Carb boot confusion: BST40 onto Bandit 1200

[Denver]

After a series of unfortunate events I'm out a set of BST36 carbs for my Bandit 1200 motor and out of pure cheapness I'm considering sticking on a set of '92 750W BST40 carbs that I have laying around instead. Though a bit of searching I've found some info ¹ ²  that suggests late model 1100M and 1100N boots will work well enough to adapt these chonkers if arranged in following order: #2, #2, #3, #3. The carbs I have are 46mm OD, 40mm ID, 85-90-85 spacing.

This all sounds good to me, where I'm a bit confused is in the part numbers. So what I can see referenced is 13120-41C0 and 13130-41C0, but what I can find on suzuki parts sites are 13120-41C00 and 13130-41C00 which are superseded by 13102-41C01 and 13103-41C01, so my question is:

Can anyone confirm that the 13102-41C01 and 13103-41C01 for sure the correct boots to be using to adapt my BST40 750W carbs to my Bandit engine?

It seems pretty cut and dry, I don't see why not, I just want to make sure before throwing money at it.

Aside from that, I gather using these bigger carbs will kill some low end torque. Just how bad would it be?

Don't have a huge stash of GSXR parts handy or even in my area so trying to get by with what I have...

Thanks!

[Captain Chaos]

Welcome on OSS.

750W has 38mm carbs, 1100W has 40's.

 

[Dezza]

750Ws have BST38s not BST40s. The spacings are wildly different to oil cooled heads so the usual way forward is to fit the BST38s from a 750L or M, with the corresponding rubbers (but good luck trying to find any decent secondhand ones). My guess is trying to fit the carbs from a W is more hassel than it's worth but I have heard a mix and match approach with the carb rubbers works but still have yet to see compelling evidence. If you find this please post details and pics in the appropriate thread at thew top of the oil cooled section

If you have deep pockets, the 750L, M rubbers have the part numbers: 13130-17DO, 13230-17DO, 13330-1DO, 13430-17DO.

Edited November 27, 2021 by Dezza

[Denver]

Thanks for the replies guys, I'm not sure if it's a matter of this 750W being a Canadian bike, or if the carbs were swapped in the past, but these are 40mm carbs.

 

 

[Captain Chaos]

I think it was @yann7/11rwho said that W carbs can be mounted with some clever use of intake rubbers.

Yann to the carbs office please

[Captain Chaos]

Page 4 in the carb rubbers topic.

[Joseph]

From the archive 

Watercooled carbs have the following spacing : 85-90-85 (total 1-4=260)

Oilcooled head port spacing is : 82-95-82 (total 1-4=259)

Oilcooled carb spacing :  78-90-78 (total 1-4=246)

Oilcooled intake boot offsets are : 2,5mm on 2 and 3 and 6,5mm on 1 and 4

You can use the same intake boots on cylinder 2 and 3 because spacing of the WC and OC is the same, but on cylinder 1 and 4, the WC carbs are almost inline with the intake, so the 6.5mm offset is too much for the carbs to fit.

With a nº3 boot on cylinder 1 and a nº2 boot on cylinder 4, you're left with only 2mm of misalignment, so it is easy enough to push them in with a bit of persuasion.

Edited November 28, 2021 by Joseph

[Joseph]

11 hours ago, Denver said:

Thanks for the replies guys, I'm not sure if it's a matter of this 750W being a Canadian bike, or if the carbs were swapped in the past, but these are 40mm carbs.

 

 

They are the same dimensions externally so it would have been plug and play to fit 11RW carbs on the 750

Edited November 28, 2021 by Joseph

[Gixer1460]

Regardless of fitting difficulties - 40mm carbs are a PITA to tune even when fitted to the correct bike at the factory especially if the airbox is removed!

[Denver]

Thanks for the info guys, appreciate ya scouring the archives for that on!!

I suppose I'll just keep looking out for another set of 36mm carbs for awhile longer before I pull the trigger on some boots. They're not cheap anymore!

It's good to know that there is an option, albeit a shitty alternative that is hard to tune. It's cheaper and could work for the time being.

The plan eventually is to apply some boost to this B12 setup, in that case, the tuning difficulties and diminished bottom end would still be present with the 40mm carbs wouldn't it? 

[yann7/11r]

On 11/28/2021 at 8:46 AM, Joseph said:

From the archive 

Watercooled carbs have the following spacing : 85-90-85 (total 1-4=260)

Oilcooled head port spacing is : 82-95-82 (total 1-4=259)

...

...with a bit of persuasion.

What he said. 

[Katana]

I fitted some water cooled carbs to my 1127 and it took forever to set them up the money I saved buying the carbs was no where near the price it cost in time and jets to set them up

[Dezza]

2 hours ago, Katana said:

I fitted some water cooled carbs to my 1127 and it took forever to set them up the money I saved buying the carbs was no where near the price it cost in time and jets to set them up

Interesting. How did you get them mounted to the head?

[Denver]

Thanks again guys. As advised I've decided it's not worth pissing around with, will keep my eye out for another set of BST36's for a fair price. I do have all winter. In the mean time I've been doing lots of research on EFI conversions. I'm a nerdy guy so I think that'll probably be the route I eventually take. It's expensive but it feels a lot better spending a G or so on the goodies for an EFI swap than spending 300-400 on some 30 year old carbs. I'll start collecting parts as the deals pop up

[Joseph]

You could just spend $800 on a set of brand new Mikuni RS and be done with it 

[Denver]

7 hours ago, Joseph said:

You could just spend $800 on a set of brand new Mikuni RS and be done with it 

Believe me I thought about it... but I've always wanted to learn to do the EFI thing. So I've bought a microsquirt and now I'm committed to sourcing the rest. More satisfaction in the end I figure