valve question

[400exmxracer]

If I'm boring to a 426 11/1 with a stage 2 cam and fcr 39mm carb and a bunch of other stuff...should I get bigger valves then the stock ones?

[matt14c]

If you do might wanna go bigger than 39mm on the carb... Id start with a port first.. Dont have to get bigger valves to get a good port job..

[JOHNDOE83]

In my opinion the fcr 39mm is pointless.

You could get a port job and do better then the 39mm carb.

If you want max power, you have to get the 42mm 450r carb.

If you are thinking of boring, valving and porting, you deff need the 42mm carb.

[400exmxracer]

I think the 39 will do fine. It's only a 426 11/1 and mild port and polish full exhaust hinson clutch basket dirt digger clutch hotrods crank hd valve springs and a stage 2 cam.

[CJM]

FCR doesnt make power like you would think. Its mainly a high horsepower carb and doesnt hit hard like the butterfly style keihin carbs.

[400exmxracer]

So you don't think it will work good for motocross racing?

[CJM]

Originally posted by 400exmxracer
So you don't think it will work good for motocross racing?

You could try it if you want. Ive ridden a few quads with the FCR, power is smoother but in my opinion it just doesnt have the overall umph like the keihins do. My friends bored, stroked and done up 06 450r is no doubt fast but damn FCR makes it feel like it has no torque.

[JOHNDOE83]

Yes like CJM said, its a good carb and has good throttle response and a good stab of horse power when its cracked open.

But for throttle response, the size of the 04-05 450r carb will have the same as the fcr simply because of its size. Also when the 42mm 450r carb is cracked open from 0 - full throttle it has alot more mass airflow resulting in more power then the fcr would have.

The fcr is a good MX carb, but for the price you could get a 450r carb and be better off and better suited for bigger mods in the future. When your dealing with 450r's and suzuki's on the race track its best to have the most power possible, throttle response alone isnt enough to win a race against bigger and better atv's.

If you got the money and time, try both and test it to see which is better for your riding situation.

[400exmxracer]

Well I'm 17 and work 3 jobs to try to afford stuff :-s and I already bought a nice 39mm for 150 so ill probably stick with that for a while

[Longdong]

Originally posted by 400exmxracer
Well I'm 17 and work 3 jobs to try to afford stuff :-s and I already bought a nice 39mm for 150 so ill probably stick with that for a while

A 39mm will be just fine. If your are just starting out it wont matter anyways.