John Deere B Compression question

[MDNOBLE]

Hello everyone

I'm sure the question has been asked before but looking for opinions with my specific issues..

1947 B has compression readings of 60 and 65psi. The cylinder with better compression the plug is usually cleaner and with a light you can see the combustion chamber is dry. On the weaker cylinder with 60psi the plug is usually dirty, and with a light you can see that the combustion chamber looks wet - for a lack of better terms.

At what point is an overhaul needed or am I at that point? When the tractor is running and if you open the petcocks individually you can tell a difference - that was my first clue. It really doesn't smoke much if any from the exahaust, but with the oil fill cap off i get some smoke from there. I don't have a gauge to read pressure in the crank case, but is there a way to judge pressure this way? With the cap off that is, to tell if you have possible blow by. I get some smoke from the pulley when its hot, but dont know if that could be from bad seals etc.

And, finally - What are opinions on products like seafoam to clean everything out?

Thanks in advance for any help everyone, its much appreciated and I enjoy learning from everyone here!

 

[Bob Harvey]

Sorry, not a definitive answer, BUT, if the sucker runs OK, why spend $$. These are low compression engines (no idea of the 'perfect' specs.) The thing of it is, I farmed my '60' for a whole year before I discovered the 1 exhaust valve had a 'pie' shaped hole in it ! Since then, rebuilt engine, did some body work and painted it. Retired and living in a heated shop (me too). Best of luck - and a Happy New Year.

 

[M-MAN]

You are only down 5 lbs on one cylinder and 10 on the other. Pretty good for an engine pert near 70 years old. While an overhaul woulden't hurt unless something else pops
up there's no hurry.

 

[Stroby]

I'm a big fan of Seafoam, but I wouldn't put it in the crankcase of an older engine! My Dad did that once on a golf cart and it removed so much sludge that there was no compression! BUT, adding it to the
fuel works wonders. I've used it on everything I own, it even has stopped issues with the check engine light on my vehicles. I have mixed it with diesel fuel in the winter and have never had an issue. I now
add it to a half tank of fuel on my car and truck twice a year to keep carbon buildup from occurring. Just my 2 cents.

 

[MSD]

The petcock on the clutch side will always blow less compression than the flywheel side. Just the way the 2 cyls. were set up to run.

 

[MDNOBLE]

Thanks for the replies everyone. It doesn't run bad so I'd prefer not to do anything to it just curious what's normal on these old things.

Very interesting, the weaker cylinder is on the clutch side. I had never heard that before. I'm still curious about the clutch side cylinder that is weaker being wet.

I think ill consider running some seafoam through the fuel this spring.

What does everyone run for fuel in their late model B? Would any additives be beneficial?

 

[620 John]

Is this an all fuel tractor??? I'm pretty sure it makes a difference if it's gas or all fuel. Maybe someone cold post up some specs.

 

[David G]

I am wondering if that is good pressure for all fuel.

 

[buickanddeere]

Run in allfuel mode with kerosene or gasoline only ?

 

[buickanddeere]

Coolant temperature ?

 

[MDNOBLE]

It is not an all fuel - its gasoline and yes according the manual the compression specs are different between gasoline and all fuel. I think gasoline is around 100 psi? Why i was curious about when an overhaul is needed. I meant as far as gasoline and additives - sorry I should have been more clear. I've just been using regular unleaded, 89 octane i think in mine

 

[coonie minnie]

Compression should be the same, but do to uneven firing, one cylinder gets more fuel than the other. That didn't get corrected til the duplex carbs of the 50, 60 and 70.

 

[M-MAN]

Compression didn't go to 100 until 1948. Yours was 70 when it left Waterloo in 47.

 

[MDNOBLE]

Thanks - that makes me feel better about the readings I got! The I&T Manual wasn't clear on that. Do you feel a difference of 5 psi is tolerable?

 

[buickanddeere]

I&T manual contains just enough info to cause confusion. The real JD manual is recomended .

 

[BushogPapa]

The "Lead" cylinder is the flywheel side and the trailing is the clutch side..

When idling, with the petcocks open, you will notice that the Clutch-side cylinder seldom fires...

The "Lead" Cylinder draws near all the fuel/air mixture available, leaving the Clutch-side with nothing much to run on..

The BEST thing you can do with your JD is get it out, put a good heavy load on it and work the Holy Crap out of it..( for at least one full hour)...That is as good for it as an Overhaul..!!

 

[NoDakInMN]

I will second BushogPapa's advice. Putting an engine under load for an extended period is good for them, continuous light loads not so much. Running under a working load allows the engine to properly heat up and that, among other things, works moisture out of the many places that it can condense in. It also causes expansion of parts due to heat and this seals things up better which improves performance. As a rule, my tractors run OK but when I get the chance to play/work with them for a couple of days they run so sweet that I hate to shut them off. If you don't have the luxury of having a place to pull an implement, find something to run with a belt, even if you have to make a crude paddle fan out of wood.

 

[MDNOBLE]

thanks for the explanation of the difference between the cylinders - make sense! And I'm glad that what I found is normal. This past summer I put it to some pretty hard work mowing and dragging a spring tooth around our place to replant grass on a few acres. Prior to that is has been sitting a lot in my parents barn. Felt good to get it out and let it work again.

appreciate all your help everyone

 

[BushogPapa]

Rislone was the product of choice ( although JD suggested 1 qt of kerosene) added to the engine oil..

Run under light load for 30 minutes and drain...

I like Rislone in my snow removal tractors over Winter, then drain in the Spring...!!

 

[buickanddeere]

If the day ever comes for a rebuild. It's fairly simple to add a whole lot more snort with the proper pistons, cam and valve job.

 

[MDNOBLE]

Could you elaborate on that more? I've read a bit about different pistons, but could you give more details into the valves and cam work? Thanks