G: Gearbox (Twin) Jumping out of third gear.

[Cyborg]

I live for overkill..... I believe that is the same jig that allows you to adjust the position of the G34 to compensate for variances in cases that have been repaired after gearbox explosions.

 

[Robert Watson]

Cyborg, "you know who" has a complete gearbox that had been cut off a set of cases for a special and comes with a cutaway G2 plate. You can put the whole plot together and then go in with little dental mirrors and see exactly what is happening.......

 

[Cyborg]

I’ll have to give the whole thing some thought. Given the crankcases I’m using, combined with a newly manufactured G2.... ultimately the proof will be in the pudding. The cutoff gearbox might help me establish that all is right with distance between the bearing bores.

Len, Greg’s suggestion to check the selector mechanism is a good one. Years ago I had a similar problem and was able to correct it by spending some time adjusting things. It was over selecting if I remember correctly. I clearly remember the bike jumping out of gear mid corner. Instant understeer and the bike drifted rapidly to the outside of the corner towards the guardrail.

 

[oexing]

I would not see a real need for this jig. You can fill all gears into the left/clutch side of the engine case including cam plate and select all gears and see engagements with a little mirror.
When not pleased about positions of camplate notches relative to selected gear, just dremel the notch a bit. Or if you think a bit more overlap in engagement would be desirable, mark the camplate slot at the right place, dremel one side and weld up the opposite side in the slot to move the selector fork over to more engagement, no rocket science. Check slick motion of camplate without gears to see if the slot is wide enough for the pin. Don´t worry , any mishaps can be welded a few times till satisfaction. Some medium hardness weld is allright for the camplate and will most likely outlive the typical Vincent user.

Vic

 

[Bill Thomas]

Good idea Vic', But most of us are repairing while the engine is together.

I hope everybody is making a copy of some of these photos,
I like the Cyborg one, Very handy,
For if the Forum is lost !.

Another very good bit with Vincents is the gear indicator,
You can with your hand put it in whatever gear you have trouble with and road test,
If you think it might be just the selector mechanism !,
Don't know any other Bike that has that ?,
But Len has been with Vincents a long time, He knows that.

 

[erik]

I had the Problem with Jumping out third gear when I reassembled my Rapide.I had to cut the foreward facing ear of G61 and move it more backward to give more actuating way.Third gear was healed and the othere gears stayed unimpressed.Regards Erik

 

[clevtrev]

I

wish I could say it was mine... I could use it right about now.

View attachment 42130

I suppose I could always make another one.
The reason for making this gives one the ability to check the amount of engagement of the gears, and the relative positioning of the selector forks.
I have come across gearboxes where the pin in the selector fork needed to be repositioned. One was from Michigan when the owner bought his parts over, we fitted it and could see what needed to be done. The bike was noisy when in neutral, the cause was the layshaft gear touching the first gear, altering the pin position enabling the layshaft sliding gears to be equi-distant between the two fixed gears on the shaft.
Don`t assume all the parts in the boxes are the same, I seem to remember the works drawing for the double gear was around issue 50.
There`s another of these fixtures in France that operates under power, for a finite check.

 

[oexing]

Instead of repositioning the fork pin I´d rather dremel the camplate, less risky for loose pins. Each fork has to be at the right spot on the cams so you can or have to do mods on the camplate only at two places, two gears for each fork. I did not do any pin repositioning but set spacers on gearshafts as good as can be done. The rest was welding and dremeling the camplate to my likings. Certainly you do this when rebuilding the engine and all can be checked while in this stage. Basically this task should not be required with a once finished engine. The weld can be seen just below the "2" and some dogleg at the opposite slot face for better engagement.

Vic

 

[Bill Thomas]

Something else I found.

 

[Cyborg]

I

I suppose I could always make another one.
The reason for making this gives one the ability to check the amount of engagement of the gears, and the relative positioning of the selector forks.
I have come across gearboxes where the pin in the selector fork needed to be repositioned. One was from Michigan when the owner bought his parts over, we fitted it and could see what needed to be done. The bike was noisy when in neutral, the cause was the layshaft gear touching the first gear, altering the pin position enabling the layshaft sliding gears to be equi-distant between the two fixed gears on the shaft.
Don`t assume all the parts in the boxes are the same, I seem to remember the works drawing for the double gear was around issue 50.
There`s another of these fixtures in France that operates under power, for a finite check.

Thanks for the offer. Somewhere I do have drawings for one, but if I remember correctly there were a couple of dimensions missing. I really should make my own... if for no other reason than to amortize the cost of the equipment in my garage. I know I can accomplish the task without the jig, but enjoy making tools... plus this is a hobby, so applying logic isn’t a necessity. Would you consider trading drawings for my eternal gratitude? Beer? Whatever?