Bing to mikuni

[James Niebrzydowski]

I have a 72 Six Days with a 6a motor and Iam considering putting a mikuni on it. Any advice on model number,size and jetting would be helpful. I live in Pa.

Thanks

[tooclose racing]

Use the Search function (subject line) with Keyword Mikuni or Mikuni and Six Day.  The last post in this thread is pretty dead-on with its recommendation of going with the 28mm and jetting settings. Looks like exactly what I used on my SD, or pretty damn close.  I think you would only consider a 30mm if you have ported the cylinder and are just going to  race motocross or flat track.  Umm..."flat track" was a joke....

 http://www.pentonusa.org/forum/topic.asp?TOPIC_ID=2388&SearchTerms=Mikuni,for,Six,Day

[brian kirby]

28mm Mikuni's are no longer in production, but you can still find them on eBay. For anyone but an expert I would recommend a 26mm (which is still in production) if you can not find a 28mm.

Brian

[Mickey Sergeant]

Strickly Hodaka had a shelf full of new 28mm's a couple of years ago when I got mine. Check with them.

Mickey

[brian kirby]

I didnt know that, that is good to know. Also, apparently the 28mm Mikuni was used on a LOT of snowmobiles, so possibly look in that area instead of motorcycles on eBay.

Brian

[Ed Barth]

Hey Jim, I parked next to you at vintage days. I'll be watching this topic. I might do the same thing

Thanks,

Ed Barth

[James Niebrzydowski]

Still tuning the bing its better then it has ever been.the biggest problem is when it starts to bog down on a uphill in 2nd gear it has a hard time cleaning out. I was wondering if a mikuni might help with this . It might just be me not used to riding a 125cc.
 idle 45
main 140
needle jet 2.73
#5 needle 2nd from top
air screw 1/2 out
I did file a 2mm x 3mm groove in slide

Hi Ed

[Dale Sonnenschein]

James, I have the same problem with my 175. It seems like its more like worn parts, like needle seat or slide from what I have found. I spoke with Gary Ellis about it and he thinks this could be the problem with the bing.

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
82 husky wr430
10 ktm 250xc
02 bmw r1150r

[Ed Barth]

Jim,

Did the groove in the slide help? I just got a new needle and needle jet from Al. We'll see if that helps my bogging issue.

Ed Barth

'73 Penton 125 Six Days
'73 Yamaha DT3 250
'04 KTM 125 SX
'06 KTM 250 SX
'13 KTM 250 XC

[KJDonovan]

James / Dale / Ed,

I had the same issue with my Jack Piner loading up, primarily going up or down steep inclines and got so frustrated with it that I switched to a Mikuni.  Thing was, the Bing that was on it when I was having this problem was brand new, so it was not an issue of worn parts.  I have since learned ( I think I read it in a thread here or on NETRA) that this condition is often caused by fuel sloshing into the cylinder and this problem can be reduced by making sure the little screen that goes over the main and down into the bottom on the bowl is in place.  Just finished the carb for my 400 and I made sure I ordered in that little screen from Bing.  Figured I would pass this along as it may help resolve this.

Thanks,

Kevin


Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner
72 Six Day
74ish Mint 400
74 Hare Scrambler
71 Suzuki TS125
72 Montesa Cota 123

[Ed Barth]

Kevin,

I'm not sure if I remember a little screen in there. I might not have one and that could be my problem. Only a heavy load (like going up a steep hill) does it load up if I am running it anything but wide open.

Thanks,

Ed Barth

'73 Penton 125 Six Days
'73 Yamaha DT3 250
'04 KTM 125 SX
'06 KTM 250 SX
'13 KTM 250 XC

[KJDonovan]

Ed,

The screen is item #10 in this diagram http://bingcarburetor.com/pdf/54x1.pdf

Thanks,

Kevin

Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner
72 Six Day
74ish Mint 400
74 Hare Scrambler
71 Suzuki TS125
72 Montesa Cota 123

[James Niebrzydowski]

Ed the groove helped with the bogging very little, it seemed to help with the transition from low rpms to the power band . In the parts book it does not show the screen over the main jet , the bing on my husky has the screen. My slide is not worn as far as I can tell but it looks as if it has some erosion. At vmd hs I think I had my floats set a little to high and I think it flooded the crank. My bike runs great except for the bogging maybe you just have to be very precise with your down shift timing .

[Ed Barth]

Kevin,
I will have to order that little screen! I do not have one. Might get a couple different main jets sizes too to try out.

Jim,
I messed with my float so much before vmd. Can't tell you how many times I had that carb apart.

Ed Barth

'73 Penton 125 Six Days
'73 Yamaha DT3 250
'04 KTM 125 SX
'06 KTM 250 SX
'13 KTM 250 XC

[Edd 44k]

I have a brand new Mikuni 28 jet for sachs 125. FOR SALE  EDD@ 847-692-9337

Lot of Penton parts for sale.  Inquire via email.