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engine running backyards

N

Nicholas C

Member
Hi everyone. I have a 1939 JD-H tractor that I have to start manually. I'm getting better at it, but still haven't found that sweet spot yet. I still look on Youtube for starting procedures all the time, thinking I missed something. On one of the video's, the guy mentions to rock the flywheel back and forth slowly a few times, allowing the engine to pull fuel in. He then cautions to be careful because the engine could run backyards??? Is this possible?? Harmful?? Dangerous?? Just wondering. Thanks, Nicholas C.
 
I can imagine if you're gripping the flywheel and it pops in a direction you are not expecting, you could get hurt. Same as a crank start on other tractors. Many people have had wrists and thumbs broken, been cracked upside the head by a flying crank, etc. from using bad technique on cranks.

If there's a proper technique for "throwing" the flywheel, make sure you learn it and always use it.

Running backwards is no big deal. Most 4-stroke engines can't run backwards for more than a revolution or two, because it's trying to pull fuel from the exhaust valve, and there is no fuel there.
 
It might run backward a few hits, but not sustained.

Only until the gas vapor in the exhaust system was consumed can it run backward.

Now a 2 stroke motor can run backward, but the timing won't be right for it to run very well.
 
I can see that happening if the mag is static timed early but only firing once and coasting a couple of turns. That could still hurt you, though. I don't think the impulse coupling would let the mag run backward. Don't believe everything you see on youtube.
 
I've seen it happen in diesels,mostly Macks.The worst part is no oil pressure.Guys would pull into a jobsite full of frozen ruts,and just before they would hit the clutch to throw it into reverse the front tire would strike a frozen rut,and throw the truck backwards a few inches.They would clap it in reverse,let the clutch out,and shoot ahead.Then they would yank the knob to kill it.It never happened for more than a few seconds.
 
Your post reminds me of the old Harley Davidson golf carts. The engine ran one direction to go forward and the opposite direction for reverse. Ignition timing on those was critical. Yea, I know, apples to oranges
 
My brother had an old Indiana Chief with spark advance on one had grip, throttle on the other.

If you didn't retard the spark when you kicked it and got spark before TDC, the Indiana would kick you back, very painful.

So yes an engine can run backwards

Same with tractors and hand cracking.
I was taught to never have your thumb over the crank. It could break your thumb.
 
The US Coast Guard training ship, Eagle, was originally a German training ship that was taken by the US after WWII (The Big One) as a prize of war. It had a Mann diesel engine in it that was designed to run in both directions. That was the only way they could reverse course when under engine power. The engine had to be shut down and the camshaft quickly flipped end for end and then started again. Made for some anxious moments coming into dock. The ship was completely renovated in the ensuing years and two modern diesels replaced the Mann which included a transmission to reverse the propellers.
 
Little hand crank Hatz diesel on compactors will too, for as long as you leave the fuel in run position. Makes a heck of a mess exhausting through the oil bath air filter!
 
Several diesel engines can run backwards along with two cycle engines. The 100 series Bosch pump on IH tractors have a slotted drive in the pump head to throw it way out of time to prevent it from happening.

Many Deere two cylinder diesels have been known to run backwards. I don't recall the way they prevented it from happening.
 
There were some Mercury outboards like that, late 50's, early 60's.

Had a double ended starter drive, duck bill valves in the water pump, timing moved by the throttle position. No shift, no neutral, just direct drive.

You would hold the button down on the throttle lever, move it from forward to reverse, the engine would have to come to a stop, then restart in reverse.

That was the plan anyway, called them 'suicide motors'! How anything so ridiculous could ever be manufactured is beyond all logic!
 
As you know well, a well warmed up Farmall letter/or 3 number series, fresh from the furrow can fire once (energetically) backwards making the mess described. Our solution was to shut our 400 off in High gear direct drive and let out the clutch as it came to a stop. I think much of that issue was poor gasoline delivered to our farm tank. Jim
 
IIf your timing is set right it won't want to kick back on you. Usually if you have it advanced to far it will do it then.
 
Newer Ski-doo snowmobile engine run backwards for reverse. When you press the button, the engine stops and then immediately restarts in the other direction. Its absolutely fascinating to me.
 
It could make one might pop once and coast to a stop going backwards but the engine in that particular tractor is not set up to sustain running backwards. When it does make that one mighty backwards pop and the flywheel is ripped out of your hands it scares the bejeepers out of you.

This post was edited by fixerupper on 06/09/2022 at 07:45 am.
 
Merc, Evinrude and Johnson all had that back in the sixties. The strange thing is manufacturers not keeping reversible snowmobiles for a span of several decades, then deciding its now needed. OMC was really ahead of their time on that one.
 
Mercury was the only one I ever saw do that.

It was a miserable failure, unreliable, had to wait for it to coast to a stop...

Without reliable reverse you have no brakes!
 
Many marine 2 cycle engines are designed to function that way for reverse. I ran a Detroit powered log skidder backwards once. I was backing up and clutched and shifted to forward and when I let out the clutch it just kept backing up. I stalled it immediately, but my grandfather saw it and I got chewed out. Got to wind those Detroit up.
 
I dont think we are talking about the same thing. I had all 3 of those models, currently still have the Johnson, they all had service brakes.
 
OK, I see now, snowmobiles, never knew Mercury made them.

Never been around them, no market for them down here.

I'll take liquid water over the frozen stuff any day! LOL
 
That is a easy starting tractor. From your
description, it sounds like you crank it awhile, load
up the muffler with fumes and some leaked voltage
at the wrong time (dirty/damp/greasy mag interior)
fires a cylinder in the wrong position and spins the
engine with enough speed for the mag to spark
without the impulse coupling. Get your mag
serviced and properly timed, and some new copper
core wires and new plugs.A stiff breeze blowing
through the radiator will start that tractor....
 
(quoted from post at 08:51:20 06/09/22) The US Coast Guard training ship, Eagle, was originally a German training ship that was taken by the US after WWII (The Big One) as a prize of war. It had a Mann diesel engine in it that was designed to run in both directions. That was the only way they could reverse course when under engine power. The engine had to be shut down and the camshaft quickly flipped end for end and then started again. Made for some anxious moments coming into dock. The ship was completely renovated in the ensuing years and two modern diesels replaced the Mann which included a transmission to reverse the propellers.
Click to expand...
would like more details on that "remove & flip the camshaft end for end to acquire reverse". For any camshaft to be removed & flipped quick enough to reverse/maneuver coming into dock just seems unimaginable to this guy.
 
(quoted from post at 20:29:43 06/09/22) After rereading these I have to ask. Are you thinking it's running backwards because of the pulley?
Click to expand...

Sounds more to me like he's worried about it starting backwards due to the "warning" on the video that he watched.
 
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