1993, 900ss, anyone using Mikuni TM 40-6 carbs - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 43 (permalink) Old Mar 11th, 2019, 7:43 am Thread Starter
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1993, 900ss, anyone using Mikuni TM 40-6 carbs

hi all,

very curious !
i want to mount flatslide carbs for obvious reasons, but dont wanna spend well over 1000 bucks.....

are there any members who have, or know one who has, experience in using Mikuni flatslides TM 40-6 ?

TDMRs are well known but also very expensive.

with using short(er) intake manifolds and possibly other alterations, it should be possible to mount those with good result right?

they are very affordable and i can do quite some things myself when it comes to metalwork.

lets hear it !
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post #2 of 43 (permalink) Old Mar 11th, 2019, 8:19 am
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Because of familiarity the Keihin is the Go To choice but Mikunis are good carbs and I donít see why they wouldnít work well. The issue is that youíll be paving new ground installing and tuning them. If you donít mind that challenge it sounds like a great project. You say they are cheap, would you elaborate on that ? Were they OEM on another bike ?

'96 Ducati SS900CR, '07 S4RS, '06 Busa, '77 Bonny,
'00 Superglide, '85 Sportster, '78 SR500
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post #3 of 43 (permalink) Old Mar 11th, 2019, 8:29 am
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I have bee working on Ducati's for over 20 years professionally, even at a top north american race/service shop. I have seen 1 Ducati in all that time run Mikuni flatslide carbs. I have a customer who is in the process of building a TT1 replica and he is going to run Mikuni flatslide carbs for the same reason you mention price. I should get the bike some time late spring/early summer for dyno work and some experience but cannot give you much more than that.

I have seen Keihin FCR's used 95% of the time as they simply are the best carburetors, but pricey. Next would be Delorto's and they work well for not much money with possibly the same design flaw that the Mikuni's have. Throttle springs. One of the benefits to the FCR's is that the slides run on rollers so you do not have issues with throttle hang-up. To get around this on the Delorto and Mikuni carbs they use very strong throttle springs which means a strong throttle hand is required to open them. If you use light springs the throttle slide gets sucked against the carb body and does not return with a light spring. It becomes a balance of stiff throttle vs slide drag.

I have run Delorto's on the track and just installed a set of Mikuni RS flatslides on a vintage GSXR750 the power gains will be similar to Keihins and both can be jetted to work. As long as you are fine doing the legwork that others before you have not and do not mind a "mans throttle" then I say go for it. Hey with increased costs someone has to start the ball rolling to help build a data base of alternate carburetors and educate us on the good and the bad. I look forward to getting the TT1 on the dyno just to start answering this question myself, but getting the bike on the track to judge throttle return will also be important as throttle hangup does not always happen on the dyno.
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post #4 of 43 (permalink) Old Mar 11th, 2019, 9:14 am
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There you go, he man slide springs. That is something workable, IMO. You may be able to get around this with a longer lower rate spring. I have a Mikuni flat slide on one bike and no issues but itís a single carb set up so Iím only squashing one spring. I donít see this as a deal breaker, just something to work out.
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post #5 of 43 (permalink) Old Mar 11th, 2019, 12:15 pm Thread Starter
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With cheaper i mean a set of 2 TM40-6 carbs can be bought now for 416us dollars. Ex shipping.
Im not an experienced tuner but i dont mind to do some dirty work and try things.
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post #6 of 43 (permalink) Old Mar 11th, 2019, 5:17 pm
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They seem to be common in pairs on snowmobiles,...

1991 900SS
1995 900SS SP #746
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post #7 of 43 (permalink) Old Mar 11th, 2019, 7:06 pm
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there's some cheap polaris pairs on ebay, but i'm guess they're 2 stroke ones and probably don't have pumps?

know all wanker
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post #8 of 43 (permalink) Old Mar 11th, 2019, 7:10 pm
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I saw many that specifically said they have pumps and the larger displacement snowmobiles have been 4 stroke for a while.
Mikuni TM Flat Slide Carburetor 40mm with Accelerator Pump
CARBURETOR TYPE FLAT SLIDE
CHOKE TYPE PLUNGER
COUNTRY OF ORIGIN JAPAN
HEIGHT 165MM
INTAKE BELL O.D.55MM
MAIN JET165 (N100.604)
MANIFOLD TYPE SPIGOT
MANIFOLD TO MANIFOLD 100MM
NEEDLE 9DJY4-96
NEEDLE JETY-6 (568)
PILOT JET17.5 (VM28/486)
SIZE 40MM
SLIDE TM40/81
SPIGOT MOUNTING O.D.44MM

Here is a picture of a used one in a pair off of an Arctic Cat but there are new ones available too.


1991 900SS
1995 900SS SP #746

Last edited by RockAZ; Mar 11th, 2019 at 7:37 pm.
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post #9 of 43 (permalink) Old Mar 13th, 2019, 10:07 am
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Tried a pair way back. Almost took both hands to wind them open, and you would need a very large diameter throttle tube to keep the required turn ratio down to something reasonable. Also as there is no data for jetting, that would take a while on the dyno to get sorted out. Their design just isn't as efficient as the FCR's. I'm sure with diligence you could make them work. The Keihins are almost plug and play. Money and time getting the Mikunis right or spend a bit more on FCR's and be done.
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post #10 of 43 (permalink) Old Mar 19th, 2019, 11:05 pm Thread Starter
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Ok after reading a bit...ive decided to up my budget and go for something i know that will work.
Fcr 41s it will be. Then there is still a choice to be made......
Split or banked. Ive read that split is more difficult to tune? And its more expensive because of intake manifolds and airfilters.

What would be your recomendations?
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