Mikuni carb

[Mickey Sergeant]

Looking at a new 26mm vm round slide carb for a 74 Berkshire.Would this be a good choice.Or maybe a 28mm.Is this carb legal for vintage racing.If so would it mount corect or does it require a different boot to mount on cylinder?

 Mickey Sergeant
 74 Berkshire

[Dwight Rudder]

Actually a great choice for that bike.

[joe novak]

Sometimes the MIKUNI type carbs must be mounted to the Sachs cylinder by using a rubber hose which looks like a short radiator hose, using two radiator clamps.  I think this is an idea set-up for several reasons.  The rubber insulates the carb from heat and vibration, it lengthens the plenum (is this the correct word and spelling?).  I think either size carb will work, depending upon what type of riding you intend to do.  The smaller carb (26) will be more of a stock replacement, and work better for low and mid-range power.  The larger carb will be a performance improvement.   I ran a larger BIG carb on my 1974 Penton Berkshire and it worked great, but the engine had quite a bit of port "cleaning", and an internal Moto-Plat which enhanced the upper end of the power band.  Either carb must be jetted correctly!  Just be sure the carb is sealed well so dirt does not get in... and check the spark plug for color which shound be a light chocolate brown.

[brian kirby]

If you intend to race AHRMA, 28mm is the maximum allowed in the rules for a 100. Mikuni made a 28mm but it has been discontinued. The 28mm can still be found, but right now Mikuni makes either a 26 or a 30 and the 30 is a larger body size than the 26-28 which makes it harder to mount. I love Mikunis, and generally prefer them to Bings, but I would recommend you find a 28mm Model 84 Bing, it will make noticeably more power than the Mikuni and it mounts like stock.

Brian

'72 Berkshire

[Mickey Sergeant]

Are you talking about radiator hose that can be purchased at any automotive store.I'm guessing no one makes a rubber boot for this aplication.

[Ernie Phillips]

Photo shows small body 28mm Mikuni mounted with radiator hose and hose clamps.  Note how you have to squish the air box boot to get it to fit.  We mounted the Mikuni becaude Christopher was having a hard time after a spill with the Bing loading up.  Now that he is a better rider, if we race this Berkie, it will have a Bing.  

As a side note, last weekend at New Blaine I watched several Husky riders with Mikuni's kick-kick-kick ... if they only knew how to tune a Bing;)



Ernie P.
Chattanooga, TN

[DKWRACER]

Ernie P, is correct with respect, with the mounting of a 28mm Mikuni. I have an article "Super Sach's Secrets" which describes modifications......Authored by "Bill Wright", so like, who was this guy? was he privy, to the ISDT, and tuners of a place in Penton History. The article is pure, I will send it , just ask.......
Never seen a 28mm Bing, is there such a thing?
Tom Brosius

[brian kirby]

I definitely have a 28mm Bing Model 84 on my 100, dont know what it was originally for because it is not stock and was on the bike when I got it. The number on the carb is 1/28/511, I know Bing can tell what it was for with that number but I've not called them to find out. Bultaco Sherpas and Alpinas also came with 28mm Bings, which  have the choke circuit along with the tickler, but they were the "male" flange where mine is the standard "female" like on a Penton.

Brian

'72 Berkshire

[Mickey Sergeant]

Seems to me that you might as well spend the extra money for a bing.They mount without any modifications.Am I wrong or am I missing something?

[brian kirby]

The trick is if you plan to race AHRMA you are limited to 28mm and the one on my bike is the only one I have ever see with the female flange. Victor Monz says he has some, but I've only seen mine in person. The Bultaco 28mm Bing would be just as difficult to mount as a Mikuni since the flange is the same type. If you do not have to worry about AHRMA rules I would put a 30mm off a Jackpiner since they are very easy to find.

Brian

'72 Berkshire

[Mickey Sergeant]

Does anyone out there have a good used type 84 bing 28 mm carb to save me some $ from getting a new one.
 74 berkshire

[brian kirby]

I think the 84 is only available new in 32mm for ultralights so you will have to find a good used one.

Brian

'72 Berkshire

[Dave Mitchell]

Seems this bing vs mikuni thing is always good for an uproar.I first did the swap in 72 on a 72 six days.And most recently last summer on a 72 six days.Again the same results.It's a three kick starter cold,one at operating temp.parts are cheap as are the carbs.I prefer to use the automotive hose that goes between the filler neck and gas tank.Holds up better being it's intended to come in contact w/fuel.I buy mine at napa.Last carb came from sutco,installed it and ran right out of the box.I myself just like to ride and working on the bike is part of why I do it but the Bing thing for me has been an easy fix since the seventies,I don't run them.
Dave

[joe novak]

Great tip on using gas tank filler neck hose to adapt the Mikuni carb to the Sachs cylinder.  What is the general size hose which is used.  I assume it would be an inside diameter, right?  Do you mount the carb right against the Sachs intake extension, or leave a space?

[VICTOR MONZ]

Mickey.

I have been soaking up some Florida sunshine for a week or so and will check on my supply of 28 Bings when I return home, what cylinder do you have...female or male carb fitting....have you tried the 27 Bing, I think, if I am not correct 27.5 actually, but it is a 53 series Bing.  I have been using the 28 on my 125's and also the 100, when I get back and install my fresh 100 motor, I have rebuilt a 27 Bing for the 100....kinda thought the 28 was too much for the 100 when it was running, although now it should be a "rocket ship" with the 'secret work" my R&D Department has performed, probably "blow" the head off with the first start up...the 84 series looks more mechanical/beefy, but the 27 mm 53 series, tuned properly, I emphasise TUNED PROPERLY, for me anyway, has been a good runner, on either bike and easy to find. Jetting and float management, vital, yet simple to do.  I believe in the Bings performance and I have just gotten to where I can shut my eyes and rebuild, tune and dial it in....most times with some patience.

I will check back in towards the weekend, when I return to California.

Victor