You came up with a blank page ? I wonder why :sidelaugh ..

Probably because that just plain can't happen... :sorry1: Lem'me ask this , Where's the fuel coming from to make this engine start up and run? , Let alone - long enough to "spin the blades off" ..

 

this is a good start..

 

it can happen but i have never heard of it on a lawn mower engine i have a 1939 john deere B and if it has enough compression and conditions are just right i have had the old thing spin forward and try to start then pop and roll backwards it has set an run for 30 min. and you can even drive it they have no power but they will still run backwards

 

it can happen but i have never heard of it on a lawn mower engine i have a 1939 john deere B and if it has enough compression and conditions are just right i have had the old thing spin forward and try to start then pop and roll backwards it has set an run for 30 min. and you can even drive it they have no power but they will still run backwards

Care to explain that..?


As in - How "usable" fuel enters the combustion chamber and then be ignited when there was No compression stroke...

http://www.howstuffworks.com/engine1.htm


Are you saying that you ran your engine 30 mins - backwards..?

 

2cycle?

 

Yea that was my first ?.. a two cycle can run backwards..Welcome to the forums Bob..

 

Welcome to the forum!

 

Maybe he mounted a mower deck under his snow mobile then popped it in reverse (which on newer models of course reverse engine rotation to move in reverse) Or maybe the threads have just stripped out of the blade bolt

 

The early D600 engine could run backwards very easily, as the CD module would fire in either direction. This is why the governor thrust collar has a scroll in it, the purpose was for it to rotate backwards and close the throttle. This wasn't a big deal with a push mower, but was an issue with a SP model, imagine engaging the drive and having the mower move toward you. LB solved this by changing the flywheel on SP models to retard the spark, thus eliminating the tendency of the engine to run backwards. This flywheel resulted in a slight power loss as I recall.

 

That dosen't explain how the engine could even run to begin with though... :fing20:

 

Two cycle engines will and can run either way...google engines running counterclockwise...reed valves dont know the diffrence..:trink40:

 

Friend of mine when I was riding dirt bikes had a Yamaha YZ 250 run backwards and it had power. He use to drive it like that as a joke! I'd heard the older tractor engines could do this. Man Bear Pig, think about it, the exhaust cycle on any 4 stroke never completely clears the cylinder of the fuel mixture so all you have to do is pre-ignite on the upstroke and voila, engine running backwards!

 

Friend of mine when I was riding dirt bikes had a Yamaha YZ 250 run backwards and it had power. He use to drive it like that as a joke! I'd heard the older tractor engines could do this. Man Bear Pig, think about it, the exhaust cycle on any 4 stroke never completely clears the cylinder of the fuel mixture so all you have to do is pre-ignite on the upstroke and voila, engine running backwards!

Maybe that was me... I had the 250 and I just coasted it back a little and poped the clutch... I never ran it to long because i was worried about the lube pump...

 

Had a Military 2-1/2 running backwards. Going up a hill, it bogged down and stalled. Brakes fadded, so I popped it in 1,st and rode the clutch to slow my backward movement. At the bottom I let the clutch fully out to start the engine. I placed in reverse to back up, and proceeded to climb back up the hill foreward.

 

My old HD ...two cycle will fire backwards its a old Hummer..and i could kick -it to start..and know when it was running backwards..nothing like putting it in gear and it had a reverse...:trink40: then i would act like i stalled it.and restart and go on...lots of head scratching ...

 

Boy Bobb- This has sure sparked some debate.. No wonder you haven't spoken up again! There are a few causes of this so please give us more info and we can have more debatage!

And BTW- :MTF_wel2:

 

Well yes - :Welcome:

But - I really do not think of this as a debate...

It's silly to even talk about.

the exhaust cycle on any 4 stroke never completely clears the cylinder of the fuel mixture so all you have to do is pre-ignite on the upstroke and voila, engine running backwards!

And if you think about it , this statement isn't accurate at all ..

Where did the combustable gasess come from ? , the carburetor that you have mounted to your muffler...? got you there don't I?:sorry1:

 

http://www.animatedengines.com/twostroke.shtml

 

Thats a neat site Byron, :thanku:

 

I read once about a guy who had a real old 2 stroke motor that as he got close to the dock somehow he could stall it and just at the right time give it fuel and it would run backwards to slow his approach. Of course one day he tried it and it fired up in the RIGHT direction and he ran into the dock.

 

I would think it all had to do with the cam specs. on the particular engine in question, whether it was possible or not. And maybe the timing is off on Boy Bobb's engine.

 

The timing is "off". I have two (2 stroke) snowmobiles (Polaris & Ski-Doo) and they both have a switch to run in reverse. The motor shuts off - the timing is retarded - and the motor fires right up, this all happens in about 3 seconds. And away you go - no gearing changes, the motor runs in reverse. One of the all time greatest inventions. Happy trails..

 

I found the answer on a site where people are not so derogatory. The woodruff key sheared of, releasing the flywheel, causing the timing to be 180 degrees off.

Removed my membership to this place! And thanks for the jokes. Ha Ha Ha!

 

Sorry ..you might have read them.better..some young ones don't know..

 

Ive heard of Diesel engines running backwards, but not gasoline. Interesting.

 

I heard that "expression" a lot in my line of work, but it's a miss conception.

What really happen in a 4 cycle engine is carbon deposit accumulate in the compression chamber with time and come so hot that is ignite the fuel at the wrong time so you have the "impression" that the engine run backward.

I don't know how you say that in English but in French it's call "auto allumage"

 

I've heard of this phenomena before but never witnessed it. People I've grown to trust here are saying they have seen it. I believe it can occur.

I suspect the valve overlap would have something to do with this and I also suspect an engine would have to have quite a bit of advance in the ignition.

This would be different than an engine wanting to run in reverse due to detonation and would be interesting to watch. One thing I've learned for sure is never to be overly convinced I've figured out machinery. There's always more to learn and I, for one, don't have all the answers.

Mike

 

Pigheaded big bear head: what was you tring to acomplish..!!

 

Pigheaded big bear head: what was you trying to acomplish..!!

I wasn't trying to accomplish anything , Certanly NOT trying to drive someone away from here..


Why even think so...?

 

for anyone interested,if you put the terminals on your battery wrong,the starter will spin in reverse.

 

What!!!!!!

 

A bit off topic, but speaking of odd things that happen, you can hook your coil up backwards, and the spark will jump the gap the other way. They say that a careful eye can spot it when looking at a spark plug. Read that in a Ford magazine.

 

A bit off topic, but speaking of odd things that happen, you can hook your coil up backwards, and the spark will jump the gap the other way. They say that a careful eye can spot it when looking at a spark plug. Read that in a Ford magazine.

This is true, GM apply this technique on many cars today, you can see the difference whit two old spark-plugs one will have the ground electrode wear, the other will have the center (+) electrode wear.

It's reverse polarity.

 

Wouldn't that spark travel at the speed of electron flow? IIRC that would be 186,000 miles per second.

The old 6 volt Fords were positive ground and I don't recall anything being extraordinary about their electrical systems.

With the modern cars I'd sure hesitate to hook the battery up backwards, I suspect the electronics would burn out at just about the speed of those electrons.

Mike

 

Most of the time if a battery is hooked up backwards in something "new," it will just blow the fuses to the sensitive circuits.

The old positive ground 6 volt Fords had a positive ground coil. I read that too many people do a 12 volt conversion improperly (and unnecessarily), and screw up the coil & wiring. They don't last quite as long if hooked up wrong.

I re-read this whole thread & visited the website with all the different kinds of engines. That's cool.

 

Interesting topic. I have seen 2 strokes do it and even a diesel. A four stroke regular carbureted engine??... well it sure can do it for a few seconds but not SUSTAIN itself as the carb. becomes the exhaust and the muffler the intake, it can only run a few seconds if it so happened the exhaust was rich with fuel...But a half hour running on a carbed 4 stroke?? I need proof! lol. I think that is where manbearpig was going with this.

 

that kinda surprised me that it did that but it can truth no joking around. most of the time its as you said 30 sec to 2 or 3 min but she ran for around half an hour back wards

 

A lot of golf carts with 2 strokes use a starter-generator that'll crank the engine backwards for reverse and the other way to go forward--no tranny needed!..

I have only seen a 4 cycle engine run backwards fron "dieseling",or "run on " after hot carbon or valves ignites the fuel mixture--but it'll only "run" backwards a few seconds that way..you CAN get a 4 stroke to run backwards by swapping a different canshaft in,as they do in many inboard marine applications..

Most car starters wont spin backwards if the battery is hoioked up backwards,you must change the wiring to the brushes for it to reverse the rotation..permanent magnet starters might spin backwards ,but the starter drive wont engauge...most newer cars have diodes in the fuse box that pop to protect sensitive electronics from damage if someone hooks the battery up backwards..sometimes they even work in time!..