A mystery in reverse.

[Athame57]

Many years ago when I was a dispatch rider in the 1980s I had a flat mate, a girl called Becky, also a dispatch rider. She bought herself an aging Yamaha DT175 to take the strain off her haloed CBX550, (or maybe to preserve the cam chain tensioner?  ) Well, one morning she started it, went into gear to move off, and....WOW....it went backwards!  After a few more reverse starts it behaved itself again.
Until it had an electrical fire ( it seemed) one night that caused a fire so hot in her garage it practically melted both bikes. 
Ok, what on earth might have made it go backwards though?

[Bryanj]

Timing slightly wrong, rd 200 twins used to do it, when you went to start they kick back a bit and rotate backwards and being two stroke run happily

[Skoti]

I wonder what year that DT175 was, because I seem to remember that some 1970's Yamaha's were fitted with a diode to prevent that happening.

[McCabe-Thiele (Ted)]

I owned an Arial Arrow sometime around 1965, I loved the two circular plumes of smoke from the rear silencers when you gave it some welly.

I was returning home from a ride out with my mate who at the time ran a Triumph Tigress 250 Scooter, as we were approaching a junction my Arrow lost its ability to move forwards, as if the final drive had failed. It also sounded odd, the clutch seemed to feel normal, all the gears seemed to select but no forwards motion.

At some point I decided to switch off the engine for closer investigation. It would not restart so it was a push home of about a mile. Engine was removed but I could not remove the crank from the casing, transpired they had some sort of coupling in the center of the crankshaft that had failed. Lots of metal in the bottom of the engine. The reason the engine would not start was that the kickstart was not rotating the cylinder that had the points/magneto.

I managed to find a brand new Golden Arrow Engine advertised in the local paper at Matlock for a very reasonable £30. On collecting the engine I recognised the seller as working in the parts department for Derby bike dealer. Only later did I wonder if the engine was a knock off.

[TrickyMicky]

Many years ago when I was a dispatch rider in the 1980s I had a flat mate, a girl called Becky, also a dispatch rider. She bought herself an aging Yamaha DT175 to take the strain off her haloed CBX550, (or maybe to preserve the cam chain tensioner?  ) Well, one morning she started it, went into gear to move off, and....WOW....it went backwards!  After a few more reverse starts it behaved itself again.
Until it had an electrical fire ( it seemed) one night that caused a fire so hot in her garage it practically melted both bikes. 
Ok, what on earth might have made it go backwards though?

Please excuse me, but I only got out of bed a little while ago, but when you describe your friend Becky as a flat mate, I thought that you could have done better than that!!!  Back on the reality stakes, many years ago  some Bond Mini cars were wires up so you could start the villiers engine backwards allowing you to reverse.

[AshimotoK0]

I had a Mitsubishi Carisma GDI (petrol, 11:1 compression ratio) that rolled backwards at a zebra crossing and started up in reverse ... cacophony of noise, plumes of smoke out of exhaust ... but nobody I tell this too believes me ... yea it did happen and this is April 5th not the 1st 

[Athame57]

Thanks for the answers everyone.  Skoti, maybe the diode was broke or missing, the bike was a bit of a heap. Micky, I got a GF later, but the real reason I teamed up with Becky was to exploit the so called the Greater London Mobility Scheme, it was a GLC thing of the day were if there was two of you they would get you a flat quickly, we had both been living in Earls Ct bedsit land.
Ted My first bike was an Ariel Arrow too, the trouble is mine was the Airfix!  I should have left it in the box, they are worth a lot of money on fleabay, I just checked! 
Bryan You seem to have answered the question for me, ok so bad timing can cause reversing! 
Well, I won't be buying any DTs, if I do it will be down to DRINKING!
If I want to ride in reverse I'll get myself a Ural outfit.

[Bryanj]

Sold a new ural once but the man wanted the posh sidecar not the military one, all sorted EXCEPT chair on wrong side making it an absolute pig to ride!

[Athame57]

Sold a new ural once but the man wanted the posh sidecar not the military one, all sorted EXCEPT chair on wrong side making it an absolute pig to ride!

I'd be one nervous passenger! 

[K2-K6]

I had a Mitsubishi Carisma GDI (petrol, 11:1 compression ratio) that rolled backwards at a zebra crossing and started up in reverse ... cacophony of noise, plumes of smoke out of exhaust ... but nobody I tell this too believes me ... yea it did happen and this is April 5th not the 1st 

Quite possible as its direct into closed cylinder injection. Likely it SHOULD work backwards in a fashion, by drawing air in through exhaust system and opposite for intake temporarily.  It would have both late fuel and late ignition, probably ran at lowish rpm  ?  Although no throttling on exhaust side to control it, just system restricted air supply. That retarded, effectively, ignition now at atdc would stop it running away.

[K2-K6]

Timing slightly wrong, rd 200 twins used to do it, when you went to start they kick back a bit and rotate backwards and being two stroke run happily

A friend had an RD250 do similar years ago. Washed it and rinsed with hose, tried starting it and with probably water compromised plug caps etc, it kept backfiring when kicking. Perseverance saw it start with a distinct and odd sounding run, put it  in gear and pulled away backwards   

[K2-K6]

Here's a hotbulb diesel starting  https://youtu.be/kCoOTbhapnk?si=SQ0y9_2zXopDRLw1

Notice he bounces it off compression to spin it initially, then slows it right down while running, to then "bounce" it off compression again and flip the rotation to how he wants it.  Watch the flywheel rotation as its at slowest running speed to see it reverse. 

[AshimotoK0]

I had a Mitsubishi Carisma GDI (petrol, 11:1 compression ratio) that rolled backwards at a zebra crossing and started up in reverse ... cacophony of noise, plumes of smoke out of exhaust ... but nobody I tell this too believes me ... yea it did happen and this is April 5th not the 1st 

Quite possible as its direct into closed cylinder injection. Likely it SHOULD work backwards in a fashion, by drawing air in through exhaust system and opposite for intake temporarily.  It would have both late fuel and late ignition, probably ran at lowish rpm  ?  Although no throttling on exhaust side to control it, just system restricted air supply. That retarded, effectively, ignition now at atdc would stop it running away.

It sounded like a bag of spanners and yes very low revs... at least you believe me that it could happen ! Only the second person though !

[Bryanj]

Even more fun with truck with V8 GMC stroker(Detroit), they had an emergeny flap that dropped accross the supercharger intake as the govenor did not work when running backwards