Afternoon all

I installed a Brosol H30/31 carburetor on my Beetle motor this morning in place of the original 31PICT carb.

As I was test driving it the throttle stuck open varying amounts several times.

It seems to happen when the car is warmed up. I let it cool down and the throttle worked fine. I took it out for another run and it eventually started doing it again. When I got back it was consistently sticking open.

It seems to only get stuck after you open the throttle all the way up.

I've eliminated the accelerator cable as it never did this with the old carb and just moving the throttle lever on the carb will cause it to get stuck.

My second thought was that the carb was a different size and it was interfering with the alternator when you opened it all the way up, but there are definitely no clearance problems.

Also the spring is okay. It feels considerably tighter than my old carburetor actually.

If you move the throttle lever by hand you can feel it resisting as though it's caught on something, and it will actually resist quite a lot of force pushing it closed.

Anyone got any ideas? I'm stumped. I guess I'll take it off again and see if I can see where it's sticking.

Cheers

Andrew

Have a look for scrape marks inside

My guess is the throttle plate / butterfly is getting caught on the carb body

It was the butterfly rubbing on the body of the carb. The most likely cause for this is that it's missing half of the screws it's supposed to have holding the butterfly to the thing that the butterfly mounts onto.

Since I couldn't scavenge an equivalently sized screw from the original carb, I've swapped them back.