Carburetor differences??

Mon Oct 08, 2012 1:30 pm

I've searched around the forum a bit, but have not found an answer to this: (Chances are, I'm just not looking hard enough, so I apologize.), Is there a difference between a regular cub and lo-boy IH OEM carburetor? I'd like to replace the Zenith on my 1950 Cub with an IH type, but don't want to waste the money on the wrong one.
I only assume that they are the same, as the engines are alike. ? . But we all know what you can get when one assumes...


Re: Carburetor differences??

Mon Oct 08, 2012 1:56 pm

The older F-Cub and Loboy carbs are all basically the same (except for maybe jet and discharge tube sizes) up till around 1968, the with the Numbered Series, the carbs throats were opened up for more airflow. Then they all changed to the Zenith style in 1975.

Re: Carburetor differences??

Mon Oct 08, 2012 3:03 pm


This is the chart I always refer to. As Raymond said, the main jet and discharge sizes are different. A 15/32" venturi equates to .47" whereas the Zenith venturi at 15 mm equates to .59". Quite a bit of difference.


Re: Carburetor differences??

Mon Oct 08, 2012 4:43 pm

The 1970 parts book, lists the same part number for the IH carb for both cubs and lo-boys, so it does not appear that there was a different carb used between the two, just a later carb used on later models. The 1954 parts book only lists one part number for the complete carb (the same as the first column in the page in Bob's post). So, if you just want to go for a period correct look, either IH part number in Bob's post should be fine. However, if you are trying to appease the "correct police," you want the 251 234 R94.

Re: Carburetor differences??

Mon Oct 08, 2012 5:05 pm

Early F-Cub (1950) carb on left, 154 Loboy (1970) carb on right:

You can probably get away with either one, as long as you don't mix tops and bottoms and use the correct jet and discharge tube for the model of carb. If you use a numbered Loboy carb, you'll need to swap over the choke shaft.

Re: Carburetor differences??

Mon Oct 08, 2012 7:09 pm

Carb 364 579 R91 was used from engine 196900, about when the Lo-Boy came out in '55. Prior to that, there were some jet and discharge nozzle changes (and some other minor changes).

The 154s used a different version, not shown in the table above.

Re: Carburetor differences??

Tue Oct 09, 2012 9:41 am

Thank you for the replies. I managed to pick one up fairly cheaply, but the rebuild kit from the IH dealer is 90 dollars! Way more than I paid for the carb! Think I'll stick with the Steiner kit and save a few pesos to restock the garage fridge.

Thanks again!

Re: Carburetor differences??

Tue Oct 09, 2012 9:51 am

The kits for the IH carbs is one place you really get what you pay for. Tear it down and check what you need before buying one. If you need throttle or choke shaft seals or a throttle shaft, get the IH one. If all you need is the gasket and float valve the Steiner is al right.