B running rough

I got my NH rake gearbox finished yesterday. I took it out in the pasture today and raked up some hay the cows didn't clean up. Rake did great. The B however spit, sputtered, and cut out like crazy. It's only been started two or three times all winter. It could use some fresh gas, but I don't think that's all of it. I cleaned the sediment bowl a couple of times. It didn't help, and I didn't really see anything in it. I put half a bottle of seafoam in it and pulled the rake around hoping it would straighten out-nope. Then I played around with the carburetor. Here's something I don't understand. It has a marvel carb with the fixed jet. I can turn that one screw all the way down as far as it will go, or I can turn it out till it's just about to come out and it doesn't do anything. I can't tell a bit of change from extreme to the other in the way it runs. Another strange thing, I can't choke it out. Pull the choke, it keeps running, no noticeable change. I put my hand over the breather-same thing. It doesn't seem to choke it down. This isn't the first time I've noticed these things, although it usually runs better. It always starts good. It's starting good now, just not running right. Any suggestions appreciated.

The screw adjust the air mixture for idle alone. When you have the throttle set above idle you can take it out and put it your pocket and go back to work. When you try to idle then it will die.

Any engine speed depends on the opening of the throttle plate!

The idle speed is set with (the throttle plate opening) the stop screw on the back side. The screw is adjusted for a fuel air mixture that makes the engine run smooth at the desired slow idle or how small the throttle plate opening. Your sputtering can be a dirty non adjustable power jet or it might even be dirty points.

Ranse wrote: I can't choke it out. Pull the choke, it keeps running, no noticeable change. I put my hand over the breather-same thing. It doesn't seem to choke it down. .

Edited by nella(Pa) - 12 Apr 2019 at 7:03am

As for the ignition system, I've never opened up that magneto before. I could probably file the points and see if that helps. To be honest, I'm a little afraid to mess around in there to much. I might do more harm than good, like getting it out of time.

Ranse wrote: Dick, I didn't know it worked like that. I tried adjusting the screw at high engine speed and lower speed too, but probably not slow enough. If I throttle it down to much the engine will die. That's how I usually shut it off.

The back stop screw and the air mixture screw will have to each be turned a little at a time alternating between the two to keep the engine runing as you reduce the speed. The slower the engine runs the more your on the idle circuit of the carburetor. When entirely on the idle circuit the more necessary it is to have the proper fuel air mixture to keep the engine running.

Take it easy on filing the points or using sand paper. A piece torn off the corner of a poster board or even a business card will clean the points from just setting for a while. If the points have a spot on them that do not seem to clean with the paper they need changed. You can file them but soon will need changed or filed often. That depends on how much you filed off.

The more compression the engine has the more suction you will have at the carburetor. The breather pipe can be letting air in thru the crimp in the pipe or at the cup. Remove the hose and check at the carburetor to feel the actual vacuum. Steve mentioned the tight valve lash/clearance which could cause lower vacuum which would also give problems with carburetor adjustments as well as sputtering. Valves not sealing from an improper valve job. I hesitate in saying valve grind as some think lapping is the same thing as a grind. Without grinding the proper angle on both the valve and seat is only temporary at best if a good seal is even achieved.    

Edited by Dick L - 13 Apr 2019 at 8:30am

Ranse wrote:  It's a new hose and clamps, looked ok the last time I had the carb off. That's the only place it could be drawing air unless there's a big rust hole on the back side of the breather that I've never seen. I never had it off the tractor.

That is NOT the only place it can draw air. If you have a leak in the manifold, whether it's where it mates to the head OR internally, it can and will draw air from the area of least resistance. You could have a rusted thru spot inside the manifold, letting exhaust gas be sucked back into the engine.

Ranse wrote: I haven't had a chance to tinker with the B since the other day. I'll probably drain the fuel tomorrow. That valve lash is something else new to me. I've heard of adjusting valves, but I don't know exactly what you are referring to when you say "valve lash". I'm also going to check the suction at the carburetor to see if there's more vacuum there. I don't believe there's a manifold leak, not an obvious one anyway. If it's internal how can you tell? I have a suspicion the compression isn't good. It's just a suspicion, I have no way to check that either.

valve lash is the distance between the valve end that the rocker arm pad is allowed to move. Or the thickness of a feeler gage that will fit between the end of the valve stem and the rocker arm pad. To make checking the clearance when not have done it you can find TDC in the inspection hole and under the valve cover one cylinder will have both rocker arms up to where you can get a feeler gage of some thickness. I personally want .012 thickness. Every time the TDC is in the inspection hole one of the pistons are at TDC. Thinking this way about it takes the confusion on finding the compression stroke on number one that is most generally suggested. Any time TDC shows one of the pistons happens to be on the compression stroke even though it might not be number one.   

If the leak is internally in the manifold the tractor will most likely not start. That is caused by core shift when the casting is poured. It is also rare.
Checking at the carburetor first will tell you if you need to look farther.

Here is one I sectioned.



Edited by Dick L - 16 Apr 2019 at 6:12am

Valve lash or gap needs to be adjusted when the piston is at top dead center so the cam has the valves closed. The gap is there to make sure the valves close tight when pressure in the cylinder from combustion is greatest and to allow for heat expansion of the length of the valve stem, heat warp of the rocker arm, and heat expansion of the pushrod between the cam follower and the rocker arm. Lack of a gap leads to valve leakage which burns the valve and the valve seat and makes the engine run poorly, more so if its an intake valve pushing combustion products into the intake manifold.

Gerald J.

Ranse wrote: Dick L wrote: valve lash is the distance between the valve end that the rocker arm pad is allowed to move. Or the thickness of a feeler gage that will fit between the end of the valve stem and the rocker arm pad. I always called that the valve gap. I guess valve lash is the proper mechanic term. My Dad and I rebuilt the old original six cylinder motor in a 1955 Chevy pickup. We got the neighbor to adjust the valves because he was a better mechanic than us. Watching him was the only experience I've had with adjusting valves. I was 16 years old at the time. I remember he used a feeler gage, I don't recall him rotating the motor.

I understand. He would have had to rotate it some or adjust them at idle. I also do not check for TDC on each valve adjustment. I was explaining how you could adjust them without wondering if you did it correct. You can only adjust correctly when both valves on one cylinder is closed. There exceptions to this rule when you fully understand what you are doing. As I stated above to not be (confused) this is the way I suggested.

I was 17 when I learned how to adjust valve gap/ clearance/ lash! All being the same deal! That was at an Oliver dealers on a six cylinder with the engine at idle.

Edited by Dick L - 16 Apr 2019 at 10:31am

Well I've got a ton more suction at the carburetor than I did at the breather pipe. I can choke it to death in an instant with my hand. I'm not sure if that's good news or bad. The tractor does seem to run better with fresh gas and no breather, but it's still sputtering. Especially at idle. The adjustment screw still don't seem to do much. I think it's safe to say at this point that it's not an adjustment issue.

My question now is how was it getting air before? I still don't think that hose was the problem. Over condition of the canister looks good. It's made a little different than the one on the D10. How do you get the mesh out so I can wash it? It looks like this bottom flange is painted on, but it's hard to tell. It could be pressed on. I believe it will knock off, but I want to know for sure before I start whacking on it.

    

Is there an o ring in the air cleaner for a seal so it wouldn't suck in air at the oil cup joint

Edited by nella(Pa) - 16 Apr 2019 at 9:02pm

nella(Pa) wrote: Is there an o ring in the air cleaner for a seal so it wouldn't suck in air at the oil cup joint

Edited by nella(Pa) - 17 Apr 2019 at 5:38pm

First off you can never get the carburetor adjusted properly until you get it to idle with the lever all the way back. Something is wrong with the linkage as well as the stop screw setting if it closes the throttle plate enough for the engine to die at half throttle. My I suggest you remove the carburetor and while looking down at the throttle plate adjust the throttle plate stop screw so it will not close tight leaving about a 1/16" gap so you can see what it looks like.

What I would do if I was adjusting it is to run the tractor as slow as it would run where ever the lever is setting if it had the Zenith carburetor. I would then adjust the stop screw to hold the throttle plate so when moving the lever back the stop screw would keep it from killing the engine. I would then loosen the set screw at the throttle lever and move the lever back and tighten the set screw.

Since the linkage for the MS carburetor is most likely shorter or longer than the Zenith carburetor the linkage from the carburetor to your lever at the steering wheel might be out of adjustment at the cross over arm as well as at the steering wheel.

When you know that the throttle plate can not close when against the stop screw remove the connection at the cross over arm. With the linkage pulled forward and the throttle set wide open the linkage from the carburetor should just drop in or be 1/16" shy from dropping in. If is not in that position the arm needs to be bent until it is. From there you can see where the throttle lever is located and then can be adjusted if needed.   

A person can get into the same problems using two different Zenith carburetors as well as they have different lengths levers operating the throttle plate on the back.

I have 5 of these engines running and none have ever had a gasket on the air cleaner cup. They might have had at one time but I have never seen one or put one on.    

I finally did a little more work on the B. I got the carburetor cleaned and back together. I'm telling you, if this carburetor gets any cleaner, someone else will have to do it. It is as clean as I can get it. It probably ain't perfect, but that's the way it is.

I put the carb on and it actually ran worse. It would only run a second or two at first. It would not idle at all, it would only run at half throttle or more. It spit, sputtered, and cut out worse than before. It smoked more and backed fired when the engine died. I even seen fire shoot from the muffler. It never done that before. It did seem to run a little more consistent with the choke pulled out. No way to adjust the carb with the tractor running like that.

I decided to clean the plugs. All four looked really bad. Number one and number three were dry with lots of dry powdery carbon build on them. Number two and four were wet and oily looking. I thought this was odd, but I don't know what it means.

After cleaning the plugs, the tractor ran better. I did as Dick suggested. I set the stop screw were the throttle plate would stay 1/16" open. By doing this I was able to run the tractor with the throttle all the way back (no linkage adjustment done). I then turned the stop screw until the engine died, then turn it back in just a touch. I restarted the engine and attempted to adjust the air mix screw. At times I thought it was helping, other times I couldn't tell.

In short, I'm still clueless. I think the tractor is cutting out to bad to tell what I'm doing to the carburetor. I think I may need to look else where. I bought new points and condenser. Any tips on installing them without screwing it up worse?

Dick,
The only jet that was hard to get out was the one below. That was mainly because of where it was at. Every screw driver I had small enough to go thru the hole above it was to small to grab the shoulders of the jet. I ended up grinding down a larger screw driver. I didn't heat anything. I didn't use drill bits, I used a tip cleaner for a cutting torch. The discharge tube I think you are referring to, I run the tip cleaner thru the center. However, that's a big tube and the cleaner wasn't tight. The tiny holes in the bottom part I could see daylight thru them, and I sprayed carb cleaner thru them freely. Everything was disassembled and soak in a bucket of carburetor solution for two days. Then I sprayed with carb cleaner and blew it out again and again. It all seemed free to me. I know its got to be cleaner than before. Like I said, if it gets any cleaner, I'll have to get a professional to do it. It ran worse at first, but I think it may be a little better now than before. It's a long way from being right.