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hi have a small problem . just replaced cylinder head and piston on my 350 sport rebuilt carbs . new inlet manifold an air filters bike starts first kick an revs like agooden but for the life of me cant get ticker below 2000 revs any advice or ideas would be greatly appreciated thanks

Have you checked the float heights, if they are too high, this can cause it to run rich?

As has been said quite often, are the slides in the right way round? (Cutaway towards air cleaner)
Easy mistake to make.

slides were actually in the wrong way wen i got bike but correctly fitted now 2 ml slack in throttle cables. needles set in middle position . ignition bob on .steel inlet stubs were loose aswell all tightened up no air leaks . will check float hights wen i get home

George 350 wrote: ↑09 Jul 2025 09:08 As has been said quite often, are the slides in the right way round? (Cutaway towards air cleaner)
Easy mistake to make.

I made this mistake first time a cleaned carbs in 76 Strada, messing about trying to hold the spring in didn’t look got both slide wrong, realised as soon as I started it.

Has the bike done it since you had it ? or just since rebuild ?

i bought bike as a none runner so never heard engine beforehand. but i did fit another set of refurb carbs of another 350 sport that i have an same problem happened

OK, so for the idle to be too fast, something isn't right. There is too much air going in from somewhere.
Have a look at the following for some more ideas.

I will assume that the throttle stop screws are wound out to have no effect on the slides and the slides fully close in the bodies and that there is still slack in the cables when like this.
New manifolds would seemingly remove those as a leak source, so where else?
Later carbs (VHB25HS) had a 'balancing' port just in front of the 'choke tower'. Do you have this type,and if so are they properly blanked off?
Are the rubber pads still in place at the bottom of each choke plunger? Are they still soft or as hard as stone? If so, replace them. (Were £5each on ebay.) Also, do the choke plungers go fully down.
Let us know how things go.

Regards,
George

fitted new choke plungers last week new type not affected by ethanol made no difference. bike is a 1978 sport with correct filter box and all the above has been checked .going to morini trackcday cadwell next week an feel a bit pensive about it