Interchangeability of carbs and carb rubbers for oil-cooled engines

[Dezza]

3 hours ago, Lachie04 said:

@Dezza

The Flat slides did not go on the 98+ teapot rubbers, as far as I know, you can only alter the internal spacing of RS Carbs between 2-3 to 85mm not the outer pairs but I have never played with them that way

 

Which rubbers did you use to mount the RSs to your dot head? Do you have any id measurements of the rubbers you used?

[Ted M]

8 hours ago, Dezza said:

 

Also, Ted, what is the od of the MK2 inlet stubs on the BSR36 carbs? I cannot quite make it out from the pics

I’ll check in a bit. I’ve got a dot head with no rubbers I’ll measure the inlet port spacing if you think that would help

[Ted M]

The OD of the Mk2 inlet Stubbs is 42mm

[Dezza]

10 minutes ago, Ted M said:

The OD of the Mk2 inlet Stubbs is 42mm

Excellent! The stubs are probably a little larger than on BST36s and probably have walls a little thicker It's a shame the rubbers are all to cock spacing wise or otherwise these could be used to mount RSs and BST38s from the 750 l or m

[Captain Chaos]

15 hours ago, Dezza said:

MK2 carbs and rubbers can be transferred to a MK1 head as a complete unit.

I once had B12 Mk1 carbs and wanted to put them on a Mk2 head + rubbers and they went in without too much trouble, but they didn't stay in. One fart/sneeze near the bike and they popped out. Tightening the clamps did not help much.

[Dezza]

8 hours ago, Captain Chaos said:

I once had B12 Mk1 carbs and wanted to put them on a Mk2 head + rubbers and they went in without too much trouble, but they didn't stay in. One fart/sneeze near the bike and they popped out. Tightening the clamps did not help much.

That makes sense: they seem to be a little larger id than for the BST rubbers.

[Svsam]

On 11/20/2019 at 2:00 AM, Dezza said:

Thanks Ted. Your set up confirms that the MK2 carbs and rubbers can be transferred to a MK1 head as a complete unit. What I cannot understand is if the 98+ teapot carbs and rubbers are the same as MK2 Blandit items, how using the 98+ rubbers enables the mounting of a set of 77-93-77 RSs on a 750 dot head, unless the 98+ teapot heads have a unique casting with different inlet port spacings.

 

Also, Ted, what is the od of the MK2 inlet stubs on the BSR36 carbs? I cannot quite make it out from the pics

I have been in the garage every night after work this week trying to fit the mk2 bandit carbs on my b12 dot head, I have the original dot rubbers, the original b12 rubbers and 3 more sets of rubbers that I've purchased and no joy 

ive got a set of 40mm carbs with rubbers which won't suit the engine but tomorrow I will try fitting them to confirm the head spacing is 'unique ' which will be annoying if so as I've just ordered a set of 38s  when I guess I may need dot specific... hmm

[bluedog59]

If wonder if they are the same spacing as early w/c engines ? I have a set of w/c 38's that measure up at 38 I/d, 45 o/d,  85-90-85 spacing. 

[Dezza]

2 hours ago, bluedog59 said:

If wonder if they are the same spacing as early w/c engines ? I have a set of w/c 38's that measure up at 38 I/d, 45 o/d,  85-90-85 spacing. 

Funny you should say this as I thought the same so then the 750W BST38s would go onto an oil-cooled head using MK2 Blandit rubbers. Unfortunately, the Blandit MK2 spacings are 80-85-80, so thanks for that Suzuki

[Dezza]

3 hours ago, Svsam said:

I have been in the garage every night after work this week trying to fit the mk2 bandit carbs on my b12 dot head, I have the original dot rubbers, the original b12 rubbers and 3 more sets of rubbers that I've purchased and no joy 

ive got a set of 40mm carbs with rubbers which won't suit the engine but tomorrow I will try fitting them to confirm the head spacing is 'unique ' which will be annoying if so as I've just ordered a set of 38s  when I guess I may need dot specific... hmm

If they'll go on at all, then I would suggest the MK2 Blandit rubbers. Other rubbers will give you 77-93-77 carb spacings, which is all to cock for MK2 Blandit BSR36s.

 

I assume you have a 750 dot head on a Blandit 1200 engine. With the MK2 Blandit rubbers on is it the spacings preventing fitting or something else, e.g. fouling the frame, angle of the carbs causing problems etc.? My guess is that with the MK2 rubbers, the spacings should be fine for the MK2 carbs, but that does not preclude other problems causing fitting problems. A 750 dot head (from GSXR 750 j,k or some 750 teapots) will have carb spacings of 77-93-77 when used with the rubbers from other OSS bikes except MK2 Blandits and 98+750 teapots

 

E.g Although I used 750L rubbers to mount RS38s to a Blandit 12 MK1 head they still wouldn't fit as the throttle linkage bracket fouled the frame. So please post your findings as they will be very useful.

 

All this is in the latest version of the article (will post soon) so I am going to stop here to avoid me turning it into.........

Edited November 22, 2019 by Dezza

[Svsam]

8 hours ago, Dezza said:

If they'll go on at all, then I would suggest the MK2 Blandit rubbers. Other rubbers will give you 77-93-77 carb spacings, which is all to cock for MK2 Blandit BSR36s.

 

I assume you have a 750 dot head on a Blandit 1200 engine. With the MK2 Blandit rubbers on is it the spacings preventing fitting or something else, e.g. fouling the frame, angle of the carbs causing problems etc.? My guess is that with the MK2 rubbers, the spacings should be fine for the MK2 carbs, but that does not preclude other problems causing fitting problems. A 750 dot head (from GSXR 750 j,k or some 750 teapots) will have carb spacings of 77-93-77 when used with the rubbers from other OSS bikes except MK2 Blandits and 98+750 teapots

 

E.g Although I used 750L rubbers to mount RS38s to a Blandit 12 MK1 head they still wouldn't fit as the throttle linkage bracket fouled the frame. So please post your findings as they will be very useful.

 

All this is in the latest version of the article (will post soon) so I am going to stop here to avoid me turning it into.........

Yes it’s a dot head from a gsxr on a bandit motor. 
When using the mk2 bandit rubbers the outer stubs 1 and 4 line up but the inner 3 and 4 don’t. Same with all sets of rubbers to be honest. 
in terms of other things getting in the way, the throttle cable bracket sits too high stopping the tank from going on. That’s the biggest problem..if I ever get them on comfortably. 
I’ll attach a couple of pics I nipped out and took before work. 
and over the weekend I’ll measure the carbs on a gsxr750 j/k I got and see how the bandit carbs line up against the long stroke 750 engine I got in the shed. 
I have a feeling it could be the dot head casting that is slightly different 

 

Edited November 22, 2019 by Svsam

[Svsam]

[Svsam]

Another evening in the garage. 
so none of the carbs line up with any of the carb rubbers on the dot head. 
the gsxr750j/k that I use as a run around has got bst40s on it...don’t think that’s standard, but the carbs seem to be space right for the rubbers on the other (problematic/project) bike, but obviously won’t take 40mm carbs. 
ive worked out the rubbers that were on the dot head originally were mk1 bandit 600 rubbers..

I have written down my carb gap measurement. 
and you can see the difference in the carb stubs. 
 

oh, and the bsr36 carbs pushed straight onto the 749 (not dot) engine. then logic would say use them rubbers on the dot head, but I already had a set of those rubbers and didn’t work 

[Dezza]

Performance carbs for 750 slingshots are sold with 'normal' spacings, 77-93-77, so with 750 j,k rubbers they should go on. Your BST40s come from a watercooled model so it is a mystery as to how they went on an oil-cooled bike. Can you do some cross referencing of the part numbers on the rubbers? You seem to have an eclectic mix there! Is your 'dot' head from a 750 teapot 98+? If these have dot heads they are likely to differ to the usual dot heads, i.e. those from the 750 j,k or the earlier 750 teapot, because from 98+ these bikes had BSR36 carbs not BST36.

[Sagot]

Hi guys. I'm new to this forum and just happened across this post.

I am building a 1987 GSXR 1100 with a 2001 Bandit 1200 engine (MK II) (82-86-82) so...

If I buy MK I rubbers, I should be able to mount 77-93-77 carbs on the MK II head.

Is this correct?

MK II carbs (BSR) are hard to find!! For some reason.

Apologizes  if I'm being redundant .

[Dezza]

2 hours ago, Sagot said:

Hi guys. I'm new to this forum and just happened across this post.

I am building a 1987 GSXR 1100 with a 2001 Bandit 1200 engine (MK II) (82-86-82) so...

If I buy MK I rubbers, I should be able to mount 77-93-77 carbs on the MK II head.

Is this correct?

MK II carbs (BSR) are hard to find!! For some reason.

Apologizes  if I'm being redundant .

I am going to stick my neck out here: yes! Please post your results. Obviously, get the complete set of rubbers from the donor bike. MK1 Blandit rubbers will probably accept the most different models of carbs. If you want RSs, then use GSXR750 l,m rubbers (getting difficult to obtain) or else enlarge the Blandit ones.

[Sagot]

Thanks I'll try it.

[Svsam]

On 11/22/2019 at 10:37 PM, Svsam said:

Another evening in the garage. 
so none of the carbs line up with any of the carb rubbers on the dot head. 
the gsxr750j/k that I use as a run around has got bst40s on it...don’t think that’s standard, but the carbs seem to be space right for the rubbers on the other (problematic/project) bike, but obviously won’t take 40mm carbs. 
ive worked out the rubbers that were on the dot head originally were mk1 bandit 600 rubbers..

I have written down my carb gap measurement. 
and you can see the difference in the carb stubs. 
 

oh, and the bsr36 carbs pushed straight onto the 749 (not dot) engine. then logic would say use them rubbers on the dot head, but I already had a set of those rubbers and didn’t work 

Right, 

after a lot of fiddling and a bit of buying and a lot of swapping... with my tail between my legs I can confirm that:

mk2 bandit carbs fit both 748 and 749 head using mk2 bandit rubbers. 
turns out a bit of fire helps the carbs settle in  

can also confirm that bst38s have no chance at all of squeezing into the 750 frame with a b12 engine in!

I apologise for earlier confusion @Dezzai think I was so convinced the bandit carbs would fit I just wrote them off 

Edited November 29, 2019 by Svsam

[Dezza]

The 750 carbs are 5mm shorter than those of the 1200 Blandit, so would bring the bank 5mm closer to the head. There is still no guarantee that any particular frame, carb, carb rubber, engine, head combo would fit without surgery though There are so many different possible combinations that for some all that can be done is to suck-it-and-see.

[Captain Chaos]

9 hours ago, Svsam said:

can also confirm that bst38s have no chance at all of squeezing into the 750 frame with a b12 engine in!

confused.gif

I have a Powerscreen (GSX1100F) lump in the 750L, F engine is the same size as B12 engine. With the 750L carb rubbers the 38mm carbs fit very nicely, can even fit the original airbox.

A mate also had this combo (1100F engine in 750L) and later swapped for a B12 engine and had no problems, straight swap.

 

[Captain Chaos]

9 hours ago, Svsam said:

can also confirm that bst38s have no chance at all of squeezing into the 750 frame with a b12 engine in!

looking at earlier posts maybe you mean 750J/K?

I assumed you were talking about 750L/M since that's what the 38mm carbs came on originally.

[Svsam]

4 hours ago, Captain Chaos said:

looking at earlier posts maybe you mean 750J/K?

I assumed you were talking about 750L/M since that's what the 38mm carbs came on originally.

Yes, 750j and k models. I think the dot head makes the engine a little bit taller too thinking about it as you don’t use the cam chain roller between the cams like the standard 1200 so it could just be my setup. 

[Crass]

On 11/15/2019 at 4:34 PM, baldrick said:

Or am I opening up a minefield here?

Sorry baldrick, that did make me chuckle. I used to work with a bloke who was a master at mixed metaphors and he often creased us up (opening up a can of worms / stepping into a minefield) 

[Lachie04]

On ‎12‎/‎1‎/‎2019 at 2:00 AM, Svsam said:

Yes, 750j and k models. I think the dot head makes the engine a little bit taller too thinking about it as you don’t use the cam chain roller between the cams like the standard 1200 so it could just be my setup. 

The DOT head inlets are angled up @ 5° (I have a photo somewhere if your interested) together with MKII inlet rubbers @ 5mm longer then it is possible you may run into clearance issues with that setup

 

 

Edited December 5, 2019 by Lachie04
Added photo

[Dezza]

2 hours ago, Lachie04 said:

The DOT head inlets are angled up @ 5° (I have a photo somewhere if your interested) together with MKII inlet rubbers @ 5mm longer then it is possible you may run into clearance issues with that setup

 

 

Very useful, many thanks