125 Bing / Mikuni Carbs

[Jim Panzer]

I'm finishing the frame up resto of my 1973 125 and need a good Bing carb or a carb body as mine is badly worn. Has anyone replaced the Bing with a Mikuni? Any details / information would be appreciated. I could also use a good air box if anyone has one. Thanks!

Jim Panzer

[Cal Alexander]

Hi Jim, I just recently did a Six Day restoration with a 26mm Mikuni. The bike starts and runs very clean. Its a good carb for trail riding or putting around on. I think the stock Bing has a little more punch however. I'm told by many of our POG experts that a 30mm Mikuni gives you more flow and more top end. I think on my next Mikuni conversion I will give the 30mm a try. If you use the search engine on this site you will find many posts on the merits of each (Bing and Mikuni). There is also valuable information on Mikuni jetting that will get you in the ballpark for the initial set-up.

75 250 MC
73 Cafe MX
72 Six Day (3)
70 Six Day

[Jim Panzer]

Thanks Cal, I found a NOS VM28 Mikuni for under $100 that appears to physically match up fairly close and am going to give that a shot.

Jim Panzer

[tooclose racing]

I think the 28 is best way to go for best all round performance with the Six Day, especially if you are going to do some woods or hare scrambles. Was very happy with mine.  I think I've lost my copy, but someone here at POG surveyed owners with Mikunis for what Jetting they were using and posted a link to it.  Very helpful to me when I set up mine.

Careful with the out-of-box 28.  When I received a shiny, new NOS one, it was waaay overjetted on Main. I think most people end up 160-165 on the main?

[Denis Jeffries]

Hello Jim, I switched from a bing to a mikuni on my jackpiner. easier to start and a improvement in power. I got my mikuni from sudco, came pre jetted. slipped it on and 3 kicks later started right up. good luck. Denis Jeffries

[Jim Panzer]

Thanks for the great advice guys; I should have it running in a week or two! Please let me know if anyone has jetting info.

Jim Panzer

[Denis Jeffries]

my mikuni from sudco came pre jetted

[KJDonovan]

Jim,

I have used the following in a VM28 on a 125/6B and it worked very well.  

#160 Main Jet
#40 Pilot Jet
#5F21 Jet Needle

Thanks,
Kevin

[Jim Panzer]

Thanks Kevin ... the jetting is very much appreciated!

Jim Panzer - 211