YFZ450 carb on a 400ex

[jt53142]

I just got a yfz450 carb from work yesterday and started to mess with it to work on my 440ex. The carb fit on the intake but took a little force no need to boil. The problem comes with the airbox and gas tank clearance. The simple fix for the gas tank was to put three washers under the white plastic piece that the gas tank sits on. As for the airbox i have to get some parts today to make that work. I am leaving the airbox in stock loaction. I had a 2 1/4" piece of exhaust pipe that is the same size as the carb inlet and fits right in the airbox boot. So i'm going to get a rubber piece to fit over the pipe and the carb with some hose clamps to hold. Oh ya another problem is with the fuel line. The pet cock on the carb has to be bent to clear the frame and when putting on the tank with the carb the fuel line had a kink in it. Not sure what I'm going to do about that yet. It was still getting gas last night. This is where I am right now on it so hopefully i'll be ripping it in the neighborhood tonight. Jetting is going to be a pain because i will have to pull the carb everytime i make a change to it. I just hope I can get it close off the bat.

[2muchquad]

it can be made to work with some fiddling,do a search here on this site.Its a fcr carb that you have.Its a great upgrade once you get it dialed in.You may need a 450r or yfz450 throttle cabe if you dont have it yet.Both will fit the honda stock thumb throttle assembly.im putting one on mine once i get the top end back together.im thinking about the 37mm version though but i have a 39mm as well.try a 40 pilot and a 165 or 170 main and go from there.

thats one thing about the FCR the throttle is so smooth and it feels so controlable. Its hard to explain but I assume since the slide is lat there is so little weight to pull up it makes it feel instant and like its fuel injected or something

[jt53142]

Well i have it all installed and running. Just need to tune it now. Road it around the yard. Right now i have a 175 main jet, 45 pilot, fuel screw out 2 and a half, with the stock needle with only one adjustment. I have to get more jet but i think i'm too rich right now. I can not stab the throttle cuz it wants to kill. when when I'm able to get it to wot it sounds and feels great. My friend had a yfz450 that did the same thing. A guy from work told me to change the diaphrame and the leak jet and it should be fine. I can not wait to get this tuned right. I want to try beating some stock 450's

[2muchquad]

Yeah try the fuel screw until you get some more pilots,youcan also lower the needle a bit,chances are you may be a bit fat on there too..

[trailrider894]

foxhondarider you mean the trx450r fcr carb?? or the yfz450 carb?

Originally posted by trailrider894
foxhondarider you mean the trx450r fcr carb?? or the yfz450 carb?

i cant remeber the TRX450r one the last i had my hands on to ride and was in my garage was the YFZ450. I dont know if the TRX is the same feeling or not havent even sat on one in a long time

[jt53142]

Ya the stock needle that is it does not have an adjustment to it, just one position. I think I'm too rich in the needle too. A guy from work has a needle for it I guess. I have a few pilot jet but I think the 45 pilot is good. Could try a 42 in it too though. As for main i think i'm going to be at either a 168 or 170 but we will see. I just want to get it tuned before i'm ripping on the ice in a couple weeks. I'm doing what i can to try to beat my buddy on his yfz450

[2muchquad]

did you ever get this carb dialed in?

[jt53142]

Ya i got it dialed in. Running a 170 main, ncvq needle 4th down, 45 pilot, 2 and a half out on the fuel screw, put the o ring around the AP pump. The NCVQ needle was what made it run right because I was getting alot of bog at mid

[2muchquad]

im running a dyno jet needle that came in a kit for a yz400f,im in the 3rd clip right now,the first time i had a mid bog,i was in the 2nd from the top,so im still tuning.I think i have a 165main in there,i put the carb together a while ago.it pulls so much harder with the cam,porting and fcr that i may hold off on my 426 transplant for awhile,plus there was patches of snow on the road still,so far im impressed:D i'll play with it some more tomorrow..