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1972 Commandos - a couple of questions

Classic Norton Commando Motorcycles.

1972 Commandos - a couple of questions

Postby al1985 » Fri Apr 14, 2017 12:50 pm

Hi guys,

I'm new on here and looking to buy a Commando. My family has some history with Nortons - my grandfather raced a model 19 back in the early 1930s. I've saved up my pennies and am ready to go spend them on something. I've found a 1972 Commando (non-combat) for sale and plan on seeing it this weekend. Condition looks fair/good, though not restored, and it's a reasonable price.

My question is this - from what I've read 1972 seems to have been a bad year for Commandos. Am I right in thinking that even the non-combat engine models from this year suffer from main bearing problems? If so, then I assume that the bike I'm looking at will need a rebuild even if it's running okay (unless the bearings have been done)?

I ride a 32 year old Honda at the moment, so I'm used to fixing ancillary systems, but I've never had to do major engine work. Can anyone give me a rough idea what the cost of having the bearings replaced is?

Also, if anyone can point me in the direction of a good buying guide for this model that would be much appreciated.

Thanks for your help!

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Re: 1972 Commandos - a couple of questions

Postby al1985 » Fri Apr 14, 2017 1:09 pm

One other quick question - the bike doesn't have a center stand. Were they fitted as standard on the Commado? I guess I thought they would be necessary for kickstarting, otherwise it must put a huge strain on the sidestand.

I've spoken to the seller and he doesn't know whether the engine has had any work (he just got it in trade). It's got electronic ignition and mikunis, so it seems to have had some upgrades done.

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Re: 1972 Commandos - a couple of questions

Postby kommando » Fri Apr 14, 2017 1:48 pm

All 72s suffer from the wrongly located oil pick up location and no sump filter, the combat suffers more quickly from main bearing failure as it likes reving but all 72s will go unless upgraded to the proper main bearings.
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Re: 1972 Commandos - a couple of questions

Postby L.A.B. » Fri Apr 14, 2017 2:03 pm

Welcome,

al1985 wrote:My question is this - from what I've read 1972 seems to have been a bad year for Commandos. Am I right in thinking that even the non-combat engine models from this year suffer from main bearing problems?


The Combat tuned engines were the most badly affected, however, all early Commandos can benefit from the upgraded FAG NJ306E main bearings (often referred to as 'Superblend').

al1985 wrote: If so, then I assume that the bike I'm looking at will need a rebuild even if it's running okay (unless the bearings have been done)?



It's possible the bearings have been changed, but as it's a 45 year old bike, history unknown, and supposedly not a Combat it would be unwise to assume much at this early stage.


al1985 wrote:One other quick question - the bike doesn't have a center stand. Were they fitted as standard on the Commado? I guess I thought they would be necessary for kickstarting, otherwise it must put a huge strain on the sidestand.


Yes, it would have had a centre stand originally.
Neither stand is necessary for kickstarting, that's often how they end up broken-especially the side stand, so I reccomend you get into the habit of sitting astride and kickstarting with the bike resting on its wheels.
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Re: 1972 Commandos - a couple of questions

Postby al1985 » Fri Apr 14, 2017 2:18 pm

Thanks for the replies! Good to go into this with all the information.

I'm assuming that it's quite a lot of work to strip the engine back far enough to even inspect which bearings it has?

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Re: 1972 Commandos - a couple of questions

Postby al1985 » Fri Apr 14, 2017 2:40 pm

Sorry if I'm laboring the question here - I'm totally new to these bikes and the learning curve seems steep.

1) Are ALL pre-1973 commandos prone to main bearing failures? I got the impression from what I'd read that 1972 was particularly bad even for non-combat models due to some changes to the engine causing more stress on the bearings.

2) If the bike hasn't had the bearings changed, is it an absolute must to replace them? Is failure totally catastrophic, or will it develop some signs of problems over time?

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Re: 1972 Commandos - a couple of questions

Postby L.A.B. » Fri Apr 14, 2017 3:14 pm

al1985 wrote:I'm assuming that it's quite a lot of work to strip the engine back far enough to even inspect which bearings it has?


Yes, there would be a reasonable amount of work, as the engine must be totally dismantled. I suggest you read through the factory manual (link, below), as that will give you a basic idea of what's involved.
http://www.classicbike.biz/Norton/Repai ... mmando.pdf

al1985 wrote:1) Are ALL pre-1973 commandos prone to main bearing failures? I got the impression from what I'd read that 1972 was particularly bad even for non-combat models due to some changes to the engine causing more stress on the bearings.


Not all pre-'73/'72 are prone to main bearing failure. It can be the luck of the draw but it can also depend on how the bike has been treated during its lifetime.


al1985 wrote:2) If the bike hasn't had the bearings changed, is it an absolute must to replace them? Is failure totally catastrophic, or will it develop some signs of problems over time?


No, not an absolute must, at least not at this stage where nothing is known about it, and main bearing failure isn't likely to be sudden or catastrophic (unless the symptoms were ignored for too long perhaps).

One thing I definitely recommend you should do is upgrade the gearbox drive-side layshaft bearing to the NJ203E roller or 'Mick Hemmings' FAG 6203 TB ball bearing if it's found to have a standard 6203 ball bearing as that bearing (whether a Portuguese FAG or not) can destruct catastrophically with little or no warning, with potentially disastrous consequences for both bike and rider if/when it does.
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Re: 1972 Commandos - a couple of questions

Postby kommando » Fri Apr 14, 2017 3:15 pm

72 dual rollers non superblend is worst, 71 backwards with the timing side ball are better but superblends mains are still best of all.

Main bearing failure caught early when they start to rumble will not cause damage,but left longer the risk of secondary damage is higher.
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Re: 1972 Commandos - a couple of questions

Postby al1985 » Fri Apr 14, 2017 3:36 pm

Wow, that's great information. Thank you for the replies and help.

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Re: 1972 Commandos - a couple of questions

Postby 1up3down » Fri Apr 14, 2017 4:18 pm

Are ALL pre-1973 commandos prone to main bearing failures?


NO

depending on how they are ridden even Combats are not necessarily prone to bearing failure

Here is the issue, the 72 Combats came with a 19 tooth countershaft sprocket along with a little higher lift cam
and more compression, Norton knew quarter mile times were what sold bikes and that is exactly what they went after with the Combat which was about 1/2 second faster than a non Combat in the quarter mile, according to all the road tests from that era that I have

But with the smaller 19 tooth sprocket (compared to standard 21 or even 20) the Combat could be revved easier towards redline and because it was perceived as the hot rod bike a lot of owners revved the hell out of it, including me

and when the crankshaft is spinning that fast it begins to whip and wobble enough for the ends to dig into the bearings and races causing early failures, some in as little as 4000 miles back then causing nightmare warranty problems for Norton

but IF the motor has not been revved to death then the bearings may well be still be as good as the bearings on any other Commando of that era, if you are buying a used Combat then you don't know and that is why owners split the cases and install bearings that have kind of beveled or roller barreled ends to take pressure off the crank ends, these were called Superblend Bearings

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Re: 1972 Commandos - a couple of questions

Postby Craig » Fri Apr 14, 2017 5:27 pm

Just to add some confusion to the cast in stone history .... I do own a '72 Combat .... it runs on the original factory bearings .... quite well in fact .... I have posted previously the minor changes made to carbs ( down to one ) and counter shaft sprocket ( now 21 T ) with little reason to rev much past 4500 or so , it has given me many years of light duty service with no problems ....I use it for pure pleasure easy cruising not high speed road travel ..... I been told I'm riding a bomb more times than I can count , but so far "knock on wood " no rumbling just nice brisk performance and better sound on many Sunday mornings ..... guess when I get the tell tale signs of bearing failure I will have to actually do something ... 'till then I will just ride ....
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Re: 1972 Commandos - a couple of questions

Postby al1985 » Fri Apr 14, 2017 6:37 pm

Thanks guys, very helpful. I'm not sure this will be the one for me, but I'll be taking a look at it tomorrow anyway. It sounds like it's been in storage but has had some minor work done to get it going again. Not sure there's any history with it, so the price may be a bit high given what it's been through. Here's the ad:
https://losangeles.craigslist.org/wst/m ... 93464.html

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Re: 1972 Commandos - a couple of questions

Postby Craig » Fri Apr 14, 2017 6:52 pm

looking at photos , looks good to me , still , that's just skin deep but it looks like someone spent some time on the presentation .... not familiar with prices where you are ....
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Re: 1972 Commandos - a couple of questions

Postby lazyeye6 » Fri Apr 14, 2017 7:54 pm

al1985 wrote:Thanks guys, very helpful. I'm not sure this will be the one for me, but I'll be taking a look at it tomorrow anyway. It sounds like it's been in storage but has had some minor work done to get it going again. Not sure there's any history with it, so the price may be a bit high given what it's been through. Here's the ad:
https://losangeles.craigslist.org/wst/m ... 93464.html


Though it has been said that a Commando bottom end should be good for 100,000 miles, I myself would be Leary of a 26,000 mile bike with no documented history of engine work at that price level. There are some fine bikes being sold at that price point. Watch the market for a while. Get a feel for it before buying.
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Re: 1972 Commandos - a couple of questions

Postby B+Bogus » Sat Apr 15, 2017 1:01 am

The bike looks OK at first glance - a shorter front brake cable wouldn't hurt though ;)

I always understood the Combat weakness to be due to the non-superblend mains, but having done more research, there's clearly an issue with the scavenging on the '72 cases:
https://www.oldbritts.com/n_c_case.html
https://andover-norton.co.uk/en/sicombatcrankcase/

This explains why 'regular' use doesn't result in problems, but sustained high revs can be the killer, starving the big ends of oil and throwing a rod.

My Combat really did want to rev and I was happy to oblige :D Knowing it would stay together with the mods applied - and Superblends - was a great reassurance.
Way more fun to ride than my 850s, and I want another...

Back to the bike for sale - if there are no rumbles from the bottom end (pull the clutch in to eliminate any primary drive noises), it'll be just fine unless you're looking at standing quarter performance times.

+1 on the Layshaft bearing - an essential mod.
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