1990 gsx1100F carb parts & swaps

[GaryS-NJ]

I'm looking at a '90 GSX1100F and thinking forward about carb rebuilds// The bike has BST34SS carbs and I read that the '88- early 90 has the BST34SS and then the later GSX1100F got the BST36SS.


I know with some miles, these slingslots wear at the Slide supports which allows the jet needle to wiggle in the emulsion tube which wears the tube and needle resulting in a rough transition through mid range or erratic throttle cruise. I don't think the slides themselves wear out too much.


Yet I don't see these slide supports listed as an available part yet at least one seller (Motolab) sells them for the BST36SS.. So are these BST34SS carbs serviceable (high mileage bikes?) otherwise it there another carb that will work on the '90gsx1100F??

[shpielers]

I think 750 carbs can be made to work with rejetting. Someone did the conversion last... summer? While it was definitely a 750 set, not sure if it was pre or post.

Gsxr 1127 or bandit 1200 carbs might also be possible to make work with rejetting.

[GaryS-NJ]

pre-post BST/BSR36? & bandit

thanks! I read somewhere the MK2 Bandit 1200 used a BST36SS. And I need to find out what the BSR36SS is about.. hopefully others chime in here.

[Kreylyn]

Well theoretically any of the 36mm carbs will work for the 1100 motor. So any set 89-06 750 can be retrofitted to work. Some minor mods like swapping motor boots or airbox boots to make things match might be required, but that's not really difficult to do in the long run.

What's the difference on the slide between the bst 33, 34, 36s? Is there one? If no, then ... well... motolab part would work.

Krey

[GaryS-NJ]

any 36 mm carb?

our wiki says the GSX1100F used a BST34SS. Will a 36mm carb work without loosing a lot of midrange power?? Do the BST34's and BST36's have the same distance on bore centers? and do the intake boots have the same bolt pattern to hole center? Then what about a post pat BSR36SS do they have the same bore dimensions (is the only difference the TPS and back to a normal float assy?). I'm guessing it might be easier to maintain BSR36SS but do they have same issue with the slide supports and needles/emulsion tube wear? lots of questions and I'm sure there are folks here who have put some miles on their kat1100's


oh as for the BST 33, 34, 36 slide support, it is different (probably the bore at minimum and motolab can't get them for the BST34. I wonder where he gets them for the BST36 and for how long...

[RobertTravis]

If there isn't anything wrong with your 34s I'd leave them. Clean them up, lube the shafts and other wear items and slap it back together.

I don't think anyone can give you a definitive answer on the 36s in terms of spacing and midrange. It's something you'll just have to try.

If I was going through all that effort, I'd be more inclined to convert it to fuel injection using late model throttle bodies (off of anything that fits) and Megasquirt or other DFI. The ignition can be left as-is or upgraded too. With DFI you have complete control and never have to mess with carbs again. Just sayin'...

[GaryS-NJ]

fuel injection?

Good point on FI. I just have no experience with it so it didn't cross my mind.


I'm guessing the slide supports are worn out. along with the jet needles and emulsion tubes. bike has 30k MIles. Anyone have experience with high mileage kat1100??

If there isn't anything wrong with your 34s I'd leave them. Clean them up, lube the shafts and other wear items and slap it back together.

I don't think anyone can give you a definitive answer on the 36s in terms of spacing and midrange. It's something you'll just have to try.

If I was going through all that effort, I'd be more inclined to convert it to fuel injection using late model throttle bodies (off of anything that fits) and Megasquirt or other DFI. The ignition can be left as-is or upgraded too. With DFI you have complete control and never have to mess with carbs again. Just sayin'...

[RobertTravis]

High miles? Mine has 25k on the clock & I think she's just getting broken in. These motors are bulletproof. My slides etc are all in good shape (and currently off the bike).

If the carbs sat out in the rain, that might help them deteriorate...Did you measure the slide and the channel? How much slop is there? They aren't like a linear bearing...they're plenty sloppy when new. I just had the carb on my 2013 KLR today and it's like throwing a hotdog down a hallway....REAL sloppy. But that's how they are.

[katanarider]

If there isn't anything wrong with your 34s I'd leave them. Clean them up, lube the shafts and other wear items and slap it back together.

The Kat-1100 intake pipes (Boots) are no longer avaiable, atleast the #1 cylinder isn't. How do I know, I bought the last one off ebay from a guy that had NOS from his Gixxer rebuild...And I'm still pissed, because I can't get the o-ring to seal.

[RobertTravis]

Why can't you get the o-ring to seal? Did you put a little vaseline on it?

[shpielers]

Might make it a PITA to remove later if required, but ....rvt?

[katanarider]

The o-rings that come from Suzuki are really thin (2.5mm thick), I thought they were just too small to seal good. Then I bought some 3mm thick ones from Grainger, but those aren't sealing either. I spray carb cleaner around them after starting the bike, and the RPMs go up every time. I tried letting the bike warm up to soften the o-rings, then quickly removing the carbs to snug the screws, still no luck.
I'm thinking I'll just cut some paper gaskets and try that next.
Gary, if I had it to do over, I'd get some Bandit 1200 carbs. I've test fit the intakes from a Bandit on my Kat-1100 and they fit perfect and they're still available. As a matter of fact, I have a set that look really good/no cracks. I'll ship them for $50, which is what I have invested. If you put B-12 carbs on, you'll just have to block off one of your gas outlets at the petcock. The B12 carbs only have one gas inlet.

[RobertTravis]

Before you go through all that...I've found that I need to SEE what is going on a lot of times rather than guess or deduce what should be done.

Try this....Get a clear piece of acrylic and smear a very light film of vaseline or even motor oil onto the boot & o-ring where it is supposed to seal to the head. Then, press it against the acrylic towards you so you can see what the contact patch looks like & where the problem is EXACTLY...then you'll know what to do.

I have a feeling that maybe that boot is somehow distorted and is fighting the o-ring from sealing flat. If you get a piece of acrylic from Depot/Lowes you can use 2 clamps to mimic the mounting bolt pressure and see if it is in fact pulling down or staying distorted. You can use glass too...but obviously not a good idea with clamps.