JD B Carb

[J Bouchard]

I have a 1940 BN with a DLTX 10 carb that does not seem to run properly. The tractor seems ok at idle but will occaisionly miss, but this is worse under load. I thought it was electical changed plugs, magneto all to no improvement. Changed carb and it runs the way it should. The other carb has all passages clear, the fuel nozzle is clean and it had the stem threads redone previously. Could this repair have something to do with it running so poorly? I see nothing wrong visually. What should I look for in this carb? Should I just abandon it?

 

[PBrowning]

Now -- I read you that "the other carb" is the one that had a stem repair & it also is the one that won't run the tractor properly. Given this data, I would have to ask who did the checking of passage ways, and who did the stem repair?

Here is the way this thing works: This carburetor has two channels for air-fuel mix to get to the engine. They are the IDLE side and the LOAD side. When the tractor is under NO load (regardless of engine speed), it shouldn't be drawing any fuel thru the LOAD side of the carburetor. And so if the engine is acting up during IDLE, there can be some IDLE pathway that remains clogged. There is a simple on-tractor test for that.

Faltering under a LOAD, however, points to the LOAD side. Here, I'd be concerned about the stem repair. Where did you have the LOAD needle set? I'd start at roughly 3/4 turns out. Does the tractor respond when you open up the LOAD needle valve some? So far as the stem repair is concerned, I'd think the criteria here is that the repair don't obstruct flow of fuel into the accelerating well, and this fuel flow is through the LOAD needle valve. Inspect down in the region where the LOAD needle and casting come together.

Should you elect to remount the carburetor for further troubleshooting, there is a simple test you can perform that will shed some light on this little gem. Go to the JD-H Restoration Site (URL below). Once there, scan across to ARTICLES 1. From the drop-downs, select CARBURETORS. This is a nine-page document. On the final page, you will find the test to see if both sides of the carburetor are open. If you have already run some tests and are tired of retesting, you are welcome to call me to commiserate some. I'd say lets talk a bit before you abandon the beast. (830) 627-0430. (PatB)
Restoration Site, John Deere

 

[Mike M]

Not all carbs. will run the same way on all tractors. Then add in some wear and tear even in the passages and things may get worse ? Some were likely not drilled the same when new either.
If you have another carb. that works better then by all means use it.

 

[Elinter]

Listen to PBrowning's advice. I did when I did my carb work and ran the test discribed in the link he gave you. It takes a little time to run but it helped me set up my carb perfectly. I was also missing under load.