help asap

[jdog75]

Hi im am going to buy a fcr carb of a crf450 and my friends dad said that ill need a biger header. is this true.

[slightlybent47]

No A bigger carb will only have small gains unless you port and polish. Remember putting in more air and fuel won’t do much good if it has no where to go. The stock head pipe is good up to about a 426, anything above that and the head pipe should be replaced. If you go bigger on the head pipe you will loose some of the low end torque. I have a stock on my 416 with p&p and a 450 carb and it runs fine. I don’t know how much more hp you will get with just the carb alone. You can grind the welds on the inside of the header and it will help some. Check some of the back threads on “header grinding”.

If your going to use the crf carb you may want to do the cam and a p&p. I’d say with just a carb alone you may only get 2-3 hp over the stock one. But with the cam and p&p you will jump up 6-8 hp over stock.

[jdog75]

i agree with what your saying but if i dont get to much of a gain i might have my friends dad port and polish it. hes pretty skilled with it and he did it on all eight cylinders on his firebird

[slightlybent47]

I say go for it, but remember all the motor mods work together and for the best results you should consider doing them all at the same time. That way you’re in the motor just one time and you’re done. You can go ahead and put on the crf now and you will have better throttle response and a little more power. But just the carb alone is not going to turn into a monster.

[slightlybent47]

Sorry I didn’t read you sig befor, how long has it been since you put a new fresh set of rings in it? If it was a resent build and with the mods you already have it should perk up quite a bit.