Interchanging Hitachi Carbs

So I've still got an on going issue on cylinder 2 with it not getting as hot as the other 3 resulting in not being able to get past 60mph. I've had the carbs apart and made sure everything is in place correctly and replaced all the rubber o rings inside (fuel and butterfly valve).

The only thing that I can think of is that the long (air?) jet (I dont know the name of it - it's the one in the middle, under the diaphragm with multiple holes in it) wont fasten into the the small screw jet in the float bowl properly to allow a snug fit.

There is a little bit of play moving it up and down and just spins when trying to fasten the small jet into it.

I have a spare set of carbs where I could take carb 2 from the rack and replace my carb 2 with that one but I need to know two thing.

1) will the air jet not fastening into the other jet properly cause issues?

2) are the carbs interchangeable

Thanks in advance

 

The part you refer to is the emulsion tube. It's a light slip-fit in the bore. Holding your thumb on it usually is enough to allow the main fuel jet to tighten, but you may need to use a wooden dowel sharpened into a cone to get a better grip on it (install with the diaphram and slide removed).

So long as you have the same model of carb they will interchange (be sure the jetting is correct as the carb body was used on several models). 2 and 3 are swappable for position on the rack if you swap the throttle hardware, but 1 and 4 are not because of how the fuel transfer ports are drilled.

 

there has to be a copper washer under the main jet