Interchangeability of carbs and carb rubbers for oil-cooled engines *WARNING - INCORRECT INFO*

[Duckndive]

13 hours ago, TonyGee said:

you might be able to clear up a mystery for me here ? i was messing about with an inazuma frame/project, i was gona use a b12 engine but i only had a set of b600 carbs i was gona use till i got a set of b12 carbs.  the 32mm b6 carbs and rubbers went on no problem ( i know the 1200 zuma uses 32mm carbs as does the 1200ss )  but when i opened the throttle it moved just a few mm ? the middle balance adjuster touches the cam chain tunnel on the head.  when i looked up zuma carbs they where the same !!   i checked the zuma rubbers part number and they where just for that model,  so my guess is are the rubbers longer than the 600 so the adjuster will clear ? i couldn't get hold of a set to measure to confirm  !!!!  

The 750 Zuma also uses 32mm Carbs and there is the clue to what rubbers they use "750" ones

  

Edited November 24, 2020 by Duckndive

[TonyGee]

1 hour ago, Duckndive said:

The 750 Zuma also uses 32mm Carbs and there is the clue to what rubbers they use "750" ones

  

the 750 zuma uses 600 bandit rubbers as the cylinder head is the same physical size, the part number for the 1200 zuma rubbers are just for the 1200 zuma !!!!  but i never got hold of a set to measure.  

[Duckndive]

1 hour ago, TonyGee said:

the 750 zuma uses 600 bandit rubbers as the cylinder head is the same physical size, the part number for the 1200 zuma rubbers are just for the 1200 zuma !!!!  but i never got hold of a set to measure.  

interesting as when i sold my 750 Zuma carbs the guy was desperate to have the manifolds as well as he could not get any ...

But as they say every days a skool day  

[TonyGee]

6 minutes ago, Duckndive said:

interesting as when i sold my 750 Zuma carbs the guy was desperate to have the manifolds as well as he could not get any ...

But as they say every days a skool day  

after all this time ive just had it confirmed (on another thread) that 1200 zuma rubbers are longer than 600 bandit and gsx 750 zuma  rubbers to fit 32mm carbs.    mystery solved. 

Edited November 24, 2020 by TonyGee
,,,,,

[Dezza]

If you are going to use the Blandit 1200 engine with Blandit 1200 BST36s and rubbers, why go to all the trouble fitting the bonsai 32mm micro-mini, "make my engine asthmatic" Iwajima carbs along with their rubbers? The B12 MK1 carbs and rubbers are probably the easiest OSS carbs and rubbers to source, although you'll probably have to do some work to bring a secondhand set up to scratch .

[TonyGee]

1 minute ago, Dezza said:

If you are going to use the Blandit 1200 engine with Blandit 1200 BST36s and rubbers, why go to all the trouble fitting the bonsai 32mm micro-mini, "make my engine asthmatic" Iwajima carbs along with their rubbers? The B12 MK1 carbs and rubbers are probably the easiest OSS carbs and rubbers to source, although you'll probably have to do some work to bring a secondhand set up to scratch .

bit of a long story Dezza,  but basically i have a 750 zuma frame and did have a 1200 motor (went in another bike)  i have a good set of 600 carbs/rubbers and zuma airbox that i was gona use. the problem was the tank i modified to fit the frame would of fowled on the top of a set of 1200 carbs. if i raised the tank it looked shit and didn't sit right with the seat unit.   

ive never ridden a gsx1200 or the GS1200 ss  but what ive read is they are still very grunty low down and in the mid range but lack top end. im not bothered about doing a 140 mph    

[Dezza]

OK, that makes sense. What part of the B12 carbs foul the tank? I ask as the BST 36s from a 750 Teapot have lower tops than those for the B12 (pics on this thread). GSXR BST 36s also vary much in 'bits that stick out and may cause clearance problems, e.g. throttle cable brackets'. Finally, BST 34s from the 1100 slabby/powerscreen are really compact compared with other BSTs, e.g. low tops, don't have bits sticking out. These fit B12 rubbers and only have an opener cable.

[TonyGee]

51 minutes ago, Dezza said:

OK, that makes sense. What part of the B12 carbs foul the tank? I ask as the BST 36s from a 750 Teapot have lower tops than those for the B12 (pics on this thread). GSXR BST 36s also vary much in 'bits that stick out and may cause clearance problems, e.g. throttle cable brackets'. Finally, BST 34s from the 1100 slabby/powerscreen are really compact compared with other BSTs, e.g. low tops, don't have bits sticking out. These fit B12 rubbers and only have an opener cable.

it was the black top on the 1200 bandit carbs, they as you know are a bit taller than the 600's.  the thing is i was trying to put together a collection of parts i had lying around and build something to mess about on ( ive been on long term sick )  so cash is tight.  but that bike has been put to one side as i'm on with the 750ET    

[jwallis]

I'm fitting some BST36SS to my Slabbie 750.  They do not fit the original carb rubbers but I have a secondhand set of J/K rubbers that work and allow me to fit the J/K airbox (shortened a little to fit).  But the Intake boots do not match the head that well, they fit but the port to boot bore match is not good.  Does anyone have the same problem, would different boots fit better or is this just something to live with?

[Dezza]

When you say 'don't fit' what do you mean? I am guessing the id of the stock rubbers is too small to enable the BST carbs to go in. If so, measure the id of the rubbers and the od of the carb stub. The carb stub should be ~40 mm. UK 750 slabbies had 29 mm slide carbs as stock but I cannot remember the stub od (it's in this thread somewhere). If this is the problem then I suspect a set of slabby 1100 or Blandit 1200 rubbers will help. The J/K 750 has a DOT head and the linlet ports are angled differently to the other oilcooled bikes so this is probably where your carb rubber/inlet port mismatch is coming from.

Also, before going in first with tech questions the OSS rules state an introduction must be made so don't be surprised to get a bollocking from the management over this - RTFR

Edited December 9, 2020 by Dezza

[wraith]

As asked.

Lh head is the gsx750f DOT head.

The rh head is a b12 MK1.

You can see the carb ports difference in height

[Dezza]

For reference: as Wraith's picture above shows there is another factor that may affect the fitting of a set of carbs to an oilcooled engine. This concerns the fitting of the 'DOT' head, from either a GSX750 teapot or GSXR 750 j/k model to a larger engine, usually a Blandit 1200. As is clear from the pics, fitting a DOT head raises the carbs ~15mm so this may cause clearance problems.

NB The barrels of the larger engines are taller than those of the short-stroke slingshot 750s so this is why there is an overall increase in the carb mounting height that will be compensated for on the stock 750 engine

[Fastfredo]

Hello, I really liked your article. I have a 2000 gsf1200 "Blandit" as you referred to them. It has black widow pipes and a modified can for flow, that"s about it. I'm kind of new to the oil cooled carburetor setups and have been chasing my tail frustrated since installing the dynojunk jet kit. I'm ready to drop some serious cash on brand new carbs and am researching what is best for my needs. The bike will never see the track and will suffer stop and go traffic on the way to the backroads where it will enjoy some brief wot action through the gears repeatedly. Problem now is after much backpedaling of jets and airbox mods I've gotten the top end power acceptable but it runs super choppy up to 3500 rpm. I'm done with the stock carbs and airbox! If my research is correct then I have MK1 mikuni 36mm cv carbs now. From your article and other sources I feel like mikuni rs 36 mm or 38mm would meet my needs nicely and offer good around town driveability as opposed to 40mm. I'd like your opinion on what filter/ carb/ rubber combo you feel would suit my situation. I couldn't find an EFI solution or I would go that route. I'm a professional automotive mechanic and have some experience with motorcycles but never messed with inline four setups. Any help would be very appreciated. 

[Dezza]

Hi Fredo, please read the forum rules and take note, especially Rule 1. You can then post a specific problem about the running of your bike that will attract people who will know far more about getting Blandits running correctly when the airbox is removed than me.

This article is only concerned with mounting different carbs on oilcooled engines. Briefly, is your bike a MK2 Blandit? If so, unless you stick with the stock carbs you will need the rubbers from an earlier oilcooled bike. To mount RSs, the easiest way to do this is using the rubbers from a GSXR 750 L or M but good luck with finding any secondhand. My guess is for the road riding you describe sticking with CV carbs is going to be the best way forward. Unless you intend to increase the power output of the machine further, you'll be best taking the bike to a decent dyno operator rather than buying a new set of slide carbs. This will also probably be the cheaper option .

 

[Romski]

While doing my build, 7/11 I managed to mix up my bst38 carb rubbers. Apart from the one with pipe, they all look the same. After several attempts of playing mix and match I decided to do the job properly. A quick look on the inter web gave me the schematic and part numbers for the correct order. Attached is the layout with some numbers incase any one else mixes up their inlet rubbers. 

[Dezza]

Beyond suggesting you research carb cleaning and rebuilding in general (much information on the internet and you can use the search function on this site) I cannot offer much else only you could try LiteTek in Thailand, a carb specialist. They may be able to help you. Hope you get your machine working sooner rather than later .

https://www.litetek.co/index.html

Edited April 13, 2021 by Captain Chaos

[lupocamino]

Wow,

this is an information that is really helpful, very many thanks Dezza!!!

[ReggiePlate]

Mikuni carb question. Difference between L and M carbs. Answered.

Edited July 24, 2021 by ReggiePlate

[Fazz711]

Think the L are 36 and the M are38 so don't think so. 

Someone will be along to confirm 

[Captain Chaos]

L also 38mm 

[Dezza]

15 hours ago, ReggiePlate said:

I have 18D00 carbs on my 1991 GSXR750M. Could I replace a faulty 18D00 carb with a 18D30 or a 17D30 from a 1990 GSXR750L? What's the difference between them. 

If you read all the information at the beginning of this thread, then you will find the answer to your question. What is the fault with your 750M carbs that is so bad a replacement set is needed?  And RTFRs too .

[vizman]

@ReggiePlateplease start your own thread in the relevant section, this thread is about the interchangeability of carb rubbers..

[Fazz711]

19 hours ago, Captain Chaos said:

L also 38mm 

I stand corrected 

[Dezza]

I have just measured up a set of BST38s from a GSXR750L, and the inlet stubs are ~46mm. The rubbers have an id of 42mm so what is going on? The stubs on these carbs obviously have thick walls but how can 46 go into 42? On closer inspection, 42 is the id of the part of the rubber that sits into the groove on the inlet stub. When looking into the rubber this part protrodes from the main part of the inner surface of the rubber, which is at least 1mm larger all round, meaning the id is at least 44mm, probably a bit more. The rubbers I have are in good condition but they're obviously not new. After a careful application of low heat along with a little GT85 silicon shine (commonly known  as "Bullshit Spray" ) the stubs slot easily into the rubbers. I know for sure these rubbers will enable secure mounting of RS38s (34 and 36 have the same 42mm stub od) as that is what I have used for my project bike. Other rubbers may also work though so post here if you know of any. In the meantime the 750L inlet rubber part numbers are:

13130-17DO

13230-17DO

13330-17DO

13430-17DO (this one has a stub to fit the hose for a vacuum fuel tap)

Obviously, it's the suffix that is the important bit as all the oil cooled carb rubbers 1-4 have the same corresponding part number prefixes (thanks for that Suzuki, not), even though they vary widely.

Edited July 8, 2021 by Dezza

[Joseph]

55 minutes ago, Dezza said:

secure mounting of RS38s (34 and 36 have the same 42mm stub od)

If it's 34 and 36 RS you are mentioning, it's the RS36 and RS38 that both have 42mm stub OD, the RS34 have a 40mm stub OD

(As per www.mikunioz.com who sell the whole range and provide all the fitting dimensions)