'46 B Running rough

[Anonymous-0]

I've posted this over on Rummy's as well, and have received some good responses but nothing has helped yet. I am hopeful that some one here may have additional thoughts.

Hello all, much like some others here I'm experiencing a problem I can't seem to solve. I've searched the forum for answers and have tried everything suggested but the correction just doesn't seem to be clear to me.

I have '46 B the engine was rebuilt several years ago and not run much since then. I've decided to make a concerted effort to get it running. With the trottle at half open, the choke half closed I can get it to start and run but it runs rather rough (not good at all) pops on the left cylinder and sometimes backfires. When I remove the plug wire from the left cylinder (left as viewed from the rear of the tractor, or no. 1 cylinder) it smoothes out but obviously is only running on the right cylinder. When I reverse this and leave the plug wire on the left side and remove the right side she dies, and quickly. Clearly there is something amiss with the firing. But what? When left side plug wire is held 1/4" from the plug it sparks nice and blue but it almost appears to be a solid spark, could the mag really be revolving that fast? Possibly so, but it sure seems like its sparking a lot.

I've rebuilt the carburetor and adjusted it (the only thing I haven't tried is running it on a known good tractor), rebuilt the mag (it fires a nice blue spark), never had the governor off so that shouldn't be an issue. We've retimed the magneto twice (or more) and it fires when it should, checked the valves all are at .022. With the petcocks open there is good fuel mixture and it does fire. Checked to make sure the throttle rod was adjusted right, as it was.

When its running aside from the roughness and the occasional backfire it sounds as if its hunting. I think I've checked everything, even reviewed SM2004 and I&T manuals, did everthing they suggest. Still nothing. The tractor did sit outside for a long time with a rag stuffed in the intake port, could there be an obstruction blocking the left side intake? Not likely as it gets a good fuel air mixture (can be seen with the petcock open).

So fellas, that's where I am, it runs but not well. I hope I haven't missed explaining something, but if so please ask. I think I've tried everything, but clearly I've missed something.

Thanks in advance,

Jason

 

[greenmech]

I would try a different mag to see if thats the issue. How about the plugs? Maybe try auto lite 3116. Maybe a short in the mag cover? Ron Mn.

 

[RobMD]

all ports in carb must be cleaned with drill bits appropriate to the size hole.

governor to throttle linkage must be adjusted as per the manual to stop hunting.

how's the air cleaner? Clogged, did you clean it out?

you don't have the mag 180 degrees off and the sparkplug wires reversed, do you?

Excessively worn throttle shaft and butterfly will cause hunting and goofy surging.

Are you getting excellent flow of fuel from the sediment bowl?

Did you remove the camshaft? could be tooth off?

what about those valves- have they been reground and reseated? new guides? Pushrods straight and true?

Asking questions actually provides answers.

 

[Anonymous-0]

RobMD, I rebuilt the carb, went through it again when I encountered the trouble, ALL the ports are clean and I have the correct drill bits. The fuel flow is good and pencil sized. The carb linkage was adjsuted to half the rod size a full open.

I haven't tried to take the air cleaner line off but I will. Up to now I've had the oil cup off of the cleaner but perhaps the mesh is quite clogged.

I also haven't tried to reset the mag 180 degrees and reverse the plug wire locations. I was always underthe impression that left side (from the back) is no. 1 and the top hold on a Wico X is no. 1. I'll try 180 out and reversing the plug wires.

The camshaft hasn't been removed and the valves were lapped and seated. We took the valve cover off and observed the operation, all moved correctly and were set appropriately. New guides were not installed, if I recall correctly they were still pretty well fit. I didn't take the rocker assembly off and check the pushrods, but I may be forced to at some point.

Thanks for the thoughts, keep it up. I am still thinking is a timing/mag issue. But am at a loss to know what.

I may end up rebuilding another mag to see if it performs better.

Thanks again,

Jason

 

[Anonymous-0]

Greenmech,

I am using new Autolite 388's, as a test I even went back to the old plugs. There was no change in the running. Still would run on the no. 2 cylinder, but not on the no. 1 cylinder.

Thanks.

 

[jd b puller]

Jason, pull both spark plugs out and lay them on the block in front of you. Roll the engine over and look at the spark. Make sure the plug fires at TDC for each cylinder. It will fire on both the compression and the exhaust stroke.

 

[greenmech]

One more thing. Are you using wire core spark plug wires? Ron Mn.

 

[Anonymous-0]

Wire core.

 

[Duane Larson]

Jason,
How have you set the timing? Have you tried checking/setting the timing with a timing light? Wear can accumulate in a magneto and that will advance the timing. And have you checked the compression in the two cylinders - you may have to belt the tractor to another one to get meaningful readings.

 

[DGK]

Make sure your valve addjustments are not to tight. Compression test will tell you.

 

[teddy52food]

Have you tried a new cap on the mag? You may have a crack or a carbon track & won't fire under compression. Try changing the plugs from one side to the other. If the miss moves with the plug, the plug is bad.

 

[DEERE356]

At this point if it were me and I"m no expert on these tractors is why I don"t send replies very often but I do watch this forum on a daily basis. I would switch the plug wires at the Dist. cap. If it"s what I think it is that should switch the misfire to the right side or # 2 cylinder. I had the same thing happen with one of mine a couple years ago and did pretty much everything you"ve done so far. After looking at the Dist. cap for about the third time I found a hairline crack in the cap causing it to misfire when it was running. If that doesn"t switch the misfire to the right side I would check the resistence on the left plug wire. If nothing else this will at least tell you if the problem is from the mag back or the plug wires forward. Just my 2 cents worth. Curtis in Iowa

 

[1936]

I tuned up the mag, new plugs, and the wires was the real problem. Replaced the carb and looking good. Most often wires are the easy starting point. The listed items is about you need to look at.

 

[Sam from WA]

I"m running AC Delco C87s in my 48 B. Do NOT use champion plugs, as they will not last very long. Try switching the plugs or plug wires side for side and see what happens.

I also found in mine, the idle jet, at the end of the needle, was plugged, causing the engine to "gulp" fuel from the load side. Try taking the carburetor off and take out the plugs in the idle side and take a good look at the ports.

I"m not a gas engine mechanic, but that is where I would start.

 

[johndeereman]

i had the same prob with my 43 b found out one of the tabs under the rotor was broke so when it rotated at good speed the rotor rocked and didnt get a good spark the tab im talking about is where the rotor slides on the shaft of the mag also make sure you dont have junck wires get yourself a nice set of home made old style ones new style cant handle the heat

 

[Dan2]

I had the same problem with my B running on one cylinder. One problem I found was a cracked magneto cover.

 

[Anonymous-0]

Clearly I was missing something. The tractor is now running, and well. It was one of the elements that I thought I had completely covered. Apparently I did not. I switched out the carb with a known good one and it runs like it should. Now I have to figure out what is wrong with the other carb. I've been through it several times so I believe I'll do something I've never done and send it off to Robert's carb to fiddle with the silly thing.

Thanks for all the help and assistance, it remains very much appreciated.

Jason