What do the numbers on a Bing mean?

[Chakka]

I was reading my shop manual to determine if I have a suitable carb on my storage shelf to try on my 76' KTM 125. I noticed the 125MC and 175 share the same Bing. The numbers listed are 54/36/124. I have a Bing that came off a 76' Jackpiner and the numbers stamped on it are:
2/30/102 (near the intake manifold) and 84 Bing on the upper body. I left the workshop scratching my head puzzled.

Can this carb, correctly jetted, be used on my 125? Better yet has anyone converted a KTM 125 to a Mikuni?

Thanks
Chris

[k4uu]

The first number is carb type (54 or 84) and the second number is the size.  The carb you have is an 84 30mm.  You can order a Bing Book from Bing International.  Check suppliers.  You can rejet the 30 with the jetting for the 32 also.

Gary

Gary Hext

[Mike Lenz]

I intend to run a 34mm 84 Bing on my 76 125 I am making.  I just dont think the 36 large body carb will work very well on a 125.  84 are the older design and 54 were the later design from the 70's. You can bore out a 30 or 32 to 34.

[Chakka]

Thanks Guys, Mike, how do you go about boring a carb from a 30 to a 34? It sound like something best left to a machine shop? Also are you making an MC or GS?

Chris

[Mike Lenz]

Yep Machine shop should do it easy.  I am going to try and make a 76/77 mc-5 125 competitive.  Not a small task when you compare whats out there for mx in that class.  I remember how disapointed I was in 76 when this bike came out with the same huge (by 125 standards) bottom end. The rotating mass of that tranny is hard to overcome.  Other than fix the problem the right way KTM tried hard around the edges with the drilled out outer clutch hub and all aluminum plates and disks in the clutch.  Im messing around with the idea of trying to lighten the tranny.
Heres my plan:
1980 125 smaller/lighter conical wheels
428 chain and sprockets or 520 with a lightweight chain
1975 smaller mx tank (goes on pretty easy)
1976 ported cylinder
stuffed crank
1979 125 snake pipe
PVL internal roter/auto advance ign & 79 plastic ign cover
34mm Bing
lightened tranny?

What do you think, you experts out there...or should I just find a good 1980 125 KTM and go GP class...and no comments about the other sprung weight on the motercycle. Losing weight there is NO fun, although I'm trying...a little.  I really dont care if I do well on this bike.  Its just 125's are so much fun and dont take near as much effort to race as my 400, it makes a good second class to race.  Wait a minute I guess I do care...I just want to care my way!

[k4uu]

The first number is carb type (54 or 84) and the second number is the size.  The carb you have is an 84 30mm.  You can order a Bing Book from Bing International.  Check suppliers.  You can rejet the 30 with the jetting for the 32 also.

Gary

Gary Hext

[Mike Lenz]

I intend to run a 34mm 84 Bing on my 76 125 I am making.  I just dont think the 36 large body carb will work very well on a 125.  84 are the older design and 54 were the later design from the 70's. You can bore out a 30 or 32 to 34.

[Chakka]

Thanks Guys, Mike, how do you go about boring a carb from a 30 to a 34? It sound like something best left to a machine shop? Also are you making an MC or GS?

Chris

[Mike Lenz]

Yep Machine shop should do it easy.  I am going to try and make a 76/77 mc-5 125 competitive.  Not a small task when you compare whats out there for mx in that class.  I remember how disapointed I was in 76 when this bike came out with the same huge (by 125 standards) bottom end. The rotating mass of that tranny is hard to overcome.  Other than fix the problem the right way KTM tried hard around the edges with the drilled out outer clutch hub and all aluminum plates and disks in the clutch.  Im messing around with the idea of trying to lighten the tranny.
Heres my plan:
1980 125 smaller/lighter conical wheels
428 chain and sprockets or 520 with a lightweight chain
1975 smaller mx tank (goes on pretty easy)
1976 ported cylinder
stuffed crank
1979 125 snake pipe
PVL internal roter/auto advance ign & 79 plastic ign cover
34mm Bing
lightened tranny?

What do you think, you experts out there...or should I just find a good 1980 125 KTM and go GP class...and no comments about the other sprung weight on the motercycle. Losing weight there is NO fun, although I'm trying...a little.  I really dont care if I do well on this bike.  Its just 125's are so much fun and dont take near as much effort to race as my 400, it makes a good second class to race.  Wait a minute I guess I do care...I just want to care my way!

[rob w]

Chris, The Bing (original) on my '76 125 KTM (engine # 000360) is a 84 / 32 / 111 .  

Mike, I think that sounds like a fine plan you've got formulated there.


Bob W

[Chakka]

Thanks Rob,

That's exactly what I needed. I put the Bing taken off a Jackpiner on the bike today. The numbers 2/30/102, it's a style 84 body. Started second kick. I need to play with the idle and air screw as well as adjust cable length because at idle the bike is running like it's wide open. I may also need to replace the slide, it is showing some wear. I'm so close to finishing this project, I can't wait till the bike is screaming around the yard on the test run.

Chris