not happy with the new carb.

[R_rocket]

I put a '06 carb on my '04 450r. Now when I race other 450's that I usually beat and should beat, I am not. It also doesn't seem to pull as hard. So the question is... when u guys with the fcr carbs on, did u notice a loss in power?

[kazpr]

Did u rejet?

[400exrider707]

You went to a smaller carb, did you rejet anything? Why did you choose the smaller carb? A 43mm FCR would have been an awesome choice.

[GPracer2500]

Originally posted by 400exrider707
You went to a smaller carb...

The two carb size measurements aren't really comparable at that level--they're two different types of carb. Think of it like shoe sizes--a size 10 in one brand might be more like a size 11 in another brand.

39mm FCR (stock YFZ450) on the left. 42mm piston valve Keihin (stock 04/05 TRX450R) on the right.
http://img231.imageshack.us/img231/3055/carbs450ryfzdf6.jpg
[image courtesy of Buck]

[400exrider707]

Originally posted by GPracer2500
The two carb size measurements aren't really comparable at that level--they're two different types of carb. Think of it like shoe sizes--a size 10 in one brand might be more like a size 11 in another brand.

39mm FCR (stock YFZ450) on the left. 42mm piston valve Keihin (stock 04/05 TRX450R) on the right.
http://img231.imageshack.us/img231/3055/carbs450ryfzdf6.jpg
[image courtesy of Buck]

You would think carbs would me a little more accurate than shoe sizes. Where exactly are they measured from to get the measurement?

[GPracer2500]

Exactly where and how they're measured can vary. But beyond that, carb throat measurements aren't the end-all be-all of carb performance. It's only fair to make size comparisons if you're talking about the same type of carb. If your looking at two different carbs then there's a whole bunch more to distinguish them than just "size". Apples to oranges.

Case in point: the 06/07 TRX sure didn't loose anything by going to an FCR even though it is "smaller" than the 04/05 carb.

[400exrider707]

Originally posted by GPracer2500
Exactly where and how they're measured can vary. But beyond that, carb throat measurements aren't the end-all be-all of carb performance. It's only fair to make size comparisons if you're talking about the same type of carb. If your looking at two different carbs then there's a whole bunch more to distinguish them than just "size". Apples to oranges.

Case in point: the 06/07 TRX sure didn't loose anything by going to an FCR even though it is "smaller" than the 04/05 carb.

Yes I understand that going to a smaller carb isn't always a power loss. I believe the intake tracts are quite different as well as the port angles on the 04/05 machines when compared to the 06/07 machines. Just seems to me the 04/05 machines are pretty happy with the stock carb, and I know a few have gone larger to the likes of the 43mm FCR.

[Chino886]

04/05 carbs have a round slide

06/07s are flat slide

The flat slide is easier to go up and down in the throttle body as they are on rollers, which increases throttle response.

I think the design of the FCR is far superior to any carb I have used (for most applications)!

I have used the Lectron, FCR, and OEM (round slides).

[GPracer2500]

Originally posted by 400exrider707
Yes I understand that going to a smaller carb isn't always a power loss. I believe the intake tracts are quite different as well as the port angles on the 04/05 machines when compared to the 06/07 machines. Just seems to me the 04/05 machines are pretty happy with the stock carb, and I know a few have gone larger to the likes of the 43mm FCR.

The stock 04/05 carb is not a bad carb. I've seen some really good results on built-up engines that still used the stock carb. Nonetheless, a properly set-up FCR is almost sure to outperform the 04/05 carb in one or more areas without giving up anything. BTW, to get an FCR larger than 41mm you've got to have an existing FCR bored out. And I believe to get up to the 43 range a new center ring is required.

I'm not debating that big carbs have there place. I'm just trying to point out that size comparisons between different carb types don't mean much.

[400exrider707]

Originally posted by GPracer2500


I'm not debating that big carbs have there place. I'm just trying to point out that size comparisons between different carb types don't mean much.

Point taken;)

[Chino886]

I will be sure to let everyone know what I think of the 43.5mm FCR when I get the motor running! :devil:

[R_rocket]

[QUOTE]Originally posted by GPracer2500
[B] Nonetheless, a properly set-up FCR is almost sure to outperform the 04/05 carb in one or more areas without giving up anything.




So u r saying i need to work on my jetting more? Also, how much to get this carb bored out to a 43mm on average? And.... how do u adjust the accellerator pump on the '06 carbs

[Chino886]

Yes, definitely play with jetting.

The cost to have the carb bored is about $500-$600 dollars.

[400exrider707]

Originally posted by Chino886
Yes, definitely play with jetting.

The cost to have the carb bored is about $500-$600 dollars.

Are you kidding me? What machining could possibly have to be done to make it $500?

[Chino886]

Originally posted by 400exrider707
Are you kidding me? What machining could possibly have to be done to make it $500?

NO, I am not kidding you!

carb must be disassembled, new center ring purchased and the carb must be taper bored.

Trust me, I don't know what has to be done, but that is the going rate I believe.

[R_rocket]

Originally posted by 400exrider707
Are you kidding me? What machining could possibly have to be done to make it $500?



i was thinking $250.

[Chino886]

Originally posted by Chino886
Yes, definitely play with jetting.

The cost to have the carb bored is about $500-$600 dollars.

I made a mistake, its about $300.

[400exrider707]

Thats crazy. I dont see how it could possibly be that much.

[Flyin-Low]

The only reason it's that much, is because not everybody can do it. It's not how much labor that is involved, it's how much skill. I'd like to see you taper bore a carb to 43 mm and then see how it preforms.

-Martin

[400exrider707]

Originally posted by Flyin-Low
The only reason it's that much, is because not everybody can do it. It's not how much labor that is involved, it's how much skill. I'd like to see you taper bore a carb to 43 mm and then see how it preforms.

-Martin

If I had the machine I would.;)

[R_rocket]

is the '06 fcr carb the same or close to the same as the crf carb. As for jetting and performance wise.

[Chino886]

Very close.........

Try a 160-165 main with a 48 pilot and 55 leak jet.

Based on your mods.........bump it up a few sizes if you head is ported.

[chad502ex]

just to clear up any misconception on taper boring....

especially since I was the originator of the taper bore FCR's.... everyone else did straight boring....

anyway it costs about $250 including parts and labor

and is good for 2-3 gain on a properly tuned setup. great gains for 250 bucks....