fcr 39mm carb

[alky440ex]

I HAVE A KEIHIN FCR 39MM ALKY CARB THAT I BROUGHT BRAND NEW AWHILE BACK FOR MY 2001 400EX. THE CARB WAS SET UP FOR ALKY AND NOW I WANT TO GO TO GAS. THERE IS NOTHING WRONG WITH THE CARB BUT IT IS EASIER NOW FOR ME TO GET GAS INSTEAD OF ALKY. MY QUESTION IS CAN I CHANGE THIS CARB BACK OVER TO GAS OR WOULD IT BE BETTER FOR ME TO SELL THIS CARB AND GET A 450R CARB. ANY HELP IS WELCOME!

[CJM]

Im not real sure, but its nothing more than changing some jet sizes more than likely.

[alky440ex]

YEA I WAS THINKING THE SAME THING BUT IM NOT GOOD WITH WORKING ON CARBS AND DONT KNOW WHERE TO START WITH THE NEEDLES AND JETS.

[alky440ex]

IM NEW TO THIS SITE AND SEEN WHERE GUYS ARE PUTTING 450R CARBS ON 400EX. I CAN GET MY HANDLE ON A 05 450R CARB FOR A LITTLE OF NOTHING BUT IM THINKING MY FCR WILL STILL BE A BETTER CARB THAN STOCK 450R CARB. WHERE COULD I GET ONE OF THOSE ADAPTOR TO MAKE THE 450R CARB WORK.

[CJM]

If it was a stock of honda 450r carb I would be able to better guess. My guess is check the stock sizes for an FCR and possibly search this site as some others have used FCR 39 carbs on thier ex.

Im thinking 50 pilot and 160 main possibly. Check out the plug chop and jetting FAQ in the link in my signature. Its for a keihin style carb but the principles are all the same.

[thebig450es]

I love my FCR 39mm carb, try a 50pilot and depending on engine work check main jet size and needle. They sell a kit for alky so you can get everything to change back. Also check for a parts diagram and there real easy to work on.

[alky440ex]

Where can i get this conversion kit to change my carb from alky to gas? I love the carb with no doubt but just want to run pump gas. My bike is a 460 stroker, port job, cam, hmf exhaust, rev box, full open air intake. I was told u would have to change needle and all jets because they are bigger to run alky.

[alky440ex]

oh yea im running 12-1 on compression so pump gas will work fine?

[chronicsmoke]

Originally posted by alky440ex
oh yea im running 12-1 on compression so pump gas will work fine?

I wouldn't run 12:1 on pump gas.. maybe 94 at the least.

Most say that 11:1 is the max. 10:1 if you have an advanced timing key.

That's what I've read anyway..

On a 450r (liquid cooled) you can get away with 12.5:1 on pump.. some people run 13:1 on pump.

I have a 13:1 in my 450r and run 50/50 mix of C12 and 91 or 94.
My 426 has a 10:1 with a +3 key and I'm leary on running anything less than 94.. sometimes I even give it a splash of C12.. maybe I'm too paranoid

:bandit:

[alky440ex]

I dont know much about c-12 can you explain more to help me out. thanks

[thebig450es]

C-12 is racing fuel, i use sunoco 112 leaded.

[chronicsmoke]

Originally posted by thebig450es
C-12 is racing fuel, i use sunoco 112 leaded.

Whats your compression on that beast? How hot does it run?

[thebig450es]

right around 12:1 but i have the +6 key. Its a bat out of He!! lol even with the 16/38/20 gearing, i pull un in 4th gear. after i get in on the dyno and tune it , i bet it will pull up in 5th if i really try

[alky440ex]

Originally posted by thebig450es
right around 12:1 but i have the +6 key. Its a bat out of He!! lol even with the 16/38/20 gearing, i pull un in 4th gear. after i get in on the dyno and tune it , i bet it will pull up in 5th if i really try


i have a spark +6 key but i was told by sparks that they are not good to run in combination with a stroker build so i never put mine in the bike. So can i run it and have no problems?

[chronicsmoke]

I think you'd need like 110 octane to run a setup like that

[thebig450es]

You need atleast 110 octane fuel if you want to run a key with high compression

[alky440ex]

thanks for all the help

[moorhous]

I run 94 all the time in my 440 12:1... not saying everyone can get away with it. Most can..
.

[alky440ex]

Originally posted by moorhous
I run 94 all the time in my 440 12:1... not saying everyone can get away with it. Most can..
.


If i can do it and have no problems im willing to get on pump gas. you said 94 octane but i thought the highest was 93 octane at the pump.

[chronicsmoke]

Sunoco here offers 94 at the pump, everywhere else is 91

[alky440ex]

does your bike run hot? im going be using my bike for trail riding.

[chronicsmoke]

Originally posted by alky440ex
does your bike run hot? im going be using my bike for trail riding.

It's hot enough where I'm going to install a Spal fan. But probably not hot enough to cause damage..

I'm running 10:1 426cc, St2 Cam, +3degree key, P&P, stock valve train, 170 Main, 42 Pilot.

94 runs great, when I cant get all the way across town to get it, I splash some C12 in with 91. Again, probably not necessary, but for the 2$ of C12 its worth it (to me :p )