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Hi All recently build a Series 3 Li 150 Special. Upgraded to a 195 and installed a YSN PHBH 28 Carb. Jetting is as follows:

Pilot - 55
Needle - X13
Atomizer - AV266
Slide - 120
Choke - 200

Problem: The engine starts fine with choke, I turn of choke after about a minute. But have to maintain engine running using throttle. If I close throttle off, the engine stops.
Have tried the tick-over screw fully in and fully out but it makes no difference to the tick-over. I know this is not right.

Any ideas on what I can try to get it running correctly?

Thanks

Is it a RT kit ?

If so - look on the MB tech site - clear jetting instructions on there or the RT page on facebook as loads of info on there

Your own stated jetting figures look a litte wrong - specifically the slide & choke.

I suspect the 200 figure is the needle valve - which should be 300 or 350 - thats the control that refils the float bowl

Slide should be 40 or 45 - thats the round metal thing that the needle fits through & sort of controls the air into the carb with the throttle cable

are these copy carbs using genuine Dellorto Jets ?

Yes the cylinder conversion is an RT 195

I incorrectly listed the jetting! Correction is as follows:

Idle/Pilot 55
Needle X13 (second position)
Atomizer AV266
Main 120
Slide 40
Float Red Tip 200
Choke (not known)

Thanks will give MB site a look.

And Yes the carb is using genuine jets.

Hers one from an RT I built last year for someone

28mm PHBH/Scootopia Clubman Filter
Pilot 55
Choke 70
Main Jet 115
Atomiser AV266
Slide 40
Needle X7 P2
Float valve 300

Hi Toddy

Will try using your setup.

Thanks

Bobf wrote:Hi Toddy

Will try using your setup.

Thanks

Is your throttle cable adjusted ok seems strange your not getting a tickover with the screw is the air screw set ok ?

High All. Well Toddy fixed the necessary jets to your configuration.

Start fine but still will not tick-over, just cuts out when throttle is closed!

Have another Lambretta owner coming over this week to see if he can offer some advice.

Bobf wrote:High All. Well Toddy fixed the necessary jets to your configuration.

Start fine but still will not tick-over, just cuts out when throttle is closed!

Have another Lambretta owner coming over this week to see if he can offer some advice.

Have you tried the adjuster on the top of the carb it may be a bit of slack in your cable ?

If it likes ticking over with the throttle on, it likes being richer than it is. As the pilot you have doesn’t appear on the weak side, I’d suspect you may have an air leak somewhere.

Do you have an air filter fitted ?

No at the moment open mouth but will be fitting a foam filter direct to carb.

Storkfoot wrote:If it likes ticking over with the throttle on, it likes being richer than it is. As the pilot you have doesn’t appear on the weak side, I’d suspect you may have an air leak somewhere.

+ 1

have you done a leak down test ? That would be my 1st action at this point.