Slack in Gearbox Selector

[Stephen Hill]

The shifter shaft coming out of the back of the gearbox on my 1976 LeMans has a surprising amount of slack in it.
To be clear, the slack is not coming from anywhere in the shifter linkage outside the gearbox.
A friend has a similar model Guzzi with the same gearbox, and my LeMans has about 8 times more slack than his bike at the shifter shaft, and also at shift lever.
I am guessing there is a worn or broken component in the gearbox, but wonder what I should be looking for when I go digging to find the problem.
I see from the parts book that the shaft sticking out of the box is part of the "preselection, compl.", which I guess we can call a preselector.  Is this where the problem could be?
I have also read in Guzziology about shifter springs that break, leading to slack.  Would this create my symptoms?

Any thoughts or comments would be appreciated.

BTW, the bike shifts fine.  It is just that with the slack at the shifter shaft (gearbox end), the shift lever needs to move a long way to get the bike to shift.

Stephen Hill

[Antietam Classic Cycle]

My guess is the shift return spring. It could have been installed incorrectly, the "tangs" bent open for some reason or it's getting ready to break.

[Chuck in Indiana]

That's a strange one all right, but you'll find it when you open it up. <shrug> (Charlie's probably right, but even the return spring being sacked that much without breaking sounds weird) 
As an aside, I've been fooling with the preselector spring in the V11 transmission for a while. I *think* it's fixed.

[canuck750]

The joys of tearing down a 5 speed box on a bike that has probably been ridden shall we say aggressively in a past life?

The shift return spring is simple enough and cheap to replace which is a must once the cover is off.



The selector dog faces will probably have signs of wear to the point of edges broken or worn off.

I would replace the trust washer set with this update



Inspect all the case bearings and while the gear box is out replace the U joint and U joint carrier bearing in the swing arm

[normzone]

Wow.

I actually replaced those two components pictured on my Eldo, after the shift spring (pawl?) broke and I got a mile of slop in each gear. If I can do it, you can do it.

[pehayes]

In addition to everything else, make sure to take time and properly shim the shift drum.  If it is moving fore and aft, that will add to sloppiness at the selector.

http://www.thisoldtractor.com/guzzitech.dk/pdf/gearbox-shim-pete-roper-new-tools.pdf

Patrick Hayes
Fremont CA

[acogoff]

    As said above. Would be a good time to do the shifter drum end float shim up bit- may be where some of your slop is coming from. Have a look through the oil filler hole while moving the shifter and it will give you an idea of what may be going on. There should be only a couple thousandths of slop moving the shifter fork that is visible through that hole.  Output shaft bearing coming apart could also be a problem area. That is the shaft you see through the hole.

[Lannis]

The joys of tearing down a 5 speed box on a bike that has probably been ridden shall we say aggressively in a past life?

The shift return spring is simple enough and cheap to replace which is a must once the cover is off.



The selector dog faces will probably have signs of wear to the point of edges broken or worn off.

I would replace the trust washer set with this update



Inspect all the case bearings and while the gear box is out replace the U joint and U joint carrier bearing in the swing arm

I have the transmission out of my '83 1000SP for a clutch replacement.  41,000 on the bike, there's no problems with the transmission shifting, no slop, U-joints and carrier bearing are all in good shape.

Does it make sense on this bike to remove the rear transmission cover just for a pre-emptive replacement of the shift spring?   Will I knock something else out of whack doing it, or is it pretty simple to remove the rear cover with the tranny on the bench and replace the spring?

Thanks for any opinions.

Lannis

[jacksonracingcomau]

I have the transmission out of my '83 1000SP for a clutch replacement.  41,000 on the bike, there's no problems with the transmission shifting, no slop, U-joints and carrier bearing are all in good shape.

Does it make sense on this bike to remove the rear transmission cover just for a pre-emptive replacement of the shift spring?   Will I knock something else out of whack doing it, or is it pretty simple to remove the rear cover with the tranny on the bench and replace the spring?

Thanks for any opinions.

Lannis

Return spring problem well solved by then was a 70’s bad batch. I kept changing them pre emptive as you say. One day I realised I never saw a broken one in a 80on bike.
May happen but personally have not broke one myself either.Think I only ever broke one, bike was still new then !, is 40 years in April, still my only transport
I would prob give yours seals and o rings while it is out, only change return spring if physically damaged.
OP
Return spring is only problem here may not be original worn but a bad new replacement, I got supplied one like this once, mile of slop, ended up putting old one back.
Guess there were others badly made, some people prob fitted not realising the issue

[Dharma Bum]

I'd go ahead and replace it.  My spring broke on my 96 Cali. The hardest part of the job is getting the box out.

[jacksonracingcomau]

I'd go ahead and replace it.  My spring broke on my 96 Cali. The hardest part of the job is getting the box out.

Interesting, big mileage ?
Funny cos I’ve got a 96 box in mine, bought with 26k miles, I changed bearings, seals etc but left spring
Done a bit more than 30 since.
Hope I haven’t jinxed myself but all the broken ones I saw back in day were nearly new and well marked where thay broke, def chuck if half worn through.
Was updated part number if memory serves, 28 first two digits, maybe came with mark 3 le mans
Checked see
http://www.mgcycle.com/index.php?main_page=product_info&products_id=1011
Obviously can still break but not odds on anymore

[Dharma Bum]

Mileage was about 90K, so relatively high, I guess.

[Lannis]

I would prob give yours seals and o rings while it is out, only change return spring if physically damaged.

Sometimes good original parts can be better than new ones (different cheaper alloys etc) that you might buy today.   My water-well guy told me that my 20-year-old "Red Jacket" pump would last longer, starting today, than any new replacement he could sell me, and he recommended leaving it alone ...

Lannis

[jacksonracingcomau]

Sometimes good original parts can be better than new ones (different cheaper alloys etc) that you might buy today.   My water-well guy told me that my 20-year-old "Red Jacket" pump would last longer, starting today, than any new replacement he could sell me, and he recommended leaving it alone ...

Lannis

Agree but better check
Logic says new return spring came with phenolic 3205bearings
Apparently an issue

Dharma
Did you change bearings or just spring ?
Mileage now ?

[Dharma Bum]

It was a quick in and out.Bearings see.ed OK, replaced gaskets and clutch shaft ,o-rings. Also replaced clutch  platest and throw out bearing.

[Dharma Bum]

Forgot to add there's about 10k miles on since repairs.,