FCR 41mm carb Q's

[440ex2001]

I am thinking of getting this carb for my uad but they are pretty pricey. My engine mods are 440 kit with Ross 11.2:1 piston and thin base gasket. Hot cam stage 1, P+P head, PC full exhaust no lid uni filter. How much will the 41mm help out? What are the pros and cons? I tried a search but didnt find much info. Thanks

[MIKE400EX]

The 39 will work better with the stage 1 cam. All around response will be much better. You'll probably only gain a few Hp across the rpm range, but because of the much improved response it'll seem like a whole lot more. It'll be a torque monster if it's ported right!

[NacsMXer]

With those mods, the FCR 41 would be very beneficial since your motor is far from stock. Like Mike400EX said, it would be more suiting if you went with the 39mm because with the 41 and the stage 1 cam you might not make as much torque as you would with the 39. I run the 39mm with my 452cc race motor and its a flat out torque monster, sure the 41mm might help a little bit, but I have all the power ill ever need. I think the FCR 39 will more than suit your needs.

[440ex2001]

I have been planning on going with a web cam or a stage 2. Would it woek better with one of these?

[MIKE400EX]

The stage 2 is similar to the Web 450/451 grind. The 479 grind will work even better but also requires springs & shortened guides. ALL the 400Ex WEB cams need hard welded rockers. With the stage 2 you'll be giving up some bottom end compared to the 479 or stage 1.

[NacsMXer]

Well if it helps, my previous motor was a 10:1 440 with a Webcam and I still had the same FCR39. It worked great and still does. Oh and I have the HRC cam now which is more similar to the stage 2 cam if that helps. One of my buddies has a FCR41 on his completely stock motor and it really isnt that great of a performer. I haven't personally tried the 41, but if the 39 worked for me, I don't think you will be dissapointed. I believe that the 41 produces more top end hp, while the 39 would be better at producing a more linear torque curve. I think we may need Cals400ex on this one because he's an expert when it comes to these carbs. I hope I helped a little bit. :)

[NacsMXer]

Originally posted by MIKE400EX
The stage 2 is similar to the Web 450/451 grind. The 479 grind will work even better but also requires springs & shortened guides. ALL the 400Ex WEB cams need hard welded rockers. With the stage 2 you'll be giving up some bottom end compared to the 479 or stage 1.
Mike, my previous cam was the 450/451 Webcam, and it was designated as the "all around cam" so I thought it was most similar to the stage 1 - has the most even power distribution. The 479i grind requires the shortened valve guides and heavy duty springs because it is a high lift, long duration cam that is more of a top end performer-why it's termed the racing cam. I also thought that the 479i is more like the stage 2 cam. I could be wrong though, maybe the stage 2 is more mild than I thought.

My suggestion is to look into the HRC cam. I chose it because you don't need hardened rockers, valve guides, or heavy duty springs that ultimately cause more valvetrain wear and higher overall costs. You also don't sacrifice as much on the bottom as you would with the stage 2 cam. Honda designed the motor, so they should know how to get the most power out of it while keeping things reliable at the same time.

[MIKE400EX]

The 479 grind actually has less duration than the 450/451, but it does have more lift and quicker ramps. The 450/451 is "billed" as an all around cam but is "bigger" than the HRC. White Bros. reboxes the 450/451 as their track/desert (top end) cam and sells a "smaller" grind as an all around one. I also tried the 450/451 Web cam. I felt it was good, and better than the stage 2 all over, but lacked on the bottom end. I'd bet you probably like the HRC better because it has more bottom and mid than the 450/451, and the difference in the top is barely if at all noticeable. Same reason for me going with the 479. Top end is great but you first have to get there.

[NacsMXer]

Thanks for correcting me Mike. Yeah I really wasn't that all impressed with the 450/451 cam. I was coming from a stock cam and was expecting a big difference but there really wasn't much. I then was decided on the 479i grind until I consulted Lazarus at GT Thunder. He told me the HRC would be the most beneficial because you don't always have to be on the pipe as much as the 479i. And the fact that you can just drop it in really sold me. I'm sure the 479i is the better performer in terms of HP, but i'm really impressed with the overall performance of the HRC. Both are top quality race cams as well.

[EPDP99]

it all depends on the motor work. if its just a bore then 479 might suite you better. but on a stroker the 450/451 works great with that.

[cals400ex]

one statement mike made i totally agree with. he mentioned that the throttle response with the fcr carbs is much great than stock, thus it feels like you gained 10 horsepower. in reality, you don't gain that much. i am not saying you won't gain a couple a mildly built motor, but it is nothing really drastic. i have not tried the 41mm. i have used both the 39 and the 40mm fcr's. the 39 has better throttle response tahn the 40. the throw on the lever is just shorter. i never tried both of them on the same motor so i can't compare them side to side. the 40 is a pain to get hooked up. this carb is shorter than stock so you need to rig up adaptors to make it fit properly. also, it sits taller and rubs the gas tank. i bought one of those $70 noss adaptors for this carb. well it turns out the adaptors doesn't fit the 400ex boot. i realized this adaptor was made for the 450r, but the company could not tell me if it fit or not, so i bought it. i may be able to boil my intake boot and get it to slide on, but it is a couple millimeters off. the 40mm is nice because it has a choke. the bad part is that you can't get to it with all the plastic on. the 40mm's are supposed to flow better than the 39 and 41 on a flowbench. they are just a newer style carb. the 41mm's for the 400ex actually taper down to 39mm's anyways so it will fit in the boot that attaches to the head. i thought dirtwheels tested these and the 41 actually produced more power?? maybe not, and i don't even remember what bike it was on. i thought a 400ex.