gearbox shimming and shift fork to collar clearance

C

carbcleaner

New member
Location
ny, usa
Hi my name is Andy. I am a new member. Thank you for adding me.

I am working on a Laverda Jota 1000.

EDIT 2- never mind, I found all the gear clearance specifications in the Maintenance Specification" section in the "Green Book". LOL duh...

now WHY would they put it there?!? 😆😆😆

I'm used to Moto Guzzi and Ducati manuals, where the specifications you're looking for are almost never in the "Specifications" section of the service manual... 😬



edit- the following shifting problem happens even with the sprocket cover and selector/ratchet mechanism removed.



The symptom the motorcycle is exhibiting is rough shifting 3-4, 4-5 and back down again. Also, sometimes it shifts slightly past 4th going up or down. It does this even with the sprocket cover completely removed. (I got a T-handled tool from Wolfgang in Canada) There is a scratchy or grinding feeling when going from 4-5, kind of like the feeling of lapping a hardened piece of metal on 600 grit sand paper.

I've replaced a few parts, gone over the outer selector mechanism a bunch of times, the shift drum is free and nice, I replaced the shift detent lever and spring (I found out the rollers can be different diameter)...

my next step will be to replace the bearings and maybe gear bushings. Also maybe the forward shaft, as there is a great deal of wear on it where the fifth gear rides.

I am curious if there is a specific manual I can use that has the gear bush to shaft clearance, as well as the gear and shaft axial play and positions relative to the shift forks? I found some nice technical drawings in the 750 manual from this website. Are they similar? The 1000/1200 manual seems to be for the later model with the needle bearing upgrade, and doesnt have much information anyway...

the 5th gear shift fork (brand new from Wolfgang) and the sleeve seem to have a TON of play, (0.75-1mm?) however the sleeve appears perfect– but I'm comparing this to Japanese motorcycles and Guzzi's I've rebuilt in the past.

Thanks!
 
Last edited:
I'm not sure if the triples have the same gearbox shifting drum mechanism, but the one on my 750 required some "fiddling" to position the shifter arm just right, but I'll look at the Green Book I have in case you don't have one
 
Welcome Andy.
Keep it simple. There's 99.999999% chances that your problem is setting up selector arm in relation to the drum and getting the side cover free. You'll probably find 200 pages on the subject on this forum.
If at first you don't succeed, start again, and again, and again.
Paul
 
Isn't there some issue in the later triples with the 5th gear bearing, some convert it to a bush? Beyond my pay grade.
 
Paul Marx said:
Welcome Andy.
Keep it simple. There's 99.999999% chances that your problem is setting up selector arm in relation to the drum and getting the side cover free. You'll probably find 200 pages on the subject on this forum.
If at first you don't succeed, start again, and again, and again.
Paul
Click to expand...
this happens with the selector arm, and entire sprocket cover removed
 
Vince said:
Isn't there some issue in the later triples with the 5th gear bearing, some convert it to a bush? Beyond my pay grade.
Click to expand...

TeddyG said:
I'm not sure if the triples have the same gearbox shifting drum mechanism, but the one on my 750 required some "fiddling" to position the shifter arm just right, but I'll look at the Green Book I have in case you don't have one
Click to expand...
I downloaded all the books from the workshop manual downloads section on this website. which book is "The green book"? Is that the Tim Parker/Ampersand Press book? I have that one, and I couldnt find much information about shimming specifications in it.
 
carbcleaner said:
Hi my name is Andy. I am a new member. Thank you for adding me.

I am working on a Laverda Jota 1000.



edit- the following shifting problem happens even with the sprocket cover and selector/ratchet mechanism removed.



The symptom the motorcycle is exhibiting is rough shifting 3-4, 4-5 and back down again. Also, sometimes it shifts slightly past 4th going up or down. It does this even with the sprocket cover completely removed. (I got a T-handled tool from Wolfgang in Canada) There is a scratchy or grinding feeling when going from 4-5, kind of like the feeling of lapping a hardened piece of metal on 600 grit sand paper.

I've replaced a few parts, gone over the outer selector mechanism a bunch of times, the shift drum is free and nice, I replaced the shift detent lever and spring (I found out the rollers can be different diameter)...

my next step will be to replace the bearings and maybe gear bushings. Also maybe the forward shaft, as there is a great deal of wear on it where the fifth gear rides.

I am curious if there is a specific manual I can use that has the gear bush to shaft clearance, as well as the gear and shaft axial play and positions relative to the shift forks? I found some nice technical drawings in the 750 manual from this website. Are they similar? The 1000/1200 manual seems to be for the later model with the needle bearing upgrade, and doesnt have much information anyway...

the 5th gear shift fork (brand new from Wolfgang) and the sleeve seem to have a TON of play, (0.75-1mm?) however the sleeve appears perfect– but I'm comparing this to Japanese motorcycles and Guzzi's I've rebuilt in the past.

Thanks!
Click to expand...

TeddyG said:
I looked at my Green Book and gearbox specs are listed on pages 28-29.
Click to expand...
Thanks! I just found them. oops... If they were a snake, it would have bit me 😆
 
carbcleaner said:
The symptom the motorcycle is exhibiting is rough shifting 3-4, 4-5 and back down again. Also, sometimes it shifts slightly past 4th going up or down. It does this even with the sprocket cover completely removed. (I got a T-handled tool from Wolfgang in Canada) There is a scratchy or grinding feeling when going from 4-5, kind of like the feeling of lapping a hardened piece of metal on 600 grit sand paper.
Click to expand...
Without the external selector mechanism in place the only 'stops' in the gears gears are via the indents in the internal shift plate. In normal operation the selector mech will move the shift plate just enough to allow the internal ;wheel' to drop into each slot. Not sure you can determine 'overshifting' by the method you are using. But the grittiness sounds a bit odd.

Are you rocking the rear wheel fwd-backwards while moving the shift mechanism? No way toget clean shifting with the output shaft (gearbox sprocket) stationary.
 
Have any of the internal selector forks been replaced?

The output end of the mainshaft can be ground to slightly undersize and new bushes fitted to the output gear to suit. Not many NOS shafts laying around, the used ones are on the shelf for a reason. I find most shafts show around 0.06-0.08mm unevenly spread wear, the shaft hardening is deep enough to cope with grinding.

The "needle bearing upgrade" applies to first gear only, otherwise the bush/gear clearances are identical to the twin specs... basically the same gearbox in both types. Only the (pretty rare) triple competition C-R boxes, as well as the 750SFC, have all the gears running on needles.

Gearbox output bearing is nearly always rough to knackered, keep an eye on chain tension.

The selector forks have lots of clearance within the grooves of the various gears and engaging disc for 5th., it is the slots of the selector drum that can be critical. With the cases apart, the forks must be checked in every gear, they MUST have a degree of slop in the groove of the gear, with the gear pushed hard up to its' neighbour, otherwise they will rub and be damaged quickly. In other words, the selector forks must be completely loose and without pressure in every gear. This is very often neglected. The individual gears can be adjusted, within limits, by shims, these were available in 0.5 and 1.0mm for this purpose. It is also important the layshaft has no more than maybe 0.3mm end float, this can also be slightly adjusted left to right for correct positioning relative to the forks with judicous shimming. The selector drum must also have no more than 0.2-0.3mm end float.

Very often, a selector fork for either 1st-2nd or 3rd-4th can show signs of binding. This can also very often be remedied by simply swapping the 2 forks, they are identical, but slight manufacturing tolerances may hinder ideal positioning.

Overhauling these boxes is rather straightforward, but it should be done precisely, which takes quite a few hours if not experienced. Very often, NOS gear bushes, as well as some aftermarket parts, end up with just as much slop as those they are meant to replace, before machining! I use bushes with a decently undersized ID and bore/hone them on my lathe matching them to the actual shaft diametre instead of the nominal spec.

Adjustment of the external selector mechanism is another can o' worms. ;)

Properly set up, these boxes can actually shift pretty sweetly!

piet
 
You must log in or register to reply here.
Back
Top