On a slightly modded 300ex, how big is too big as far as carb size? Is 38mm way too big?

 

actually a 38 mm is highly recommended on the 300ex.that is if you have the mods to match up to it.the only way you will really need a larger carb is if you need to get more gas flowing to acommidate for the extra air flowing in from such mods as heavy air box mods, after market filter, after market exhaust. also you can get an increase from this with a cam and valve springs. what mods does your bike have?

 

actually a 38 mm is highly recommended on the 300ex.that is if you have the mods to match up to it.the only way you will really need a larger carb is if you need to get more gas flowing to acommidate for the extra air flowing in from such mods as heavy air box mods, after market filter, after market exhaust. also you can get an increase from this with a cam and valve springs. what mods does your bike have?

 

actually a 38 mm is highly recommended on the 300ex.that is if you have the mods to match up to it.the only way you will really need a larger carb is if you need to get more gas flowing to acommidate for the extra air flowing in from such mods as heavy air box mods, after market filter, after market exhaust. also you can get an increase from this with a cam and valve springs. what mods does your bike have?

 

actually a 38 mm is highly recommended on the 300ex.that is if you have the mods to match up to it.the only way you will really need a larger carb is if you need to get more gas flowing to acommidate for the extra air flowing in from such mods as heavy air box mods, after market filter, after market exhaust. also you can get an increase from this with a cam and valve springs. what mods does your bike have?

 

actually a 38 mm is highly recommended on the 300ex.that is if you have the mods to match up to it.the only way you will really need a larger carb is if you need to get more gas flowing to acommidate for the extra air flowing in from such mods as heavy air box mods, after market filter, after market exhaust. also you can get an increase from this with a cam and valve springs. what mods does your bike have?

 

The stock carb, a 29mm is large enough for up to 350cc. In fact, I use a stock 250X carb (similar in design & same in size) on my 350X conversion.

A 38mm Round slide carb would be overkill on even a 406cc engine. Heck, we use a 39mm on our 440 kitted 400EX's!