48 Cub Smokes

rapidfire

Member
My new to me 48 Cub starts to smoke when there is any type of load on it (driving, pulling, ect). It doesn't seem to smoke at all at idle. Looks like it's burning oil? I'm not sure if this would mean valve issues or ring issues. Should I borrow a compression gauge and start with that? What would be acceptable range?

Also, my oil pressure gauge does not work. I plan on getting a new one. What is good oil pressure reading for a Cub?
 
Shoot it is old enough to have the right to smoke. LOL
So is the smoke a black or a gray smoke?? What do the plugs look like?? As for oil pressure get a gauge like what was on it when new. These old tractor did not put out all that much oil pressure so a gauge that reads say 30 at the very highest is as good as you can get. The factory gauge would just have an area saying it is normal but not give pressure reading as such.

So has this tractor ever sat for a long time with out being run?? If yes an ATF treatment may help it
 
Thanks Old,

It's looks gray to me. It has sat a month or two since it's last chore, but it's smoked while being used ever since I got it.

It's enough smoke to kind of choke you out driving it. What do you mean by the ATF method?

I am just looking at where to start to figure out what's wrong.
 
Is the oil pressure gauge not working because it is bad or is it not pumping oil because the pump lost prime from sitting ?
To prime the oil pump there is a Allen head pipe plug on the left side of the engine near where the engine mounts to the torque tube at approximately 11:00. Oil can be added using a squirt can to prime the pump. If you can not get the plug out there is a hole in the oil filter housing near the top of the housing that you can prime the pump from also.
As far as compression goes numbers above 90 psi are good.
Before doing a compression test, check valve adjustment. Valves are set to .015"
22432.jpg
 
My guess is it is piston ring issues causing blowby and then also pushing out oil mist from the crankcase.

Because of the flathead (valve-in-block) design it doesn't have the exact same fail mode as an overhead valve engine which can leak oil down the exhaust valve stem by gravity and out the exhaust stream. Oiling a flathead's set of valves is sort of a challenge because the oil has to go up.

I bet you could find an IH gauge somewhere online, ebay or other tractor part sellers & recyclers.
 
The long and short of it is, you will probably need to overhaul the engine to get rid of the smoking, to the tune of about $2000 with all the machine work and parts.

Very few Cubs are worth that much. Really only worth it if you have an emotional attachment to the tractor. Otherwise, if it runs fine and has adequate power for what you want to do, you can live with it, or find another tractor.
 
My friend and neighbor, old, uses automatic transmission fluid (ATF) for many things including freeing stuck engines, If the piston rings are stuck in the pistons, his remedy will likely work as he claims. After seeing and testing his remedy I have determined that it will possibly help everything except ED or constipation, and if ever needed,that may be worth a try.
 
ATF treat is to put say 1/4 cup of ATF in each cylinder and let it sit a few days. Put the plug back in to keep things out. After a few days pull the plugs and spin it over. Be sure to mark the plugs so as not to mess up the firing order. Then once the ATF has been pushed out of the cylinders run it. ATF frees up sticking rings and valves and also cleans carbon both of which can cause an engine to smoke
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top