Knocking noise and loss of gears

[richard77]

Hi. Riding home on my PX125 (1992) I heard a loud « crack » from the engine and then a rattling sound as I rode. Obviously stopped and then nursed it home. Unable to shift out of 1st, can just about get into neutral but can’t twist any further. Up on ramp it starts ok but the us a knocking sound from the engine. I have opened up and checked gear select arm and mechanism, all seems ok, same with the clutch. I recently changed the cables with no problems. Any ideas please ?

[mijapxman]

Richard 77, hi.
If the selector box arm is fine, while it was off, did you check the tightness of the selector rod

:https://www.scooter-center.com/en/gear-selector-rod-bgm-original-vespa-px-1984-t5-125cc-cosa-bgm6502l?gclid=CjwKCAiA4Y7yBRB8EiwADV1haRKtxy2TOSIYtBa_Yc01AOV5aM-rMvZqb304SPEzGVSFX5HsH3ctsxoCZ6gQAvD_BwE

to the cruciform? It's a left hand thread, so left to tighten, be gentle as the threads on the rod and cruxiform can strip easily.

Click it through the gears using the hand gear change with the selector box removed, to see if all is well, between the hand gear change at the headset and the selector box.


You have REMOVED the clutch to check it, and looked at the primary drive and gear teeth, all is well, I take it?
.

Could be that the gear cables you replaced have loosened off, I would try that first.

If all of the above is fine, you may need to split the engine to inspect and for piece of mind.

Mij ☺

[richard77]

Hi Mij
Thanks for that. I’ll take another look tonight if I get a chance. I readjusted the cables so they are correct but I’ll try what you suggest. If not I guess I’m gonna learn how to strip an engine this weekend!!

[mijapxman]

Richard, my gut instinct, is the gear cables need properly adjusted, as new cables can stretch.

Or the clutch cable, as both of these can give your symptoms. Check the clutch is working by: with the ignition Off, pull the clutch lever in and try kicking the kick start at the same time.
If the clutch is working, it should feel like it's kicking very, very easily.

Get back to us after checking the above.
[br
Also, here's some homework as knowledge is power 😉...

www.vespalabs.org/wiki/vespa-101/engine/gear-box


Guys feel free to jump in! As I feel my first reply, on reflection, was jumping ahead too much, in parts.

I blame the painkillers lol 😂 😂 😂.



Mij ☺

[ianmartin40]

Make sure clutch nut is tight and inside clutch housing has no scoring, keep us posted.

ian

[mijapxman]

Good advice from Ian, if the nut is loose, I'd remove the clutch completely and check the woodruff key on the crank and check the clutch itself, especially it's woodruff key slot. 😉


Mij ☺