Timing or fuel or governor or other?

[marrstree]

I have having trouble getting my Cub running. It has run beautifully for 10 years, including this spring to cut and rake hay.
Had troubles getting it started a week or so ago - have diagnosed and fixed various problems, including breaker points, timing, fuel line inlet screen pluggage, etc. It would run strong for 15 or 20 MINUTES, then die suddenly, refusing to start or run more than a few SECONDS.
I have studied on-line discussions and resources extensively, and find too much conflicting or irrelevant info for my specifics (for example, "adjust the distributor" - mine doesn't adjust)
Now I am at my wits end for solution.
Background:
Tractor: 1948 Cub. When purchased over ten years ago, it had been converted from magneto to coil ("battery ignition") from 6V to 12 V negative ground, with an "ignition kill switch" on power wire from battery to coil. So I think you would call mine a "battery ignition system", but technically the magneto is still in place and turns the distributor rotor.
I have rebuilt the carburetor (did find lots of particles packed against inlet screen). Flow out of gas tank bowl or carb float bowl is strong, jets are clear, I am pretty sure this is NOT a fuel problem.
Distributor has never been removed from magneto body, so that cannot be mis-aligned. I DID, in early stages, pull the rotor off and got it installed incorrectly for timing when replacing the breaker points (gapped at 0.020"). I tried following on-line instructions for static timing, and while using TDC pulley mark and aligning rotor tab with #1 plug wire, through trial and error got it running again (before the fuel pluggage found and fixed).
Now, with the fuel problem solved (I think), it is difficult to start, and then runs very roughly for just 5 or 10 seconds before dying. Seems to seek and surge - eventually I tried adjusting the governor linkage clevis to throttle valve (which I have never touched in 10 years, and it always worked fine...), but got only slight improvement.
I went back to timing and tested in (one-tooth steps) two steps on each side of current setting - all are even worse than current center setting.
So I guess two specific questions I would have are:
1) In my magneto-distributor setup, is the only timing adjustment moving the rotor one-tooth steps? And is the correct static timing with tab pointing at, or slightly ahead of the #1 plug connection with #1 at TDC (pulley timing mark lined up, checked by compression on #1 cylinder).
2) Is there any adjustment for the governor aside from the linkage length to throttle valve? (I have adjusted previously the "spring resistance" button on the end of the governor when it was "seeking" too much - seemed to solve that previously and ran fine for months...)

Any help will be appreciated.

Gevan in Puyallup, WA.

[Eugene]

The 15 to 20 minute run time is typically a faulty coil.

Point gap for a magneto, even a magneto converted to battery power is .013".

[marrstree]

Coil- I didn't mention but I replaced the coil as one of the first steps when this issue began, so that shouldn't be a problem (although I suppose it could be defective).

Point gap - yes, I see that the internet info I found of 0.020 is incorrect - the manual pdf specifies, as did you, that it is 0.013. I will change it (although it doesn't seem likely the main cause of exceptionally rough running, surging, and stalling...).

One other discovery I have made is that by looking back at old photos of my restoration, I found one noting that the small gear tooth on my rotor type, beneath the bakelite cover, has a timing mark, and there is a matching mark on the rotor body. I disassembled, and even with what was supposed to be the static timing (rotor pointing a bit ahead of #1 plug wire at #1 cylinder TDC), when revealed the timing marks were off one tooth, and to my surprise it needed to be "advanced". With timing marks on rotor gears aligned, and reassembled at TDC, the rotor points about 20 degrees "ahead" (that is, about an 11 o'clock position looking forward, while the #1 plug wire is at about 1 o'clock. Seems awfully advanced, but that is for sure how it was assembled and running fine for the last 10 years....so now I am pretty sure the timing is not the issue.

I did note gasoline dripping from carb air inlet, so maybe I now have a carb flooding problem (after rebuild..). I pulled spark plugs and they not only seem moist, but while out some gas drained out of the plug body. Seems to me like flooding, so next I will disassemble the carb (again...) and check float for leak and do a needle valve close seating test and check float adjustment.

Still wondering about governor adjustments - where, and how, and to correct what symptoms.

Thanks.

Gevan in Puyallup

[Eugene]

the manual pdf specifies, as did you, that it is 0.013. I will change it (although it doesn't seem likely the main cause of exceptionally rough running, surging, and stalling.

The magneto is designed to open the ignition points, firing the spark plugs, at TDC during engine start up and then advance to around 15 degrees engine running.

The .020 point gap will fire the external ignition coil early in the crankshaft rotation cycle.

Correct ignition/magneto problems, then check with a timing light.

I think part of your tractor's operation problems are ignition related. My first thing to correct would be the ignition problem(s) then move on to the carburetor.

Edit: Are you using an ignition coil with internal resistor or a ballast resister? You should use one or the other in the ignition system.

[Glen]

Hi,
If you are sure the coil is good, the condenser could be partially bad and making it quit. You could replace it with a new one, and file or replace the points, they need to be flat and shiny metal at the 2 contacts for it to run good.
Check the fuel tank vent in the gas cap, it has to be open, or the fuel flow will stop after running for some time. If you have the old original cap, the vent holes are on the top and bottom of the cap. A small wire works to clean them.
The engine needs timing with a timing light too so it runs good and has good power.

[marrstree]

Update.
I used the suggestion of checking timing with timing light. Discovered why my distributor rotor seemed to be pointing to 10 o'clock at TDC. When I pulled a plug and felt for compression, there was a mark on the pulley. So I marked the mark with white paint. But the timing light revealed a second mark....about 20 degrees following the white mark. Now I pulled #1 plug and realized what I felt was compression at the start of the upstroke, not at TDC. Actually, the compression should just disappear at TDC, I realized. Then the second timing mark was aligned. In other words, I was using the wrong mark for TDC... I had read that some pulleys had two marks, but didn't realize mine did. So now rotor points directly at #1 plug wire on distributor when at TDC. And timing light, with slow manual crank, fires right on the NEW timing mark. So I am confident I have timing correct.

Reset breaker point gap to 0.013, first bending them slightly to get good parallel contact. They are new points so that should be good.

Coil is new 12 V coil - and is marked "External resistor required" - but so did the old one and it worked "fine" for 10 years, so I figured direct replacement was fine. I do have the ballast resistor that came with the tractor (as it had 12v battery but 6v coil). Should I place that in line from battery to + coil?

Also, pulled spark plugs and they looked carbonized and damp... so replaced all those too.

STILL, would barely start, run for 10 seconds, die, and really can't get it to fire again. Gas running out of air intake.

Pulled carburetor, checked float level, and tested float needle valve. Holds flow just fine, so now...?

I do seem to get intermittent firing with the timing light. The battery has worn down several times from cranking the starter so much, and I have recharged, but I wonder if weak battery would cause misfire once started?

Gevan in Puyallup

[Eugene]

The second pulley mark to line up with the pointer is the TDC mark. First mark to line up is the advance mark for a battery powered ignition system and not for a magneto. With the engine running at anything above low idle the timing light should flash just after the 1st pulley mark passes the pointer.

Condenser fault will not permit the engine to run properly. Engine might run, but like crap.

You need the ballast resistor in the ignition wiring. Resistor drops the working voltage to somewhere between 6 and 9 volts with a 12 volt battery.

Set the engine on TDC, #1 plug, then static time the magneto. Then check the location of the rotor.

Also, do you hear the magneto click when you hand crank the engine?

[marrstree]

FINALLY!! I got it.
The keys were 1) use the timing light to figure out that while timing was correct, after a few revolutions it stopped firing... eliminated fuel as root cause.
2) advice to replace the condenser. When I got ready to do that, I found that the spade connector on the wire from the condenser was actually lying loose behind the connector. Apparently when I replaced the points I let the connecter slip off to the back, and didn't notice it. It would rub against it enough to start and run briefly, then crap out. Reconnected the wire and VOILA! fired right up and ran like a champ.

Amazing how such a simple thing could be veiled behind so many other potential causes.

Thanks for all the help in diagnosing the problem. At least I have new points, coil, spark plugs, carb parts, etc....