Can someone offer a recommendation to a carburetor (and jet sizes) to use on a Jumbo (350) ?  My Jumbo doesnt have the reeds and is not the rotary induction.  A Delorto PHBH 30mm is the OEM carb for my Jumbo.  I'd prefer to use a round slide carburetor.  So, Im thinking a newer style Delorto or a Nibbi.  Im not interested in using a OKO (I rentlessely tried a 28mm with no luck).  My Jumbo engine was just rebuilt (top and bottom end) and there are no air leaks.  No matter what I do, I can't get rid of a lean condition found below 1/4 throttle....and still have mid and top correct.... it seems to be either or.  so, Im at the point to try a new carb.  Thanks.

Edited March 20, 20251 yr by jimg
Add better description of motor

Carb for the Jumbo was 28mm, never heard of 30mm fitted as OEM.  For a non-reed engine the pilot is 50 and slide 60, needle X2 and needle jet AS272. The delorto should perform fine if it's not worn out

There is quite a difference between the reed and non-reed motors in power delivery. I tried a non-reed back to back with my reed engine bike when I had one and the non-reed was pretty flat with slow pick up off idle/pilot before surging and getting lively when the revs came up. Are you mistaking that for lean jetting? The reed engine lit up instantly

I've run Delorto and OKO back to back on my 340 Sherpa and can't fell any noticeable difference which makes me wonder if it is just the slow take up of the non-reed engine that is giving the impression of weak jetting below 1/4

Woody, thank you for the excellent reply....this is very good to know.  My carb is a 30mm, it's stamped on the carb.  When I got the bike , I was/am the 3rd owner, and I spoke to the original owner and he never changed the carb. The bike does have the CMC headstock plate....maybe that has something to do with it... that's besides the point though.  I'll run the carb through my ultrasonic cleaner Again and check the jets, etc.  I'll keep messing with it.    

My jumbo has a keihin but I had to fit a sleeve to the outside of the carb to make it fit the inlet rubber. The dellorto i took out had a similar fitting so perhaps the inlet rubber has been changed