Strange events....

Now this perplexes me.... Chasing the gremlins a short while ago I say whatever and replace my jets and such( never been done & proper Amal installed, checked for obstructions also). Okay all issues found/fixed and 850 running better than ever which I didn't believe possible.... BUT... One big exception: Motor has never before wanted/needed choke & had extremely short warm up period.... It NOW, if you desire to takeoff within 10-12 minutes, has to have at least half + choke on, or suffer spitting, stalling, popping, dying.... Granted bike pulls better, better economy, plugs look much nicer, more responsive...., but Master why has Grasshopper cured major issue only to suffer a myriad small inconveniences?.... May I never hop on and rush off again? It seems to behave as the majority now methinks. Sorry because the behavioral characteristics were completely unexpected on my part catching me off guard.

Your bike and mine are essentially the same machines. I've owned mine since new and it has always wanted the choke on cold starts. On a cold day (50's F) I would ride it for half a mile before raising the chokes. Nowadays I don't ride that cold and in the 60's I raise the choke right after starting and hold the throttle at 1500 for maybe 2 minutes then ride off. Having a throttle tensioner helps a lot with that. As for what changed on yours, I would wager idle air adjustment. Though 10 minutes is a long time.

Never installed chokes but I had similar cold running issue with new Premiers until I changed out pilot jet from 17 to 19.
Major improvement noticed on cold starting and first 10 minutes of running.

Maybe you were running it a bit rich before
And a bit lean now?

Some people are never happy unless they're miserable
Might be running 'properly' for the first time in it's life ???

jbruney said:

It NOW, if you desire to takeoff within 10-12 minutes, has to have at least half + choke on, or suffer spitting, stalling, popping, dying...

Click to expand...

If by "half + choke on" you mean that you the turn the choke lever half-way, to put is as nicely as I can, it's a figment of your imagination as the choke is doing nothing. If you mean that you put full choke on and then turn the lever a little to raise the chokes a little, then you are most likely too lean - maybe the air screws, maybe an air leak.

Starts right up, but if you want to move the choke goes on, and then it can be backed off( I say 1/2 because it's where I put it for couple of minutes). I'm on the road when it smooths out.... Screws have fresh o-rings and snug fit.... And Yes... I agree with starting like they're supposed to (pretty much) and I've just got to learn all over again. I've never had a new one I've only had my old one and know how it behaves, and what it has taken to coax reliable running from it.
Yes the machine was always a rich runner even at the leanest needle setting. I could mark the odometer reading when new plugs went in and knew when trouble would arrive..... 3 cleanings then failure... That's over now..... I'm shocked/surprised with the sudden change and pleased too, but also shutting up because further expounding furthers an adventure into ignorance on my part.

The needles have no real effect on idle. If rich in the needle's range then maybe you don't have Norton-specific needles or your needle jets are worn, or someone changed the needle jets to a larger size.

If the carbs are old, and especially if the slides have been changed once or twice, then the air leaking around them at idle will have more effect than at higher throttle. Simply turn the air screws in 1/8 turn and see if it is better. If they are already in more than 1-1/4 out, then:

If standard carbs, they are worn or the idle circuit is not fully open,
If premier carbs, the pilot jets are probably 17s and you need to put in 19s

Misunderstood me there... Starts up without choke & will idle smoothly after a minute or so. Idle circuit is doing the job. Use of the choke is necessary to operate the bike until motor warms up as it will not take a load without it.... Needles & jets which were removed for replacement were Amal & of correct size as are the new ones.
As things set I do a plug chop the plugs are wonderful looking, so I'm inclined to leave the needle sit in the top groove as it should and tolerate the lengthy(to me) warm up. Or perhaps experiment this next weekend and see what moving to the mid needle groove does and if that is a wise move.
Let us venture back 42 or so years when she came to me.... Running rich, fouling plugs, so moved needle to top groove and problem went away..... Bike stored 38 yrs. & awakened 2 years ago.... Same old 932's progressively slowly wearing get updates and characteristics are suddenly changed.
Don't know what 1st owner did, if anything to motor. I bought from 2nd who did nothing(now 4yrs. old), but bike was always very quick, ran rich, ate plugs, never required choke, gas hog. Small evidence of carb wear.... some, but very little. Carb work was just routine update/maintenance with unexpected results. Shall be replaced soon anyway.