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V7 Special gearbox return spring

Printed From: guzziriders.org - moto guzzi forum
Category: Technical
Forum Name: Loop Frames
Forum Description: Anything about the original Guzzi V Twin.
URL: http://www.guzziriders.org/forum_posts.asp?TID=9197
Printed Date: 19 Mar 2024 at 07:10
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Topic: V7 Special gearbox return spring
Posted By: GUZZIPETE
Subject: V7 Special gearbox return spring
Date Posted: 02 Sep 2018 at 15:01
Changed a weak but unbroken return spring a couple of weeks ago. The gearbox is now not selecting well at all. The spring tension seems unequal forwards and backwards, with the greater tension in the backward (down change direction). So it will jump out of first on the merest amount of overrun. 

When I change up, the lever doesn't spring back up ready for the next upchange. I've had it apart twice since first changing it with the same result both times. I'm not sure if I have done anything inadvertantly whilst in there, or if there is a coincidental fault. The only possible issue I can think of involves the pawl and gear which is visible on the RH side. I don't think I moved anything there, but beginning to wonder now.

I thought this would be a simple job!LOL


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL




Replies:
Posted By: Dave P.
Date Posted: 02 Sep 2018 at 18:33
Hi Pete. I'm guessing we are talking here about the four-speed box? Have you tried turning the eccentric adjuster in the back of the gearbox? It may be that the new spring needs a different setting to the old one.

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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: GUZZIPETE
Date Posted: 02 Sep 2018 at 21:38
Thanks Dave. Yes, it's a standard 4 speed. 
I hadn't thought seriously about touching the adjuster at this stage, as I didn't want to alter a 'base-setting' and add possible further complication to the fault finding. I've never had to adjust them on any of the bikes before, so I don't have experience of how much effect it has. I can see that the eccentric is quite pronounced, so can understand how it could affect the spring tension. I will try some adjustment and report back. 
I think you mentioned before that you have changed your spring before on one of the bikes, did you have to make an adjustment after that?


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Dave P.
Date Posted: 02 Sep 2018 at 21:47
Hi Pete. When I rebuilt the four-speed that I got from Gutsibits I took Greg Bender's advice and modified a five-speed spring to fit. He reckons that the later spring is better. So as I was working from scratch I had to experiment with the eccentric adjuster until I got it right. It's not difficult to do. The instructions for modification and fitting are on his website. Let us know how you get on.

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: GUZZIPETE
Date Posted: 02 Sep 2018 at 22:09
That's interesting Dave. I have a 5 speed spring, so I'll have a look at that article on Greg's site.

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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: GUZZIPETE
Date Posted: 02 Sep 2018 at 22:26
This sounds like it could be a good tip for pre-setting the adjuster too Dave, on Greg's site.

"When installing the small triangle shaped rear cover plate, set it in loose and check the 5 bolt holes that secure the selector cover. If they don't line up true, loosen the 19 mm lock nut on the adjusting screw and rotate as required to line the bolt holes up. This insures that the shift lever may stroke in both directions when shifting."


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Dave P.
Date Posted: 03 Sep 2018 at 09:52
Ah yes! I'd forgotten about that.

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: Amboman
Date Posted: 03 Sep 2018 at 14:33
Make sure that the spring isn't a bit too long and isn't scraping against/catching on the rear cover. I've found it necessary to trim the "prongs" of the spring so that it didn't. Also, in a few instances I've had to bend the 5 spd. spring in order to remove "slop" from the shift selector.

I had been using the 5 spd. spring, but have now gone back to using the 4 spd. spring again.


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Charlie
'69 Ambassador,'71 Ambassador,'73 Eldorado,'75 Eldorado police,'76 Convert,'77 Morini 3 1/2 Strada,'81 Ducati 500SL Pantah

http://www.AntietamClassicCycle.com


Posted By: GUZZIPETE
Date Posted: 03 Sep 2018 at 15:41
Thanks for those points.

The spring was too long, I had to grind the ends off a little.

I have of each of the springs, so I will look out slop with the 5 speed, and use the 4 speed if it's an issue. Hope to get back into it tonight.

Pete.


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: GUZZIPETE
Date Posted: 03 Sep 2018 at 22:11
Fitted the 5 speed spring and worked on 'tuning-in' the selection with the adjuster tonight. It feels more positive at this stage, but always difficult to tell on the bench.
Will finish re-assembly and road test it tomorrow.
Charlie, why did you revert to the 4 speed spring I wonder?


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Dave P.
Date Posted: 03 Sep 2018 at 23:36
The trimming of the "progs" was what I was referring to when I mentioned modifying the five-speed spring, they are too long. I thought that the later spring felt stronger so I'm also interested in why Charlie reverted to the four-speed version.

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: Amboman
Date Posted: 04 Sep 2018 at 14:01
The only reason I went with the 5 spd. spring in the first place was due to due to a period of unavailability of the 4 spd. spring. I always disliked having to trim and bend the 5 spd. spring to make it work, the 4 spd. spring was a direct fit, so when they became available again I went back to using it.

How many 4 spds. have suffered a broken return spring? In my 35 years of owning Guzzis, I can't say I've heard of one. How many 5 spd. springs have broken? Dozens! It took Guzzi three tries to make a spring that didn't break.


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Charlie
'69 Ambassador,'71 Ambassador,'73 Eldorado,'75 Eldorado police,'76 Convert,'77 Morini 3 1/2 Strada,'81 Ducati 500SL Pantah

http://www.AntietamClassicCycle.com


Posted By: GUZZIPETE
Date Posted: 04 Sep 2018 at 15:30
I can see your logic there Charlie. I'll see how I get on with the 5 speed, now that it's in there, but might revert to the 4 speed if I don't have success in sorting the initial issue.

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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Dave P.
Date Posted: 04 Sep 2018 at 23:32
Hmm, that puts a different perspective on things. I'll leave the five-speed spring in there but if it fails I'll go back to the original four-speed. I carry one on the bike anyway and with the four-speed box you can if you have to change the spring on the side of the road. Pity the later gearbox doesn't have that facility. Every day's a school day.

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: GUZZIPETE
Date Posted: 05 Sep 2018 at 21:43
Road tested the bike tonight, but it's still not right. The gear lever is still biased to the rear, so that when I change up a gear,  the pedal is not springing back up ready for the next gear without some help. This also means that it will easily jump out of first. I will have another go at moving the adjuster, but this time I will try to adjust it so that the bias is the other way, rather than setting it for what felt like an equal loading in either direction.

I don't know about changing it on the roadside Dave, but I will be able to do it in my sleep soon! LOL


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Dave P.
Date Posted: 05 Sep 2018 at 23:36
Pete, just thank your lucky stars it's not a five-speed box!

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: Dave P.
Date Posted: 20 Sep 2018 at 13:11
Any progress Pete?

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: GUZZIPETE
Date Posted: 20 Sep 2018 at 13:58
Hi Dave

Some improvement I think Dave, but still not as it should be. 

I contacted Greg Bender at the weekend, and he was kind enough to reply with some insightful suggestions. 

Apart from the obvious points like making sure the pivots and linkages are moving freely, he also responded to a question about whether there could be anything inside the box causing the issue, and he responded with this below:-

External to the transmission, I would make sure that all of the linkages and pivot bushings are in good shape, clean, lubricated, etc. If that still does not solve the problem, then I would look internal to the transmission. Specifically, I would look at the shift drum and examine how it rotates on its shaft and against the thrust washers at either end. Any of those pieces can become corroded and make for something that doesn’t want to rotate.

I'm not keen on getting into the box myself, as Dave Richardson says that they are not easy to re-assemble, and I think you need a few special tools too, so I don't see much point in ending up with a pile of parts on the bench. I guess Nigel at NBS would be the candidate for that job. 

I want to try it out on the road for a longer run and see how it fares. At the moment I have to nudge the lever back up slightly, so it's ready for the next up-change. 

One thing I did do was to mod the eccentric adjuster screw. As you know, it is only slotted on the end for means of adjustment, which makes it nigh on impossible to adjust when everything is back together. So I drilled and tapped the outer end of it and loctite'd an M6 bolt into it, so that it can be adjusted from the side rather than having to get on to the end of it. I also marked one of the flats on the bolt in line with the highers point of the eccentric on the other end for reference when adjusting it. I find a pair of ratchet spanners positioned from the side just above the UJ gaitor provide the best access.

After all that, Greg mentioned that he has never found that adjusting screw makes very much difference to the lever action in his experience.Confused

I hope your bikes are behaving?

ATB

Pete.



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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Dave P.
Date Posted: 20 Sep 2018 at 15:43
Hi Pete, this is a bit strange as all was apparently well before you changed the spring. Was it shifting OK before? Or did you change the spring because of poor shifting?
When I rebuilt my box I shimmed the shifting drum which made the lever return just a tad reluctant. Not wishing to strip it all again I rode it for a while and it freed up nicely. I think it just polished the surface of the shim washer which was plated.

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: GUZZIPETE
Date Posted: 20 Sep 2018 at 16:53
The pedal was sticking intermittently and the return action was weak, which prompted the spring swap.
The doesn't do a lot of miles, as I generally tour on the 850 T and I've been using the Convert for most of the local miles this year, so I'm wondering whether it could be lack of miles that is causing the pedal to stick a bit. But I could be clutching (no pun intended) at straws?

You have obviously carried out surgery on your box and survived to tell the tale?

Pete.


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Dave P.
Date Posted: 20 Sep 2018 at 17:06
Just a thought, or another straw to grasp. Is the gear lever shaft binding in the tunnel through which it passes? Is it clean and greased? And does it have end float? Ah! Greg's already asked you that.

I think we should have an emoticon on here of the little yellow chap reaching for a straw.    

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: GUZZIPETE
Date Posted: 20 Sep 2018 at 19:16
Ha, yes definitely!

Pete.


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1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL



Posted By: Ogmios
Date Posted: 25 Sep 2018 at 11:41
"  ... and with the four-speed box you can if you have to change the spring on the side of the road. Pity the later gearbox doesn't have that facility."
understatement of the year! Big smile
~~~
Og ~ 78k miles on a Cali 3 and twice had the gearbox out.
(... and just back from a tour of Brittany. Again. Only not on the Cali this time Unhappy )


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Appears bright from a distance / dim up close.


Posted By: GUZZIPETE
Date Posted: 12 Jan 2019 at 22:22
Update.
After making no progress at all with this gearbox problem. I took the box over to Nigel at NBS before Christmas for some investigative surgery. After collecting it today, he found that the shaft that selector drum runs on was worn, and causing the drum to bind. Also the selector shaft that the return spring is fitted to was one tooth out of alignment on the gear teeth it meshes with. That must have been me when I changed the spring. In my feeble defence, it's not easy to see when the box is still in the bike.

I will get it back in the bike over the next couple of weeks and hopefully enjoy the improvement.


-------------
1971 Moto Guzzi V7 Special
1974 Laverda 750 SF2
1979 Laverda 3CL




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