34mm / 38mm carbs interchangable?

[projectxs650]

So i know different size carbs we're used for different years. But I've always wondered. Lets say you used a 38mm (pre1980) on a 82' engine. different sizes, but is it possible? would it all work the same basically? or is it a lot of hassle and difficulty and should be avoided unless you have a lot of time on your hands.

 

[weekendrider]

The 38's are shorter than the 34's so the air boxes won't mate up. You would need a corresponding size of intake manifolds. Other than that ezpz.

 

[projectxs650]

The 38's are shorter than the 34's so the air boxes won't mate up. You would need a corresponding size of intake manifolds. Other than that ezpz.

Perfect! i don't plan to be using any air boxes so i should be set to go? the intake manifolds aren't difficult right? just need to find the right size and i'll be set?

 

[weekendrider]

Not difficult at all. I would recommend intakes from

http://www.jbmindustries.com/HOLDERS.html

 

[gggGary]

+2 Early BS38s with two throttle cables would require the proper throttle set up. Unless what you have is very broke, there is little reason to swap.

 

[xschris]

I know on the 38mm carb heads the intake ports (not the boots) are larger (35mm) than the bikes that had the 34mm carbs where (33mm)

 

[grizld1]

Interesting. I just inspected two unmodified late heads, 1980 and 1982, and they showed 35 mm. at the entry of the intake ports.

 

[xschris]

I don't know these are off a 1980 xs650g

 

[gggGary]

well the inside is just raw casting I got about 32.5 to 33 on 4 bikes from 77 to 82. I'll look at a 72 when I pull the carbs off.

 

[xschris]

I had a head off a 76 and that was 35mm.