Hi all,

After 30 years of riding bikes i have had a first today!!

I crashed quite heavly and the bike revved hard until it was switched off with the kill button.

The bike wouldnt start so we bumped it,it did start, ran fine and sounded sweet until i let the clutch out and it now goes backwards!!

I haven't looked yet but it seems like the general guess is that the woodruff key has been nudged a touch throwing the timing out.

Is this normal, is it uncomman, am i looking at the right thing, could it be the cdi sending the wrong signal??

Any help or advice would be appreciaited.

Cheers

your spot on!(i think) sometimes on bikes if the timing is so retarded it will run backwards. its a simple fix just take the flywheel of and reset the timing

2 strokes running 'backwards' are not unknown, normally it's either a case of over advanced ignition causing the slow-idling engine to briefly stop then change direction and run retarded (loads of examples from pre war Scotts onwards) or intentional (Villiers engined 3 wheelers)

It is, though, difficult to imagine how you'd bump start it backwards. unless you dropped the motor to a slow idle ...... as above.

I'd try starting it normally and see how it goes, with the caveat that you should check the ignition timing ASAP, it's hard to 'nudge' a woodruff key enough to significantly alter the timing, but not impossible to shear one in which case the timing will change constantly once the flywheel starts moving on the taper.

Edited February 16, 201313 yr by gii

over advanced ignition thats it lol

Not uncommon, I recall coming back down Cameron Hill fairly rapidly when the Fantic ran backwards. Then there was the time when I was riding the Bultaco to school (them was the days) and it coughed at the give way line - when I let the clutch out I reversed in to my French teacher's Toledo!

Not unheard of but somewhat less common now with watercooled bikes as they can run more ignition advance than the old aircooled bikes. From a piston port two-stroke engine perspective running forwards and backwards look exactly the same for "valve" timing. The only difference is the ignition timing as the spark is supposed to occur before the piston reaches top dead center. If it starts easily backwards you may have shifted your timing significantly in the crash. First order of business is to pull off the flywheel and see if you sheared off the woodruff key that locks the flywheel in the correct position. If the engine sees a big hit, particularly at full blat it's not uncommon for these to shear allowing the flywheel to move on the shaft. If you've never pulled a flywheel you will need a flywheel puller and a flywheel holder. The flywheel holder is easy to make with a couple of pieces of steel flat stock. The flywheel puller you have to buy or borrow. If you have a buddy who works on Betas or Shercos they use the same flywheel thread. There are a lot of other "methods" to hold the flywheel. None is as safe for the crank as this. Works like a charm and allows you to re-torque the flywheel nut to ~100ft/lbs with no drama.

IMPORTANT NOTE: Make sure the screws that go into the flywheel aren't too long or you will destroy the ignition coils.

While you have the flywheel off do a quick visual of the coils and wiring. The backing plate for the coils is usually near the center of the slots. If yours is all the way to one side then someone may have moved it to retard the ignition for slower throttle response or advanced it for quicker response.

Edited February 17, 201313 yr by dan williams

I can vouch for that type of holder for the flywheel. I made a similar one from some that ally i hadthat was scrap and it kept bending. I then made a steel one and its easy peesy. Make the handle section at least 450mm long so you can wedge it against the foot rest when undoing and tightening.

Your locations not on your signature. I have a puller if your near Newport, South Wales. PM me if needed.

Edited February 17, 201313 yr by pindie

Thanks for all the input.

I have stripped it out and the woodruff key has sheared, it is all clean enough, hopefully fit a new key and Bob's ya uncle!

Excellent. Just make sure you torque it up proper. It seems like a lot but it is the spec.

Mines running backwards also beta techno 98 ... Is it possible if the flyweel has play in and out the bike will change timeing as it has bad missfire and runs backwards and its popping all the time and wont rev ???

The flywheel has play in and out!? That can't be good. It won't change your timing but your crank bearings are shot. The usual running backwards problem is a sheared woodruff key and a shifted flywheel.