MX/DT not going into Gear.

[mx250]

Before I start delving into the innards, what are the probably causes? The gear lever seems to have full 'throw' so no bent/binding gear lever shaft.  It won't change into 4th. No history of jumping out just wouldn't go (select) into 5th and now wouldn't go into 4th. 

I'm sussing bent/worn selector forks, worn cam drum or pins. Any other causes known/likely faults?

[Nathan S]

100/125/175 motor, or 250/360/400?

[mx250]

250/360/400

[David Lahey]

Try for a sticky indexing plunger before you pull anything apart
(underneath, hex head, looks like a drain plug - lean it right over or drain the oil before taking the plunger holder out)

[mx250]

Try for a sticky indexing plunger before you pull anything apart
(underneath, hex head, looks like a drain plug - lean it right over or drain the oil before taking the plunger holder out)

Good thinking, why didn't I think of that.

Thanks. I'll try it .

[mx250]

Try for a sticky indexing plunger before you pull anything apart
(underneath, hex head, looks like a drain plug - lean it right over or drain the oil before taking the plunger holder out)

Tried it, seems fine. Your next guess is...............

Anyone?

[David Lahey]

It could be something as simple as the adjusting screw for the shift return spring coming loose but you will need to take the clutch cover off for that one.
Part 15 on this diagram
http://www.tytrials.co.uk/trailandtrialsuk/cat_88511--8-Shifter-2-External.html

[mx250]

As I said I haven't delved into it yet but I was thinking of having a close inspection of the ratchet arrangement simply because it on the outside of the cases and it might impact on the positive movement and selection of the gears. The only thing is I'm not certain why 1,2 and 3 seem to work fine and 4 and 5th not. The symptoms seem a little strange to me and I'm thinking it might be something simple like this shift mechanism.

Thanks .

[Freakshow]

What about that little row of teeth that inter look with the other little row of teeth on the gear change shaft ? i had a case where the bike was leaned over and they moved over a tooth caues the retaining thing wasnt seated.  Bike only got 1,2 and 3 i think or some werid combination, i know you have to do a balancing act when you put that clutch cover back on otherwise it gets me everytime, buy popping out.