Cub not firing on all cylinders.

[RedFred]

My 48 cub I just got running again after cleaning all the spark plugs now is sounding to same again. Like it's not firing on all 4 cylinders again after two uses any thoughts on why the plugs are fouling?

[ricky racer]

The first thing I would check is engine compression doing both a dry and wet compression test. That will give you an idea of the engines condition. Once you have those numbers, it will be easier to diagnose. If you don't have a compression tester, you can usually borrow one from an auto parts store for free by leaving a deposit to be refunded upon return.

[RedFred]

Ok I will get one this weekend and check my guess it's it's low cause to me the engine has not been taken apart before.

[SamsFarm]

I've never really been schooled on spark plugs and "reading" them.

But as a hunch, I would suspect any of the following;
Cold plugs
Bad plugs
Weak coil
Faulty (any one or more of the following) cap, rotor, points, condenser, wires.
Points gap
Too much gas (running rich)
Bad rings

Is there any corrosion on the contacts under the distributer cap?
I have had bad luck with the contacts under the cap being aluminum and always corroding. Seemd as the older that cap got the more frequent the corrosion!

[inairam]

Something I learned here is to do the compression test remove all of the spark plugs and open up the throttle all the way or remove the carb. You are testing just the compression in one cylinder at a time with no other loads.

If the compression checks out:

Have you replaced the cap and the spark plug wires and the plugs?

[Waif]

How happy are your valves?
Are your plugs fouling from carbon deposits breaking loose? Wet or dry carbon? Or is it something else?
Is there sludge in your oil?
Stack exhaust discharge color?

Plugs were mentioned as possibly being bad. (Heed the other potential ignition items too.) And even new plugs can be bad quality.

[RedFred]

Something I learned here is to do the compression test remove all of the spark plugs and open up the throttle all the way or remove the carb. You are testing just the compression in one cylinder at a time with no other loads.

If t he compression checks out:

Have you replaced the cap and the spark plug wires and the plugs?

I have replaced the wires this summer but the spark plugs were put in 3 years ago.

[RedFred]

I've never really been schooled on spark plugs and "reading" them.

But as a hunch, I would suspect any of the following;
Cold plugs
Bad plugs
Weak coil
Faulty (any one or more of the following) cap, rotor, points, condenser, wires.
Points gap
Too much gas (running rich)
Bad rings

Is there any corrosion on the contacts under the distributer cap?
I have had bad luck with the contacts under the cap being aluminum and always corroding. Seemd as the older that cap got the more frequent the corrosion!

The contacts on the cap on my J4 magneto are a little corroded and a tiny bit burnt looking. The plugs I will replace same with the points,coil, and the condenser the carb is running 2 1/2 turns out but won't start on 1 1/2 or 2 turns out but the rings are most likely worn because there was some oil on the plugs.

[RedFred]

How happy are your valves?
Are your plugs fouling from carbon deposits breaking loose? Wet or dry carbon? Or is it something else?
Is there sludge in your oil?
Stack exhaust discharge color?

Plugs were mentioned as possibly being bad. (Heed the other potential ignition items too.) And even new plugs can be bad quality.

They could be because the tractor doesn't work enough to burn all the carbon out of it also after running it and getting off the tractor to shut the fuel off I see some bits of carbon on the hood also the muffler is discharging some white smoke (only in the winter) in till it's warm and running good but clears off. But when you throttle it up to wide open it blows black smoke for 1 second but then clears out.

[Glen]

Hi,
Piston rings commonly get stuck, then the engine can smoke, or have less compression than it should.
You could try Seafoam oil additive in the engine oil.
They sell it at auto parts stores.
It could help the compression, if the rings are stuck, and the Seafoam loosens them.

Make the engine work doing something when using the additive, so it warms up.
I have read on here of people having good results after using the oil additive.

One of the experts on here said to use the additive for 2 oil change periods.
The 1955 Cub operator's manual says to change the oil every 150 hours of use.
If the piston rings are wornout, the seafoam won't help much.

[inairam]

I have had a hard time with points and condensers from the tractor websites. I have had more reliability since i switched to NAPA

NAPA part number

Distributor Cap Part # ECH IH350
Distributor Condenser Part # ECH IH200
Contact Set (Points) - Magneto - or battery Ag Part # ECH CS1600
Distributor Rotor Part # ECH IH300 (battery not mag)

[Waif]

How happy are your valves?
Are your plugs fouling from carbon deposits breaking loose? Wet or dry carbon? Or is it something else?
Is there sludge in your oil?
Stack exhaust discharge color?

Plugs were mentioned as possibly being bad. (Heed the other potential ignition items too.) And even new plugs can be bad quality.

They could be because the tractor doesn't work enough to burn all the carbon out of it also after running it and getting off the tractor to shut the fuel off I see some bits of carbon on the hood also the muffler is discharging some white smoke (only in the winter) in till it's warm and running good but clears off. But when you throttle it up to wide open it blows black smoke for 1 second but then clears out.

IF it is carboned up bad take it easy with additives to soften it up. Start small.
I know a Cub owner (hello) who went overboard and had a volcanic type black muck blowing out the exhaust stack and splattering where it landed. Which surprisingly had quite a range of reach.. l.o.l..

After a check of your fuel system flow and going through an ignition condition check , checking plugs when one is not performing well can help reveal a cause.
Examples I've found are a gap on one plug out of spec. And a chunk of carbon caught in the plug gap of another.

If you're getting fouled or poorly performing wet dirty plugs a brand or heat level switch can help. Champions can be hit or miss. If I buy any it's because the store doesn't have options in stock and I'm impatient. Someone else might be happy with them today.

[Eugene]

New hotter spark plugs or open up the point gap.

That's after checking the compression and the other suggestions.

[Glen]

Hi,
inairam, just a suggestion, maybe you could change your list of NAPA ignition parts, so it says the NAPA IH 300 rotor is for the IH Battery Ignition unit, and doesn't fit the IH magneto.
TM Tractor has the rotor for the IH J4 magneto, the rotor is gear driven.

[inairam]

Hi,
inairam, just a suggestion, maybe you could change your list of NAPA ignition parts, so it says the NAPA IH 300 rotor is for the IH Battery Ignition unit, and doesn't fit the IH magneto.
TM Tractor has the rotor for the IH J4 magneto, the rotor is gear driven.

Thank you for the reminder. I updated