hard starting B

I have a 1944 hand start B in the shop that has been hard to start. When I first heard it run there was a little pop in the muffler resembling a leaking exhaust valve when the throttle was opened up and the engine was loaded. I checked the valve lash and #2 (right side) intake valve was at .005 so I set it to the proper lash. I checked the compression by slowly turning the flywheel holding it against compression on each cylinder and it seemed to have good compression and not leak compression away fast on each side, each side was about the same. The carb was rebuilt by Roberts and seems to respond to adjustments OK. The mag is rebuilt and looks shiny new, the plug wires are new solid core. This is the way it was when it came into my shop.

This morning I pull started it, it popped right off pulling it, then I messed with carb adjustments with one plug wire pulled just to see if t here was a difference between cylinders #2 is the one that sputters when the throttle is wide open and it seems like carb adjustment doesn't clean it up. #2 does make the little pop in the muffler when the engine is loaded down but it idles fine. I pulled the plugs, #1 was black but clean, #2 was white on the center electrode and part way back on the side electrode. I haven't seen white plugs in an old tractor since our crappy gas came into being so this tells me #2 is running lean.

This thing won't start when the carb is set to where the engine runs right, I can't flood it with the choke with the carb set this way. If I turn the load screw one turn rich I can get a gas fog to spray out of the petcocks and that is the only chance I have to get it started by hand. If I leave the load screw at this setting the tractor runs rich.

To sum it up, this thing purrs at an idle, and responds immediately to a quick throttle opening without hesitation at low speeds. When it gets up in the revs a little and is loaded down #2 starts this popping and missing and I assume it is lean. That's about the best I can describe it. What do you guys think?

#2 is white center electrode...usually other way around. For on cylinder to run lean when both share a common port, it rules out anything north of the head port itself. Compression test? sounds like a bent pushrod and/or worn off cam lobe or such. It cant be sucking in a full fuel charge. That would explain why a load or needle richening makes it too rich...but only on the one that is working correctly to begin with.

Randy I have the same idea running around in my mind. It's gotta be in the manifold or head. The spark is OK, the carb is OK. The head and block have had the paint cooked off of them, telling me it was overhauled at some time. There is some thick oily buildup in one spot on the front of the head, telling me the overhaul was some time ago. When I get time I will pull the valve cover again and check the valve lift. The serial # on this tractor is 158703 but it has a manifold that looks like the B1787R manifold used on the 201000 and up serial#. I doubt if that would cause this problem though. I assume the B1787R manifold is a gas manifold. By turning the flywheel it feels like normal or a little better than normal compression. Come to think of it, it has petcocks. Didn't some B's come without petcocks?

I concur with Randy, It's been my experience to never be able to 'read' these plugs as one could on an automotive engine. Mine are always black with soot and she loves it.

I'm thinking the cam lobe is mostly gone on #2 intake valve so I would pull the valve cover and double check for full lift against the other side at a minimum.

I believe it was only the unstyuled "B",s didn't have comp. reliefs.