Yamaha DT125 LC2 reversed on first gear

[Rickard]

I admit, I am a newbie when it comes to bikes,

but I am quite sure a motorbike does not usually have reverse gears.
Atleast, to my knowledge, the DT125 LC I got in my garage doesn't.

I am also very sure that I am sober in all possible ways, and I am not dreaming...
But when I went to the garage today to start the bike in order to drain the carburettor (I am too lazy at the moment to take it apart to emtpy and clean it.. I will later though when my friend comes over to help me replace some parts on the bike that has been worn out by age), the noticed the tachometer needle was going up and then suddenly down completely and moments later the engine died.

When I started the bike again, the needle stayed down, and I noticed some noise comming from the engine.

I stopped the engine, started it again and the noise was gone, but the needle stayed down.

Ok I though, Let's take a look at the tachometer later, put the first gear in, slowly released the clutch, and the bike reversed.
Fortunately not very fast, but still....
I immediately went back to neutral, shut the engine off and was thinking it all over.. what the hell happened?

I decided to try again.

This time, the tachometer worked normally again, and the bike had no problems at all.
I was not able to get it to reverse again.

Is this even possible to happen? And if so, how?!
I will check up on it next weekend when I go back to the garage, but until then, I atleast hope to find some kind of clue as to what actually happened.

Hope you guys could help me out a bit!

Thanks!

[fil77]

2 strokes will happily run backwards. Used to be a trick in my earlier days to push start a bike backwards then let an unsuspecting "Know it all" go for a test ride. Not sure why yours started backwards but once running they are pretty happy at it.

[Airhead]

:D

[Dt rich]

2 strokes will happily run backwards. Used to be a trick in my earlier days to push start a bike backwards then let an unsuspecting "Know it all" go for a test ride. Not sure why yours started backwards but once running they are pretty happy at it.

Haha sounds fun I never knew this is it damaging?

[Rickard]

I think I know now what happened.
After reading your post Fil77, I searched google for "twostroke engine running backwards", and found out how it could have happened.
Turns out that if the ignition comes prematurely when the piston is on it's way up, it can be knocked down again and if timing is "right", it could gain enough momentum to complete the backwards revolution.

When thinking some more about what happened yesterday, the tachometer needle was indeed going up as I reved up the engine.

After a while it was about to die, to I gave it some more throttle to rev the engine some extra, this was when the needle immediately went to the bottom while the engine was still running.

The engine died after a while because I was looking at the tachometer, wondering what the heck went wrong, it probbably died then because it was cold and I didn't keep on giving it enough throttle to keep alive.

What happened after that, I found could be explained with not pushing the kicklever hard enough.

As this could give the exact same problem as with when the engine started reversing.. piston going up slowly, a misfire pushing the piston down and backward it goes.

When I finally got it to go as it should, maybe I kicked it harder.

Anyway, now I know what to do during the winter.. bringing my friend over to help me go through the ignition to see if it's fiering prematurely or not.. and then, make sure to kick it a bit harder than the soft push I sometimes give it.

(It has been starting so easy, so I never thought it would be a bad idea to be a bit extra carefull when kicking the lever.. ofcourse, I shouldn't apply all my weight on it with the hardest kick I got, but maybe just a tad bit harder than the soft push I sometimes give it)