Farmall Cub Forum -- Questions and answers to all of your Cub related issues.
Moderator: Team Cub
Notice: For sale and wanted posts are not allowed in this forum. Please use our free classifieds or one of our site sponsors for your tractor and parts needs.
So, we just got a ton of rain here in SW Michigan over the last two weeks, and unfortunately my '50 Cub sat out through a little too much of it. Push it into the garage and let it sit for a weekish, and it still wasn't running - it would seem to only fire on one cylinder once every few rotations - just enough to disengage the starter, but no more. I replaced all the gas, including draining the carb. I had a couple plugs out and I was seeing spark. I also replaced the plugs to no effect.
I got desperate so I did a bunch of reading, and then pulled the distributor off to check it. The points had a bunch of oil in them (probably a teaspoon or so), but it wasn't milky or anything. I tried to be careful not to change the point gap setting while I was in there. Long story short, I got it back together and sparking (made a couple wrong turns through this process, but the internet is a wonderful place ). I had made marks to line the distributor back up, and my timing appears to be right. I don't have a timing light, but by using the hand crank, feeling for pressure on the #1 cylinder, then watching for spark it looks like it's at least close. Between that looking close, and my marks on the distributor/frame lining up I think my timing is good.
After that, it started up, but it was surging and very low power. I could barely climb a couple of the small hills (more like mounds) I have here in 1st gear. I would have to really play with the clutch to keep it climbing. Choke didn't seem to affect it, but it was hard to tell. It was irregular enough that it was hard to really nail it down. Definitely seemed to start better on choke. We slowly rotating the distributor back and forth a tiny bit while it was running to see if that helped - but it didn't seem to make hardly any difference.
I read that could be bad fuel supply so I cleaned the main jet, which didn't appear to be fouled, and that didn't make a difference (I just blew it out good, I didn't run a wire through or anything).
I gave up for a couple days because I was out of ideas, but then decided to change the plugs back to the old ones just in case the gap on the new ones were wrong or something. The old ones definitely had a wider gap than the new ones. I should have double-checked it was still running before I swapped plugs, but I didn't - I switched to the old plugs, and I was back to the original symptoms: couldn't get it started, just would pop one one cylinder once in a while. I probably shouldn't have done this - I by hand tried to match the gap of the new plugs to the old ones (using my eyeball and a flat-head screwdriver) and no change. I have spark, but nothing but the occasional cylinder firing when I try to start it.
So I feel like I'm back where I started, and I have already exhausted 150% of my total engine knowledge haha. I'm totally learning as I go here.
Anyone got some wisdom for me? I would REALLY appreciate it. I'm out of ideas. Right before the rain it had been running beautifully.
When adjusting the spark plug gap be sure to use feeler gauges. The same thing applies when adjusting point gap within your distributor. I would not suggest trying to gauge it by eye.
The spark plug gap should be set at .023
The point gap should be set at .020
Are you using the same brand and model of spark plug when you swapped them out?
Make sure you wipe out any condensation that may have formed inside the distributor cap.
Be sure you are using the correct timing mark on your crankshaft pulley when verifying things, there is a BTDC and TDC mark.
You can use a small 12v lawn and garden battery and a timing light to verify things.
Something else to check, you say that you are getting spark, but are you getting spark from the coil to the cap and from the cap to each individual plug?
cubguy - Thanks for the response.
I didn't change the point gap at all, and I realize I should have used feeler gauges on the plugs, but I didn't have any and I was desperate because it was beautiful yesterday and I was running out of day :-/.
I didn't wipe out the inside of the distributor cap, but there didn't appear to be much moisture in there. Maybe a tiny tiny bit. Certainly something to try next.
I was reading that the TDC mark is for a magneto, and the BTDC is for a distributor/coil. It appears to be right at the BTDC line, or maybe just a touch after. Hard to tell without a timing light. Either way - wouldn't getting that close, and then lining up the marks on the distributor body and the frame mean that I have it exactly at the original setting?
I'm getting spark at each cylinder as near as I can tell. I've been pulling the plug and then holding it against the frame and watching it for spark as I hit the starter.
Getting spark and getting spark at the right time is critical.
You are correct that a magneto uses the single TDC reference mark. But you also use that same mark for a distributor setup.
Turn the engine with a hand crank slowly when checking TDC, not with the starter, it's easier to do.
When using a timing light here are some suggestions and apply to the two notch pulley you have:
-with a fixed timing light verify that the first mark (BTDC) lines up with the pointer at high idle and the second mark (TDC) at low idle.
-with an adjustable timing light, the same above info applies but be sure your gun stays set on "0"
It is also very important that any adjustments to the distributor be made at high idle only.
You mentioned you have rotated the distributor slightly. I suggest setting things back to TDC, checking your rotor position, make changes if needed and verify everything with a timing light.
Last edited by cub47 on Tue Apr 23, 2013 10:11 am, edited 1 time in total.
I rotated it maybe 1/4" and then back. I'm really nervous deviating too far from that mark since that's where everything was setup at before. I want to get a timing light to look, but I don't understand why if I have my marks lined up that my timing could be different from where it was before.
I am not saying your timing is the culprit or the only culprit, just something to check.
The fact that you said all old fuel was drained, to me that eliminates any moisture issues there.
The symptoms you are spelling out sure sound like a timing issue or something internal within your distributor.
Take your time and back track thru the distributor and timing process, it does not hurt to check the condition of your points and the gap, the same goes for the plugs.
Something could have changed while you were initially looking through things.
You are probably off a tooth or two when you reinstalled the distributor. You need to correctly time the distributor to the engine - - and then time the ignition (spark) to the engine. Two step process.
Your marks could appear to line up and you ignition timing still be way off. An error in ignition timing at the distributor is doubled on the crankshaft.
As Brian stated, you use the 2nd mark, TDC, to match the pointer to initially set the timing, static time the engine.
I have an excuse. CRS.
So I just learned that I have some other wacky complexity going on. I have a magneto/coil hybrid. They (whoever owned this before) left the entire magneto assembly (which I thought was called a distributor), removed the magneto (or whatever it's called that generates the spark) off the top, and have a coil wired into the points. So that's a little wacky. So basically I have this:
But with the black part in the top middle gone, and a coil wired into the points instead.
Anyway - per the teeth thing, it doesn't really engage with teeth - maybe the magneto assembly is different? It engages with two bolts (you can see them in the image at the far left) that fit into a slot. So you can only be off by 180 degrees - not just a tooth.
I didn't realize it was this strange hybrid until now. Certainly makes the learning curve more interesting! lol. Sorry to be confusing. I'm pretty much learning about simple engines as I go.
What's additionally frustrating is that after all this I still don't have a great explanation for why the rain did this. I haven't like found a bunch of water anywhere to blame this whole thing one. That would make me feel like I at least did something useful!
OK. Magneto with external coil. Starting over.
1) Does the magneto click when hand cranking the engine over?
2) Points gap is .013 for the magneto.
3) There are timing marks on the rotor. Rotor can be incorrectly installed.
4) Spark color and quality Yellow or blue?
5) You need to treat this hybrid system as if it were a magneto when static timing.
I have an excuse. CRS.
Just a little moisture in the cap is all it takes.
There is a video in the how to section on timeing the mag.
The coil on there now is ok it just cost a lot less then the one that goes in the mag.
1975 cub (LouAnn) serial # 245946, 1941 John Deere Model H
Good judgment comes from experience,
and a lot of that comes from bad judgment. Will Rogers
I had an issue similar to yours and what ended up being the problem was the insulator on the kill switch post....it had a hairline crack in the plastic insulator .....after a decent rain I wouldn't be able to start it again for days...
item 45 in this capture
Charles Patek III
Some days - Chicken.......Some days - Feathers
Words to live by....
Not sure I know what you mean. There is no "clicking". I have seen videos on timing with a mag, and certainly noticed the click the mag makes, but mine doesn't have anything like that.
Alright. I can double-check this, but I tried to take care to not budge the point adjustments when I was cleaning it out.
I had to play around a bit with this to get spark. Does rotor position effect timing? Or does it just have to be at the right place so that the spark can go to the right place?
Um... blue, I think.
k. I'll look at that in the How To section - but I'm still a little lost as to why.
Excuse my total ignorance on the topic - but if this is using a battery-powered coil for generating spark, why is it still treated like a magneto? Isn't it essentially just a distributor then?
Thanks for all the help!
Oh! That certainly seems plausible.
How did you go about repairing it? Do they sell that piece individually, or did you manufacture something?
Who is online
Users browsing this forum: Glen and 7 guests