Hi BAinLA, Back in the day we had some alcohol race bikes. Rule was double all jet sizes. That would bring you really close. Thinking of our E10 &other difference in California fuel I find 5% more jet may be needed. It seems on all I tune it ends up between sizes... So I to the richer side. John Healy made a tuning guide which I find very helpful. Making the grip in 1/8s compensating for cable slack bars pointing straight. Print the needed pages. Take in on road tests. Do several & digest the guide & feel for backing off throttle. Choke doesn't have effect until the slide is raised to expose choke plug. Experiment with that. I personally keep choke as I'll occasionally need to start bike at 25-32f. It doesn't actually help firing of motor, but reduces stalling & dying after start up & prevents stumbling while underway cold. I like the look of the lever also. https://static1.squarespace.com/sta...2/1481956877861/Amal+MK2+Carb+Manual.pdf
I've a fair amount of experience with worn slides/bore. The main effect is at idle & just off idle. Turning throttle slowly as possible from idle, heat soaked motor. If it dies or wants to die, that's from wear. Good will raise rpm smoothly no matter how slowly you turn grip. Also once you get feel for it, while riding slowly in the twisty roads you'll back throttle to idle & very slowly rolling on. The motor does a tiny stumble as it dies for a tiny instant. Will do this in slow traffic as well. Much worse in heat of summer. I bet now you'll notice this on next road test. Find a road test route that tests all stages of carburation. Stick to the route for tuning. That makes feeling changes much easier as you memorize feel. I do main jet by going too big until it 8 strokes. Ah ah ah ah misfire. Backing throttle will take it away. More throttle brings it right back. Kind of scary on your first feel of it. I then go smaller size at a time until 8 stroking goes away.
I'm probably start with moving needle full up now. Lean at this position is a piston killer. The needle wears a groove where you ride most often. You'll see that. This makes rich spot. The needle jet wears also from needle moving in it. Really you should have at least new needle before tuning. AMAL
now makes a 1065 needle jet if you need a little more fuel on straight part of needle. A worn needle jet can give similar effect. I've done that worn jet, new needle a few times.
You will be shocked at how little throttle you are usually riding at. Needle is still well on straight part so clip position is not even in effect. Again marking grip will tell you that. Slide cutaway is a more costly experiment... Snap throttle is the main test, but actual riding you can feel it as well. On my bike I found it ran better overall with 3 instead of normal 3.5 cutaway. I have .106 & 1065 needle jets. I probably have a $100 worth of jets now from tuning carbs. Very time consuming & takes some practice. Forget Mikuni
or SU carb experience you may have. They have full tapered needles & tune differently. AMAL Concentric
is it's own thing. New premier has looks same, but has many changes. I may need different slide, jets that original did. Float level is very different.
Looks like Premier castings are on back order from supplier, so AMAL
has back ordered carbs. Some still in stock in USA. Tiger carbs may be more available in USA?
What float are you using? The original hollow plastic is a fire hazard as our fuel softens the plastic allowing flooding & fires. I had that on my bike. If you can't find new, worth cost of new stay up float & needle kit, needle & a few jets. At your mileage carb should be very worn, but you can nurse it along until new can be found. You can learn to ride around the dying off idle by raising idle speed. Cheat idle mixture slightly lean. Never open throttle slowly off idle. I rode nearly a year like that. Took me time to learn all this. Then carbs were on back order. I've covered 10k miles on my premier now. Just check for wear. Slide & bore have zero wear!! Needle & needle jet have expected amount of wear for 10k miles. About time to replace now. Not horrible though.
I ended up tuning my old carb using used slides, new needle & needle jet, new main jets until I found best combination. I then ordered carb from AMAL
direct as they would build to my request. I wanted new banjos & top as well. Generic carbs are often not correct for what may want. Sellers seem more willing to make changes no charge these days. Old banjos & tops can usually be swapped over to new premier.
Yes I have my "dip stick" timing tools from the old days... Haven't used them in years, but I have '64 Cub awaiting me to get it running. That takes dip stick.
Knock sensor would be nice. Vacuum advance like cars have would be nice. Vacuum advance to electronic cell to computer EI would be nice. None of that is going to happen. I don't want dual plug heads. I finally through in the towel & put 7.1 Harris pistons in 650s & 7.4 in T140s. You'd think it would reduce power greatly. In real riding it doesn't. You need octane we don't have for 9.0 pistons to take advantage of the compression ratio. I don't have any fight left in me. I just use lower compression pistons. Allows me to take the long rides to mountains & through valley in 110+f heat with no issues. No more race gas needed. A mechanic at Rabers lived in Scotts valley area near Santa Cruz. Commuted to work on later 60s Bonnie over the pass hwy 17 to San Jose. Got tired of the ping & having to use 3rd & rev motor so high. Installed 7.1 as an experiment. Never looked back. Neither do I. Just makes bike more fun to ride for me. There are other ways to stop ping & add power if that's what you want. Sounds like you may want that?? Thing is these bikes are just different from modern to ride. Primitive & so much fun!