First days with a Commando

We'll, I've had an interesting first couple of rides on my newly acquired mk3. I rode to work on it on Friday, 10 miles at about 6 degrees C; what an overwhelming experience that was! It feels so different, odd, in so many ways compared to bikes I'm used to. It steers quite nicely, though slowly, but needs work on the carburation & seems quite low geared - does 4000rpm for 70mph sound about right? Also the side stand is an oddity - instead of sticking out largely sideways it points largely forwards at about 45 degrees - is that normal or is the stop worn out?

The way home seemed a little easier, with a glimmer of familiarity starting to form. I get the isolastic effect & it seems to work, though there are some strange effects on the overrun where the engine seems to do a tango. Quite interesting!

I went out on it this morning for an errand, and on the way back my eye was caught by the RH exhaust dancing about wildly - the exhaust nut has shaken loose. Ah we'll, here we go...
This bike is basically in pretty good nick but I suspect hasn't had a lot of riding in the last decade or so, good in that it hasn't been worn out and needed a rebuild, not so great in that a few of the jobs that would be done with riding haven't been. So, the gear change is stiff, the clutch cable feels lossy, etc. Still, this is the time of year for fettling bikes...

This bike seems so original I'm loathe to change too much. Certainly, carburation needs sorting early on. My plan had been to put a single carb on it, preferably a mk1 Concentric, but reading up on here that option may blunt performance. I may just rebuild / replace the 932s to keep it standard. Oh, and I should sort the electric start out, I was told it needs a sprag, though it has been through a couple of them in recent years.

So, there it is, my first impressions. Is there an idiots guide to these bikes, other than the factory & Haynes manuals, a distillation of the accumulated wisdom of the years? If so, sign me up for one!

Cheers, Jon.

Boxerfan said:

& seems quite low geared - does 4000rpm for 70mph sound about right?

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How fast do you want to go ?
Thats about the same gearing as a BM 1000cc, unless it had a full fairing.
Bigger gearbox sprockets are available, but knock off some of the low-down around-town performance.

Boxerfan said:

I went out on it this morning for an errand, and on the way back my eye was caught by the RH exhaust dancing about wildly - the exhaust nut has shaken loose. Ah we'll, here we go...

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Keeping an eye on things, and keeping things tight is part of the ritual of ownership.
Making them then stay there is a battle the factory only partly solved. !
Stainless nylocks are available these days, that helps to keep some of the smaller items stay where they should be.
Carrying an exhaust nut spanner, and checking with it, is a regular chore.
Others may impart a more permanent solution they found.
When you find the happy spot, the exhaust will stay there...

Enjoy !

Boxerfan said:

seems quite low geared - does 4000rpm for 70mph sound about right?

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Yes, that's about right. How many teeth on the output sprocket (you can count them if you lay on your back with your head under the gearbox :mrgreen: ) ?

Boxerfan said:

Also the side stand is an oddity - instead of sticking out largely sideways it points largely forwards at about 45 degrees - is that normal or is the stop worn out?

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Yes, that sounds about right but some wear in the pivot is to be expected.

Boxerfan said:

I get the isolastic effect & it seems to work, though there are some strange effects on the overrun where the engine seems to do a tango. Quite interesting!

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I can't say I've ever experienced that?
Have you checked the Isolastic clearances yet? If the Isolastics are old they may need replacing.

Boxerfan said:

I went out on it this morning for an errand, and on the way back my eye was caught by the RH exhaust dancing about wildly - the exhaust nut has shaken loose. Ah we'll, here we go...

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Your "boxer" exhaust spanner (presuming you have one?) should fit the Commando exhaust rings nicely.


Re-tighten the exhaust ring/s while the engine is running and is good and hot. Exhaust lock ring tab washers are available (Norton part 062412).
Worn or stripped exhaust port threads is a reasonably common Commando problem. If the pipe becomes loose again, or the nut jumps the threads when you tighten it with the engine really hot then the thread probably needs to be repaired (usually fixed with a welded-in threaded insert).

Boxerfan said:

the gear change is stiff,

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This can be caused by wear in the MkIII cross-shaft mechanism. The MkIII gearchange also develops a sloppy feel, again due to wear in the cross-shaft assembly, however the parts are not too expensive.

Boxerfan said:

the clutch cable feels lossy

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"Lossy" I can't comment on :?

Boxerfan said:

I was told it needs a sprag, though it has been through a couple of them in recent years.

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Yes, the sprag is a known weak point, setting the overload-backfire device correctly may help to reduce sprag failures.

http://www.oldbritts.com/e_start_backfire.html

Boxerfan said:

Is there an idiots guide to these bikes

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No, not really. But keep asking, as somebody will either give you the answers you need or point you in the right direction.

Try to get some more miles on it before changing too much. The exhaust header is best tightened hot and you must be very carful not to damage the threads. The finned nut can be put out of round by applying too much force in one spot. Keep re-gripping the nut in different locations around the radius until it stops turning from light pressure, then torque on it some more while changing the position of the grip to different fins. Try to grip the fins inward close to the head where the fins join the main body of the nut and not on the outward side of the fins where they will bend easier. I used a pipe wrench back in the 70's for this with great success however some people here have blamed the tool for damaging this nut (put out of round), however if you do as I've stated and keep rotating the tool it will work. I now have a c spanner for the job but it too must be rotated and the nut tightened a bit at a time from different angles.

The side stand sounds good. If it sticks out 90' then the bike could roll only a bit before the stand would go into the fold up position causing the bike to fall. With it past centre like that it would take more than a nudge to move the stand to the fold up position past centre or 90'.

There is a down loadable manual in the links section in the top tool bar of this site.

4000 @ 70mph sounds normal but you can change the gearing with the final drive sprocket on the trans. The low gearing is good for being caught in traffic and parking lots etc plus general performance around town. Higher gearing is better for hiway use.

Look in Tech/Photo section for parts book and Norton club generated upgrade and work around, published error correction handbook. Play with air pressure in tires, harder makes smoother-sooner isolation and I find front needs couple lbs less than rear for easy natural low effort steering. Do keep eye on brake fluids till you know they ain't blowing away unknown to find out with no brake at all suddenly no warning. Not really many places nylocs needed or work d/t heat, generally just good nip up with a dash of mild loctite holds non power unit fasteners on as isolatics protect a good bit on their back offs. Loose / worn isolastic gap mainly makes a softer sooner isolation on set but does bring on hinged handling upset sooner. That is always lurking so creep up on flings till conditions eventually reveal what to watch out for. Commando's are rather tire condition sensitive and hardly anything can be said or adjusted until both tires in good shape. If something fouling power unit and frame, that can give intermittent annoying unexpected vibration getting through. The real issue about exhaust rings is getting them off once tight enough on, I've settled on Milk of Magnesia though most have gotten by with the greasy anti-sezie not completely melting away. Japanese pretty much made Norton fall back on milder curiser models by time 850's introduced, so not same mettle that gave the Unapporachable moniker, but still quite handy short of go to jail speeds.

If you have a conventional cable of some sort on there now, changing to a Venhill featherlight clutch cable will make the clutch pull much easier. Making the clutch plate stack height correct, a fairly simple procedure, can also help immensely.

Glen

A properly timed ignition and properly tuned carbs will help the life of the starter sprague.

You have to be mechanically inclined with a valid credit card. Exhaust loosenings, STOOPIDLY tight. Stand on the lever-wrench. Hot. Never use retaining rings as they will retain the big nut and rattle out delicate thread$. Enjoy.

Fit a pair of new amal premier carbs if you want to kp it as it is. That way you can keep air box, fuel pipes, filters (or use a K&N inside standard airbox), cables and manifolds because al these will need replacing with a sing carbs so the price of fit a single will work out about the same as fitting two. Plus you will loose power and as many people have said the fuel savings are not that different on a well set up pair of new carbs verses a single carb its as the carbs wear that problems start an owners kept missing about with old carb that should be thrown away.

You blokes are brilliant! Thanks for all of the useful feedback. I wrote this last night in response to Rohan's reply about gearing, then went to bed without hitting send -
As far as the gearing goes, i've had big BMWs and a 1200 Sportster... the H-D always felt comfortably long-legged, BMs, even 1200s, surprise me with how fast the engine spins. I thought the 850 Norton would be closer to the Harley somehow.
Maybe I just need to get used to spinning it over at 5000+rpm? I suppose I'd like it to feel happy at an 80mph cruise - it's early days yet, still on the nursery slopes of the learning curve.

Here's a picture of the old thing to be going on with -

Put in 21 count trany sprocket to get the long legged easy torquer Nortons, expecially 850's are known for. 4000 rpm should give about 80 mph then, 3500 for 70. Allows staying in passing gear 2nd to 80's mph which should please you on the pull power. Mostly the ole Amals beat the pot metal slides and bores to leak too much air, just getting Anodized slides with a smaller cut out has solved that for me low term though Permiers version would also solve long term. Your other bike can out hp a Commando but up to the 80-90's should about match em. These Nortons are supposed to take upper 5000 rpm all day long. When gone though and working well I find a Commando more refined addicting ride than Harley or big ole BMW. Otherwise feels like a ratty clunker with too much effort on every control.

http://www.youtube.com/watch?v=mulfQYSmFPk