Spitback

[dapper]

As Lambretta decided to do away with the one way drain valve on the bottom of the carb bellows (bloody cheapskates) and a lot of us still suffer with spitback on piston ported kits, I'm thinking of getting a mate at a local factory to knock up some brass drains with a 1mm. bore drain hole to which you can attached a length of clear plastic drain tube that would be long enough to at least hopefully stop your side panels, fan cowl and rear wheel getting covered in crap. There would be a dish shaped 10mm. wide part inside the bellows and a 3mm. threaded part on the outside of the bellows to which a nut& washer could be tightened, with the 1mm. bored tube exitting through it. It wouldn't be a one way valve as in the original as I think this would be too difficult to manufacture, unfortunately. It would mean making the 3mm. hole in the bottom of the bellows where the spitback collects.
I've been running open mouthed on my carb this year and the underside of the runners, flywheel cowl and rear wheel etc. are absolutely filthy. I tried running with a breathe sweet filter, but the spitback collected when stationary at tickover at traffic lights, etc, and caused engine to flood, leading to embarrasment and numerous kicks to get her started again.

What do you reckon?? A complete waste of time and effort??

[wack 63]

I've tried something similar but unfortunately it doesn't work as the bellows need a reservoir to collect the spit back , GP type bellows just hold the fuel as a meniscus forms over the small drain hole. Maybe a larger hole would work but what we need is a dealer to get the GP hose remade as per the 18mm bellows with the trap.

[goldeneye]

I used a vespa brake adjuster trunnion, with the hex head bit ground down to a flat, a hole drilled in the bottom of the bellows, and the adjuster pushed through, with its locking nut on the outside, and a bit of clear hose going to the original hose clip on the fly cowl. worked well on a 30mm dellorto with a remote filter.

[dapper]

Well, at least I didn't get ridiculed

[DigDug]

Well, at least I didn't get ridiculed

Give it time...

[dapper]

I was waiting for you to pop up

[sunrisemac]

brass drains with a 1mm. bore drain hole to which you can attached a length of clear plastic drain tube that would be long enough to at least hopefully stop your side panels, fan cowl and rear wheel getting covered in crap. There would be a dish shaped 10mm. wide part inside the bellows and a 3mm. threaded part on the outside of the bellows to which a nut& washer could be tightened, with the 1mm. bored tube exiting through it.

Did just that on a standard GP when I first rebuilt it and had flooding problems and it drained the bellows beautifully, I did have quite a longish pipe ending just below the flywheel cowl.

[dapper]

I used a vespa brake adjuster trunnion, with the hex head bit ground down to a flat, a hole drilled in the bottom of the bellows, and the adjuster pushed through, with its locking nut on the outside, and a bit of clear hose going to the original hose clip on the fly cowl. worked well on a 30mm dellorto with a remote filter.

Any chance you could point me to said Wesper brake adjuster trunnion??

[Architecten]

I tried this and it did drain but not sufficiently enough to allow me to jet the carb. I'd bought the bellow/ramair combo from MB and ended up cutting off the filter and clamping to a bellmouth on the carb and cutting a hole through the side panel. I've probably got the drain in box somewhere if you want it... it's basically a small brass fitting and drain tube that fits into a 3mm hole at the bottom of the bellows.

[Architecten]

Here it is in action...