1950 Model M Saga Continues

[Danny in CO]

I have posted several time about my neighbor's 50 Model M. My neighbor is not tractor savvy at all. I am an old wrench head but not at all familiar with JDs.

It has a backfire and we think an intake valve is sticking. Here is what we found. There is no oil coming from the block up through the oil line to the head at all. Oil pressure is at 30-40 PSI. If I squirt oil on the valve stem the backfiring stops momentarily. Any idea why there is no oil coming out of the block. I'm thinking about taking the oil pressure gauge out and putting a tee there and running the oil line from there to the head. Any thoughts?

Thanks!

 

[Mike M]

Someone installed the cam bearing wrong. It feeds a wee amount of oil to that fitting and line up to the head. Or it is clogged up from sludge ?

 

[jCarroll]

I had a '59 Pontiac with a plugged pushrod that I fixed with an oil line from the block to the valve cover to drip on the rocker arm.

Worked for me - I bet an external oil line will work for you.

 

[Courtland508]

Not sure if it was mentioned, Make sure you at least have the right carb...been there done that. If you have say a carb for JD-420, too large amount of fuel and you can't adjust your way out of it.

 

[Roger in Iowa]

Carb has nothing to do with no oil to valves.

 

[Roger in Iowa]

You have found the problem of backfiring. You now have to figure out where the problem is with the oil that is supposed to go to the
valve cover area.

Your solution of running a line from the gauge to the fitting on the head may fix it. But it might supply too much oil.... Might have
to make some sort of orifice to control amount.

 

[Dave H]

MikeM has the answer. Install of the rear cam bearing is key in letting oil pass thru and to the tube to the rocker arms.

take the oil supply tube loose/off on the top end and see what comes out and then post back.

 

[Courtland1949]

Backfire does....

 

[M-MAN]

Went back through your old posts and found the problem. You stated fresh overhaul. The rear cam bearing was installed incorrectly. You really can't fault the machine shop
as they had no way of knowing an M cam bearing does not install like an automotive one. There are special instructions in the Deere service manual for installing it. I
posted the page so print it off and take it with you when you take the block back to the machine shop. Yes it could be rigged up to work but it woulden't be smart. Be
sure you put the correct bolt in the rear of the rocker arm assembly when you put it back together.

 

[ET]

One of the studs that holds the rocker arms on has a flat area where it screws into the block. It allows oil to get to the rocker arms. If somebody switched places with the two studs it would cause a no oil situation.

 

[ndgregor]

I have not seen your previous post, but I have a model M I restored and experienced both of these problems (backfiring and no oil to rockers).

While it can be many things, my backfiring happened twice: once was when I tried running the tractor without adjusting the valve tappets correctly. I quickly bent a pushrod. The second cause was a bad condenser. I replaced it when I built it, but it must have been defective. Only lasted about 6 hours before going, and it ran like a top once I replaced it.

My no oil to rocker arms was due to a worn oil pump. Once I generated proper pressure it began to feed oil to the rocker arms. Note that when operating properly, there is not a whole lot of oil being pumped up there. Just enough to keep things lubed up.

 

[jeo46]

I had no oil to rocker arm assembly also.

Machine shop had installed rear cam bushing with oil passage hole incorrectly located-I failed to
notice this. Had to separate engine from bell housing, remove cam, knock out soft plug, remove
bushing, reinstall bushing correctly, and reassemble.
This is a lot of work but worth it to be original.

Machine shop said tough luck-we are not standing behind it.

I was more than a little upset with their reply.