Carb experimentation, cold start issues.

Anything related to Lambrettas... ask tech questions, post helpful info, or just read and learn.
Warkton Tornado No.1
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My thoughts have just been prompted by the other active Post on this forum:

viewtopic.php?t=41411&sid=781db5c56e012 ... 37f41d6ef7

I'd personally persevere with the PWK, but although they are great carburettors, they rely entirely on the Lambretta OEM type fuel filter which should always be augmented by an inline filter. If you haven't already done so, it is essential to blueprint the PWK with regard to float setting/orifice checking & if you investigate on-line, you will find other modifications worth doing. The float stops in the bowl are best removed & the bowl drain plug hole can be cut back to allow replacement of the pilot without having to remove the bowl itself.

However, whichever carburettor is chosen, I tend to take for granted that the starting point to be applied is an adequate pilot jet. Plug readings (even if it doesn't start) will soon show a wet or dry plug :!: Unfortunately, the pilot & choke being the smallest of the jets, they are the first to be affected by any sort of blockage/flow problems due to the very fine sediment that can get through to the bowl. It doesn't necessarily completely block the pilot as the vibration - once the engine is running - tends to clear a partial blockage. Petroil mix needs to be fresh, particularly with ethanol in it these days & a modification worth applying is to fit a miniature drain valve to the float bowl screw which runs off any bowl fuel via some tubing to a catch tank/cup/jug when necessary. it saves a lot of mess & money when jetting in a 'new' engine set-up......

As a matter of interest, what are the jetting details that you have tried with both carburettors? My guestimate - presuming that the engine is piston ported - would be for the pilots:

Dell'Orto: 50ish
PWK: 32ish

However, it would be best that you Posted the complete slide/MJ/PJ/atomiser/choke/float bowl 'jetting' details where applicable for the carburettors that you have tried & confirm piston ported or reed for any intelligent diagnosis to be made.....
tippo88
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Joined: Tue Apr 07, 2015 2:31 am
Location: Kuala Lumpur
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Sorry very long delay in replying, was travelling a lot and haven't had time to work on the scoot which has been following its very erratic behaviour.
I'll post the full carb setup in the next couple of days. In the meantime was going to ask is this https://www.miniriders.com/threads/keih ... ods.26815/ the guide you use for blueprinting? I can't find any other.

Cheers
tippo88
registered user
Posts: 189
Joined: Tue Apr 07, 2015 2:31 am
Location: Kuala Lumpur
Contact:

Warkton Tornado No.1 wrote:My thoughts have just been prompted by the other active Post on this forum:

viewtopic.php?t=41411&sid=781db5c56e012 ... 37f41d6ef7

I'd personally persevere with the PWK, but although they are great carburettors, they rely entirely on the Lambretta OEM type fuel filter which should always be augmented by an inline filter. If you haven't already done so, it is essential to blueprint the PWK with regard to float setting/orifice checking & if you investigate on-line, you will find other modifications worth doing. The float stops in the bowl are best removed & the bowl drain plug hole can be cut back to allow replacement of the pilot without having to remove the bowl itself.

However, whichever carburettor is chosen, I tend to take for granted that the starting point to be applied is an adequate pilot jet. Plug readings (even if it doesn't start) will soon show a wet or dry plug :!: Unfortunately, the pilot & choke being the smallest of the jets, they are the first to be affected by any sort of blockage/flow problems due to the very fine sediment that can get through to the bowl. It doesn't necessarily completely block the pilot as the vibration - once the engine is running - tends to clear a partial blockage. Petroil mix needs to be fresh, particularly with ethanol in it these days & a modification worth applying is to fit a miniature drain valve to the float bowl screw which runs off any bowl fuel via some tubing to a catch tank/cup/jug when necessary. it saves a lot of mess & money when jetting in a 'new' engine set-up......

As a matter of interest, what are the jetting details that you have tried with both carburettors? My guestimate - presuming that the engine is piston ported - would be for the pilots:

Dell'Orto: 50ish
PWK: 32ish

However, it would be best that you Posted the complete slide/MJ/PJ/atomiser/choke/float bowl 'jetting' details where applicable for the carburettors that you have tried & confirm piston ported or reed for any intelligent diagnosis to be made.....
It's a 24 mm UMA PWK copy. Piston ported 185 SR that's been cleaned up. I checked the jets and it had a 40 pilot and 100 main. Changed the pilot to 32 and it started first kick. So hopefully some progress but let's see, it's started first kick for a while in the past....

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tippo88
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Posts: 189
Joined: Tue Apr 07, 2015 2:31 am
Location: Kuala Lumpur
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tippo88 wrote:
Warkton Tornado No.1 wrote:My thoughts have just been prompted by the other active Post on this forum:

viewtopic.php?t=41411&sid=781db5c56e012 ... 37f41d6ef7

I'd personally persevere with the PWK, but although they are great carburettors, they rely entirely on the Lambretta OEM type fuel filter which should always be augmented by an inline filter. If you haven't already done so, it is essential to blueprint the PWK with regard to float setting/orifice checking & if you investigate on-line, you will find other modifications worth doing. The float stops in the bowl are best removed & the bowl drain plug hole can be cut back to allow replacement of the pilot without having to remove the bowl itself.

However, whichever carburettor is chosen, I tend to take for granted that the starting point to be applied is an adequate pilot jet. Plug readings (even if it doesn't start) will soon show a wet or dry plug :!: Unfortunately, the pilot & choke being the smallest of the jets, they are the first to be affected by any sort of blockage/flow problems due to the very fine sediment that can get through to the bowl. It doesn't necessarily completely block the pilot as the vibration - once the engine is running - tends to clear a partial blockage. Petroil mix needs to be fresh, particularly with ethanol in it these days & a modification worth applying is to fit a miniature drain valve to the float bowl screw which runs off any bowl fuel via some tubing to a catch tank/cup/jug when necessary. it saves a lot of mess & money when jetting in a 'new' engine set-up......

As a matter of interest, what are the jetting details that you have tried with both carburettors? My guestimate - presuming that the engine is piston ported - would be for the pilots:

Dell'Orto: 50ish
PWK: 32ish

However, it would be best that you Posted the complete slide/MJ/PJ/atomiser/choke/float bowl 'jetting' details where applicable for the carburettors that you have tried & confirm piston ported or reed for any intelligent diagnosis to be made.....
It's a 24 mm UMA PWK copy. Piston ported 185 SR that's been cleaned up. I checked the jets and it had a 40 pilot and 100 main. Changed the pilot to 32 and it started first kick. So hopefully some progress but let's see, it's started first kick for a while in the past....

Sent from my SM-G985F using Tapatalk
Started first kick today with choke. Left for 4 mins, stared first kick no choke.Ran it round the block, seemed to be running OK. Back home turned off and tried to start. Only way it would fire was with throttle wide open and then it would chug at very low rpm amd then stall.


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tippo88
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Posts: 189
Joined: Tue Apr 07, 2015 2:31 am
Location: Kuala Lumpur
Contact:

tippo88 wrote:
tippo88 wrote:
Warkton Tornado No.1 wrote:My thoughts have just been prompted by the other active Post on this forum:

viewtopic.php?t=41411&sid=781db5c56e012 ... 37f41d6ef7

I'd personally persevere with the PWK, but although they are great carburettors, they rely entirely on the Lambretta OEM type fuel filter which should always be augmented by an inline filter. If you haven't already done so, it is essential to blueprint the PWK with regard to float setting/orifice checking & if you investigate on-line, you will find other modifications worth doing. The float stops in the bowl are best removed & the bowl drain plug hole can be cut back to allow replacement of the pilot without having to remove the bowl itself.

However, whichever carburettor is chosen, I tend to take for granted that the starting point to be applied is an adequate pilot jet. Plug readings (even if it doesn't start) will soon show a wet or dry plug :!: Unfortunately, the pilot & choke being the smallest of the jets, they are the first to be affected by any sort of blockage/flow problems due to the very fine sediment that can get through to the bowl. It doesn't necessarily completely block the pilot as the vibration - once the engine is running - tends to clear a partial blockage. Petroil mix needs to be fresh, particularly with ethanol in it these days & a modification worth applying is to fit a miniature drain valve to the float bowl screw which runs off any bowl fuel via some tubing to a catch tank/cup/jug when necessary. it saves a lot of mess & money when jetting in a 'new' engine set-up......

As a matter of interest, what are the jetting details that you have tried with both carburettors? My guestimate - presuming that the engine is piston ported - would be for the pilots:

Dell'Orto: 50ish
PWK: 32ish

However, it would be best that you Posted the complete slide/MJ/PJ/atomiser/choke/float bowl 'jetting' details where applicable for the carburettors that you have tried & confirm piston ported or reed for any intelligent diagnosis to be made.....
It's a 24 mm UMA PWK copy. Piston ported 185 SR that's been cleaned up. I checked the jets and it had a 40 pilot and 100 main. Changed the pilot to 32 and it started first kick. So hopefully some progress but let's see, it's started first kick for a while in the past....

Sent from my SM-G985F using Tapatalk
Started first kick today with choke. Left for 4 mins, stared first kick no choke.Ran it round the block, seemed to be running OK. Back home turned off and tried to start. Only way it would fire was with throttle wide open and then it would chug at very low rpm amd then stall.


Sent from my SM-G985F using Tapatalk
I have a Armadillo elbow with a drain "tube" in the bottom and marrchand filter on top. I might try removing the filter and elbow and see if that changes things.

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Warkton Tornado No.1
registered user
Posts: 296
Joined: Mon Oct 17, 2011 6:16 pm
Main scooter: Lambretta SX200
Contact:

tippo88 wrote: Mon Oct 17, 2022 6:49 am Sorry very long delay in replying, was travelling a lot and haven't had time to work on the scoot which has been following its very erratic behaviour.
I'll post the full carb setup in the next couple of days. In the meantime was going to ask is this https://www.miniriders.com/threads/keih ... ods.26815/ the guide you use for blueprinting? I can't find any other.

Cheers
There's useful information there but Mid Atlantic Trials used to have a web page with lots of relevant stuff. I can't find it but haven't tried Facebook for them....
Warkton Tornado No.1
registered user
Posts: 296
Joined: Mon Oct 17, 2011 6:16 pm
Main scooter: Lambretta SX200
Contact:

tippo88 wrote: Thu Oct 20, 2022 7:51 am
tippo88 wrote:
tippo88 wrote:It's a 24 mm UMA PWK copy. Piston ported 185 SR that's been cleaned up. I checked the jets and it had a 40 pilot and 100 main. Changed the pilot to 32 and it started first kick. So hopefully some progress but let's see, it's started first kick for a while in the past....

Sent from my SM-G985F using Tapatalk
Started first kick today with choke. Left for 4 mins, stared first kick no choke.Ran it round the block, seemed to be running OK. Back home turned off and tried to start. Only way it would fire was with throttle wide open and then it would chug at very low rpm amd then stall.


Sent from my SM-G985F using Tapatalk
I have a Armadillo elbow with a drain "tube" in the bottom and marrchand filter on top. I might try removing the filter and elbow and see if that changes things.

Sent from my SM-G985F using Tapatalk
PWK's are critical on float height but once set, should be fine as they have an inbuilt overflow tube in the bowl. I've never had hot start issues with them even with filters......unlike PH's :roll:
tippo88
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Joined: Tue Apr 07, 2015 2:31 am
Location: Kuala Lumpur
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So today started first kick from cold, did the same loop as yesterday but turned petrol ofg shortly before getting back.
Started again no problem so round same loop again but didn't turn petrol off and doing the full throttle chugging thing again.
So seems like spit back related? Bit strange as I thought the Armadillo drain hole was supposed to prevent spit back build up.
So was thinking tomorrow might experiment with open carb and also maybe with smaller pilot jet and filter etc.
Should I be checking float height as well, could that make a difference?
Cheers

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tippo88
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Posts: 189
Joined: Tue Apr 07, 2015 2:31 am
Location: Kuala Lumpur
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Am sure it's probably unrelated but by carb has a power jet. On line there seems to be mixed opinions about whether these should be used or blocked off?

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tippo88
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Posts: 189
Joined: Tue Apr 07, 2015 2:31 am
Location: Kuala Lumpur
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Ao today's experiment. Thought would try starting from cold without u bend and filter. Wouldn't fire at all. Put U bend on, no filter, wouldn't fire at all. Put filter on ,so back to as previously, wouldn't fire at all. Left it 10 mins and started after say 10 kicks.
Rond the block, fuel off just before home. Stopped and it started first kick. Round the block again left fuel on . Stopped then started first kick unlike yesterday.
Left for a couple of hrs started first kick round the block left fuel on and again started first kick.
So no chugging at all today. But I know for sure that when I actually need to go somewhere and stop the chugging will return. Just can seem to get any consistency.

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