[GSX1100S] Check It Out Now! The Legendary Katana’s Stock “Mikuni BS34” Carburetor Inspection

I absolutely love vacuum carbs with air cleaner boxes.
I used to say “Keihin carbs are the way to go,” but… there’s this theory that Keihin carbs wear terribly.
When you think about it that way, Mikuni is abnormally robust, and I’m genuinely rediscovering that now.

Plus, the BS34 has such a long history…
It was used all the way through the last GSX1100SY. And it became a twin-cable setup, which is nice.
To be precise, using the BS34 from the SR/SY should definitely be better.

I’ll keep moving forward without saying anything unnecessary.
The earthquake preparations have settled down quite a bit.

Boing! Extremely simple! BS34

Basically, Mikuni vacuum carbs are extremely simple *except for the BSR.
Well, but for this generation, “the co-tightening plate is annoying” is the thing.
The throttle cable, idle screw, and choke linkage

are nothing serious once you get used to it.

There’s some age-related deterioration.

Since it’s been over 30 years, serious work gets complicated.
It’s important to consider cost-effectiveness as you proceed. Spending more time and money doesn’t necessarily mean better results.

BS34’s unique fastening method.
Circlips… lots of parts involved.

The plastic pin has positioning too, so be careful.

Only #2 shows signs of ignition.
The others were fine.

While the parts are out, I’ll replace the small parts.
*Surprisingly reasonable.

This time, a simple top-and-bottom overhaul.

I’ll remove just the top and bottom and replace only what’s necessary.
It’s reassuring to poke new parts with a cotton swab too.

This part is interesting.
If the tank rusts too much, it clogs and causes stalling…
Also, there’s a filter that goes into the T-fitting, which can also cause stalling, so be careful.

Actual fuel level or float level?

Probably, what matters is the actual fuel level.
The actual fuel level is real, so if you can see it, you should check it.

Mikuni makes this special angled extraction tool. Or did they?
It looks convenient, but I have some doubts about the flow logic.

Lock nut-style synchronization brings back memories.

When you lock it tight, it moves, so you need to factor that into your adjustment.
Carburetor synchronization should be “quick and good enough.” Don’t waste time running the engine hot and stressing it out.

It’ll drift anyway, so “good enough” is the tricky part.

All done quickly.

I’ve been so focused on earthquake prep, it’s been a while since I worked on something like this.
Things are progressing steadily!