new here and to norton

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Sounds like float level low with lean back fire so bump valve seats back down a tad so pilot screws can have effect adding air. Can never poke a pilot hole enough or too often going by ages of joy afterwards. Zinc oxide is not organic solvent friendly. Staring back fire can also be aggravated by dash too much spark adv.
 
ozbowhunter said:
my friend has looked at the carbs and told me they are 932 but the needles seem very big as I said the best idle we get is with them at there highest slot and no idle screw adjustment so they are to the bottom fully what would be the correct jetting and needles as for the backfiring it is in the right exhaust what can we do to eliminate this
Click to expand...

My 70 engine came with 930's. and the main jets were 220's, the needle jets were 106, and the needle position is the middle slot. You might want to read this:

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

your backfiring into the exhaust is probably an intermittent ignition issue. Maybe a poor ground if it's an electronic ignition or maybe a bad plug or plug gap... Do you have points or electronic ignition?

Edited to add, If your bike is popping on the "downthrottle" as you coast, that's an indication of an air leak in the exhaust... and will go away once you get the air leak figured out.. warm the bike up, pry the exhaust nut stop rings off the fins of the exhaust nut and tighten up the exhaust nuts firmly. Re-engage the stop rings.
 
Normal Norton oil tank on Atlas has a tower on the top, with 2 small diameter tubes , one where the breather pipe from side of engine returns oil, (other tube from tower was an outlet to oil chain on top of the rear chain guard) early Commandos were also like this as they had modified Atlas engine.
On your round oil tank you appear to have no provision for this :?:
 
Your needles should have 2 identification rings at the top. (Not to be confused with the 3 notches for the clip)

Also early, early Concentrics had shorter main jet holders. A photo of your carb pieces could help diagnose any mismatch.
 
ok more info the jets etch where all wrong so ordered new parts the needles had for id rings and three asjustment slots the needle jets where correct 106 and the mains where 260s so we ordered new needles928/104 needle jet 622/122 how does that all sound to you guys
 
As I said before, I don't have 932's. I have 930's, but the 260 main sounds too big to me,.... but since you are building a custom bike, with parts from different years of production, you may have to figure out the details of which jets, needles, mains, and their related positions by going to the amal site and seeing if you have matching parts. After you learn how amals work, you'll know which part to change or readjust to tune each increment of throttle position as you accellerate.


http://amalcarb.co.uk/rebuilding-mark-1 ... arburetter
 
ozbowhunter said:
ok more info the jets etch where all wrong so ordered new parts the needles had for id rings and three asjustment slots the needle jets where correct 106 and the mains where 260s so we ordered new needles928/104 needle jet 622/122 how does that all sound to you guys
Click to expand...

sounds right. that is what comes with the new premiers. Do you have the 928/107 stepped spray tubes?
 
gortnipper said:
ozbowhunter said:
ok more info the jets etch where all wrong so ordered new parts the needles had for id rings and three asjustment slots the needle jets where correct 106 and the mains where 260s so we ordered new needles928/104 needle jet 622/122 how does that all sound to you guys
Click to expand...

sounds right. that is what comes with the new premiers. Do you have the 928/107 stepped spray tubes?
Click to expand...
sray tubes forgot about them is that what we would need?
are they just for the choke? if so will we need them as we took out the choke slides not really needed here in Florida
 
Old Scratcher said:
Sorry to thread jack. But did you adapt the isolastics for the Featherbed Ashley?
Click to expand...


No Isolastics as that was why I wanted to go the way I did, my crank was balanced at 72% for the featherbed frame and the motor is pretty smooth and don't have any problems with vibrations, all steel hard mounts (5mm plates and a strong head stay).

Ashley
 
ozbowhunter said:
gortnipper said:
ozbowhunter said:
ok more info the jets etch where all wrong so ordered new parts the needles had for id rings and three asjustment slots the needle jets where correct 106 and the mains where 260s so we ordered new needles928/104 needle jet 622/122 how does that all sound to you guys
Click to expand...

sounds right. that is what comes with the new premiers. Do you have the 928/107 stepped spray tubes?
Click to expand...
sray tubes forgot about them is that what we would need?
are they just for the choke? if so will we need them as we took out the choke slides not really needed here in Florida
Click to expand...

The standard needle for a 750 carb (either 30 or 32mm) would be the 2-ID ring 622/124, and flat-topped 622/074 spray tube.
The 928/104 4-ID ring needle should be used with the stepped 928/107 "Norton" spray tube, but on the 850 models.
http://amalcarb.co.uk/rebuilding-mark-1 ... arburetter
new here and to norton


As a general rule the most noticeable difference between a 2 Stroke and 4 Stroke carburetter is the spray tube, the brass tube visible as you look through the carburetter bore. 4 Stroke spray tubes are cut off straight, 2 Stroke spray tubes are cut off at an angle sloping towards the mounting flange. Some later 850cc Norton Commandos use a spray tube with a square cutaway step while Triumph Triples use an angled spray tube cutaway from the mid point of the spray tube rather than right across as in the 2 stroke version. 2 Stroke and 4 Stroke bodies are not interchangeable and will not run correctly if used on the wrong type of engine.
Click to expand...

new here and to norton
 
Amal did tests that showed various height difference in manufacture/placement of spray tubes between carbs did not affect flow mixtures. I used a triangle file to notch Trixie Combat Amals and with floats set rich and only a #3 slide cut out I get distinctly more ass end kick out ease on loose and slick surfaces or city traffic short darts.
 
update time
we got all correct carbs parts and cleaned and setup the Amal
we got it running but no idle ands still backfiring out the pipe I'm sure we have an ignition issue
so a new Boyer ignition and Boyer battery eliminator is on the way once in we will go over everything one more time and see what we get
 
Alrighty gortnipper we might start a trend on notched spray tubes set a notch lower installed and helped by a notch less slide cut out too along with a notch higher float level. Main place I appreciate this is on grass or grit to just blip rear a bit this way and that and less sense of lugging chugging response on highest throttle w/o engine accerating up a steep. Lugging is officially defined as state of opening throttle but engine speed does not respond.
 
Hi Les, just to confirm for my own sake re the spray tubes.
Was the stepped spray tube introduced when later exhausts systems and air boxes were introduced and therefore not used in all Commando models?
I read somwhere recently the stepped tubes were in carbs fitted to Mk 3 's only

I am running 2 x 32mm Premiers on my race bike with straight cut spray tubes and although not looking for a low idle as in a road bike, I dont notice any difference in throttle response.
Regards Mike
 
Brooking 850 said:
Was the stepped spray tube introduced when later exhausts systems and air boxes were introduced and therefore not used in all Commando models?
I read somwhere recently the stepped tubes were in carbs fitted to Mk 3 's only
Click to expand...

Well, there has been some conflicting information about the actual specification Amal are currently building their "850" carbs to, but, according to Amal's own Norton factory spec. list, all original 850 carbs had stepped spray tubes and 4-ring needles-regardless of whether they were fitted to the Mk.3 or the "low noise emission" Mk1A and 2A models with the black plastic airbox and annular discharge silencers [Edit] or standard noise emission (peashooter) models.

installing-premiers-t22424.html#p293797
installing-premiers-t22424.html#p293846
 
I have a spare set of 32mm Premiers and will fit a set of stepped spray tubes that I have in my carb spares and see if that makes a difference
Thanks for the reply
Regards Mike
 
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