Your Questions & Answers

Dear Marj

I'm stuck on the shoulder of an Italian Autostrada. My Commando has a blown head gasket. All I have with me is my 3G 'phone. How do I get the cylinder head off?

Ok, well maybe you're not in quite such a desperate situation, but if you have any Commando related questions you'd like to ask, write in and if we can't answer ourselves it's likely another one of our readers can.


18 June 2003

I am a student studying for an MA in Automotive Design. For my final project I have chosen to do a Norton branded sports car. In project I am attempting to design and style a 'non-two wheeled vehicle' with the motorbike in mind. Unlike the way Honda and Suzuki both have a car and motorbike division but the two do not really share any familly conections, I wish to design a sports car that has the feel and aesthetics of a motorbike. I am currently conducting the research report stage of the project which is to be completed within four weeks, and the design and quarter scale model by September. I would be grateful if anyone could provide me with any relevant information for the project. I am looking for company, design and styling information such as company profile, company history, design philosophys, target markets, up-to-date contacts etc. Also any personal ideas for the project direction will be very welcome.

Euan McDougall-Brown
Coventry

Norton is one of the great names in motorcycling. Although they never made any cars, single seater racing cars, powered by Manx Norton single cylinder engines were built in the 1950s for the Formula 500 series. Norton wouldn't sell Manx engines on their own, so car racers would buy complete Manx Nortons and throw the chassis away. This led to the development of the Triton : although the Triumph twin had a fast engine, it's chassis wasn't very good. So Triumph engines were slotted into discarded Norton Featherbed frames to create a rocker legend.

But Nortons are no longer being made. Ok, there's a strong spares operation around the Commando twin, and there are people who will build you a 'new' Commando. Plus, at least two outfits, Andy Molnar and Petty, build new Manx engines; more powerful, but even more expensive, than the original.

And the project.
More than two wheels but the feel and aesthetics of a motorbike. So : light weight; good power to weight ratio; good handling; open topped; minimalist. How about a rotary engined, three-wheel sportster. That would be an appealing and innovative blend of old and new.


12 June 2001

Clutch slip or clutch drag.
Having tried all the recommended solutions which all work until you try to keep up with a Japanese 250 on a twisty road. Or fit the bronze plates and almost kill yourself in traffic. Then I read the Americans fit "Bates clutches", what's this? Nobody has heard of them in the UK. As the Commando was born just about the time of  the moon landings, and technology has moved on a pace since then, they might just stop me selling the beast and go for that 250. Anybody out there tried them ?

Paul
Scotland

Well some technology may have moved on but, if NASA wanted to go to the moon tomorrow, they couldn’t. The Commando uses a diaphragm clutch, the same as a car, even Formula 1. It’s two drawbacks, common to most motorcycles, are : it runs in oil and is operated by hand rather than foot. Difficult to see what can be done about hand operation, fit a longer lever maybe, but dry clutches are wonderful and one of the better reasons to fit a belt drive. I’ve always found the Commando clutch to be equal to the job but they will require some attention as the years pass by. The key points to remember are :

 


4 June 2001

Any suggestions for a place to start, in terms of the needle, slide cut away and jets for a pair of Amal 33mm smoothbore carburetors. The motor is an 850 cc Commando, with a PW3 camshaft (Mick Hemmings), the longer rubber mount intake manifolds (ditto), a Hemmings big valve head ( intake valves 1 5/8" or 41.2 mm) and compression ratio is 10:1. To run at a mile above sea level.

Michael Homs
Denver, Colorado

These are the settings I use on the Amal Mk2 34mm Smoothbores fitted to my Commando race bike (4S camshaft).

Main Jet 270
Needle Jet .106
Throttle Slide
Needle 2C3 - middle position

Amal velocity stacks fitted, no air filter.

The major improvment came from changing the needle, and I'm indebted to Dave Nourish for his advice. You will find you need to use too large a main jet with the standard needle, 2A1 (I think), and this messes up the rest of the carburation. Note that 2C3 needles are longer than standard and should be shortened to 2.75" by grinding off the tip.

Does anyone have any thoughts on the adjustments required to run in near earth orbit?

And what about replacing those heavy, heavy throttle springs?


24 May 2001

I’ve equipped my Commando with an additional Hyde Yoke and progressive rate Wirth springs. Used oil is a 10W-40 engine oil. After fitting the above the fork tends to " top out", i.e. slider is fully out on heavy bumps. Very surprising with a drivers weight of approx. 300 lb !!!

Christian
from Munich / Germany

I'd go back to standard; if a production Commando can lap the TT course at over 100mph, it doesn't need any help from Mr Hyde. In general, I don't like progressive fork springs : the damping can't match both low and high rates and, in corners, the soft part is compressed by the cornering load leaving the hard part to deal, rather harshly, with any bumps. Ok for cruisers maybe, but then handling isn't an issue.

Cold, a 10w/40 engine oil should be equivalent to a SAE 10 monograde, i.e. it is too thin. So your forks are topping out because there’s not enough damping and they are “over-shooting” on the rebound from a bump. Moreover, I would guess that the springs you’ve fitted are a higher rate than standard, further compounding the problem.

  1. Use fork oil. SAE 15, e.g. Castrol Medium Fork Oil 15w/30 or Silkolene Fork Oil SAE 15, would be appropriate for standard rate springs. Maybe SAE 20 for higher rate springs. SAE 10 is standard on modern machinery and you may find the thicker oils harder to come by.
  2. Renew the alloy caps on the damper tubes; they control the rebound damping and do wear out.
  3. Check that the damper rods are straight and moving freely (and, of course, the forks themselves are straight and move freely).
  4. Put in at least the recommended amount of oil - a little more doesn't hurt. (Don't go mad though because it might blow your seals.) And try to get the same amount in both sides. Ideally, you'll do this on oil level rather than volume, although you need to be fairly determined to do this on the standard Roadholder fork.

Finally, there is no bump stop on fork extension so they will knock a little if you get the front wheel off the ground.

At 300lbs/140kg you are essentially two-up when solo. But a Commando is more than capable of coping with this kind of load. With a standard set-up, you would be most likely to notice the forks bottoming when braking over bumps. Ideally, you would match the springing, damping and ride height to the machine and riders weight and it’s intended use.

Ride height:
As a good starting point, aim to use up 1/3 of the available travel with the rider seated normally, feet up, bike at rest. You can determine the fork movement by fastening a cable tie around the fork tube - it gets pushed up when the forks move. Adjust by adding spacers above the top of the spring.

Spring rate:
On a smooth road, brake steadily but quite hard from about 75mph/120kph to a standstill (braking over some distance removes the effect of damping). With the correct spring rate there should still be around 1/4 of the travel left. You’ll need a selection of springs to experiment with.

Damping:
This is very subjective and, within quite broad limits, depends on the kind of ride you want and needs to be tuned by feel out on the road. Roadholder forks suffer from “stiction” and a static test is no real substitute but as a starting point, “pump” the forks with the front brake applied. They should move quickly and freely but not “bounce”. On a Commando, you are limited to changing the weight and quantity of oil. You can mix up your own weight of oil by combining two different monograde fork oils, e.g. 12.5w from 10w and 15w. Extra oil introduces air springing and improves the ride but you do risk blowing the fork seals. Note that too heavy an oil or a mismatch between compression and rebound damping can make hydraulic units "jack up" over successive bumps (whether it “jacks” towards full extension or full compression depends on the fork characteristics).

Check out Maxton Suspension for a conversion to modern internals. But, on the outside, it looks completely standard. They will match the fork to the machine & rider’s weight and intended use.


14 January 2001

I'm interested in fitting mag wheels to my Commando ( pause here to let outrage die down).

The problem lies in the cush drive fitted to the back wheel. I assume that if I just remove it the lack of shock absorption will have an adverse effect on the transmission.

K Schafer

Can't see any reason for outrage. Peter Williams did it.

It is inevitable that the transmission, principally the gearbox, will suffer and ideally you would have a large cush drive like the 850 Mk3 or a modern Jap. But whether this becomes a problem depends on the use you expect to make of it. The original Commando, and Dominators and Atlas before, didn't have a cush drive and many of them ran up high mileages without destroying their gearboxes.

The early cush drive, on the drum bake models, was a rather puny affair and it's debatable whether it added any more shock absorbtion than the tyre. I don't know of any shock absorber clutch or engine sprocket/pulley conversion, although it sounds like a good idea.

Belt drive exponents say that they provide a degree of shock absorption. And, although I'm not entirely convinced, there's no doubt that replacing that heavy chain and clutch basket with lightweight items is beneficial to the gearbox.


7 March 2000

Just got my hands on a Dunstall 810 kit for my 750 Commando but the original (Norton) head bolts/studs are to short?

Darren Jeffery

Can anyone help?

Drew Robertson was making copies of these big bore kits; does anyone have contact details for him?


14 Jan 2000

My Mk3 Commando leaks oil regularly, more so when left to stand for prolonged periods. The sump is filling with oil, does this make it leak more? I notice that the anti-drain "valve" has been removed from the timing cover, is there any reason for doing this?

Steve Bailey

Mk3s were the best assembled of all Commandos and, as British bikes go, were quite good in the oil leak department. But the years pass, bikes get taken apart and put back together, plus the Japanese have increased our expectations. No Commando should leak badly, even with a sump full of oil, but your wife is never going to let you bring it into the kitchen. If you're worried about your garage floor just put a newspaper underneath to catch the odd drip.

The anti-drain "valve" was fitted primarily to improve starting, the electric start is feeble at the best of times and stands no chance with a sump full of cold oil. So long as the anti-drain valve operates freely there is no reason to remove it (although I leave it out of my race engines, it's just one more complication). The only leak problem peculiar to the Mk3 is the primary chaincase which needs to be kept full of thin oil for the chain tensioner.

To reduce leaks, take a look at the following :

Because oil leaking from one place runs down or is blown around, it can appear to be coming from somwhere else. You'll have to wipe the bike down with a rag and keep checking to see where the problem originates. Tiresome but worth the effort. Finally, if you have eliminated the probable then look to the impossible. For example, I had a set of crankcases with porous castings. Fortunately treatments are available to cure this.

 

Update 7 Mar 2000

The oil is apparently coming from the air box via the engine breather. All above points have been checked. Replacing the timing cover anti-drain valve has improved matters a little. The Mk3 breather oil seperator has been removed by a previous owner.

Does anyone have any suggestions about the oil leak? Also, why doesn't the Mk3 breather oil seperator, which is connected to the inlet manifold, mess up the carburation?


10 July 1999

I'm a new Commando owner and I need to replace my head gasket. Are there special tools involved? Head nut number 2 and the cylinder nuts seem to be an odd size. A 1/2" wrench is too small and 9'16" is too big. I miked the nut at 17/32". What is that? How do I get this head off? The manuals say nothing about this problem.
GS

The fittings on a Commando are a mixture of BSF and UNF/UNC with the odd Whitworth and Cycle (26TPI) thrown in for good measure. As a basic rule of thumb, anything that was new on the Commando, i.e. the chassis, is UNF/UNC, anything that can trace its history back to the Dominator, e.g. engine/gearbox, is BSF/Whitworth. Engine cover screws etc. are Cycle thread. After 25 years a Metric bolt or two may have crept in as well.

Off the shelf bolts can often be identified by markings on the head as follows :

UNF/UNC A small circular depression about the same diameter as the bolt stem (nuts stamped with a line of circles)
BSF/Whitworth A plain smooth head
Metric "M" but see below

Other markings, e.g. "8.8" indicate the grade of bolt. "8.8" is a high tensile bolt and is the most commonly specified for general use. Note that older bolts may be marked "M" or "H" to indicate a high tensile bolt ("M" medium, "H" high). Confused? Well each bolt manufacturer does his own thing.


There are 10 bolts/studs holding the cylinder head down. Four you can see easily near the spark plugs, one bolt & two nuts down holes at the front of the head and three nuts underneath going up through the barrel - one at the rear and two under the exhaust ports. If you've never done one before, look at a head gasket to figure out the positions.

To remove the head you will need a minimum of a 5/16BS-1/4W 3/8" drive socket, with suitable extensions, and 5/16BS-1/4W & 1/4BS-3/16W ring spanners (British for wrench). The head bolts are tight; if you use the wrong size spanner and round off the corners of the recessed nuts you will never get it apart! You may need to relieve your spanner to fit between the bottom rear nut and the barrel.

Turn the engine to bring the pistons to the top of their stroke. The bolts/nuts should be released in sequence and incrementally (i.e. back them all off 1/4 turn before going back to the beginning) starting with the centre front bolt. After backing off the bolts/nuts leave the centre front bolt engaged while you remove all the others. The head should then lift on the valve springs when you remove the centre front bolt.

Refitting is the reverse of disassembly. Torque settings are: 3/8"bolts/nuts - 30lbft, 5/16" nuts - 20lbft. However it is strongly recommended that you obtain either the Haynes "Norton Commando Owners Workshop Manual" (ISBN 0 85696 125 6) or the official Norton workshop manual before proceeding.


23 May 1999

I own a 1970 Norton Commando Fastback & am interested in converting twin
Amals to single carb, either Mikuni or Amal. What do you recommend &
can you recommend distributor/kit?
L.Wood

I had a single carb conversion on my ex-police Interpol Commando 850.

Advantages :

Disadvantages

The Stirling single carb conversion for Norton Commandos is available from Mick Hemmings Motorcycles. Available to suit either Mk2 or Mk1 Amal carburettors.


9 May 1999

I am having trouble finding the original pipes and silencers for my S-type Commando Roadster. The pipes on it are less than perfect due to a slight brush with pavement a few years ago.
Geoff Rotheram

A beautiful and distinctive bike with absolutely no ground clearance problems. Demonstrating the S-type ground clearance. And a guest appearance by Pete Lovell.

S-type pipes (headers, silencers, heat shields and brackets) are being manufactured by T J Wassell and should be available from your dealer. In case of difficulty or trade enquiry contact Tim Wassell .


4 Jan 1999

I just purchased a Norvil rearset kit from Mick Hemmings. Do you
possibly have any suggestions on how to fit the kickstart so that my
foot can reach the gearshift?

Joseph,
Sweden

The answer to your question is basically a big hammer! (but see below).
It depends which model Commando you have, how you fit the rearsets and, most importantly, which kickstart lever is fitted. Let's assume you have a Mk2 850; the rearset's gear linkage is in the Tickle style which pivots on the footrest with a long curvy pedal arm and the kickstart lever kinks out some 60mm to clear the standard footrest and exhausts. With rearsets the kickstart lever doesn't need to kink out at the gearbox so you'll need to heat the lever to red hot and bash the kink to reduce it to about 25mm - just enough for the gear lever to go between it and the gearbox. Needless to say, you must take the lever off the bike when you do this! The lever must still bend out to clear the exhausts so kink it out again, much shallower this time, about half way up. Also, reduce the bend at the bottom of the lever so that instead of coming up at right angle to the pinch bolt, it is nearer 45 degrees to it. I'm afraid you'll have to experiment to find the best shape for your bike and it will make rather a mess of the lever. Fit the kickstart lever so that it is angled forwards to clear your shin. You can also try bending the gear lever outwards.
My personal preference is not to use the gear lever supplied with the rearsets at all; all those pivots and the long lever make for a very sloppy change. Better to reverse the standard gear lever. If you can't live with a Triumph style 1 down, 3 up shift you can fit a reverse action camplate. This is how the Commando production racers were setup. With a reversed gearlever, the kickstart needs to be essentially flat at the gearbox but again it should kink out about halfway up to clear the silencer and footrest. Check it clears the gearbox inspection cover screw.
Take a look at the kickstart on Mick Hemmings' Production Racer.
Clearing the silencer with the kickstart can be a problem, especially if you have the wrong front pipes for the silencers or badly fitting pattern ones so that the right-hand exhaust doesn't run close into the lower frame rail. I'm lucky, my bike has an S-type system with 2 high level pipes along the lefthand side.

Sammy Miller has recently introduced a folding kickstarter in the Ducati/Suzuki style. Pivoting at the gearbox, it lies flat to the bike but folds out to clear footrests and exhausts. In conjunction with a reverse gear lever this is the perfect solution. Available from Sammy Miller direct or Mick Hemmings Motorcycles.


4 Aug 1998

Please could anyone help me to find a wheel builder to rebuild my Commando wheels
Ginger Payne

Central Wheel is highly recommend. They instantly recognised a bare Mk3 Commando rear hub - most impressive.
Central Wheel Components Ltd, 8&9 Station Road, Coleshill, Birmingham. 01675 464221.

In the south there's Alf Hagon, 7 Roebuck Rd, Hainault, Essex (NE London). 0181 502 6222.

While you're at it, consider fitting 18" rims, WM3 front & WM4 rear are a good choice to take 100/90x18 and 120/80x18 tyres respectively (don't be tempted to go too wide or you'll suffer from high speed weaves). Metzelers (ME33 front, ME1 rear) are good but there's lots of choice, unlike 19"ers.


16 Jul 1998

Mikuni carb conversion :
I can't say enough about this. The best improvement I ever made to my Commando. Better starting, smoother idle, no leaks or fouled plugs. And the bike pulls like a freight train.This sounds so good I think it's time for a ride.
Barb Barber

Mikuni carburettor kits are available from Allens in Nottingham, 01949 836733 and Rocky Point Cycle, 2509 Linebaugh Road, Xenia, Ohio, (513) 376 9792.