26mm Mikuni Set-up

[chuck]

Does anyone have the set-up details for a 26mm Mikuni for a Berkshire 100cc. I've searched the POG forum but only found info. on manufacture specs.

Thanks,

Chuck

[OhioTed]

Hi, Chuck.  I am running a 26mm Mikuni on my Six-Day.  I researched all info available on setting it up, then decided to just try it with stock jetting to see how it works.  Well, although I don't have much time on the bike, it works perfectly so far with no changes other than dropping the needle one notch.  The bike starts first kick, pulls nice and clean off the bottom, and revs out fine.  Of course, my 125 is just for putting around on.  What do you intend to use the Berkie for?  Other POG'ers, with more time and experience on Mikuni-equipped bikes may have better-informed suggestions for you.  

                                                                 Ted

[Larry Perkins]

What do you mean by stock jetting since the Berkie came with a Bing? Same size as Bing jets or...?  Could you clarify for those that are not sure?  Thanks Ted.

Larry P

[brian kirby]

I think he means stock as in what the Mikuni had in it. I've found that if the carb fits the bike the generic Mikuni jetting will be in the ballpark, and sometimes perfect.

Brian

'73 Berkshire

[Larry Perkins]

Brian,

Sorry to disagree but you can buy a 26mm Mikuni with any number of jet combos in it including a dozen different needles so it seems that is not very zeroed in and needs more clarification to help others with a 26mm Mikuni attempting to put it on a Berkshire.  All 26mm Mikunis don't come jetted the same is what I am trying to say so that stock has no true definition.  In jetting numbers is the name of the game.  A 26mm Mikuni will fit a 100 reed Yamaha, a 125 piston port and reed Yamaha, a piston port and reed 175 Yamaha, a 100 Penton, a 125 Penton, and a 175 Penton but all require different jetting.

Larry P

[brian kirby]

I'm not saying a Mikuni will work on any bike, I am saying the two I have installed them on were nearly perfect with the generic jetting they came with. For a 100 I would use a 27 or 28mm Bing since they flow more and you are limited to 28mm by the rules. I have a 28mm model 84 Bing on my 100 and it flat out rips.

Brian

'73 Berkshire

[Larry Perkins]

Brian,

I agree on the Bing and it would be my choice also but you were just lucky on the Mikuni jetting as surely you see all the bikes I mentioned require different jets and one would not work so well on another.  Acceptable and jetted are 2 different things also.  The point is that there is no generic jetting-different bikes require different things and to help this rider jet his Mikuni close would require the jet sizes as there is no "stock".

Larry P

[Ernie Phillips]

Chart below is complied from user experience and POG research for Mikuni carbs on 125cc except as noted.  Look toward bottom - in yellow.  This is our 28mm Mikuni jetting on 100cc Berkie. Performance mods include Cranke spec pipe, bump in compression, and PVL.  Stock porting.  Make sure you get a good connection between carb spigot and cylinder spigot.  Carbs WILL come loose if not careful.  Also check the float needle valve jet size.  A 1.5 is will not flow enough.  You need 2.3 or bigger.



Ernie P.
Chattanooga, TN

[Larry Perkins]

That should help a bunch of people.  Thanks for the info, Ernie!

Larry P

[brian kirby]

I'll post what I have in my 28mm Bing too just in case anyone gets one and wants a baseline.

Brian

'73 Berkshire

[chuck]

Thanks for the help. I'll let you know what works.





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