High tickover

With points a tickover taking a long time to drop to normal levels is a sign of the auto advance sticking advanced, service by checking slots for wear and giving it a good lube, also check for loose worn springs. Other one is an air leak but then the revs stay high and do not drop. To check for air leaks spray WD40 on the manifold joints etc and once it hits the leak the revs will change. Also the O rings on the throttle stop and airscrews can crack and leak.

Separately and not related to tickover speed.

If you have gone from black cap to pea shooters then main jets need to be changed from 230 to 260. Once you have it running well then the needle position may need slight adjustment. 

did you use a strobe to check timing : 28 fully advanced, and a lot less at lower revs? That should show advance is at least moving, even if it still needs overhaul/lube.

Using your strobe light set the timing to 28 degrees@3500rpm.

Best to park the bike on the side stand otherwise it will move around with the motor vibration.

I use a Morgan Carb tune connected to both balance pipe outlets https://www.carbtune.com/  

First check the carbs are synchronized (both slides open at exactly the same time) then adjust the mixture screws for fine balancing.

The columns on the Carb tune gauge need to be within the tolerance spec stated.

Good Luck!  

so with the strobe, it should show 28 degrees as maximum: it starts less and as you rev, will move up to the mark and STAY THERE as revs go higher than 3,500, just to be clear.