I have a kx 125 1992 model and i cant select neutral. i had to rebuild the engine last week and ive been told ive put the gearbox back together wrong, what do i do ?

You need the transmission fault codes read, but I suspect you will need to rebuild the transmission.

if you are stuck in gear it is not a basic rebuild but a bad rebuild
because of the design of the gear selection process , it is impossible to have 2 gears selected together as one selector shaft will not move unless another selector shaft is in the correct position ( neutral ) to allow the detente balls to move out of the way so the next selector shaft can move
it is possible that the gear stick is not in the correct position when it was installed back onto the top of the box and one gear was selected and the end of the lever came out of the selector slot or all the selectors were not in the neutral position and so the end of the lever went behind a selector rail
pull the gear lever turret of the top of the box, move the selector rails until they all line up as a slot across all of them , then put the gear lever end back in that neutral slot

Think you have simply frozen your piston from lack of proper fuel and 2 stroke oul mixture. Bike will move in neutral and with the clutch in, just won't kick or bumpstart ! Time for a top end rebuild my friend...good luck !

there is no forth gear as such as that selection just locks the input and out put shafts together by a sliding dog
if you can move the lever across the selection gate (sideways movement) but not forward or back to select a gear , you will have to pull the box for major repair
indicates that a shift rail is not in a neutral position or what I suspect , the spigot bearing in the end of the input shaft has seized up and locked the shafts together

you dont need racing piston,,get the first gear fixed,some v-force3 reeds and a good pipe and you will blow the kx into the weeds

Hello, With so little information, I would HAVE to assume that this is a rod knock. Does it make noise in neutral too? Or only when you drive it. Try to put it in neutral and step on the gas....Does it still knock? A rod knock means you need to rebuild that motor. A rod knock can usually happen from beating on the car or a timing belt slipped a couple of gears. I would check your engine oil level, not transmission. Because low levels of engine oil can create this sound too. Good luck and feel free to write me back with much more detail so that I can further assist you.

i would say you have a serious leak?the questian where is it coming from in the 1940/1950 old engines could not hold oil engine or gearbox.so what the troops did was put a piece of paper under the engine and have a look next morning to see where the oil was coming from?but in modern engines it will show up on the engine somewhere.If you look about the engine and cant see a oil leak then you have a big problem as its loosing it internally ,but you will see blue hint smoke from exhaust.adrian,,,,,,,,,

Selecter forks could be damaged, gear shift shaft bent, return spring faulty, clutch dragging maybe! Try rocking it backwards and forwards engine off and see if you can find that gear! Good Luck - The Yeti

hi,i'm ck .my audi c5 2.4 model 2001, when put on D while driving, it go to neutral?

Hi All

Does the engine turn over when you turn the key, if it doesnt it is the automatic park/neutral switch on the gearbox. This gets hot and the contacts seperate and no go.
Remove the gearbox switch, pull apart and clean, when putting back together, put a bead of silicon across the joint and put back. It will keep running for ages.