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A question for the masses! Has anyone here ever run a set of Mikuni VM29SS carbs on a GS1000 engine? I recently puchased a set and intend to give them a shot on my project. Comments?
NorCalSuperF
NorCalSuperF
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Did those ever come OEM on any bikes or were they always an aftermarket thing?Comment
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The VM29SS were the OEM carbs originally mounted on the 85'-86' GSX-R 750 (NON U.S.A.) models. Mikuni's first flat-slide, racked, production carbs. I believe that the DR250/DR350 bikes used a very similar carb, the TM33 in the early 90's.
The center of the throat of the VM29SS has a bore of 33mm with the opening at the cyl. head side slightly larger at 33.65mm, the filter/intake side is reduced to an opening size of 29mm. I thought that I had read on the net that some have bored these models to a straight through 33mm which I see as impossible since the slide itself measures a maximum of 32.85mm wide.
NorCalSuperFComment
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VM29's were preformance carbs for the GS750/850/1100 small port heads to replace the stock VM26's. The larger port heads 80 up they went to the VM33 carbs also as a preformance upgrade. Flatslide are another later model carbComment
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Allow me to school you on the subject.
I'm not posting on the topic of the well known Mikuni VM29 "Smoothbores" or the VM33 for that matter. Ths carbs I'm referring to are an entirely different deal, they are VM29SS "flat-slides", follow the link and it will help to clear this up.
http://www.gixxer.com/forums/showthread.php?t=178425Comment
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Vm29ss
I HAVE JUST PUT A SET ON MY KAT 750 S2,..IT RUNS GREAT WITH THEM.,FITTED STRAIGHT ON & THEY FIT INTO THE AIRBOX RUBBERS OK..BUT YOU WILL NEED A PUSH PULL THROTTLE UNIT FOR THEM,(I'VE FITTED A SPRING ON MY CARBS FOR THE TIME BEING THOUGH, TO ENSURE THE THROTTLE SNAPS SHUT,TILL I CAN FIND MY SPARE PUSH/PULL UNIT). I RECON THEY WILL BE A BIT ON THE SMALL SIDE FOR THE 1100 MOTOR,BUT TRY THEM SEE HOW IT GOES...THEY WILL PROBABLY GIVE YOU LOADS OF BOTTOM END,BUT BE RESTRICTIVE ON THE TOP END. ALL THE BEST DEANOTEK.
the guys over on oss recon theyre a great carb for a [COLOR=#0000ee! important][COLOR=#0000ee! important]stock[/COLOR][/COLOR]ish 1100 motor. though if you start tuning to any high degree then you might need to go for a bigger set of flatslides. however, they are very prone to wearing the slides. my fave on the kat motor is the cv flatslides off the 750 slingshot, 36 or 38 mm iirc, bonkers acceleration yet still able to pootle round town
Comments on this auction
Hey there, what sort of condition are they in? Would I be able to use them in there current state? Cheers Greg. posted by: sunwukong1 (113 
) 12:06 pm, Tue 8 May
Howdy.Basically a complete set of working carbs.May need to be rejetted to suit application.Only thing I find with these is that they have a tendency to ride a little when the throttle is shut off.Not as good in that department as say a set of CV's with throttle butterflys.Cheers 12:46 pm, Tue 8 May
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Thanks for the extra example links posplayr! Those are the units.
NorCalSuperFComment
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NorCalSuperF
U should probably post a question over to OSS to find out about them carbs. More stuff I found.
Pos
This was covered a few months ago in a post covering boring (as in enlarging) standard slabby VM29ss flatslides. The pumps only work for a short while when the carbs are opened - mine don't wor continuously from shut to open. The plungers feed fuel to the neighbouring carb aswell as to its own carb. I'm not convinced they are needed if you either have the revs well up or can feed in th ecarbs smoothly. I think their main use is to give the engine a dollop of fuel when the carbs are snapped open from low revs when the air flow is low and there is not enough vacuum to get onto the main jet. Mine were blocked and it still carburated OK. Cleaned them up when I bored the carbs to 33mm straight through and radiused and polished the throats and now they do squirt. Note that they squirt out of the side of the tube not the top.
I used o be a carbophobic too but slide carbs are relatively simple to work on because the y do what you tell them to. CVs on the other hand skare the living sh*t out of me.
I can tell you what jetting I have used on various incarnations of my slabby carbs if you nedd the info.
canamant
Anyway, moving on to carbs. As far as I know the only flat slide carbs (as opposed to "flat slide CV carbs) fitted to GSXRs were 29mm. Yes, they do appear to be "doctored" 33mm jobbies where the front plate has been reduced in height to 29mm with the bottom of the front plate and the bottom of the main carb body at the same level. You can take the front plate off if you have the correct driver, mount the "bell mouth" in a lathe, and open up the throat to 33mm. Thi stakes nothing off the bottom, 4mm out of the top, and 2mm out of each side. The slide still seals and full lift still clears the top of the venturi. You will need to radius the new bore on the front plate. I polished mine for good measure too.
I jetted up to 142.5 (well I drilled a set of old jets cos I have machining facilities in my lab) and raised the needles to the bottom groove on the clip. The unmodded carbs were jetted at 137.5 with no airbox and just the rubber trumpets from the airbox.
Lez. What exactly was the acc pump arrangement. If the pump jets were missing, but the plungers were in place, the petrol would just dribble out of the opening from the float bowl.
Canamant
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Hey! Pos how did you find out about trademe?Originally posted by posplayr View Posthttp://www.mypixshare.com/rdaries/a11473
Comments on this auctionHey there, what sort of condition are they in? Would I be able to use them in there current state? Cheers Greg. posted by: sunwukong1 (113 ) 12:06 pm, Tue 8 MayHowdy.Basically a complete set of working carbs.May need to be rejetted to suit application.Only thing I find with these is that they have a tendency to ride a little when the throttle is shut off.Not as good in that department as say a set of CV's with throttle butterflys.Cheers 12:46 pm, Tue 8 May
dont want the the prices to go up
CheersComment
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KiwiGS
GooglemeisterPos how did you find out about trademe?
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Now worries, shipping would be a killer to SCal
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PosComment
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