anyone compare fcr 41 vs 39?

[cals400ex]

i was wondering if anyone has compared the two fcr carbs? i know you would think the 39 has better low end and the 41 has better top speed, but i want some facts. if you have tried them both, what were the mods on the bike?

[Chef]

I have ran both on my 465EX. Motor mods are: 14:1 JE Piston, Billet Megacycle cam, 3mm O/S Intake Valves, 2mm O/S exhaust, shortened valve guides, Ti Valve Springs and retainers, Ported on the flow bench for the valves, polished ports, lightened flywheel, lightened and polished crank and rod, and a K&N Filter.

With the 39 on, It was tough to keep the jetting consistent, I was changing the jets every weekend. Dont get me wrong, I still had plenty of HP, but there was just somethin not quite right.

With the 41 on, I jetted it up a few sizes from when I had my 39 on, threw it on there (after some modifications to my air boot, it wouldnt fit. That is mostly because of the intake bell of my carb is aftermarket) and it ran GREAT. I think I put a 205 in it to start with. I felt more HP all across the board. I put a 215 in, just to see what it would do, and it helped it even more. Next weekend, went to a 220, and it had even better feeling pull. I'm at a 230 now, without much more to go, and it runs really good.

So, after all, I didnt feel any loss of bottom, and I gained alot of everything else. It also took on a little different sound, too. My motor sounds like a big block compared to the rest of the built EX's I have heard...:cool:

[cals400ex]

i have been thinking about the 41 because i need high rpm performance and low end power isn't a concern. but, my motor isnt built like yours either.

[cory]

Chef, is your motor on methanol? Or do you run race gas? Reason why I'm asking is because your main jet in the 41 sounds high....thanks.

And how did you like the lighter flywheel?

[Chef]

Its on VP Ultimate 4. If it sounds high, thats because it is....it sucks more fuel down than my Banshee does.

I love the lighter flywheel...it doesnt seem like it stalls any easier, but theres alot more power everywhere to keep it from stalling, too.

[montyjcm]

So, what about a ex with a 416 kit? Do the lower bores need the 41mm or would they do just as well with the 39? Thanks.

[Chef]

All the 416's I have been around have ran awesome with the 39. I dont really see where you would need the bigger carb on it.