timing a 75 dt100 (runs backwards)

[chris_avakian]

so, i've been having a ton of troubel with this bike i bought. its a 2 stroke yamaha dt100b 1975 model without points, just the mageneto stuff. then it breaks off to this small black box, and then to the coil, and plug. i got it running, and it runs ok, but it runs backwards, every time. i've adjusted the timing on the magneto coil both ways, and it doesnt seem to do anything. i dont know what to do at this point.

thanks

 

[Tom68]

Turn the motor around like a Husaberg. Sorry couldn't resist, I doubt the black box has a timing curve so you may need to get more adjustment, have you put a timing light on it and have you cleaned all the connections.The timing light will at least indicate which way you have to adjust.

 

[oscaman]

Have you tried putting the handlebars on the other end of the bike? Seriously, somehow you must be spinning the motor backwards, two strokes will run either way. Goofy motors !! You know you could get a four stroke !!

 

[oscaman]

backwards

It might help a bit to be sure you are setting the static timing btdc (before) and not atdc (after). That wont necessarily fix it, but will make it easiest to start in the foreward direction of the crankshaft. Trading for a fourstroke would still be an option.

 

[oscaman]

Any luck yet ? I put a similar motor (a ct2) in a minibike to use for a "show and tell" pit bike (it is WAY too fast) and cant imagine how you could be having that kind of trouble. Maybe it kicks back on the kick starter just enough to get it running backwards. Let us know !!!

 

[Coop37]

I had an old Yamaha ty80 do the same thing, the keyway was sheared and the flywheel had slipped to ATDC,
Check the keyway.. I would bet that is your problem.
Let me know.