Jumping gear
Post Reply    Forum -> Not-So-Modern
Author Message
Hooked
1974 200 Rally, 1970 180 Rally, 1980 P150X and P200E
Joined: 22 May 2017
Posts: 120
Location: South Africa
Tue Feb 05, 2019 10:11 am quote
I have a rebuilt Sprint V engine that jumps out of 3rd into the neutral position between 2nd and 3rd. The gearcross is brand new and the selector arm protrudes by the specified 1.5mm above the face of the selector box.

According to my reasoning the gearcross does not engage enough in the 3rd gear. And since the selector arm can't protrude any more, the problem should be with the 3rd gear.

Logic tells me that the mid section of the 3rd gear should either be thicker, or the distance (depth) to the mid section should be smaller. I have now measured 10 x 3rd gears, and the thickness of the mid sections are all the same and the depth to the mid sections are all the same.

Thus, for the gearcross to engage more, the 3rd gear will have to move forward. And to achieve that, I will have to use a more modern driveshaft where you can put spacers behind the gears in order to move them forward.

Is this the (only) solution, or do I have it totally wrong?
Hooked
GS160, V50R
Joined: 11 Jun 2014
Posts: 253
Location: Åland
Tue Feb 05, 2019 10:38 am quote
First that comes to mind is if you have turned the third gear in backwards, if you disassembled the stack. Not saying, just thinking. Easy if you for example drop everything on the floor whilst doing other stuff, like I did.

Granted you have the same gear selector as when it worked correctly.
Hooked
1974 200 Rally, 1970 180 Rally, 1980 P150X and P200E
Joined: 22 May 2017
Posts: 120
Location: South Africa
Tue Feb 05, 2019 10:49 am quote
No, the gear is the correct way round. (The engine is a built-up one. The casing was a matched pair, but everything else was built from loose parts, either in perfect condition or new.)
Addicted
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 993
Location: London UK
Tue Feb 05, 2019 8:32 pm quote
Check the gear selector before taking the engine apart. These can really wear and because of the spring pressure on the batwing it just doesn't notice.

Take the selector off the engine. Remove the spring. See how much free play is in the pawl pivot. There are refurbish kits for the worn parts (Including a new spring if the old one pinged out and is now lost).
Rallies Europe 2016   Vespa Wasp Pin Badges   AF1 Racing Vespa Austin
Post Reply    Forum -> Not-So-Modern
[ Time: 0.3604s ][ Queries: 23 (0.0491s) ][ Debug on ]