Discussion in 'Norton Commando Motorcycles (Classic)' started by pierodn, Apr 12, 2018.
Ha ha "swarf" sorry,
A pair of new concentrics I bought had the flat top spray tubes and 4 ring needless fitted!!!!!
The slides were so sharp you could shave with them
This was around 18 years ago so I'm not sure where they were being made then?
I thought I'd treat my bike to a brand new pair as my old ones were a bit worn but they went on my mates combat and they are still on there and still running well,
The only work he has done to them is new needless and needle jets
Are these those trouble free, all problems fixed, Anals you blokes were telling me about?
18 years ago? They were probably Spanish ones then.
No Ken... they aren’t the same ones... and you know that! We’re talking Premiers as being the new saviours, not old Spanish MK1s.
Apart from the too small idle jet, the Premiers on my Bonnie are faultless. Combined with a Tri-Spark the bikes starting and low speed running are transformed.
They are definitely not trouble free but are very good once set up right,a bit like a Norton commando
Why is it that bikes are running better with 19 thou pilot jets? Is it the change in petrol?
My mate has a big bore t160 with 30 mm amals and 21 thou pilots in re sleaved carbs with a premier pilot conversion
My t160 has three 28 mm VM mikunis and he has never forgiven me for it
Does the number mean ‘thou’?
I thought it was to do with how much is flowed?
Anyway, to answer your question; I haven’t a clue!
I did find it interesting that Amal only do 3 sizes of Pilot jet for Premiers #15, #17, #19.
The old MK pilot pilot jets were available in a gazillion sizes.
Surrey Cycles stocks both Amal and parts made by Autocycle and you can mix and match (probably at Autocycle too).
The best combo looks to be Amal premier bodies in Aluminium alloy not zinc alloy & Autocycle brass slides chrome plated.
Amal tried chrome plating but it failed, Surrey/Autocycle have been doing them for years and no issues, I use one on a B25 in a new pre premier body and have no issues, wear is not an issue and the chrome shows no sign of lifting.
Good info, thanks for sharing that. Not sure why I thought there were only 3 sizes??
Regarding fuel, I think there is a big difference in fuels over the years, and, apart from ethanol issues, I think they run better on modern fuels. Or we might just have learnt things in the meantime.
"only way to have a decent (not good) setting is to go with only half turn of the air unscrew from all tight. With 1 and 1/2 turn of air screw the bike go to 2000 RPM." >
Pilot air screws are as sensitive to float level as they are pilot jet size. Half turn out - as 'best' idle implies float level too low/lean so can't open pilot air much or acts more like opening throttle. Air leaks past slides can act similar, almost stalls to get slow idle by pilot screw then rev's up on slightly more pilot opening. Of course if ignition system not set right, or fails to fully retard, can give similar frustration.
I like the anodised slides, stay up floats and the aluminium viton tipped float bowl valve. I think these are standard in new Premiers.
The float level is arrived flat to the top of the bowl, not under.
The Pazon timing is 31 degree to 5.000 rpm checked with strobolight.
In any case, the spark plugs are lean.
You might consider checking fuel level, rather than float level?
From the Amal website: The correct fuel level for all Mark 1 Concentric carburetters is 0.21" plus or minus 0.040" below the top edge of the float bowl. Thus when the needle valve is being held shut by the tangs of the float, the level of the fuel will be between 0.17" to 0.25" (4.33mm to 6.35mm) from the top of the bowl.
Who knows, mysteries like this often turn out to be nothing any one thought to mention. Might still diddle float up/dn for "fuel level" to see if any affect. Unless crank degree wheel indexed, or even if it had been, Pazion may yet be a tad over advantaged for nice idle.
From a 2014 post to the NOC about the new Premiers:
"i did have a problem however with the new style removable pilot air jet in the left hand side. I could not cure an air leak problem even though I had taken get care fitting the new carbs this included setting the float hight as from the factory they seem not to come ready set for the sloping fitment of a commando. The fault turned out to be the removable jet had been screwed in ti tightly an sheared in the body when made. This took some finding as I had not touched the jets thinking they would not need removing as they were new an so not blocked."
Also from the same thread:
" i got two for my mk2a an had to file them as they where supplied as they where to Norton back in the day. If I had known a would have ordered the mk3 type that come with the flats already machined on and the later sectioned spray tubes. "
And here's another resource that I had never seen before. Mostly about the pre-Premier, but does mention the Premier when appropriate, so not ancient:
Piero: Did you get this sorted yet? What's happening?
I sm wayting the new 19 pilot from Andiver.
But i think this will be not solve the problem of idle and air leak.
Now with the 1972 old carb the bike runs great.
I prefer old carb than Premier that i dont use on my bikes.
Better to spent money to overhaull the old carb.