Throttle roll off

[Ihateyoubutler]

Apologies if it's in in the wrong section, but I'm sure it's a basic problem.When you shut the throttle and the revs stay high for a short period, then settle down, can anyone tell me the cause? (Tmx 35).Also,can anyone tell me where I can buy an extra spring to fit inside existing carb spring, to help throttle close when grip is released?
Thanks.

[soulsurfer]

Running lean, possibly pilot jet. What jetting do you have and what kit?

[Avantone]

It could be something as straightforward as a pinched or kinked cable.

[soulsurfer]

It could be something as straightforward as a pinched or kinked cable.

Or a fuel filter

[lifes a drag]

it could be a air leak , check carb rubber and reed valve if it has one
cable could be sticking , give it a wagel or fit a new one
the spring in it shoulb be strong enough on its own if everything ellse is working as it should

[J1MS]

Petrol frothing in the float bowl can cause this... tuned lambrettas on standard 22mm type solid mount carbs quite often suffer with this, any solid mount carb on a high vibration single cylinder two stroke can have this problem... but rubber mounted carbs show similar symptoms if the fuel level is too low ....and there are a few common causes ....Petrol filler cap vent blocked slightly...float hight set wrong ...type of float used.... float needle type (there's more than one type) ...fuel pipe too narrow kinked...float valve and needle valve too small ... dirt in the fuel supply....an air leak in the inlet ... a worn carb body and slide... and lots more.....many different faults that can cause a similar symptom...

[Ihateyoubutler]

Thanks for the replies, it's a mainly standard ts1 kit with tmx35 and devtour.The main is 320, pilot (I think) is 20, slide is 6 and needle is 6en11-57 2nd clip from top.Seems to run ok across the rev range, but I'm trying to run it in.Cable doesn't seem to be kinked and slide appears to shut properly when throttle shut.Plug is probably a little on the dark side, but not bothered about that as I'm trying to run it in.20 miles and counting It's just when I shut off and it takes a little while for ther revs to return to tickover.Otherwise, carb seems pretty clean,picks up well and not much spraying out etc.
Thanks again.

[J1MS]

Thanks for the replies, it's a mainly standard ts1 kit with tmx35 and devtour.The main is 320, pilot (I think) is 20, slide is 6 and needle is 6en11-57 2nd clip from top.Seems to run ok across the rev range, but I'm trying to run it in.Cable doesn't seem to be kinked and slide appears to shut properly when throttle shut.Plug is probably a little on the dark side, but not bothered about that as I'm trying to run it in.20 miles and counting It's just when I shut off and it takes a little while for ther revs to return to tickover.Otherwise, carb seems pretty clean,picks up well and not much spraying out etc.
Thanks again.

Im not a Mikuni man when it comes to Lambrettas, so wouldnt even think of suggesting any jetting details.... but its most probably carb related, failing that a light air leak somewhere....but really only a guess....Someone else on here will be better able to help ... wish you all the best...

[soulsurfer]

Check for air leaks or try a 22.5 pilot

[AndyS]

Try adjusting the mixture screw at the front of the carb, that changes the rate at which the carb returns to tickover