First start Commando

Hi everybody, I am Dimitri from Belgium. A new member, even though i visited this forum many times in the past. Even when i did not have a Norton at all. The forum provided loads of good info for my bonneville, especially Amal-related.

For the moment I have a total of 4 brit bikes. 2 oldtimers (Commando Roadster and a Bonnie) and 2 modern retro bikes (a Thruxton and a Commando 961). I do all of my maintenance and rebuilds myself. I built some custom bikes for friends, mainly retro or caferacer style bikes.

The commando is new to me. I bougt it a few months ago. The first vehicle i bought that was rebuilt by someone else. Nice job the man did visually, but i find it hard to thrust people claiming they did an engine rebuild. So i basically paid for wat i saw from the outside and took the rest for a surprise. The commando was once driven after the rebuild. And the owner told me it needed adjustment. It was in his garage with a dead battery so i never heard it before i bought it.

This week, i finally found some time to get the Norton going. Trying to start as-is with charged battery was no success. After 30-40 kicks, nothing but kickback. The compression is very high compared to my 750 bonnie. I can kick the bonnie very easy. But i can stand on the kickstarter of the commando, with my 80kg, without it getting past compression.

Anyway. I did not like the kickback, so replaced the boyer by a Pazon Surefire. Connected everything and i have a nice spark. I do have a voltage drop in the wiring harness to sort (kill-switch probably, cause the harness is new). But a bypass-wire is connected.

I cleaned the amals, and made basic settings to get it running. (i know amals from my triumph that runs really perfect with them). I noticed the float bowls to be a little warped (gaskets do not seal perfectly, so this needs to bee fixed). And after a while, the commando started. But... it would only keep running when playing with the throttle, and after a minute or so, it quit. It looks like the engine burns all the fuel from tickling, and can't suck up fuel itself.

Now my questions: the carbs are not tuned yet and the pazon is only set statically. Both are difficult to fine-tune if i can't get the engine to at least idle. The only irregularity i could find was the warped float bowls, but i assume (float chambers operate at atmospheric pressure) that would cause only a leak and no poor running. What is the basic air screw setting for a stock commando 850? I use 1,5 turns like my Bonnie now.
And last question for now. Is there an easy way to balance the carbs static? I do have vacuum gauges, but for basic adjustment on my bonnie, i can remove airbox panels, and reach into the bore of the carbs. The commando airbox doesn't allow this, and the sound of the slides touching the bottom of the bore is not really noticeable either.

Hi Dimitri and welcome.
Thereare others here much more knowledgeable than I am, however I can tell you that my stock Mk3 has the ar screws set around 1.5 turns, as you have yours set now.
Spitting back usually means an overly lean condition exists. Are the carb to stub and stub to head seals good? Also, be careful when tightening these up. Overtightening will cause the flanges to temporarily warp and leak or sometimes cause the throttle body to warp and sides to stick on a carb that has low wear.
If air is getting in those connections it could cause the problem you have described.
Another thought- reclean the carbs, you may have some crud in one or both. I have found the best way to do this is in boiling soapy water. Take the carbs apart as much as possible and throw everything in a small metal pail.
Heat the pail with a camp stove or similar and get the water boiling rapidly for five minutes or so. Remove the parts with tongs and use compressed air to blow all ofthe water away from the carb body. It will dry very quickly and completely because of the heat still in it along with the compressed air.
Finally check for good fuel flow from the tank. Actually, this should be done before taking the carbs apart for recleaning as that may prove to be unecessary if the fuel taps or screens are partially clogged.

Glen

I forgot to answer your question re carb balancing. This is tough to do perfectly without the bike running well, so I would start by using a drill bit that lifts the slide to what will hopefully be a high idle position. You will need to remove the rubber hoses that go from the carbs to the airbox. Slide a drill bit of appropriate size in just under the slide cutaway so that you can see the end of the drill bit hanging out of the carb. Turn the idle screw in until the end of the drill bit drop a tiny bit. Do the same for the other carb and then using two drill bits of the same size inserted in both carbs, adjust the throtte cables until both drill bits drop a tiny bit at the same instant when you turn the twist grip just beyond taking up cable slack.

Later on you can set the individual air screw and idle stops by ear, then use the drill bits again (not necessarily the exact same size this time though) to synch the slides for throttle pick up.

Glen

Hi Glen, thanks for the reply.

As for your suggestions: i stopped overtightening many years ago. So that is fine ;-). I checked good for air leaks. And allthough also difficult to check with one hand at the throttle. I am pretty confident the manifold-head and manifold-carbs are sealed properly. But i will triple check.

Carb part cleaning is done in my heated ultrasonic cleaner, after that all parts go for 10 minutes in clean running water. And after that, all parts are blown dry with compressed air. So i think that will be fine too. But... you're right. A carb can't be clean enough.

You did get me thinking about something else. I noticed the float needles are still the brass type. And the fuel level in my tank is near empty. I struggled a lot with that combination on my triumph. If i tickle the carbs with low fuel tank level on the Norton now, it is clear the needle of at least one carb closes fuel supply by it's weight

And that was the tip i was looking for to make the basic balancing adjustment. I did not know the rubbers were removable. The drill-bit thing is my step one on the triumph also.

Definitely clean the carbs. Sounds like the typical low-speed plugged passages. Does the bike have a fiberglass tank? May be gumming up the carbs with deteriorating resin.

I paid special attention to the idle circuit of the amals. the passages were perfectly clear but that would not exclude the possibility of blocking jets immediately after turning fuel taps on. I'll clean them again tonight.

Tank is not fiberglass, but even if it was (i have some fiberglass tanks on other bikes), our fuel does not contain harmful additives for epoxy resins.

quote: "I noticed the float bowls to be a little warped (gaskets do not seal perfectly,"

I remember there is a side passage in the bowl itself where fuel is drawn up through the side of the bowl and into the main body casting. This is the fuel feed for the idle circuit IIRC.
A leaky bowl gasket in this area may play havoc with idle circuit fuel supply as will any leaks around the little aluminum discs used to plug the cross drillings.
Are the o-rings on the mixture screws in good order?
Be certain the idle circuits are clean, leak free, the fuel level is properly set and any air leaks are minimized.
Look up the Jim Bush notes about the Amals, the info is valuable.
Another thought, any condition that causes low vacuum will contribute to idle difficulties.
All the Best.

Okay, i got a little further this evening.

Removed carbs again, checked and cleaned everything again, and noticed that the needle from one carb was not fully seated in the slide. is was in the first spring winding. I did not remove them before, so did not notice. Put everything back together, tried to start.. nothing

Removed spark plugs to check. Only one coil is giving a spark. So i had 2 problems this morning. Bad running and starting probably caused by the needle. And cutting out after a few minutes caused by a failing coil.

Made a test setup with another coil i have laying around (also a bad one, but at least i knew it works when cold. Bike starts at first kick and idles/runs as can be expected (good, not perfect yet). So a good starting point. Finetuning this weekend with the Bonnie coils, and hopefully no more issues.

@AntrimMan: you were right about the idle circuit fuel pickup. It can be a problem when air gets in caused by warped bowls.

See what this guy have done about the idle circuit issue http://www.motos-anglaises.com/technique/carburation/tuto_circuit_ralenti.pdf Sorry in French but pictures are self explaining.

When you see it , it looks so simple that you think :" Hey FTW, why don't Amal do it first place ?"

JRD said:

See what this guy have done about the idle circuit issue http://www.motos-anglaises.com/technique/carburation/tuto_circuit_ralenti.pdf Sorry in French but pictures are self explaining.

When you see it , it looks so simple that you think :" Hey FTW, why don't Amal do it first place ?"

Click to expand...

Interesting solution. Here is a google translation:

can
-
be a solution for r
solve the sealing of the
circuit
idle
on Amal concentric
Unevenness
:
The
e clamp (excessive) of the vessel deformed,
this
which generates an air intake in the
circuit
idle, to the joint plane.
loss part
Miss or complete idle.
Cutaway view
partial
before
.
It is here that we will intervene
.
Cutaway view
partial
after
modif
.
The conduit is extended by a tube which
will prick
in an O-ring
housed in the
vessel.
Extraction of the cork.
For cleaning rules.
drilling
an inspection opening side
jet
.
For the same reason.
Deburring
brushing
belt grinding
Carefully, s
ur all along
u
eur
the conduit, s
auf the sector
u plug
conical (direct sealing).
Type of in.
the
solution
stuck
e in the conduit
.
Realization of the
Amage
.
installation of
'
u
n
s
iège
.
... then j
anointed
.
tube
emm
a
nchée.
View p
Seamless lace
vessel.
Manufacturing a cylindrical plug.
realization
simple wireless
e
mounting
or tapping the body.
drowned cap
a few millimeters
in
the
housing
existing
previously polished
.
Reb
or
cap
swimming.
Once in place
.
combined stop
between the two bodies for
maintained.
It is finished.

E.E. Cummings road a Norton? Hey Kenny, any relation?

Hobot's French cousin.

I have a copy translated to English using MS Wordlingo. Not sure how to get it to the forum.

Saber13 said:

I have a copy translated to English using MS Wordlingo. Not sure how to get it to the forum.

Click to expand...

Copy and Paste?