Stuttering up to 3k rpms, won't idle without choke.

[JTGS850GL]

I don't think so. The 4-1 may need a larger main or a slightly raised needle position but that shouldn't have any effect during idle. In fact it should have more effect at the higher RPMs.

[Spiff]

Okay! Today I tried to adjust the carbs but to no luck, it still stumbles and rattles and idled erratic, no matter how I turned the fuel screws it didn't seem to have any effect unless I turned them all the way in which would make it die...

Finally I turned my attention to the spark plugs and NONE had the correct gap plus I don't know how old they are.
I adjusted the gap and boom! Instant results. Smoother idle, smoother engine, less rattling. I can rev it over 6000 now whitout the engine sputtering and stop!
Also the rpm gauge now follows all the way up to 7000 whereas before it would stop at 5000 and go haywire! (connected?) I didn't dare any higher 'cause it's raining and the tires are old....
A definate improvement but still not 100% perfect. I'm gonna buy some new plugs and take it from there. Any suggestions as to where to go from there, carb sync obviously but idle mixture appears good now.