Atlas - newly acquired, problems with running

Chris,

Welcome to Norton ownership. Only going by what you say, I wouldn't say you bought a pup, unless you paid well over the odds.

As soon as you mentioned that carb I saw trouble, although some people still like them. A lot less trouble to set up would be a 30mmAmal Mk1. I don't have an Atlas but I have a Mk1 Amal on my 650ss and the carburation is one area I don't have problems with.

I looked in the Roy Bacon book of Norton twins and I see that your plugs are correct and it would appear that you are running a very rich motor. There will be Atlas owner on here I'm certain will advise you to correct carb settings etc. However, you can buy a new Mk 1 Amal for £89, last time I looked, set up to suit your bike. Fettling a Norton is all a part of the fun, let's hope that carb is your only problem, an easy fix.

Let us know how you get on and maybe a bit more about the bike.

PS: If you are going to leave petrol in your tank during periods of non use, try and avoid ethanol contaminated fuel. If you are NOT in SW England then BP Ultimate is E0 currently. Otherwise you may find corrosion in an unlined tank, melted rubber parts inc O rings and petrol pipes and alsodeposits in the carburetor. This won't help either.

I run my Atlas on a single Amal monobloc. The Mikuni is probably excellent if set up properly, but a monobloc or concentric is easy to set up and the settings are well known. Clearly yours is running extremely rich so that's the first thing I would check. I use NGK B7ES spark plugs - I don't seem to have much luck with Champions. The Atlas is a great bike once it's going properly. Gordon.

Because your plugs are sooty does not indicate that you have a rich mixture and means nothing unless you do a proper plug chop

If you ran the the motor at full revs, then chopped the motor (a plug chop), and found sooty plugs- that would indicate a rich mixture.

The sooty plugs you are finding are caused by your misfire

Mikuni carbs are normally good, everybody with one fitted praises it, and if yours was running ok a few days ago it isn't likely to be the carb is it ? except maybe if your tank is rusty inside it may have blocked the pilot jet.

What about your battery, is it a good one fully charged? Are all your earths good? Corrosion free terminals everywhere? That's the sort of thing I would be looking for first

I find NGK plugs far better in my Commando than Champion

Just thinking, you aren't inadvertainly running with the choke on are you, since you say this is all new to you!

Paul

The Mikuni single carb is usually quite good once set up correctly. Although they do tend to need a minute or two of engine warming before riding off without the choke on.

A big clue in your case might be that you mentioned the demo ride was fine. In which case, I would be looking at electrics first and carb second.

The Lucas Rita ignition system draws a lot of current and generally needs a good battery to keep the sparks flowing. How about trying jump leads to your battery to check a low voltage posibility?

Ethanol in fuel is a real nuisance with classic bikes. It causes parts to disolve or not function correctly ( ie float/fuel level) and many owners complain or rich running.

Lastly.......as someone has mentioned above. Are you leaving the choke on? On Monoblocs/Concentrics you pull the leaver to take off the choke. On an SU you do the opposite. A Mikuni????

The Mikuni single carb is usually quite good once set up correctly. Although they do tend to need a minute or two of engine warming before riding off without the choke on.

A big clue in your case might be that you mentioned the demo ride was fine. In which case, I would be looking at electrics first and carb second.

The Lucas Rite draws a lot of current and generally needs a good battery to keep the sparks flowing. How about trying jump leads to your battery to check a low voltage posibility?

Ethanol in fuel is a real nuisance with classic bikes. It causes parts to disolve or not function correctly ( ie float/fuel level) and many owners complain or rich running.

Lastly.......as someone has mentioned above. Are you leaving the choke on? On Monoblocs/Concentrics you pull the leaver to take off the choke. On an SU you do the opposite. A Mikuni????

hello ethanol getting to be a nuisance with new bikes too , if I were the owner of a Atlas I would fit a SU carb and bin the Lucas Rita ignition and fit electrex world generator with ignition and for spark plugs I use Bosch from Green spark-plugs.co.uk they make for easy starting and reliability. try Bosch W7DTC .I run my 650 manxman on them with no trouble, I rode though the worst rain storm we ever had I was on the M62 for 40 miles homes Hull was flooded the M62 was bad But my manxman never missed a beat it was like a Steam loco with steam coming of the engine, but putting the bike way I got more drenched than coming the 40 miles down the motorway As our roof looked like Niagara falls . the first thing was to clean the bike and then sort me out, well good luck with it all . yours anna j

I believe on Norton twin engines with flat top or concave pistons you want to fit plugs with the 'long protusions' as this puts the spark more central within the combustion chamber and promotes quicker burning of the air/fuel mixture as the flame front developes as a sphere.

The shorter plugs place the spark at the combustion chamber surface and the flame surface area is smaller and dome like thus slower burning. We're talking tiny differences here but every bit helps.

NGK BP7ES in that case. I have used both - no noticeable difference but then I'm not the most sensitive of souls. Gordon.