please don't laugh at this topic Cu's my mates is just about in tears and I'm still crying with laughter  right here's the thing my mates just brought a kx125 98-99 model and when he went to pick it up he said the blokes just done a bottom end rebuild any way we was just about to set of riding this morning and just got the bikes started and when my mate put his bike in 1st gear he started to go backwards so he then put it in 2nd and the bike started to go backwards again its like the bloke who did the bottom end rebuild put the gears in back to front is that possible well it must be Cu's I'm sure by the end of the week my mate will be the best backwards motocross rider given enough practice how do we fix this problem    

I had a buddy that had the same thing happen. His happened cause he tried to put a different magneto in it than what was supposed to be in it. I would guess that his timing is 180 degrees off or something. Check the timing and see if it is up to spec. Make sure all the timing parts are the correct ones.  

PDK nailed it.  We used to do this as a practical joke as teenagers to our buddies!  If you set the timing ona  2-stroke too far advanced or retarded, the motor will run backwards!  I used to practically pizz myself doing this to guys I knew - so funny!

At any rate, reset the timing and it will be fine - common mistake (or prank, depending on whether or not it was intentional)  

Thats great Will have to remember that one.  

whats the best way and how do i to put it wright so the bike rides normal  

Take the stator cover off (left side of the motor), make sure the piston is at top dead center, and check the timing marks on the stator - they will line up when the timing is rignt. I bet it's 180 degrees off...like PDK said  

That is brilliant, i'll have to try it to one of my mates! lol  

the thing is i have just taken the casing of the magneto and the the center line out of the 3 lines does line up with the 1 line on the casing  

How far off is it?  and was the piston at top dead center when you checked the lines?  

there's 3 lines on the stator and there's 1 line dead across from them that's part of the engine casing the l line on the casing is nearly in line with the center line on the stator its probably 1mm of dead center but there's also a line on the flywheel magneto when the piston is right at the top the line on the flywheel is of about 20mm from the bottom of the line on the stator  

Pull the flywheel off and see if the keyway pin is broke out. If the flywheel is not in its proper position on the crank then it will be out of time.  

Or if who ever rebuilt the motor lost the pin and just and thought they could get away without putting it back in then that is another idea. I would pull the flywheel off and check it out.  

I would start by advancing (before TDC) the timing as much as possible and then adjusting One line at a time until it runs the best. (that is if no one can give u the correct timing mark). My first Hillclimber was a GT550 3 cylinder two stoke that we made an electronic ignition for by using one from a Honda CBX  "6" cylinder. At first we had similiar problems with it running backwards. Craziest holeshots I've every pulled!!