Air Hose Drain Valve

[dapper]

On early scoots/carbs they used to have a one way drain valve at the bottom of the air hose, presumably to drain off spit back collecting in the bottom of the hose, causing rich starting problems once engine was warm. This was done away with on later scoots/carbs. Anyone want to offer a reason why?
I had this issue on my OKO and was recommended to drill a 1mm. hole to drain off the spitback. Like to hear some thoughts on this.

[J1MS]

Don't know when they were first fitted or to what model carb. But I it was a cost cutting exercise when they stopped fitting them.
I think they would work well on most air box fed carbs.
The vacume caused the valve to seal then when the engine is stopped the valve releases and allows excess fuel to drain away, would still work today on a 22 dellorto, Lambretta must just have been cost cutting.

[wack 63]

I have tried drilling a hole and it doesn't work ,I think it seals over because the hole is too small.What we need is a dealer to get some new hoses made with the old style valve in.

[coaster]

I have tried drilling a hole and it doesn't work ,I think it seals over because the hole is too small.What we need is a dealer to get some new hoses made with the old style valve in.

I seem to remember Storkfoot tried glueing one into the remote filter hose on his 30mm PWK to cure the warm starting issue but it didn't work

[sean brady scooters]

the warm starting probs can have many causes..
build up of spit back fuel in the bottom of the hose is only one...and a hole or drain valve will usually help..
but if the fault is caused by say worn rings,excessive flooding due to wrong float heights/worn needle valves etc then the prob may well persist as they did even on the original lambos that had the drain valves...

in other words..if a drain hole does not cure matters ..then your problem and cause of it is more serious...and elsewhere...

[storkfoot]

I seem to remember Storkfoot tried glueing one into the remote filter hose on his 30mm PWK to cure the warm starting issue but it didn't work

Shhhhhhhh, yes, one of my less successful ideas . The petrol quickly disintegrated the glue

[pasner]

Any other idea? I´ve got the same problem with my new muggy 186, pwk28-30 and I dont like to wait for a minute untill the lammy starts working properly when hot. Should I check the float bowl?

[storkfoot]

My prob was on a Mugello 186, bgm PWK 28, PM expansion. After much messing and changing of needles in particular, I managed to almost jet my way out of slight boggyness mid range, and when coming off the throttle and quickly going back on. However, I didn't completely sort it until I put a hole in the panel and shoved a RamAir straight on the carb.

Before you do all this though you are right to check your float. Check both floats are level and set at 21/22mm

As a workaround until you get it jetted out, turn your petrol off just before you come to a stop

[chris2470]

I have a PWK 30 which although starts fine and runs OK it has become very boggy up to 1/8 throttle and I'm curious about the float levels. It now run a MB short manifold which tilts the carb backwards, the question is should I adjust the float levels to compensate for this?

[pasner]

I will check the float levels, but I think they´re correct. Does the 1mm hole work? It has to be many muggy users with pwk carbs with the same problem, I cant believe that everybody is having the same problem without a known solution