??? - gearbox - transmission/kick start maintenance and inspection

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joe czech

joe czech

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very little knowledge on the subject, so the question - are there any components within the gearbox that are inherently prone to wear - bushings, bearings, etc., or are the gearboxes pretty much bullet proof. as part of periodic and preventative maintenance, and aside from general lubrication, is the gearbox something that should gone through every so often and given a thorough inspection?
 
"a 30hp transmission behind a 60hp engine"

google search "accessnorton layshaft bearing"

and second gear....
FC5ECC00-1389-488A-8631-5DCB0321D7E5.jpeg
627914BC-28B8-4836-AAA8-DE224ADAA8D1.jpeg


Not what I would consider "bulletproof" compared to anything else in my history.
 
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The layshaft bearing will usually give notice of wear by allowing the kickstart to fall under acceleration, probably more noticeable when it returns and taps you on the back of the leg :)
 
Assuming that the gearbox is shifting properly and is not operating with any abnormal behavior prior to disassembly:
The parts that I would replace if the box just needs an overhaul would be the Lay shaft first gear bush. 040046 which I have seen crumble away on several Commando AMC gearboxes. Normally the 2nd and 3rd bushes are OK to leave but make sure they are a sliding fit in the gears. I would replace the two 4th gear sleeve gear bushes with the longer Mk III's, 06.6203 instead of the shorter bushes 040062's .
If you never been in the box or don't know the history then...Here may lay the infamous Portuguese grenade lying in wait... get the superblend layshaft bearing: 06.77105 or the Mick Hemming's Roller bearing which I don't know the number so search here on the forum. The first bearing I mentioned will need shims. Search for the Portugese bearings in the search on the forum for more info. Quad O-rings are available to replace the originals so go that route. The Kick start pawl takes lots of abuse and I have seen several with chunks missing so a new one is recommended. 06.2015. Depending on how much rust is in there I would get a ratchet spring 040038 as they sometimes thin out at the contact points and break. Keep the two tines parallel and with about 0.005" thou clearance but no contact at the gear shift pawl.
But hey that just touches the surface. Until you open the box you may have a lot more rabbit holes to fall down into. e.g. A consistently loosening kick start crank on a worn out Kick start shaft will not be beneficial unless both are purchased new at the same time. Look for cracks at the kick start shaft near the pawl in the shaft. If you see a crack...replace. Then there are the gears... with any Brinelling marks on them......IMHO you got to get into the box to know what you got.
And I almost forgot gaskets: if you want leakproof then get the J.S motorsport silicon gasket set for the box.
Good luck,
Cheers,
Tom
joe czech said:
very little knowledge on the subject, so the question - are there any components within the gearbox that are inherently prone to wear - bushings, bearings, etc., or are the gearboxes pretty much bullet proof. as part of periodic and preventative maintenance, and aside from general lu brication, is the gearbox something that should gone through every so often and given a thorough inspection?
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CanukNortonNut said:
Canukian????.... that's a new one, to me. What the slang for New-Zealanders ?
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Kiwis.

I was born in Minnesota and grew up in Seattle. Used to go to a lot of hockey as a kid in MN - North Stars and the Gophers. Vancouver Canucks made all those from Canada "Canuckians" to me once in Seattle. ;-)
 
If the gear box and gears are changing smoothly then I would leave it alone just do a oil change first and see if there is any bronze filings in the oil, if not then leave it alone, depends on how many mile is on the GB if more than 12k miles then chances are the Lay Shaft bearing has been replaced, my stock GB has over 160k miles on it the lay shaft bearing blew in the first few years and in the 46 years of ownership have replaced 4 kick start pawls, the kick start gear because where the pawl sits was worn and a kick start shaft (because some idiot in a bike shop welded my kick start on the shaft because it was lose and snapped at the pawl end two weeks later) if you ride normal and don't bash it into gears then the GB will live a long time and will show signs when thing aren't right, but if you are worried then its a easy job to pull the outer and inner case off for a true inspection, but most problems with gear change is mostly clutch related and primary chain adjustment.

Ashley
 
gortnipper said:
Kiwis.

I was born in Minnesota and grew up in Seattle. Used to go to a lot of hockey as a kid in MN - North Stars and the Gophers. Vancouver Canucks made all those from Canada "Canuckians" to me once in Seattle. ;-)
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At lease you were smart and move down under ;) .
 
ashman said:
if more than 12k miles then chances are the Lay Shaft bearing has been replaced

Ashley
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Dont be so sure. I have had my 74 mk2 for 30 years, though it spent ten in the shed under a cover before 2015. When I tore it all down for restoration then, it still had the Portuguese layshaft bearing. Of course, this was all before knew anything at all about them grenading. Luckily, it still was intact and working fine up until I binned it.
 
My 74 850 MkII had the Portuguese LS bearing within when I overhauled the GB at around 12k on clock (presumably but not certain)
Followed the Hemmings DVD and got his overhaul kit with his recommended ball bearing phenolic (no shaft shimming and better handling of shaft flexing under load as per Mr. Hemmings during a phone chat).

Surprises within my G B were the clutch operating lever badly worn down and evidence of some monkey using a chisel to work the clutch operating body locknut. Did all the bushes, bearings, springs, seals and gaskets while there. Nearly all in kit.
 
Mine is the official exploding F A G bearing, maybe it has superblended barrel shaped balls.

The one out of the Fastback was not in such pristine condition.

??? - gearbox - transmission/kick start maintenance and inspection
 
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