at your mods and I wasn't saying your jetting was rich for you just implying for a stock bike its pretty rich.  Now my bike is running at 0-1000' elevation.  I have my airbox desnorkeled, FMF powerbomb with FMF Q4 exhaust but the engine is stock.  Maybe I should have quantified my position by stating my mods and elevation etc but when I said your jetting was too rich it wasn't to say on YOUR bike it was too rich, I was purely comparing your jetting to mine(+30% at 0-1/2 throttle) and that being said if his IS stock like I assumed then it is my opinion that the jetting you suggested is too rich from 0-1/2 throttle for a stock bike.  I wasn't trying to dial his bike in perfectly just trying to steer IIja into a direction that he might want to try.  Nothing personal bud.

ch33rs
DG

Edited by D0T-C0M, 16 May 2012 - 03:07 AM.