Commando Running rich no matter what

I had an issue with extremely sooty plugs to the point where the lack of spark was causing poor running conditions. I run a single Mik 34 with a K&N filter and a Pazon EI. I removed the carb, cleaned it and checked the float levels. Also cleaned and re-oiled the filter. It got somewhat better. Then switched to a hotter plug (NGK BP6ES). Issues resolved and a nice tan color on the plugs. I have a Pazon EI.

We both have the same bike here. My float level is even with the bowl gasket though and my main jets are 240. Breathing through a K&N and out through straight unrestrictive peashooters. My sparkplugs will get a bit dark if idling a long time (I think) and will when tuning. Just installed a new ignition and through the process of adjusting the ignition timing, idle, engine off, engine on, etc. plugs did get much darker than their normal almost white to light, light tan color. Is this bike ride able? If with new plugs you hop on it right away does it perform OK? It's very hard to diagnose carb problems through a forum and one never knows the level of expertise of the poster. Are you sure without a doubt the carbs are assembled correctly? Could be the needles have slipped their little locating clips on assembly, both of them doing so would be a bit unusual though. Spray tube configuration would have absolutely nothing to do with a chronic super rich condition though unless, I believe, the needles are not matched to the style you have. A notched tube should be paired with the longer, and slightly leaner, needles identified by 4 thin rings located above the 3 clip grooves. Shorter needles, identified by only 2 thin rings above the 3 clip grooves, should be paired with non notched spray tubes only. Having these needles installed in 850 spec'd notched spray tube'd Amals can cause a rich condition I believe. To the extent you are experiencing I'm not sure but it is an example of miss matched parts I have seen in customers bikes. Along with, believe it not, Idle speed screws switched with idle mixture screws. :roll:

Check that the main jets are tight, these can come loose for whatever reason. B8ES NGK is not the correct plug however Champion N7 YC is. NGK BP7ES is correct.

COME ON YOU GUYS. THE MAN SAYS IT RUNS RICH. Idle mixture adjustments are simply adjust the air bleed into the carb, not fuel in. the idle adjustments will make no difference at all if the carbs are running so rich. [ if they are running rich ] Someone has mentions oil fouling. does the bike blow blue smoke that smells like oil, or does it blow black smoke that smells like petrol.
It would be a pity to buy new carbs to have the bike do the same thing.
I have done a lot of work on my old carbs that are probably worn out, but I can still get 73 mpg [ imperial gals that is ] when I ride very quietly. When I was only getting 45 mpg, the bike still ran well and did not exhibit any signs like described here. IF it is running rich, something is allowing excessive fuel to get through. I also run N9YC or BP6ES or BP6EY plugs [ in both 750 & 850 ] because most of the time I don't ride that hard. .

A good question to ask would be does the bike run ok above 30 mph or does it miss and fart around. If it runs smoothly, maybe it is fuel. If it stuffs around and misses, maybe its ignition. Or maybe its both. Thats the $64.00 question.
Until you can establish what is wrong, you will be banging your head against a brick wall.

does the bike have 3 1/2 slides, Buying the correct new main jets and needles is not expensive so could be a good start. the very basic design of these carbs leads to rapid wear of the jets because of the flopping round of the slides. Pity they didn't copy S U's idea, then we would have carbs that lasted as long as the bikes [ maybe ]
Sorry to say you are going to have to work this out correctly or take the bike to someone who knows what he is doing. that will cost, but at least you will end up with a good bike.
All the best. Dereck [ mechanic ]

Are the plugs fouling because of an over rich mixture.... OR are the plugs fouling because of weak spark....OR maybe you're burning oil and need new valve guides or rings? Just some things to think about......Skip

Why oh why do people talk of main jets ? Replace the NEEDLE Jets and needles.

Torontonian said:

Why oh why do people talk of main jets ? Replace the NEEDLE Jets and needles.

Click to expand...

yes agree, that's the first thing to do. but as a rule, if they are leaking, you know it right away as the carbs will spill petrol when the fuel cap is left on without the engine running.

Derrick, I agree with you on the plugs. Most of my running is around town and I use NGK #6 plugs in both my Norton and Triumphs with great success....Skip

CHARGER said:

I have read and youtubed alot, haven't had heaps of hands on experience though

Guess you could say they are unknown.... I bought the bike a few months back, it had been sitting for a while
last started probably a year before I got it but hadn't been properly ridden in maybe 10 or more prior to this,
has 28000ks on the clock, real kilometres honestly unknown, rear speedo drive missing.

Where I am at now is I just re checked the float levels, adjusted them down even a tad more
to where they are probably between 2-3mm below the lip.

Triple checked the pilot circuit, I can push silicone tube against the pilot screw hole with screw removed
and clearly blow through the passage, have ran fine guitar string through the pilot hole, it has never appeared
blocked even sicne my first tear down of the carbs, they always looked mint inside actually, no varnish

Have tried the single cylinder tune suggested in the manual however I get the same results, my pilot screw
tweaks seem to make no change to it running rich as hell

Guess I lean towards worn needles or slides now, I did notice one slide was a little wet with fuel, could this
suggest excessive wear?

I just ran it again then after the Bowl re adjustment and only after 2mins the plugs are 100% black

Think I mite just buy new carbs and be done with it, any suggestions on the cheapest place to buy?

Click to expand...

Did you verify flow through the passages into the carb throat? A spray solvent like brake cleaner sprayed into the pilot screw hole should shoot two streams of solid liquid up into the carb throat. I've used this method for decades with Carlos Hathcock results. Even if you're dead sure you've wired them out, blown air through them, the chamber that exists could still be full of crud. The welsh plug you see from the float chamber is the bottom of it. Let us know what you find.

concours said:

CHARGER said:

I have read and youtubed alot, haven't had heaps of hands on experience though

Guess you could say they are unknown.... I bought the bike a few months back, it had been sitting for a while
last started probably a year before I got it but hadn't been properly ridden in maybe 10 or more prior to this,
has 28000ks on the clock, real kilometres honestly unknown, rear speedo drive missing.

Where I am at now is I just re checked the float levels, adjusted them down even a tad more
to where they are probably between 2-3mm below the lip.

Triple checked the pilot circuit, I can push silicone tube against the pilot screw hole with screw removed
and clearly blow through the passage, have ran fine guitar string through the pilot hole, it has never appeared
blocked even sicne my first tear down of the carbs, they always looked mint inside actually, no varnish

Have tried the single cylinder tune suggested in the manual however I get the same results, my pilot screw
tweaks seem to make no change to it running rich as hell

Guess I lean towards worn needles or slides now, I did notice one slide was a little wet with fuel, could this
suggest excessive wear?

I just ran it again then after the Bowl re adjustment and only after 2mins the plugs are 100% black

Think I mite just buy new carbs and be done with it, any suggestions on the cheapest place to buy?

Click to expand...

Did you verify flow through the passages into the carb throat? A spray solvent like brake cleaner sprayed into the pilot screw hole should shoot two streams of solid liquid up into the carb throat. I've used this method for decades with Carlos Hathcock results. Even if you're dead sure you've wired them out, blown air through them, the chamber that exists could still be full of crud. The welsh plug you see from the float chamber is the bottom of it. Let us know what you find.

Click to expand...

This is something I think I have overlooked and mite be taking back my "the pilot circuit is 100% not blocked" statement!, did a lot more research last night and took into account everyone's opinions on here and I think logically it has to be the Pilot circuit still, have purchased a #78 drill bit today and am going to pull the bowls off tonight and test thoroughly

I am confident the fowled plugs and smoke is fuel, definetely not grey/blue smoke nor does it smell oily or disipate up in the air slowly
like oil smoke, it is definately fuely and black. After its warmed up and I clean the plugs and run it I can rev it out so everything points
to pilot circuit still.

Will report Back

A plugged pilot circuit(s) will create a LEAN condition so look elsewhere.

Are you sure the choke is off.

Chokes removed

FYI this is the plug after probably 3 minutes of running

Torontonian said:

A plugged pilot circuit(s) will create a LEAN condition so look elsewhere.

Click to expand...

I see now, hmmmmmmm

Plugged pilot jet(s) will make it run on the needle jets, very poorly usually, and they will be rich.
And also make it idle rather ragged - you may need to keep blipping the throttle to keep it alive ?
Does it actually idle - before it soots up the plugs ?

If the carbs are flooding, then it will do what you are seeing - black and sooty plugs.
You checked that the fuel level needles are clean and debris free.
Are the fuel needles those viton tipped efforts ?

What happens if you turn the fuel taps off.
Will it run cleaner and smooth - as it runs out of fuel...

Rohan said:

Plugged pilot jet(s) will make it run on the needle jets, very poorly usually, and they will be rich.
And also make it idle rather ragged - you may need to keep blipping the throttle to keep it alive ?
Does it actually idle - before it soots up the plugs ?

If the carbs are flooding, then it will do what you are seeing - black and sooty plugs.
You checked that the fuel level needles are clean and debris free.
Are the fuel needles those viton tipped efforts ?

What happens if you turn the fuel taps off.
Will it run cleaner and smooth - as it runs out of fuel...

Click to expand...

Ahh ok, it will idle "high" and then after the plugs fowl up it hunts a bit then dies
and definetely have to blip the throttle to keep it running when it start fouling

I have pulled the carbs again, getting to be a fekin expert at pulling them off and putting them on anyway's that's
for sure!

In this pic it looks like the "welsh" plug things at the bottom of the pilot jet have been Fecked with yes?
if they have been breached could that be an over fueling issue?

CHARGER said:

In this pic it looks like the "welsh" plug things at the bottom of the pilot jet have been Fecked with yes?
if they have been breached could that be an over fueling issue?

Click to expand...

Who knows what might be going on if they have indeed been messed with.
That complicates things no end.
Don't think we have ever ventured into that territory here....

CHARGER said:

Rohan said:

Plugged pilot jet(s) will make it run on the needle jets, very poorly usually, and they will be rich.
And also make it idle rather ragged - you may need to keep blipping the throttle to keep it alive ?
Does it actually idle - before it soots up the plugs ?

If the carbs are flooding, then it will do what you are seeing - black and sooty plugs.
You checked that the fuel level needles are clean and debris free.
Are the fuel needles those viton tipped efforts ?

What happens if you turn the fuel taps off.
Will it run cleaner and smooth - as it runs out of fuel...

Click to expand...

Ahh ok, it will idle "high" and then after the plugs fowl up it hunts a bit then dies
and definetely have to blip the throttle to keep it running when it start fouling

I have pulled the carbs again, getting to be a fekin expert at pulling them off and putting them on anyway's that's
for sure!

In this pic it looks like the "welsh" plug things at the bottom of the pilot jet have been Fecked with yes?
if they have been breached could that be an over fueling issue?

Click to expand...

If those carbs were mine i would flick them... Pull the tank, flush and clean it, then seal it. The carb on the left looks like it had water in it long enough to leave corrosion.. and they both look like like there a various "bits" of flotsom and jetsom residue hangin around.. :roll: :roll:

"In this pic it looks like the "welsh" plug things at the bottom of the pilot jet have been Fecked with yes?"
It looks corroded partially away.

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