New member, old troubles...

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Jan 10, 2006
Hello, everyone from this side of the map! First of all I'd like to say sorry once for all for my bad English, and hope you'll be pacient and comprehensive with my mistakes.
I bought my Commando MK2 1974 in Barcelona at some 700 Kilometres (thats about 428 miles)away from Madrid, where I live. I brought it home riding the bike without main troubles. As soon as I got home I dismantled the bike and installed a Boyer ignition (besides many other things...) but now I'm not able to use a strobe as long as it won't rise up 4000 revs. Before the Boyer it did nicely rise, but... The point is that I put the strobe anyway yesterday and I could see one of the rotor marks (mine has two of them) on the far left side, but as I revved up, it just went off and couldn't see it again even at almost 4500revs... Carbs aren't in the best of shapes, but it run great before the boyer.
By the way and in order to keep the box of worms closed I'm not thinking of getting the points back.

Thanks everybody for letting me in and for the help!! :D
Your initial timing is way off or you have the wring connected incorrectly.

To correct the initial timing you need to reinstall the boyer plate with the static timing mark showing through the correct hole, there are 2 holes and only one of the holes works for Commando's, the other hole is where the rotor turns in the opposite direction. The instructions should explain which hole to use, commandos use the Anticlockwise hole which is the topmost hole.

If this checks out then make sure the Boyer Stator wires are connected as per the instructions, if they are the wrong way round then the timing retards instead of advancing as the revs increase.
Thanks, Kommando for your help I belive the Boyer is well installed after taking a look at the link you sent...
I've watched that the bike won't start from cold if I pull the starter, but without it the bike fires after (quite) a few kicks. This afternoon I've pulled the starter just a little bit in order to close the air entrance and the bike revs perfect. I thought, ok, it's just a matter of mixture, but after enrichening a little It just smoked like hell and stalled. Should I change the amals? Good Lord, I long for riding it again soon... :(
Thanks again, mate!
Amals do wear out quickly, these are the likely culprits in order of which wears out first.

Needle Jet
Main Body

But first I would look for something simple and a lot more common than you would think, take off the carb bottoms and make sure the main jets are still in place, they can loosen off and drop into the bottom. The bike will run but full throttle is a mess.
Main jets are still there, but after taking the air filter off I can feel with the tip of my finger that the left hand carb throttle gets jammed without the help of the vibrations of the engine to move... Im seriously thinking of getting new ones and see what happens... I've been looking around and I've found to be the cheapest... Do you know of any others? It's ridiculous, but Amals are made here in Spain and they're really hard to find here. Not even spares or gaskets or...
Thank you!
When you say you pull the starter I am assuming that you are refering to the choke lever. If you are new to British bike ownership you may be unaware that when the lever is in the closed position the choke (or cold starter) is fully on, however the bike should be run with the lever open as far as possible. This is in my view somewhat counter-intuitive and the opposite of most modern bikes where a cable must be pulled to operate the choke. I suggest you hold the throttle wide open with one hand and put a finger inside the carb inlet to check choke slide positions.
You say that your norton ran fine before you installed the boyer.

Doesn't that point towards an error in your boyer install ?

If your bike ran fine before, why pull carbys apart at all ?

Just curious.
Thanks, Dave for your answer. If I hold the throttle slides opened, the choke is fully closed. Now I've opened them a little but have to go to work. I'll tell you later about what happened.
I've thought of changing carbies probably in desperation, because of the slide jamming I reffered and because the bike rises the revs when I pull the choke lever just to line it with the handlebar... :?, but you're probably right, Nortonfan, I just thought that a new Boyer ignition is more reliable than 25k miles amals (and I pressume this should be, in case both of them are in the right hands...)
Thanks a lot, guys!
Unless later model Amals were different, the slides aren't interchangeable from one carb to the other. They're lapped to fit. If one is jamming, maybe they've been swapped over.

I had one jam wide open in second gear in city traffic after I "squirted" round a bus. It was as well that that bike (a 650SS) was magneto ignition and had a kill button right next to the throttle.
I finally replaced the -73,90000km, original Amals on my bike with new ones last spring.
The oldies had new slides, new neeedlejets/needles, but towards the end I wasn´t able to get them to behave decent!
The new ones made me smile,until the slides began to stick.I was reluctant to work on the new slides, but gave them some polishing to make them "fit". This scenario was repeted several times, and I was in dispare!! A friend of mine gave me the suggestion to add some two-strokeoil in the petrol.....The sticking was gone!! My theory is that new tight Amals, doesnt work that well with the unleaded harsch petrol of today!!

From then on, I always add 0.1-0.2l oil when filling gas!

How much oil you add? does it affect the engine's behavior? how about smoke? This really makes sense to me...
My bike have the Interstate-steeltank with approx. 27litres capacity.The volume I mostly fill, is 20 litres.To cure the carbs I add 100-200cc 2-Stroke! That would make a 0.5- 1.0% oilmix! The engine is in my opinion unaffected by the oil, and I have not seen any noticable smoke. I have not yet tried out the lowest amount of oil,that still will do the job,but it might be less than 100cc!!
I´ll try that next summer.

The amal carbys on my 73 850 were well used when I accepted the bike as a trade in on my last 750 Interstate.

I replaced the needle jets straight away, along with the rubber orings.
Also, while they were apart, I gave them a good clean out.
I have found soaking them overnight in your preferred carby cleaner does the job.

They have travelled around 10,000 klms since that "rebuild".
On the way back from a trip to Sydney recently (1000 klms away),
the front of the left hand slide broke off & I presume was eaten up by the engine.

So, I purchased two new slides, one for each carburettor. The rioght hand side fitted fine with a bit bit of "polishing". But alas, try as I might, I could not get the left hand slide to "fit". I ended up ruining the left hand carby very patiently trying to "massage" the new slide to fit into the egg shaped carby body.

In the end I rang a mate that had a spare manifold to mount a single amal carby. He has given it to me on loan to see if I like running the commando on one amal mk1 carby. He has fitted many of these setups over the years to many commandos & loves the setup. I have always thought, well they were built with two, I am going to run two.

Having had the single amal carby on for a week now & done quite a few miles already, I am impressed. I would suggest any commando owner try the setup for themselves. Currently I am running a 270 main jet, everything else is the same.

I also replaced the gearbox sprocket with a 22 tooth one. I have replaced the layshaft bearing also, for any of you that are wondering. I am basically getting the bike ready for a trip around Australia "two up". I did consider buying a newer bike for the trip but I reckon this commando can do the job averaging say 400 klms per day.
I also plan to replace the wiring next with "trailer wiring", that is 7 core. This will get rid of all the excess standard wiring cables. It will also mean no electrical problems, touch wood. I will also replace the standard rectifier & zener diode & put a new battery in the bike before we leave.

It is approximately 15,250 klms around Australia if any of you are wondering.
I've had brand new MK1's on my 850 since a complete engine/gearbox rebuild 2000 miles ago, and it didn't take long for the slides to start sticking (and always as you're taking off from the kerb with plenty of people watching.......!) One trick the I was told to overcome the "oval" carb body is as follows: mine always stuck at, or near, the top of their stroke. So, remove the slide and you should see some wear marks on the slide that show which parts of it are binding on the body. Now get the slide into the "stuck" position and gently at first, start squeezing the carb body with the a large pair of grips on the opposite sides to that which the wear marks are indicating the slide is rubbing. With a bit of experimentation, and the carb in the vertical position, you should be able to see or hear the slide drop when you've hit the right spot and squeezed the right amount. Use something to protect the carb body from the jaws of the grips, as the pot metal is soft and easily marked.
Although I was told it works best with the carbs installed, I found it easier and quicker to do with the carbs off the bike (specifically if you have trouble getting the slide into the carb body in the first place).
This strick has worked for me, and I had to do it all over again whilst selecting the best of two carbs to convert to a single MK1 (as has already been said by "Nortonfan", this is highly recommended if top-end power isn't your thing and you want a 100% dependable warm tickover like I do running around town on my daily commute). I've ended up with a totally smooth slide action right across the stroke of the slide, whereas, when I started, I couldn't even get the slide into the carb without a lot of downward pressure.
Sparkplug - Even if you discover you have an issue with the Boyer, if your Amals have done 25K miles, they will certainly be due for replacement/sleeving. Mine were at 23K and total scrap......
and I had to do it all over again whilst selecting the best of two carbs to convert to a single MK1 (as has already been said by "Nortonfan", this is highly recommended if top-end power isn't your thing and you want a 100% dependable warm tickover like I do running around town on my daily commute).

so it is feasible to take one of your carbs (in my case, a 71 750 with amal 930's) and use a dual manifold? I don't need super top end as I will be cruising rather than racing. For now this might be a great option for me, as my budget for the rebuild is moderate and one of the carbs looks great and the other is trash. I thought that I'd HAVE to install a 34 mm carb if I was going the single carb route

if nothing else, it'll get me up and running quicker and , as budget allows, I can get a 34mm mikuni setup further on down the road.

what a great forum: getting helpful hints from the UK, Sweden, Europe, and even USA all from the comfort of my little computer station!


Karl Hoyt
Yes, you can use either carb (depends on which hand you prefer to tickle with :lol: )
You can also use the standard throttle and choke cables, just remove one of the ends of the "Y" and put it in a safe place for the time you ever go back to dual MK1's. You then have a choice of air filter setups. I just went for a clamp on pattern conical K&N type filter and remounted the ignition switch. There's not much clearance below the frame spar so make sure whatever filter you choose has some clearance. Be aware you do get a rather cosmetically challenged "open" look to the area where the standard airbox was unless you invest in one of the single carb airbox front plates like that which Norvil sell in the UK. I think I read somewhere you need to shorten the width of the perforated filter surround as the single carb sits further back than standard when it's on an RGM single manifold. Not sure about the Norvil manifold or other alternatives.
The MK1 works well as it's great at flowing air, so a single 32mm will perform OK at the top end (rather than great). Going up a size or two on the main jet is all you'll probably need to do. Where a Mikuni scores is it has a more sophisticated idle circuit with a tunable pilot jet. I spent three weeks trying to get a single Amal MK2 to work satisfactorily - I have to say I wish I hadn't bothered. A single MK1 works really well on a Commando. Dead easy to start and tune. No more synching carbs every week if you use it as your daily driver as I do.
Thanks, Hal:

yet another 'helpful hint' I picked up here that I will save in my personal file of helpful hints!

Karl from Cape Cod, Mass,USA
It still seems like a Boyer installation problem to me. If it ran fine before the Boyer was fitted, and the timing marks dissappear from view with the strobe, I don't understand why you should be looking at the carbs.
While at Norton, my ride to work was a company 650SS that we tried a single carb manifold on. I think it was just one of the twin carbs with maybe a main jet change. We'd had a query about maing a more suitable side-car hauler than the stock bike, and this was one idea.

It had better low-end torque than the twin set-up, but ran out of breath earlier. Top end power was off maybe 15 percent. I did have a problem with a head gasket burn-thru, but that may just have been old age. The bike had about 100,000 miles on it at the time.
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