Carb problem

[Rushy]

Hi. I've got a Li150s 1964 standard set up. I'm having trouble with when I set off 1st gear pulls ok change into 2nd and it what I will call a hic up and then pulls ok through the rest of the gears. I've stripped the carb and cleaned it. The carb is an Shh2/22 with a main jt 130. Pilot 50. Atomiser 5899.2 with a big bore exhaust. Can anyone please point me in the right direction to solve the issue. Thanks Rushy

[Rushy]

A quick update I've just checked the ign timing and it's 18 degrees.dont know if that could be a problem.

[hullygully]

pilot & main jet seam tooo big for a standard 150 setup with only a big bore exhaust bud

[Rushy]

I've got a selection of main jets on order what pilot would you recommend.
Cheers

[Storkfoot]

I’d strongly recommend that you look at the carburettors settings section of either Sticky’s manual or the old Lambretta Workshop Manual. That will give you a strong indication of what slide, pilot and main you need. At the moment your jetting appears too rich right throughout the throttle progression.

Conventional wisdom, when fitting a 42mm big bore exhaust, has usually been to keep the jetting as standard but with an increase of 2 on the main jet. That’s with the original carburettor though.

[Rushy]

Thank you i will go back to standard settings

[Rushy]

I might have to start from scratch I've only had this scooter for a few months and was told that it was standard

[hullygully]

has it a cast iron barrel or an aluminium one, as timings a tadge retarded for a cast iron 150 standard barrel, has it a GP crank?
as previous have said, 'IF' its a standard 150 cast iron top end, then take the jetting back to a GP150 with plus 2 on the main jet due to big bore exhaust
anymore probs don't hesitate to use this forum for any help

[Rushy]

Thanks for the reply. I'm just waiting for the jets to arrive and I will let you know how I get on. It has a cast iron barrel and head so I think it could be standard?

[hullygully]

Thanks for the reply. I'm just waiting for the jets to arrive and I will let you know how I get on. It has a cast iron barrel and head so I think it could be standard?

or a 175

[Peterp]

Hello Rusty,
I’m not in a position to offer advice yet, but, as Hully said, use this forum for help. To date all the people I have come across on here have been very helpful and knowledgeable, very Lambretta experienced.
I’ll use this opportunity to thank all those who have helped me so far, you know who you are, many thanks again.
Pete

[Rushy]

My jets are due tomorrow there are several things making me think it's a 175. We will have to see what I can find.

[Rushy]

I changed the pilot jet and kept the 130 main and did a plug chop and here is the result

[hullygully]

is that with new 150cc jets? if so up the main jet by a couple then re plug chop rusty

[Rushy]

I've left the original 130 main jet. I'm beginning to think that it's got a kit on it. Will have to wait till winter and I will strip the engine. Might do another plug chop.

[Storkfoot]

To get that plug chop, did you turn off the ignition at wide open throttle or when you were running largely on the pilot jet?

[Rushy]

I tried to switch it off at full throttle but not sure. I'm going to try again so its full throttle and switch off and pull the clutch at the same time

[Storkfoot]

I tried to switch it off at full throttle but not sure. I'm going to try again so its full throttle and switch off and pull the clutch at the same time

Yes. Be careful. I try and use a going uphill stretch in second or third gear for several seconds.

In your picture, your plug looks quite new. If that’s the case, personally, I’d go for a ride of several miles before I do the plug chop.

[Rushy]

Ok will do

[hullygully]

you could allways take your exhaust & u-pipe off & measure the bore thru the exhaust port