1950 John Deere B idles well, stalls under load or fast

[AJ32]

Hi all, first thanks to everyone that runs and participates on this forum - it has been a great resource over the years! This one has me running out of ideas; though, so I'm hoping someone might have some advice for me.

I'm struggling to get a 1950 Styled 'B' running well again. After the work I've done so far, it starts and idles very well; however, the problem is it doesn't run well anywhere but slow idle. If I open the throttle quickly from slow idle, it puts and sputters and either stalls or barely manages to get up to RPM, where it will run but every few seconds blows pressure out the air intake and almost shuts itself down. It's enough to rattle the oil bowl on the bottom of the air cleaner, and if I remove the bowl it behaves the same way, the air pressure coming out when it backfires (?) is enough to sting you hand if you hold it under the air cleaner, but there doesn't seem to be any sign of ignition (fire, heat, or smoke) coming through that way.

The same thing seems to be happening under any kind of load. The exhaust is clear. Closing the choke slightly seems to mitigate the issue slightly, but the exhaust then has thick black smoke.

So far here is what I've tried:

Ignition: Wico 'X' magneto. Installed a tune-up kit and re-set the points, new plug wires (copper core), new 3116 plugs. We always used Autolite 388s but I learned during this process that non-resistor 3116s are better for the mag. I checked the timing against the flywheel marks and by listening for the impulse while watching for TDC on the piston. I spaced a spark plug out to 3/16" and placed it on the block, confirmed consistent bright blue spark from both cylinders.

Carburetor: DLTX 67. Took it apart and rebuilt it with new parts, bought and used the special drill bits to clean out the passageways. They were fairly gunked up, as was the area around then nozzle.
Verified good fuel supply by opening the petcock on the carb bowl and confirming solid flow of fuel for at least 30 seconds.
Adjustment needles set to 1 1/2 for idle and 3/4 turn for load. Engine will idle with the load needle shut completely. Adjusting these further only seems to make things worse, never better.
Later I tried adjusting the float level in both directions versus the factory spec. of 3/8" from the gasket surface, this seemed to have no effect on the issue.

Fuel: New fuel, ethanol free 90 octane.

Engine Oil and filter have been changed. The crankcase will get gasoline in it if the tractor sits long enough with the carb bowl petcock closed (the valve on the sediment bowl doesn't completely seal). After the carb rebuild I'm hoping this isn't an issue since the needle and seat have been replaced.

After all of the above, it starts and (slow) idles better than it ever has while I've owned it, which is nice, but there's been no or little improvement with the fast idle / under load performance.

So, does anyone have any pointers of what I should look at next, or something I may have missed? What could be causing the backfire (if that's the correct term) through the intake? I'm not sure what to look at next. Any help is greatly appreciated!

 

[NoDakInMN]

The obvious thing to look at first is the load side of your carburetor. Idle setting starting point is 1 1/4 to 1 1/2 turns once this is set for good idle, leave it alone. Load setting is usually around 3/4 turn open. The tractor will idle with this needle closed because the load circuit is not utilized during idle. Make high RPM adjustment with load needle only.

Having said that, and based on your description, I think it would be worth your while to go through the passages in your carb again. You may have gotten some gunk knocked loose that could be obstructing flow, which could be causing the symptoms you describe. If you do not have Roberts Carburetor Repair video, I would get one as it is well worth the money spent. This would insure you are getting all the passages clear.

 

[Dan in Ohio]

AJ32,
Have you adjusted the throttle rod so it is 1/2 hole short of the carb with engine off and the throttle lever set at full throttle. Some places say 1/2 hole short at the carb others say 1/2 hole short at the governor end. (Don't know if it matters) but this adjustment is critical when throttling up the engine.

Just to be clear you are setting the idle screw when engine is at full throttle, right? The manual says setting should be 1 - 1 1/4 turns out.

This post was edited by Dan in Ohio on 10/09/2022 at 03:15 pm.

 

[AJ32]

NoDakInMN: I set the idle to 1 1/2 and the load to 1 based on the instructions in the carb rebuild kit. I try to set the idle further with the engine at WOT, but since it hardly runs at WOT, I'm not sure I'm getting anything valid. I've taken it down until the engine starts to run (even more) rough, then took it back up a 1/4 turn.

I had the load needle all over the map trying to see if it had any effect on the issue, but it didn't seem to change anything (unless I closed it to less than about a half turn, in which case the engine stalled almost immediately after putting a load on it). I ended up just leaving it at 3/4 since I've seen that suggested quite a few times.

It sounds like I may need to pull the carb again and look into getting the video from Roberts.


Dan in Ohio: I checked the throttle rod adjustment and found that it was a full hole past the throttle lever (engine off, throttle lever all the way forward, throttle valve wide open). I adjusted it back to being a 1/2 hole short. The problem with pressure back through the carb / intake persists, and now when trying to go to WOT it just dies, firing back through the exhaust in the process (much louder than when it fires pressure back through the intake).

Also, with the throttle rod adjusted to 1/2 hole short, I can no longer shut the engine off by closing the throttle lever, it just hits the idle spring. Though, now that I'm thinking of it, maybe that screw that hits the spring needs adjusted?

Thanks for the help so far!

 

[greenmech]

There are two brass plugs on the stem, did you get those reamed out? Sounds like a plugged orifice somewhere. Ron MN

 

[J.Wondergem]

I agree. Somethings plugged up in the carb.

 

[AJ32]

Alright, I'll take the carb off and go through it again. I also purchased Robert's carb repair video, and I'll go through that when I get it.

greenmech: I only recall 1 brass screw plug on the stem, there is also on on the top next to the idle screw, I've cleaned both of these out with the drill bits.

Appreciate the help so far, I'll post an update if I get it working.

 

[greenmech]

I think if you remove all brass plugs and drill out you will be OK. Ron MN

 

[JDBRIDER]

Isn't the fuel level in the float bowl suppose to be 3/4 below the bowl gasket.

 

[BobY]

Since it backfire back through the intake, I wonder about the ignition timing. I purchased a tractor that had the impulse coupling setup wrong so that when the tractor was running it advanced the timing [u:0e0437bda8]too[/u:0e0437bda8] much and before TDC. So while it was correct to the flywheel when rolling it over slow, it was too advanced at operating speeds.

This post was edited by BobY on 10/24/2022 at 02:06 pm.

 

[AJ32]

I swear I'm not one of *those* people who ask for help on a forum, get some ideas, then leave everyone hanging by not following up with the eventual solution! I've just been unable to return to this project until the last week or so.

I went through the carb again, no change. Then again with Robert's video. I've got to have the cleanest DLTX 67 carburetor around! Still no change though.

I went back to the ignition. Seemed like it should be pretty solid - new coil, condenser, points, contacts, cover, copper core wires, and 3116 plugs. Laying on the block, both plugs fired very hot and consistently. However, I got my hands on one of those inline spark gap testers, and discovered that the right hand cylinder was losing spark as soon as the engine fired and picked up any speed. Fortunately, being a pack-rat, I still had all the old magneto parts, so I went through and tried each old part. Eventually discovered that the *NEW* condenser was the problem. With the old condenser (and all the other tune-up along the way), the tractor runs great!

It took me a while to get to the condenser, since I figured it couldn't have been something common to both plugs, but in hindsight, I suppose with the un-even firing timing of the B, it makes sense that the right hand plug would be more likely to be effected.

So, lesson (re)learned: Don't always assume that new parts are good parts.

It was definitely good to go through the carburetor thoroughly as well, it needed it.
Thank you all for your help and suggestions!

 

[Kansas rhody]

Nice to hear you found the problem, after many years of people posting about bad new condensers I now always reuse my old ones when I am tuning up the tractors, new points, new rotor, new cap but old condensers, I probably have 6 new ones sitting around but afraid to use them, lol

 

[620 John]

Glad you got it figured out.

It's amazing how many bad condensers cause "fuel starving" issues. Trying to find a good condenser is a joke. So far I've had the best luck with Napa Echlin RR174 condenser. Running one in a 620 with delco dist and late model B with Wico XB dist.

Poor quality parts is why lot of people are switching over to electronic ignition. Same with regulators for generators. Installing an alternator saves headaches there too.

 

[Dan in Ohio]

Glad you got your B running again. Had a similar problem with my 1950 B after replacing all of the ignition system I had a hard start (no start) situation only to find out that the new coil was junk. I too keep my old parts unless I am certain they have failed.

Thanks again for your follow up.

 

[nlastovi]

(quoted from post at 11:51:02 12/11/22)
Eventually discovered that the *NEW* condenser was the problem. With the old condenser (and all the other tune-up along the way), the tractor runs great!

I, as well, have wasted an entirely good Saturday afternoon struggling with the same issue on a Chevy pickup. Did a tune-up and replaced all of the components (plugs, points, rotor, condenser, and cap). And no go. Shuffled parts, tested, and cursed to no avail. Finally, one of the iterations ended up with everything new except the old condenser.

These lessons are learned till the next time we forget.

 

[J.Wondergem]

''


Thanks for coming back and telling us what you found. I too bought new parts and threw into a tizzy. Traced it to the points cleaned them again, wound up filing them and finally got juice to go through them.