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Loop frame gearbox

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=8323
Printed Date: 19 Jan 2018 at 01:22
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com


Topic: Loop frame gearbox
Posted By: hendy
Subject: Loop frame gearbox
Date Posted: 09 Jan 2018 at 21:02
Hi all.
The last time I came in search of knowledge, I was about to dismantle the gearbox on my V7 as it was (is?) very noisy.  So now it's apart.  Apparently this box has suffered a bearing failure at some time, so the mainshaft and the 5th gear selector fork have seemingly run askew and left witness marks on the end case.  The bearing appears to have been repaired, but the 5th gear cogs both show signs of damage on the teeth.  Other gears' teeth may be damaged also - I can't be sure without some way of closely examining them.
Anyway, the question is - can I fit a later model box into this bike?  I have read on this forum that all the 5 speed big block transmissions are interchangable.  However I have the right side gear change lever which uses the end cover casting to carry a shaft from left to right.

Gutsibits may have a gearbox from a Tonti frame bike.  Can the internals be swapped around?  Or does the whole box have to be used?

Has anyone done this, and can tell me if they had any issues? 

Regards
Roy



Replies:
Posted By: Dave P.
Date Posted: 10 Jan 2018 at 00:08
You can fit a later 5-speed box but I'm not certain if the later ones have the provision in the casting for a right foot change, I think many do but the chaps at Gutzibits will be able to advise.They are very helpful, in my experience.
It's just dawned on me that we are talking about a V7.So surely you should be looking for a four-speed box.What is the year of manufacture?

-------------

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: 10 Jan 2018 at 00:25
Just found the photo of your 1971 V7 Special Hendy, same as mine.It would have left the factory with a four-speed box.Mine had a 5- speed box when I bought it.Said box exploded on the banks of Loch Leven some years ago.Gutsibits supplied me with the correct four-speed replacement which I much prefer.

-------------

TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

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


Posted By: hendy
Date Posted: 10 Jan 2018 at 09:44
I believe you are correct.  This box must have been replaced at some time, so I'm not too precious about changing it again.  Your idea of reverting to 4 speed makes sense, as these bikes don't need a lot of cog-swapping.  I'll see what Gutsbits have in stock.


Posted By: cyclobutch
Date Posted: 10 Jan 2018 at 10:42
I have an Eldo running a 5 speeder. Return spring broke just three weeks after I bought the bike. Rather than strip the box myself and introduce any amount of dirt – my garage just ain’t clean enough; I pulled the whole thing out and sent it whole to Nigel at NBS. New spring fitted, drum shimmed, all other components inspected – bearings good, some dogs needed welding and then grinding, all for not much money.

He can surely advise on this, and may well have some parts. 



-------------
Butch


Posted By: Amboman
Date Posted: 10 Jan 2018 at 14:49
You can use a later 5 speed, just change to the early rear cover. Usually it's a bolt on swap, no reshimming of anything necessary.


-------------
Charlie
'69 V700, '69 Ambassador, '72 Ambassador "mongrel", '76 Convert, '85 Morini 350 K2
http://www.AntietamClassicCycle.com


Posted By: hendy
Date Posted: 10 Jan 2018 at 17:10
Ah - so all shafts, bearings etc. are identical?  So theoretically the complete cluster could be swapped over. 


Posted By: Amboman
Date Posted: 11 Jan 2018 at 14:28
There were numerous changes during 5 spd. production, so some parts don't interchange. But if you swapped all of the "guts" as a whole from one case to another, you should be okay. But really, all you need to swap is the rear cover itself, to use a late transmission and still retain the inner support for the shift shaft.




-------------
Charlie
'69 V700, '69 Ambassador, '72 Ambassador "mongrel", '76 Convert, '85 Morini 350 K2
http://www.AntietamClassicCycle.com


Posted By: hendy
Date Posted: 11 Jan 2018 at 20:28
The plot thickens.  As noted this is not the original gearbox.  It also doesn't seem to be from any early model. The 5th gear cog pair is 28/21 teeth ratio, which corresponds (after trawling a few parts listings) to certain models of california, Le Mans, Centauro and a few others.  Which obviously affects my search for replacement cogs, which had met with little success when I thought it was an Eldorado box.
Duh.  Onwards..




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