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mikuni 28mm roundslide carbs

charles d cannon jr

Active Forum Website User
VOC Member
I've got pair of two Mikuni 28mm round slide carbs that I'm contemplating using on my Shadow. Does anyone have any main jet sizes, needle positions, and throttle slide cutaway sizes that have worked well for them? Thanks, Charles Cannon
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Dear Charles,
I have two VM28 Mikuni carbs fitted to my Rapide. They were supplied to me with the following settings.

Main Jet 190
Needle Jet P-6 (182)
Needle 5FL 14
Slide 2.5
Pilot Jet 30
Air Jet 2.0

I have subsequently reduced the main jet size to 160 and have used these settings for around 30,000 miles. My motor has 7.3:1 pistons and Mk1 cams. It regularly returns mid to high 50's to the the imperial gallon.

You could use the settings in the table as a starting point and then tweak them to suite the specification of your motor, exhaust system, etc.

I've got pair of two Mikuni 28mm round slide carbs that I'm contemplating using on my Shadow. Does anyone have any main jet sizes, needle positions, and throttle slide cutaway sizes that have worked well for them? Thanks, Charles Cannon
 

stumpy lord

Well Known and Active Forum Website User
VOC Member
Hi, These are the settings that I came up with following a session on a rolling road

carbs are 28mm vm mikunis
Main jet 150

pilot 30

airjet 0.5

needle jet 159 p5

slide2

needle 6f5

the rear needle is in the top grove and the forward one is seacond from the top, appart from that both carbs are set the same.

the bike is fitted with mark one cams, eight to one pistons, and is twin plugged in both cylinders. Ignition is by Francoi grosset ignition ,and is timed at 26 b. t..d. c, fully advanced giving about 3 degrease fully retard.

at the end of the session the bike was turning out 45.5 b.h.p an increase of 5 B.H.p, and now on the road feels a lot crisper.
Well worth the money spent.
stumpy lord [norman]


I've got pair of two Mikuni 28mm round slide carbs that I'm contemplating using on my Shadow. Does anyone have any main jet sizes, needle positions, and throttle slide cutaway sizes that have worked well for them? Thanks, Charles Cannon
 

ClassicBiker

Well Known and Active Forum Website User
VOC Member
I've been running VM28 Mikunis for awhile. I compiled a table from what people have said their settings are on their various sized Mikunis (34mm down to 28mm) on this forum and on www.theVincent.com. I've tried to attach it to this reply. The table not only contains the main jets, throttle valves, pilot jet, air jet, needle jet, and jet needle, but also the annulus area created by the needle jet and the jet needle. Incidently my settings are the last one listed as 180 main, 3.0 slide, 35.0 pilot, 3.0 air, 169 P-2 Needle Jet, and 5DP7 Jet Needle. Hope this helps out.
Steven
 

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