1948 Z still having problems... Grrr.

Few weeks ago I had this posting about the problems with the 1948 Z:

http://forums.yesterdaystractors.com/viewtopic.php?t=1146731

Total story here...

Tractor was sitting for about 2yrs when I initially tried to get it going the summer of 2012. My dad had passed earlier that year.

So far as I knew at the time it was running when parked. I had to clean off the points in the magneto to get spark. Then it would start and idle OK but would run rough, cut out and miss when the throttle was opened up or any need for some power was needed such as driving up a hill. I was trying to pull a hay rack around last summer to haul some cut trees and brush around and it was a delicate operation to keep the tractor from stalling.

When I first got it running I found out the kill switch was not working. I eventually found that the little tab under the cap was apparently missing so the stud for the kill switch wire was not connecting to the points. I found the tab fallen down inside and got it put where it belongs. My Mom recalled that my Dad had someone out to work on the mag a few years before, but I have no way of knowing now what was wrong with it and what they did.

So, this spring I installed some new plugs thinking that could be the issue. Didn't matter at all.

Then, as per the other posting, I noted that there was some hissing around the throttle shaft when the governor would open up the throttle. Thought that was messing up the mixture and causing the problem.

So, I had the carb apart and replaced the egg shaped throttle shaft and put a new rubber seal on it. I cleaned up the carb (inside was pretty clean actually) and resealed it. I had problems getting the tractor to start after re-install but that was due to the idle stop and idle mix screws being totally out of adjustment after I had things apart.

I have gotten the idle stop and mix screws sorted out now and the engine starts up and idles just fine again. But, still I have the problem I cannot rev the engine up much over a fast idle and as soon as I try to drive the tractor around up a slope or pull anything it cuts out. So, the vacuum leak around the throttle shaft must not have been the problem.

I even vented a bit of propane around the intake manifold looking for vacuum leaks but didn't find anything.

What else could be causing this? Does a mag have spark advance on it? Could the timing be messed up? It does not appear the mag has been off the tractor in decades but I am not sure. I tried to see if there was any arcing around the plug wires but didn't see anything.

I will mention I had the power valve in the carb unscrewed but didn't have the seat out. I blew air through there and put it back were it was. I tried adjusting it in and out a couple turns either way while test revving by forcing the throttle open via moving the governor arm but it didn't improve it any, actually tended to make it worse if anything.

I am about out of ideas. My next trip to the farm is over Labor Day and I am hoping to come up with something to try next by then...

Thanks.
 
What are your mag. points gaped at ? I'm thinking
.015-.020 is what you need . Maybe somebody has the
exact setting for you .
 
Are you sure you are getting enough gas to the carb? Open the carb drain and let it run out, gas should run out, not drip.
 
I would agree with Brian. I had the same problem you describe on a MM R. Turned out to be an obstruction in the fuel line. It would let it idle, and run at low RPM. But when it needed power it ould stall out.
 
Well...

I had the carb off and apart twice. I broke the brass elbow on the fuel inlet when taking it off the 2nd time after I could not get it to start from my "rebuild" and then replaced the steel fuel line from the sediment jar under the tank with 5/16" hose.

I must have overtightened the flare fitting and didn't have a wrench on the elbow to support it so it snapped off the fitting flush to the carb body when I tried to re-loosen it. I could not get a replacement so I got a elbow with a hose barb instead.

Made sure the hose was not too long so its got a even slope down to the carb. When I turned the fuel back on after that I left the carb drain at the bottom open for a bit so any dirt in the hose would be flushed out. I had a nice stream there so it does not seem like the fuel is blocked up. I am sure it would not hurt to check the sediment jar though.

I still wonder about the mag and timing though. I need to find out how to check that.
 
Points on mag should be set at .020. When timing assumming mag hasn't been removed. Go TDC on #1 cylinder. Make sure both valves are closed and crank over until piston at top. On flywheel should show DC 1-4. Measure 1 1/8" past DC. If impulse in mag is correct this is when you should get spark on #1 plug wire. Most mags correctly timed will sit crossways on block.
 
The reason I mention this is many years ago I got a 1947 UTS. I got it to run fine around the yard, no problem, but when I went to the field it seemed to become starved for fuel and run rough or stall. I cleaned the carb a few times, still bothered, I thought it was getting enough fuel. It really had me stumped. After a while I figured out the "stack of wafers" screen in the sediment bowl was not letting enough fuel through. I had tighten the screw too much, and that was not letting enough gas through, gas would come out of that in a slow stream and I thought that was OK, but as it turns out when I had it out in the field it needed more fuel and what was coming out of the screen was not enough. Anyway, I loosened it some and the problem was fixed. I can't remember if I still have that type of screen in there or I went with a wire screen. I can't help you with a mag, I have a few, they work, I keep them dry and I don't touch them. Another idea, is there something in the gas tank that could plug the outlet temperairly? Like a soybean?
 
Really sounds like a fuel
problem. Try this. Put gas
in a squirt bottle. Open
carb throttle by hand.
When it starts to stall
give it a squirt into carb
air intake. If it speeds
up fuel supply, if not i
wrong
 
It really sounds like fuel issue as others have said. Drain fuel sediment bowl and reinstall and turn fuel on - see how fast if fills. If its slow or starts fast and slows down, you have a fuel problem - may not be only problem, but it should be addressed.

I assume you have checked the tank itself - not cruddy / rusty on bottom. In my experience this is most likely single problem on old tractors - especially with Alcoholic fuel that is old.

Next make sure fuel is flowing freely from tank - cap should be a Vented type cap - if not it will flow initially then slow down as tank goes into a vacuum mode if not vented. If you get slow/no flow condition, simply take cap off to see if it changes - yes = bad cap.

And sediment bowl - the valve itself can get clogged up especially with Alcoholic fuel over time. The alcohol damages most rubbers causing initial swelling and then hardening over time. Also make sure screen is not the problem as noted elsewhere - try running with no screen - not the best, but for short term, it will answer question. New sediment bowl (Chinese) is about $20-25 at Tractor Supply - maybe a bit less at Fleet & Farm.

Next, if you are running a rubber line, you probably put a secondary in-line fuel filter in it. If your fuel system is in great condition otherwise, this may be OK - but if it is challenged, the additional resistance to flow on a gravity feed system (as opposed to a fuel pump system) may be too much.

As to fuel line elbow, you should be able to replace that from a good hardware store. Also note on some carbs, there may be a filter screen inside carb behind or as part of this fitting. You can clean or eliminate this filter to see if it solves problem. If you want metal line, good old hardware stores can probably make you one from your pattern. Personally I prefer the metal line, but if you are using rubber, make sure its Alcohol Compatible.

Recommend you put a petcock drain on carb - many came with this option particularly early tractors for draining gas / water from gas in carb - later tractors were mostly pipe plug, but again you can go to a good old hardware / farm store. You can use this to drain carb for storage and to verify you have flow to carb.
 
thanks for the tips.

I am going to be down at the farm labor day weekend and will see if I have time to try some things. It will be a busy weekend as usual.
 

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