John Deere 420u Engine Help

EHuffman

Member
Hello, first post but have been a long time lurker. We are restoring a 1958 420u and rebuilt the engine. It will backfire out the carb and exhaust but will not take off and run. I have good spark, have messed with timing, have a carb on it off a running tractor, and the head is also rebuilt. Any ideas? I am at my wits end.
 

Have you checked compression in the current engine condition?

Did you have the distributor out/off during your engine work?
 
sure sounds like timing is backwards, agree try switching plug wires.

Remember, there are two TDC's, only one should fire.
 
Alrighty thanks guys, tried the timing again and I was 180 off. I have a new issue now tho :cry: I am not getting any oil to my head-rockers. I checked the external pressure line and I am not getting any pressure out of the block. Any insight? I did not have the cam bearings out and I am positive that the main bearings are installed right.
 
Did you happen to remove the 2 studs in the head that holds the rockers down? One of the studs has a flat spot machined into the threads. I'm 99.9% positive that this stud needs to the in the rear location to allow oil to pass through the head and into the rocker. The flat spot on the threads get threaded into the head, if not you will have no oil getting to the rockers.

If no one else confirms, I will look it up in my service manual tomorrow night about the location of the studs.
 
(quoted from post at 19:34:34 08/14/18) Did you happen to remove the 2 studs in the head that holds the rockers down? One of the studs has a flat spot machined into the threads. I'm 99.9% positive that this stud needs to the in the rear location to allow oil to pass through the head and into the rocker. The flat spot on the threads get threaded into the head, if not you will have no oil getting to the rockers.

If no one else confirms, I will look it up in my service manual tomorrow night about the location of the studs.
Yes, I did but I have that right. I am not getting anything to the head out of the block...
 
it does take a little time for the oil to get up into the block and go through the line up into the rocker arms.
what i mean is after starting your tractor and seeing your oil pressure gauge go up, counting to 10 wont do it.
try running it a little longer.
but MAKE SURE you do have oil pressure at the filter guage.
also make sure that the corks that are in each end of the rocker arm tube is in good shape and not rotten.
if they are bad and leaking you will not get pressurized oil to the rocker arms, it will just leak out each end of the pipe.
let us know how you fair out.
 
We got it going finally, I did not realize that the oil pump also had to be timed on these tractors. The oil pump timing cause us to be 180 off. Thanks jd addict , we didn't have it running right and we're not giving it enough time to get oil to the top end. Patience is a virtue I guess
 
after you make sure the flat is in the back and if you still do not have oil up there pull the feed tube and see if oil comes out there.

no oil there and my guess is that the rear cam bearing was not installed in the right position.
 

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