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View Full Version : FCR Carb in TRX450R - revisited



FatBoy Racing
06-12-2004, 05:25 AM
I've got some questions about swapping out the stock carb for the FCR40 from the CRF 2-wheeler. I'm not just asking to talk about it, I've ordered my carb, but I need more input, cuz I suspect I need more parts.

I'll be honest with you. I got spanked several times hill climbin' in the dunes and that just plain pisses me off. Lets face it, I'm twice the age and weight of that string bean teenager that smoked me up the hill, so I need all the help I can get. The HRC kit is on the way, the exhaust is done, my head is off to get reworked, so all I got left short of drillin' a bigger hole in my new motor is this carb swap.

Yes, I realize this subject has been beat to death. Just to clarify, I seached the heck out of this topic here (and on trx450r.org, where I got the mass of the info) before posting, so I'd like some input and perhaps we can put this subject to bed. I'll even document the swap well enough to put it in the tech section so we've got a place to refer others to once I screw it all up, sound fair?

Okay, all that being said, here's what I'm after. FYI, I want to keep the stock hot-start function and thumb-throttle;

Item 1: I ordered the carb from servicehonda.com for an '03 CRF, which runs approx $355 right now. Short of jetting variations from year to year, are all of them the same carb for years '02 '03 and '04?

Item 2: TPS -- from what I understand, I just need to splice some wires together here, but no new parts needed, correct? Gabe -- is this step obvious once I have it all in my hands or do you have some juju on this?

Item 3: HotStart -- Some of the posts I researched said this needed to be purchased as well as the carb. Do I need to order this? Gabe -- here again, looks like you made the stock cable work fine, any notes on this step?

Item 4: Adapter -- Ordered from Noss Machine. I understand that I need to file a lip off the carb -- anything a common rotary tool can't handle here?

I think that just about covers it for now -- the thread found on the other website was very helpful, so if some of you who have completed this conversion successfully can confirm what I have found, I sure would appreciate it.


Thanks!

Hammer trx450r
06-12-2004, 05:58 AM
from what i understand you are right on track with the 03. Seems the jetting is spot on in the 03. The hotstart lever needs the crf 03 cable to work and maybe crf perch but not real sure on that. Let me know how you do because i was going to order the same thing thisweekend. Thanks and goodluck

twisted threads
06-12-2004, 12:54 PM
Originally posted by FatBoy Racing
I've got some questions about swapping out the stock carb for the FCR40 from the CRF 2-wheeler. I've ordered my carb,



you should do a step by step "How To" when you do yours.....that would be cool. And let us know how you like all the mods you did once you get them done. Im going to be getting a trx450r soon and I have a feeling a cam, carb, and pipe are going to be on it really shortly after I get it home.:cool:

lukester720
06-12-2004, 02:18 PM
It looks like your on the right track fatboy, the wires for the tps appear to be color coded so that shouldn't be a problem at all. Good luck

400exBro
06-12-2004, 05:10 PM
when done and completed correctly would you be able to post a how to" thread so that many others out there can do this same mod...i am planning on doing it aswell and would like some information on how to do it porberly so i know what i am getting myself into...

FatBoy Racing
06-12-2004, 11:14 PM
I'll gladly put together a how-to article once I get to the how-did part :)

86atc250r
06-13-2004, 03:10 AM
To complete the installation all you need is the carb and the adapter. Yes, a little time and a rotary tool will work nicely on the lip. Make sure to tape up the carb well to keep metal shavings out. I used JB weld to epoxy and seal the adapter to the carb.

I spiced my TPS sensor connector from the stock carb into the FCR -- after I doing it, I realized that a person may be able to just swap the whole TPS - unsure... Either way, splicing will work.

The colors on the TPS wires do not match up. Some testing with a VOM will guide you. If you have trouble - shoot me a PM and I will tell you what colors to match.

Also check the TPS adjustment per the service manual.

Hot Start - Yes, you can keep the stock hot start. Use the internal valve & spring from the FCR & the black piece and cable from your stock carb.

Make sure you use the cable position on the hot start lever that allows the hot start valve to close fully.

Don't expect any huge gains in top end - I haven't seen them myself. However, do expect impressive gains in throttle response.

In a 300' drag my time is roughly the same with the 40mm FCR and the stock carb. The FCR is a lot more fun to ride because the power is more "explosive".

FatBoy Racing
06-24-2004, 03:35 PM
Got my carb, adapter, and HRC kit early this week. I'm hopeful to get this put together this weekend, with good pics for a how-to article. Though I've already gone with a yosh complete exhaust and I'm swapping the carb, maybe I'll walk thru the HRC kit article first, then do another for the carb. I wont really be able to comment on the results of doing 'just' the HRC kit, but I think there are plenty of threads here that talk about the results anyways.

JWhite
06-28-2004, 03:00 PM
How's it coming?

FatBoy Racing
06-28-2004, 03:29 PM
Got it buttoned up for the most part over the weekend, but have not gotten to ride it yet. Gabe is gonna cough up a conversion for the wiring of the TPS later today/tonight, and I will give 'er a shot this week. I did start it for a minute or two and between the carb and the cam it sure sounded scary. I didn't run it long enough to even warm up so once I get the wiring right, I'll take it down the block a few times. For what little its worth, it was alot snappier and revved very fast. It did stumble a tad though, but most likely 'cuz it was cold or wiring or may need a little tuning. I have not touched the jets yet. I'll post what i've learned once I get a shot at it in the next day or two.

86atc250r
06-28-2004, 03:47 PM
It will stumble if the TPS is not connected or not connected correctly - as well as if it's cold.

jgfarmsracer
06-28-2004, 06:16 PM
got a number for Noss Machine

FatBoy Racing
06-28-2004, 07:13 PM
http://www.nossmachine.com/honda_quad_parts.htm

www.nossmachine.com

Telephone
918-358-3804
FAX
918-358-3923
Postal address
Rt. 1, Box 560 Hominy, OK 74035
email: dlnoss@nossmachine.com

06-28-2004, 07:51 PM
***SPAMMER***

86atc250r
06-29-2004, 04:55 PM
Come on now Jason - asking us for FCR info after calling the 450R underpowered ;)

I saw that auction :o

jgfarmsracer
06-29-2004, 05:58 PM
well it is!!!! LOL

that piston really makes it come alive / and i'm sure this carb will too!?

86atc250r
06-29-2004, 07:24 PM
Well, I haven't had much trouble out of the Yamahas - maybe it's the rider :eek:

Seriously though, so far I haven't got any better times out of mine at the drag strip - but I feel throttle response is much better & the better times on top may come as I finish dialing it in.