Commando Running rich no matter what

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Charger
Sometimes it is better to change tact than drive yourself mad trying to resolve a singular problem with an ancient possibly worn out set of carburettors. A single Mikuni runs a Commando beautifully. I'd be looking at that as an option long before solving your current carbi nightmare. Just chuck em. They are crap!

I don't want to upset anyone but if you like tinkering forever, go for it. If you like riding your Commando, junk the problem and move on.

Phil
 
CHARGER said:
Doesn't seem corroded it's very shiney and clean looks like someone has epoxied the holes
Or something I just picked that orangey stuff out and seems like epoxy to me.

I would assume when the bowls are full fuel would be flooding from these holes into the pilot mixing chamber?

Wonder if those holes are stock and normally under a welsh plug or have been drilled by someone.... Either way I assume
They have to be plugged up
Click to expand...


Yes someone has been in there.

When we have a set of carbs that are being difficult we often remove those plugs and really clean out underneath them and make up sliighly oversized plugs to tap back in - but only clean not modify.

But if a PO has been in there who knows what has been done.

Honestly I would look at a new set of bodies at least.
 
Charger, you're photography is great! Plug pictures clear up any doubt about whether fuel rich or oil fouled, definitely fuel. Can you post some more shots of the carbs and parts from different angles?
 
olChris said:
Commando Running rich no matter what
Click to expand...
1. If your carbs have the pressed in air/pilot jets then these would be a small threaded holes.
2. If your crab have been modified (pressed in pilot drilled out and plugged from the other side) to take a screw in pilot jet, this is where they would go, into the small threaded hole.

Either way, yours seems to be screwed up big time.
Sorry!
 
That's not quite right pete, the threaded hole you speak of is just out of sight at the top of the photo. Would be drilled on the flange in line with the cast in pipe on the left of the right pictured carb and on the right of the left pictured carb. That thoroughly messed up plug shown should be nice clean brass. It is used to plug the hole needed to drill the two tiny holes in the bore of the carb.
 
Cheers

Well I have filed the holes with some steel bond "epoxy/metal" filler
And I'll see how it goes got nothing to lose.

When shopping for new carbs other than 932 are there any specific
Model numbers or anything I need to look out for? Ones in my eBay
Link on page one seem like they will fit the bill?
 
Hi

I think jerry doe sells carbs ,check it out.

Need carbs myself amal premier 932 72 bat bike. Problems like you're having can give you information overload, I like to step back and mull things over,but I an a lazy bugger.

Crack on
 
Biscuit said:
That's not quite right pete, the threaded hole you speak of is just out of sight at the top of the photo. Would be drilled on the flange in line with the cast in pipe on the left of the right pictured carb and on the right of the left pictured carb. That thoroughly messed up plug shown should be nice clean brass. It is used to plug the hole needed to drill the two tiny holes in the bore of the carb.
Click to expand...
Thank, Biscuit. They still look pretty messed up though.
Just to add, a worn out Amal is going to introduce air causing a lean condition and the inability to idle.
Although a clogged pilot circuit will effect idle by blocking air also, it would still run and not cause that kind of fouling IMO.

Needle and needle jetting may be more likely the problem.
Totally blocked aircleaner? Bad or poor spark? Weak voltage? Blocked exhaust?
 
CHARGER said:
Cheers

Well I have filed the holes with some steel bond "epoxy/metal" filler
And I'll see how it goes got nothing to lose.

When shopping for new carbs other than 932 are there any specific
Model numbers or anything I need to look out for? Ones in my eBay
Link on page one seem like they will fit the bill?
Click to expand...

Those are correct, but be aware, there is an improved Amal available, called the "premier" which looks the same, has hard anodized slide, removable idle jet. They cost only a bit more. Read all about them here, complete with a fitment chart that shows the proper part number: http://amalcarb.co.uk/
 
I actually wonder if the hole left after those plugs were removed for whatever reason, were filled totally with epoxy or something, thereby effectively eliminating the entire idle circuit. There is a real tiny mixing chamber in the body of the carb sealed by what should just a thin piece of brass. If you Charger, or the PO have filled that down into that chamber I think you're screwed. I think Rohan is correct in saying maybe running through the main and needle jets at "idle" will cause your chronic richness.
 
Biscuit said:
I think Rohan is correct in saying maybe running through the main and needle jets at "idle" will cause your chronic richness.
Click to expand...
If the pilot system is somehow blocked,you won't be getting enough fuel at idle. You won't yet have enough air flow to pull any fuel through the needle jet.
Even when the needle jet begins working, fuel from the pilot system is still necessary to give the correct mixture. Without that pilot fuel,you'd still be too lean ,not too rich.
Even at full throttle and maximum power,about 1% of the fuel flow is coming through the pilot jet.
 
My guess is those plugs were removed from the carb so as to enlarge the 2 small orifices just behind the spray tube. It is common practice with an alcohol conversion. In such cases the pilot jet is also enlarged. A screw in pilot jet in the threaded hole in the body will fix the pilot jet problem but if those holes have been enlarged then you will never get the bike to idle on regular fuel and it will be rich like you describe. Been there and tried that.
See if you can visually compare the orifices alongside another Amal from another bike. If they have been enlarged it is easy to see when compared alongside a good carb.
Ando
 
CHARGER said:
When shopping for new carbs other than 932 are there any specific
Model numbers or anything I need to look out for? Ones in my eBay
Link on page one seem like they will fit the bill?
Click to expand...

As I already mentioned, there are at least six variations of Commando 932 carb. For one thing, those ebay items have the wrong banjo fittings to suit a MkIII, they are also listed as having number '3' slides and the original 850 slides were '3 1/2'. Original 850 carbs also had the 928/107 stepped spray tubes and special 928/104 needles. Original MkIII carbs apparently had the 622/056 float bowls with the larger 0.125" float needle seat drilling, however still I'm not sure why this was somehow necessary for the MkIII?

Note that the original Amal carb specification would've been stamped on a pad on the right hand side of the carb. This number can often be used to identify its original specification and which make and model of bike the carb belonged to originally (unless the number is '300/301') so what are the numbers on your carbs (L/R 932/??)?
 
Another thing to be aware of is if you compare your old carb bodies with new replacement look very carefully at the mounting flange and the part of casing that doesn't have throttle stop screw in it but would have if carb was machined to fit on others side (on premier its about removable pilot jet).
You should see small flat this stops carb bodies fouling each other as the space between them is to tight. If your carbs don't have these flats you will need to file them on or carbs will not seal to flange before the foul on each other. Then you will have big air leakage issues an you may even bend the mounting flange if you mistakenly just keep tightening the nuts down.

It has been said that because carbs where common to different makes an models Norton originally just bought them then machined the flat's in house. But for the mk3 they got Amal to do it so only if you order Mk3 carbs will they have these important flat's.

That said if you order direct from Amal they may put them on for you. They did however advise me that they felt the mk3 was the best spec of carb due to cut away spray tubes an that they recommend that you should fit that type to earlier Commando.
 
toppy said:
They did however advise me that they felt the mk3 was the best spec of carb due to cut away spray tubes an that they recommend that you should fit that type to earlier Commando.
Click to expand...

That's strange, according to Amal's (Burlen's) own spec. list, the 928/107 stepped spray tubes (and 928/104 needles) would normally be fitted to all 850 carbs, not just MkIII type.
 
X-file said:
Biscuit said:
I think Rohan is correct in saying maybe running through the main and needle jets at "idle" will cause your chronic richness.
Click to expand...
If the pilot system is somehow blocked,you won't be getting enough fuel at idle. You won't yet have enough air flow to pull any fuel through the needle jet.
Even when the needle jet begins working, fuel from the pilot system is still necessary to give the correct mixture. Without that pilot fuel,you'd still be too lean ,not too rich.
Even at full throttle and maximum power,about 1% of the fuel flow is coming through the pilot jet.
Click to expand...
You may be right about this, but I was talking about the entire idle system being blocked, mixing chamber perhaps being filled with epoxy even. In this case not only would fuel be nill, air that should be mixed with it would be absent too. Charger said he could keep it running only a short while before the plugs fouled by blipping the throttle. The only way to do this without an idle circuit would be to drag fuel up through main jet, needle jet, and past the metering needle. In a good carb there is a momentary richness as the throttle is snapped open to prevent a flat spot. My thoughts are that by blipping the throttle, to keep the engine running, you are getting this initial richness but when the throttle is closed you are not getting the pilot air to maintain the fire...equaling plug fouling richness. Admittedly I'm trying to think like an Amal carburetor here and may be a bit off, but no matter what the issue is the carbs both have to be mechanically up to snuff before this richness can ever be tuned out of them. To bad you don't live in the states Charger, I have a nice set of used 850 carbs you could try. Is time of the essence?
 
L.A.B. said:
toppy said:
They did however advise me that they felt the mk3 was the best spec of carb due to cut away spray tubes an that they recommend that you should fit that type to earlier Commando.
Click to expand...

That's strange, according to Amal's (Burlen's) own spec. list, the 928/107 stepped spray tubes (and 928/104 needles) would normally be fitted to all 850 carbs, not just MkIII type.
Click to expand...


I bought a pair of Premiers for my mk2a 1974 850cc not knowing about the flat's an thinking they would fit as they were a direct replacement (yes I know silly me :roll: ). So after check on this forum and with Roger at RGM that I had got the right carbs I filed my nice new carbs (very carefully). Then a problem with removable pilot jet of L/H carb ment it would not run or tick over correctly. The carb was returned to Amal how fixed the issue and returned carb with hand written note saying I should have got mk3 version due to spray tube mod an fact that flats where machined on by them.
 
Should be able to spritz the passages to see if blocked or not. I filed V notches in my Combat Amal spray tubes for a bit more off idle throttle snap response. Notched spray tubes were first used in 2smokes at they lack low down suction so an 850 w/o the noise baffle flow redistricting mufflers don't really need them but all Cdo can benefit. Amal did study if the height of spray tube matters and found it didn't but I have found a bit lower seating helps the low down response a bit more yet.
 
Ok so that didn't work still rich

eBay carbs look the wrong spec so......

Looks like the premier carbs I need are "PACK 114", think ill just order direct from amalcarb.co.uk
 
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