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Im running a sweetbreathe filter on my muggy 225 with lth reed valve.I had to fit the sweetbreathe to get enough air to the carb.Having rebuilt the top end after a holed piston im struggling with the jetting as it seems not enough air is getting in the mixture and im running rich.Its not too bad what ever I do makes little difference.I have a vent in the panel grill,any ideas?
Im running 138 main AV266 atomiser x7 needle on leanest clip 53 pilot 70 choke 300 float valve.I daren't go any leaner,the plug is dark brown,and its a bit boggy low down.Also have agusto fitted.
This setup worked before,I cant think of any difference apart from the piston,a mitaka.(Avanti)

jonno wrote:Im running a sweetbreathe filter on my muggy 225 with lth reed valve.I had to fit the sweetbreathe to get enough air to the carb

Are you saying that before you had the sweet breath, you ran on the Lambretta Airbox?

I had a similar type filter fitted before I fitted the LTH reed valve,this gave the same problem so I fitted the sweetbreathe and it was ok.Now Im having the same symptoms.

You may have had an air leak before, which caused the holed piston. The rebuild may have cured the air leak but now left you running rich........

138 main seems a tad high.

Are you rich on all settings....pilot, needle, main, etc ?

Quick check to try and isolate the problem?
Does it make any difference with the filter off?
If it doesn't it's not the filter.

My limited experience only.
Fitting the aftermarket reed and TS1 piston made a huge difference to my rapido, so much so that I ended up having to get it on a dyno to set it, it seemed so far away from where I started, I assumed I was doing something very wrong.
Pilot went from a 50 to a 62
Atomiser from a AV266 down to a AV262
Main went from a 125 up to a 128.
I was worried about the settings but 600miles on its still fine, so they got it right, picked up 1hp across the whole range and flattened my huge mid range rich spot.
Hope this helps

I run exact same set up
Muggello 225,broadhurst reed
Ive solidly mounted a 30 phbh to allow room for a breathesweet filter on my sx
Ads 3 pipe
Ive set it up wth a gamma display and ive ended up with
140 main
X7 needle clip 3
Av266 atomizer
It breathes fine...your panel isnt squashing the filter elbow is it.?

I had been trying to set up the carb with the panel off and was getting either lean or rich. Put panel on and basically had to start again.I took off the filter and there was no difference.
I diconnected the agusto and set the timing to 17,and it was a lot better.Its smoking a lot more than it used to on tick over,and Im getting a black plug colour at 30 mph and a brown/purpley colour at 50 mph.It looks brown with a tinge of grey.therefore purpley to me lol.
The filter has been cleaned hardly any dirt,and is not squashed by the panel.
Ill have a look at the reeds,the parts have been on the shelf for a while tho they looked ok when I assembled it all .And its effin loud .

Could a bad squish cause probs? The replacement piston was a mitaka which was supplied as a replacement for the original muggy one.

The mitaka piston has the same height as a standard piston and the profile is about the same so the squish shouldn't be that different but you'd be advised to check it in any case.

As somebody prepared to admit that in my haste during a race meeting I neglected to check the squish (if that’s any excuse! ) to discover the hard way the variation in ‘identical’ pistons when the engine grenaded, you’d do well to follow rossclark’s advice…

Mag seal had gone,replaced and all a lot better.I do have a flat spot between 1/4 and 1/2 throttle.Put on the choke and it gets worse which I guess means its a rich flat spot.Would a leaner slide make it better? have read AV jets have a flat spot.

Re: Not enough air
Post by jonno » Wed Jul 06, 2016 3:58 pm

Mag seal had gone,replaced and all a lot better.I do have a flat spot between 1/4 and 1/2 throttle.Put on the choke and it gets worse which I guess means its a rich flat spot.Would a leaner slide make it better? have read AV jets have a flat spot.

I think you would be best to read through all the replies you’ve had already. That’s not intended to sound ‘snotty’ but both meds & camel give almost conflicting, but well intentioned responses.

Now that you have acknowledged an air leak all along, perhaps you will ‘dare’ to drop atomiser size?

That’s what I would try....

Im pretty sure the set up was the same as camel,perhaps I remember it running better as wishful thinking.Im not sure about going down to a 262 warkton.I ran an x7 needle and it was a bit lean at about 50mph.Im doing plug chops btw.It was better with an x2 needle.
Been checking 2 stroke plug colour on the web and motox sites suggest a white plug is good Im sure its choccy brown for Lambrettas tho.

A white plug is bad

Post by jonno » Sat Jul 09, 2016 10:12 am

Im pretty sure the set up was the same as camel,perhaps I remember it running better as wishful thinking.Im not sure about going down to a 262 warkton.I ran an x7 needle and it was a bit lean at about 50mph.Im doing plug chops btw.It was better with an x2 needle.
Been checking 2 stroke plug colour on the web and motox sites suggest a white plug is good Im sure its choccy brown for Lambrettas tho.

I wouldn’t suggest going from an AV266 to an AV262 without trying an AV264 first.

X7 may be very common as far as Lambrettas are concerned, but look @ the needle chart as you may need any of X2, X7, X12 or X13 from memory.

Unless I’ve missed it, have you stated what slide you have?

You are correct in aiming for chocolate brown for plug colour.

jonno wrote:I
Been checking 2 stroke plug colour on the web and motox sites suggest a white plug is good Im sure its choccy brown for Lambrettas tho.

if you want a hole in your piston or a engine seize up then a white spark plug colour is perfect
You should be aiming to have a light tan colour ideally but if you are running in or doing high speed motorway milage then a slightly richer digestive biscuit colour would be safer

Im running a 40 slide,was wondering if a leaner slide would cure the flat spot 1/4 to 1/2 throttle.Ive tried the leaner needle x7 as I stated which was too lean at full throttle.Has x2 in atm.