I have a Brosol H30/31 (well a copy) on a 1600TP (on the beetle but hopefully someone can help here!). Was bought when I had a 1300, but since been rejetted to suit the new 1600 (via advice on vw resource pages). It won't idle on the idle circuit. Set throttle arm to paper thickness plus half turn in. With the normal base settings it just runs, very slow and you can see a black haze and smell the fuel coming out the exhaust - mega rich. If I screw the air screw out it helps, but not massively. If I screw the mixture screw in it will run even with it all the way in. Only way I can get it to idle well is by cheating and using the throttle stop to effectively bypass the idle circuit. Set like this it works well. Only confusion is then if I pull off the idle cut off valve power lead it still stops the engine, even though the idle circuit is bypassed. If it were the other way around and I needed to richen it right up I'd guess air leak allowing air in, but this appears to be allowing fuel in somewhere as I can't get it lean enough? Is it the idle jet too big (to be fair its as specified by vw resource who I've found good in the past) do you think? Or is there some other possibility? Driving me mad, its a simple carb but it doesn't seem to work as it should. Got an old solex 34, rebuild kit and metal bushes on the way to replace it, but want to understand this!!
Cheers! Idle is 55. Float height was checked, it was bang on what it was supposed to be (can't remember what that was!) handy as it didn't come with any spare washers. Don't think valve is leaking, it did on the old carb and you could see it coming out the overflow. Worth a check though. Noticed that there is a small gap round the jet shoulder should there be an o ring in there sealing it? Nothing on the old one nor in my solex....
