Keihin Twin Carb Mods?

[Gorkon]

Well it isn’t really mods so much that I want, I just don’t know what else to call it. I got the carbs for the SS 338 project and sat down with a couple of good small files and cleaned all the casting flash up on them. There was a bunch on the outside of the tail end of the venture tube and I cleaned that up, but then noticed that there is quite a bit of a mess on the leading edge of the venturi as well.

The thought occurred to me that maybe there is some gurus out there when it comes to increasing airflow in these carbs? I have seen articles years ago on doing things such as I have in filing off the casting flash, right down to some guys filing the down the butterfly screws!

I don’t think I’ll even go that crazy, but I’m looking at pictures of modern venturis and the way they’re shaped compared to these flat, rough looking things and thinking that maybe they should be shaped the same. But I don’t know for sure and don’t want to screw up a pair of carbs!

I know that I would have to drill out the passages to do anything much to these, and I don’t think I’m maybe quite prepared to go there yet. But perhaps someone can enlighten me to the things I can do, or where I can go find out more.

I was looking at the Boyesen power wings at the sled show last week and thought I might make a pair for this old girl. Lol.

I don’t think it would be too difficult and I can’t see why it shouldn’t provide just about the same benefits to this application as it does to the others. It’d be fun anyway. Thanks. G.

 

[yamaha one]

Drill out your low speed jet too a much larger size, it will help your take off speed from 3500 to 6000 rpm.

 

[Gorkon]

Okay, perhaps you can clarify that for me? I've been searching for a thread here I recall about Mikuni's vs Keihins that has some information in it, but can't seem to find it. On the left side of the carb is two screws/needle valves, and at the back there is a brass ball plug to a passage. Those are the only things I can see. It looks like that passage goes to three small holes in the floor of the carb just ahead of the butterfly, very obviously so the thing will run and idle at least.

Can one still buy parts for these carbs? There must be rebuild kits, or should I say, must have been for all the soft parts inside, diaphragm and o-rings etc. I have a friend who has and is suggesting a pair of banshee carbs, but I'd really like to keep the oil injection working. I can see lots of tinker time in the shop coming. Thanks. G.