Fuel/air problem

[Torson]

I need help diagnosing a problem. My 1948 cub sometimes only runs if I have the choke partially open. It stalls if I open or close it all the way. What could be causing this? (I also notice a puffing sound coming from the engine every 2nd or 4th stroke?) Thanks for any advice.

[Barnyard]

Remove the main jet on the side of the carb and clean the orifice with a small copper wire and spray through it wit carb cleaner.

[Torson]

Thank you. I decided to clean the carburetor while I was at it. Now I have to wait for a manifold gasket before I can see if the problem is solved. The old gasket tore in half at separation.

[Sadcub]

I have had a similar problem. You are too lean and that is why the need for choke. Barnyard nailed it. My main jet was clogged, even though I took everything apart and cleaned it. The orifice is so small it takes a wire to get it cleaned out.

[Barnyard]

[Torson]

Thanks very much for the help. I finally got the gasket, reattached the cleaned carburetor, and the tractor is running well. However, discovered I have a bad oil leak. I think it is coming through the seem between the clutch housing and the half moon shaped plate that is bolted to it. The plate is bent in two places. Any thoughts? Thanks.

[Bob McCarty]

Sounds like your rear main engine seal is leaking. The fix is to split the tractor and replace the seal. The replacement seals that are sold only fit a later retainer. You'll need to have the old retainer machined for a larger seal. Tim Talleur (forum name tst) does that. He may have a post on the Vine (classified) sub-forum.

Edit: viewtopic.php?f=223&t=106799

[Glen]

Hi,
Below is the Cub and LoBoy service manual. I suggest you read section 1, the engine section before splitting the Cub to replace the engine rear seal.
Section 4 has info about splitting a Cub.

http://farmallcub.com/rudi_cub/www.clea ... index.html

There is info in the How To section on here about making splitting stands, at least one post I saw the stand has a wheel at the bottom.

Be sure to use wooden wedges at the front axle pivot before splitting a Cub or LoBoy, they are heavier on the left side and can tip over without wedges. You will need to make the wedges.
Hammer them in tight, and check them some during the work, to be sure they don't loosen or fall out.
Below is a pic from Dale Finch.