1100 Slabside Carburettors RS FCR BST

[Metralla]

I have an 87 1100 and I struggle with the BST34s.
The problem I have is that they require rebalance when I take them out and change needle position etc.
Also another problem I have is that they are very rich below 3000rpm with OEM filter and there is no free flow filter available, currenly I am running an old UNI foam filter, but at somepoint it will perish. K&N was not helpful, they old told me it is NLA, therefore with the airbox, the only option is normal paper filter. I am also running an old Dynojet kit.
I have tried to source '88 (J) carbs, but slides sliders had lots of play, they were rattling badly and I have been told this is a weak point of those carbs. If the plastic sliders are available please let me know.
Thus I am thinking of fitting Mikuni RS34 or Keihin FCR35. The challenge I have with mechanical carbs is that I will need to fit push pull throttle tube. I have 750 switch that could be used, but can I use 750 cables? Are they compatible length and endpoints wise?
I am using 750 clipons and I do not want to use aftermarket clipons.

Edited September 26 by Metralla

[Markz9]

Part of the problem is the carbs are so old and worn its not worth trying to refurb them i would go for a new set of rs34 or 36 you will notice immediately the improvement 

worn slides is a problem with all flatslide carbs its not just the slide itself that wears but the alloy body as well, if this was a race bike it would be minimal difference since you should have it pinned open anyway but a road bike is much harder to live with 

so i would recommend a new set, i just bought a new set of rs40 for £606.00 from orient express but i am working in the usa so that helped keep the cost down 

the push pull trottle is easily resolved with different right hand throttle casing, venhill will make any cable fittings and any length you require

[Metralla]

42 minutes ago, Markz9 said:

Part of the problem is the carbs are so old and worn its not worth trying to refurb them i would go for a new set of rs34 or 36 you will notice immediately the improvement 

worn slides is a problem with all flatslide carbs its not just the slide itself that wears but the alloy body as well, if this was a race bike it would be minimal difference since you should have it pinned open anyway but a road bike is much harder to live with 

so i would recommend a new set, i just bought a new set of rs40 for £606.00 from orient express but i am working in the usa so that helped keep the cost down 

the push pull trottle is easily resolved with different right hand throttle casing, venhill will make any cable fittings and any length you require

Well, what RH throttle casing is compatible with the wires (switches) and the OEM RH clip on?
Also do the RS offer vacuum outlet for the OEM petcock?

Edited September 26 by Metralla

[Upshotknothole]

It's usually easier to wire up a switch housing that doesn't have a throttle integrated in it and use a standalone push pull throttle. Motion Pro makes a cheap one that works but isn't terribly fancy. Otherwise Domino makes a bunch.

RS carbs do have vacuum ports for syncing that you can use for the petcock, but depending on the size carbs you go with, RS carbs can push a stock petcock to the limits of how fast it can flow at wide open throttle.

Also double check the size of carbs you want. RS34s are really small. I wouldn't even run them on a 750. RS36s are usually used for good mid range and streetability, personally I prefer RS38s for the street, but you give up some bottom end.

Your clipon shouldn't make any difference to anything outside of throttle cable lengths.

With the mechanical carbs are you planning on keeping the airbox or going with pods? Do you have a full exhaust on the bike? Plan on scheduling some time on a dyno for tuning it too, RS carbs just come with standard baseline tunes, they'll need to be adjusted.

As far as syncing your carbs every time you work on them, try getting them tuned the best you can first, and then sync them last to sort out any final running issues. Syncing them after adjusting the needles seems like a big waste of time if you're still making other adjustments.