Penton Owners Group

I'm sure this has been debated here before, but I'm going to replace the carb on my 75 KTM 250.  Before I order a carb, cables and anything else which would you go with and why, a Bing or the Mikuni.

Note: I'm just a Novice racer and I'm not concerned with ultimate power output.

Thanks!

Racing the "FaltaNator" in 2009

I think properly jetted both are good but the Bing 36mm flows what a 38mm Mikuni will or close anyway.  I like the Bing because I understand it.  If it were Post Vintage I would lean towards the Lectron but it is not legal for Vintage.  My 2 cents.

Larry P

Larry,

Are the "New" Bings (from Bing Agency Intl. ??) a straight bolt-on or do you need to get a different intake mount?

Racing the "FaltaNator" in 2009

I have never bought one from them but I believe they are rubber spigot mount as opposed to the bush on ones of old. Give them a ring as they are real knowledgeable.  If you have troubles let me know I might be able to rustle up a good body-just not new.

Larry P

If you already have a bunch of bikes with Mikunis get one of those, but really as Larry said properly tuned both are good carbs. Personally, I think the smaller the bike is the more significant the higher flow of the Bing becomes. One thing that is nice for 250-up size bikes though is the tickler on the Bing, it makes cold starting easy.

Brian

'73 Berkshire

Yes it is quite true that a bing flows better than a Mikuni but it is because of the design of slide it the reason. both slides have a skirt on the bottom that create turbalance. The bing slide skirt is smaller and so therefore creats less turbalance. but there are replacent slides for mikuni that supposedly eliminates most if not all of the problem. I was working on a mikuni with one of theses special slides and it was very interesting to be sure... The tickler has some advantages in cold but I like the way that you can jet the mikuni. there are more circiuts to get a lot better power delivery. Jay look at some of the stuff that has been posted here on the subject. If you need the specs for a 75 250 using a mikuni let me know and I can get you really close...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)
72'sixday (project bike)

I ran a Bing on my 250 and a MIC with a reed, with the Bing it hit hard as the power band came on (a wild ride). The  Mic and reed made a more controllabe power band and did not hit as hard maybe because of the reed ( it still was a monster)  never ran just the MIC. I have some 38mm MICs jetted for my 250  if in need . The new Bings are the cost of your whole bike (maybe a little less). LG

Stick with the Bing and it will Sing....go with the Mikuni and it will run PUNY ! [}:)]

Heck didn't the designers select Bing for a reason ?

Could be me...what little I know of carbs, the Bings seem simple for me, easier to tinker on and, I feel, more durable construction.

Just having fun.

Victor

Well, the designers picked Bing because it was European, not because it was inherently better. I whole heartedly disagree that Bings are more durable than Mikuni, the one big plus of a Mikuni is durability. A Mikuni slide and needle jet could last the life of a bike, a Bing slide and needle jet will last a season if you are lucky.

Having said that, they both have ups and downs and on balance I dont think there is really much to choose from. I would say pick the one you have the most previous experience with tuning and be happy.

Brian

'73 Berkshire

Where can I get an adapter to run the Mikuni on a KTM 250?

Racing the "FaltaNator" in 2009

Look in the snowmobile sections from parts houses like Dennis Kirk.
They carry adapters like this that will work.
http://www.denniskirk.com/jsp/common/img_pop.jsp?skuId=18128&imgId=0
 You did not give any measurements for the carb and intake manifold but I know one of the POG members found one that will work. He fitted a 34 or 36 mm Lectron to his 75 250 using one like the above.
John D.

Thanks John!

I did a few searches and found someone had used fuel filler tube to mount a Mikuni, so I went to the NAPA store and got a foot of 1.5" I.D.

The Mikuni spigot is 40mm (1.57") and I haven't measured the KTM 250 intake mount yet.  Sudco may have those adapters also.

Now I need "Ballpark" jetting specs for a 34mm Mikuni on a KTM250.
:D

Jay

Racing the "FaltaNator" in 2009

Jay, I was thinking about you today and so I took my carb apart on my 76 250. This is what I am running. and this carb has been on the bike for several years... I am running a vm34 mikunin that has been bored out to 35.5 which is almost exactly the same size as a 36 mikuni. I did this because of the limited room on my KTM. As for the adapter. I used a piece of gas filler hose. by the way that is exactly what maico uses on their bikes to attach the bing to the intake manifold.... I ended up cutting off about 3/8ths of an inch off the intake manifold to move the carb far enough from the airbox for the airbox boot to fit right..
this is what I am using for jets. Main 290 pilot 30 slide 2.5 jet needle 6DH4 needle jet 159 Q2 This is based on 500 feet above sealevel...


Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)
72'sixday (project bike)

Thanks Thom! :)

Racing the "FaltaNator" in 2009

Run  larger than a stock 34mm . Bore it if you have to. My 38mm is a 36mm in my earlier post ,my mistake. LG

Thom,

Who did you take your Mikuni to for boring out?  I would imagine that 35.5mm must be the safe limit to bore the 34mm?

Larry,

please e-mail with more info on the 36mm Mikunis.  

Thanks!

Jay

Racing the "FaltaNator" in 2009

I have a GEM KTM 250 intake manifold for a Mikuni carb if interested.  $40.00 [email protected]

I have a GEM  KTM 250 manifold for a Mikuni carb if interested.  $40.00  [email protected]