450R carb

[kgbg]

So does anybody profess to know about putting the CRF carb (FCR4o) on? I am thinking it will, not psoitive.
If you knwo please help me out, if not, don't speculate.

[ATC83]

The only problem I can see that you might have is space. I know some people have been trying to put the 41mm FCR carb on the YFZ are they are finding there isn't enough room. I haven't taken a close look at the TRX yet but if the stock carb fit is tight then you will brobably have trouble fitting in the FCR because size for size the FCR runs a little bigger than a butterfly carb. Of coarse I hear Tim Farr runs the FCR so there must be a way to do it. The only other problem I could see is if you want to run the stock thumb throttle. You may be forced to go the to with a twist throttle with pusher/puller throttle cables.

[kgbg]

Well, I have a FCR39, its smaller than the 42 on this baby, thats a big carb. What I am concerned with is the TPS and Hot Start. I wan to make sure they still do what they are supposed to. I can get ove tthe thumb/twist deal. There are 2 plugs coming out of the 450R carb, I wan tot make sure I can still start it...lol

[2004TRX450R]

the biggest problem I see is the TPS. I don't know what all it tells the computer but it might hurt your performance if you don't have another carb on it with the TPS. I'd question the gains you will get with a smaller FCR vs. the bigger butterfly/round slide carb that comes stock on it. I wonder how much of a pain it would be to put a 40mm FCR off a CRF on it and maybe use the CRF ign. with it too. Just curious.

[tholt]

Just unplug the tps on your 450R carb and ride it and see what it does.
I have a YZ426F FCR carb on my brothers KFX and it has the TPS on it but i don't have it hooked, Bike runs great with no problems. Have heard but not for sure that the TPs just kind of helps tell the bike in some situations whether it is lean or not in the CDI box and it helps adjust itself a little bit for the condition. what i have heard. can't confirm that though.

If you buy an acutal carb off a CRF it will have the tps on it. so no worries, if you buy an aftermarket FCR carb it won't have the tps on it.

Tim.

[jeff1984]

TIM FARR IS RUNNING ONE ON HIS BIKE. I DON'T KNOW ABOUT THE TPS THOUGH

[Quadaholic]

The new CR250r dirt bike comes with a tps. One of the most common mods for that bike is to run a 2000 model carb w/o tps. You just leave the factory plug unconnected (but taped up just in case). I'm pretty sure that the 450r will respond the same. I've got a couple of calls into Honda tech to get some more insight into this. I'll post as soon as I get some good solid info. Hope it helps.

[2004TRX450R]

The TPS tells the CDI where the throttle is so that it can advance or retard the timeing for optimum power. It has nothing to do with being lean or rich. It may make a difference in power or not. It is hard to tell with out putting it on the dyno and seeing.

[tholt]

i was close, i told you i didn't know exactly. but the timing being retared or advanced will affect whether or not the bike is rich or lean. you advance timing on a bike you have to richen it up to handle.
just like if you put a dyna ignition on a kfx or Z400 you have richen up the carb for the advanced timing settings. So it does play with whether the bike is lean or rich. so if it is lean i bet it retards the timing somewhat to help it run richer.


Tim

[2004TRX450R]

Originally posted by tholt
i was close, i told you i didn't know exactly. but the timing being retared or advanced will affect whether or not the bike is rich or lean. you advance timing on a bike you have to richen it up to handle.
just like if you put a dyna ignition on a kfx or Z400 you have richen up the carb for the advanced timing settings. So it does play with whether the bike is lean or rich. so if it is lean i bet it retards the timing somewhat to help it run richer.


Tim

There isn't any way for it to know if it is rich or lean though. Just where the throttle position is.

[robby26wi]

You need to use the TPS and yes Tim is using it on his quad...

[seatec]

I believe that the TPS just does a Curve selection depending on Throttle position. I dont think its a smooth transition between timig but rather a hard selection between two curves. Not a %100 on that.

[tholt]

i know but if it helps with playing part in hard pack or slick sections what it is doing i altering timing. not a lot but a little bit. like is aid not sure about lean or rich. But again i am running one on a KFX and u don't have to have the TPS hooked up. The bike still runs good with it unhooked.

Tim.

[kgbg]

I talked to Mark Baldwin for a few about it last night. He has me covered. Thanks for the help. There are some elec/mech mods he must do to the carb. I have one on order.

[robby26wi]

The reason why it works well on the kfx is because they dont have veriable timing...I also ran the crf carb on my kfx434 last season and it ran well....But when you have the ignition there to use it i would suggest using it...

[tholt]

I have a dyna FS ignition which is programable and able to be used with the TPS. i just haven't gotten the software from dyna to setup so right now i am just running it without it being hooked up.

Tim.

[perf.m.s]

I installed an 04' CRF450 carb. Autozone has a muffler adaptor that will work for attaching the intake boot. Front boot fits right up. Found wires on stock TPS that ohmed, and same on FCR. Switched plugs so I could plug into wiring harness. Backed of idle screw on stock carb and ohmed wires. Set FCR TPS to same numbers. Removed stock hot start plunger from cable and installed FCR plunger. Stock throttle cable works fine.

PROBLEM:

In neutral from idle to wide open hesitates and then revs. Second gear starts from idle motor boggs, and sometimes dies. If you take it just of idle it does fine.

Motor has about an hour on it. Air box lid removed, spark arrestor removed.

I'm hoping it's just loading up of idle, and that a K&N and free flowing silencer will fix it. No jetting changes made.
If you have any suggestions please let me know.

[robby26wi]

I would go down one size with the pilot jet or turn the air screw in a bit...