1st Start on rebuilt engine.

And don't forget to retorque the head. With your head in carb issues it's possible to forget other things

Hello Ratboiler
I made a float level checker using the plastic version of the drain plug, a barb fitting from a greenhouse watering kit, length of clear tubing and fitting clip. Used JB Weld (what else?) to glue the barb in place.

The plastic drain plug was from Surrey Cycles https://surreycycles.com/carburettors/mk-i-600-mk-1-900-concentric/
If you decide to go down this route please pm me as I have spare barb fittings foc.
All made just before Andover Norton started supplying a ready-made checker at a good price. Doh!
Andy

I used old plastic drain plugs also. Drilled and tapped one for an old Amal main jet and drill and tapped the other for an old MIG welder tip. I also enlarged the hole in both the jet and MIG tip. Slipped on a piece of Tyson and made little hooks out of wire to hook the tubing on the ticklers so I could check both sides at once w/o spilling fuel.

For float level adjustment I use the Bushmans carb tuning article. It is great. Also Old Britts. I know this is probably wrong, but I adjust the floats to the point where they won’t close the float needle due to hitting the carb body, and then back them down a tiny bit.

The combination of #17 pilot and 3.5 slide sounds weak IMHO.

I don’t run Premiers on my Commando though, so I could be way out here, but both #17 pilots and 3.5 slides were too weak for my bog standard ‘68 650 T120 which requires #19s and #3 slides.

+1 on the 19 pilot jets on the 850

Thanks for all the tip, you guys gave me some good pointers. Yes I will re check the head bolts and adjust the valve clearances. I have also ordered a pair of 19s and 21 pilot jets.
Thanks for the offer of the float checker very nice of you but I can wait no problems.
I will return with the results upon the delivery of the new jets.
I note that the only place my pilot jet size is shown is on the box not on the jet which seems strange.

Ratboiler said:

I note that the only place my pilot jet size is shown is on the box not on the jet which seems strange.

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As shown in the link posted by htown16 back in post #17, the needle jets in Premiers are identifiable by ‘rings’ machined into them as follows:

1 Ring - 622/502-15
2 Rings - 622/502-17
3 Rings - 622/502-19
4 Rings - 622/502-21
5 Rings - 622/502-23

OP, Win, lose or draw, the idle circuit(s) are inoperative/compromised.

Please don’t be offended when I pick apart your words.
“New Amal Premiers”

....as in NEW last summer, then I decided to rebuild the engine?

or NEW last week, just bolted them on.
Sorry, but I have to do this all day every day to drill down to the root problem.

Balance tube glued in place?

Balance tube fitted and very tight.
Thanks for the pointer on the rings.

Ratboiler said:

Balance tube fitted and very tight.
Thanks for the pointer on the rings.

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Hi an update for you guys.
Many thanks for all the pointers, I received the larger pilot jets as recommended by so many and fitted them. On start up the bike was much more happy, but was spitting back through the carbs when opened up.
The choke can be taken off and the bike once warmed up would tick over happily.
I removed the slides and dropped the needle one notch and restarted the bike which made a lot of difference, it now ticks over fine and responds to the throttle, rode it up the drive and it is responding well.
Big but as we are in lock down no chance to check it other than 1st gear, so fingers crossed for a roas test. Will remove and recheck the head soon and give it a general look over prior to the road test.
Once again thanks I would never have found the pilot jet problem without you guys. Amal just kept saying it will run with 17 jet, when pushed they said it runs better on 19 jets.......why didn't they say that in the first place?

Seems like it’s always the pilot circuit. I’m glad you have it running well Ratboiler.