Sooty plugs, running rich - where do I start?

[CrispinA10]

I don't think that the plugs have much to do with it - have tried all sorts of makes, getting hotter and hotter, but they all soot up within minutes. The latest are  Denson W20ES-U 3051. The carb I took off (which looked relatively new) to start again from scratch was an Amal 930 Concentric, with 250 main. 106 needle, and No.3 cutaway. I have tried a 3.5 as well with no discernible difference.
Downdraft is interesting, but surely everyone's A10 has the same angle manifold, or is everyone making special angled gaskets to compensate? One good thing about the Wassell is that has the adjustable tangs, which the Amal did not, so I could try tweaking those a tad.
The bike does smoke a bit, which perhaps it shouldn't. As I have mentioned, I've only done just over 400 careful running-in miles since the previous owner's complete engine rebuild.
The HT leads look fine - no sparks from the insulation in a dark shed, but that doesn't mean they are, I suppose.
I can't take the bike out on the road at the moment because it soots up too quickly and starts misfiring, which I am worried could seriously affect running in.

[chaterlea25]

Hi Crispin,
A long shot but???
Is there a choke slide fitted? are you operating the choke correctly?
Pull the cable tight for "off"

If the bike has been "rebuilt"  and is smoking are the correct oil feed bolts to the rockers fitted?
These should have a restricting hole in them !!

John

[morris]

The carb I took off (which looked relatively new) to start again from scratch was an Amal 930 Concentric, with 250 main. 106 needle, and No.3 cutaway. I have tried a 3.5 as well with no discernible difference.

What number of pilot jet you got?

[muskrat]

The "new" concentrics don't have a replaceable pilot jet. The jet is equivalent to a #20 and has a 0.016" hole. It can be drilled out and a replacement jet screwed in the original position in the body.
Cheers

[morris]

The "new" concentrics don't have a replaceable pilot jet. The jet is equivalent to a #20 and has a 0.016" hole. It can be drilled out and a replacement jet screwed in the original position in the body.
Cheers

Right... Forgot about that.
Crispin, in that case can it be that the hole has been drilled by the PO to try and cure a weakness and is way to large now?
If I were you, I'd check as per Musky's information.

[Triton Thrasher]

I read the first post, but I still don't know if we're talking about an Amal or a Wassell carb.

Which needle notch is the clip in? Serious richness under ordinary road circumstances is lilely to be a worn needle jet,  too-high needle position, or too-small cutaway.

[trevinoz]

A 250 main jet seems a little large for a concentric.

[metalflake11]

A 250 main jet seems a little large for a concentric.

Been running a 250 for over 20 years in a concentric, perfect burn using a bell-mouth.

[CrispinA10]

Yes, the choke is fitted and works fine. This a new off-the-shelf carb supplied by Draganfly and set up by them for a BSA A10. There is no wear in any of the parts. Yup, it has the same fixed pilot as the previous Amal. No one has drilled anything out. We are talking about a Wassell. I have removed the Amal which was fitted which also led to sooting, but not quickly. The needle clip is in highest position, ie the needle as low as possible. It started off in centre clip. The oil feed is an Eddie Dow type and I have not yet taken the bolts out to measure or look - what should the restriction look? I'm beginning to wonder if oil could be a clue. This is probably a complete red herring, but sometimes if the bike is on prop stand, it leaks oil overnight. A fair bit. I have not yet worked out where from even by careful wiping with kitchen paper and it doesn't leak at all when running. I changed the oil about 50 miles back (first running in change) and it is clean and clear.

[terryg]

Before I fitted sump plates with drain screws, enabling draining of oil that seeps down to the sump when the bike stands unused (wet sumping), I might have posted a description similar to yours of your sooty plugs. I have since reduced wet sumping but still drain before starting unless the bike has stood for less than a week. Plugs now remain a light brown colour.
It seems likely to me that chaterlea could be on the right track, suggesting excessive oil delivery to the top end. If there is any excess gap in the valve guides such a problem will be exacerbated.

It could, of course, be something else entirely.

Having tried two carbs without any impact I'd say it's time to look elsewhere.

[Butch (cb)]

Having tried two carbs without any impact I'd say it's time to look elsewhere.

That would be my view.

[bobandbec]

Smoking on start up and running?
My very limited experience as a novice with these bikes would make me look at oil first. Oil in sump to start with then too much oil  getting through being burnt off?

Peter

[CrispinA10]

Very interesting. I'm beginning to think that this might be primarily an oil issue. I fitted an SRM sump plate with filter at first oil change after rebuild, but that certainly doesn't appear to be leaking. Bought new studs for it at the same time and it is nipped up nicely on new gasket. I had assumed that the leak must be through the large circular ally plug, although it seems tight. I bought new copper gaskets of two types but have yet to fit them. Although it does leave a large pool on the shed floor if left a while on side stand, there is no obvious place from where it is leaking, and the level doesn't appear to go down much in the tank. After much advice from RGS Bill I am using straight SAE 30 - perhaps I should look at 40 in these colder UK conditions.
How should I be checking top end? I assume guides were new at recent engine rebuild but how do I tell if flow is correct?

[a101960]

 There several possible sources for your leak when on the side stand. 1) The primary chain case, not neccersarily from the joint ( but keeping all options open it might be). Oil can also creep along the screw apatures. 2) From the gearbox oil seal ( quite likely), and if the engine has been running oil can sometimes syphon from the oil tank vent. turning to the sump. Oil can leak from two places: The plug, and or the studs. The studs do not scew into a blind cavity so unless you used a thread sealant oil can and will seep from the studs. I have long since given up on copper washers I have found Dowty washers to be far more effective. Sooty plugs can be an indicator that the timing is to far retarded, wrong float level or blocked or partially blocked jets. Do not assume because a carb ( or anything else for that matter) is new that it correct.

[Billybream]

This is an interesting thread, and I think wet sumping is the cause of your sooty plugs. I would take your sump drain plug off and check the amount of oil in the sump before next start up, and if there is say several cup fulls, you will have wet sumping. Its not a major issue, but you must drain off before start up.
This oil can be poured back into your tank, so no waste. Suggest you try and report back. What's happening is when you start the bike the piston comes down and pressurises the crankcase and forces the crankcase oil either out the breather or up the bores past the pistons and into the combustion chamber, hence sooty or oily plugs.