For information, here's a photo illustrating something I've just spotted. The float is a quite sloppy fit to the brass arm on top. It's the two black rivets that are not firm so it can rise and catch on the side of the bowl. I've not put anything under to make it stay there. The float valve is raised by the arm so this might cause fuel starvation. There are scratch marks on the float showing that this has probably been happening. I've tried a good float and this doesn't happen. Actually I've been trying to locate reasons for high fuel consumption. I'm assuming this wouldn't contribute to that, but I'm keen to receive suggestions.
I may have hit onto something. I've just been and had another look and it can also stick at the bottom too.
From receipts I have it looks like the carbs I have have done around 30,000 km from new. The pic above isn’t one of them, just a clapped out carb I use for parts. However, what’s involved in fitting new bushes, and how much for a couple of sets?
I never seen tight bushes on solex carbs - even the ones that looked new(and they are 40 y old carbs however you look at it ) - remove throttle plate and spindle, cut thread into old bushes and tap them out, press new one in. i have them for £8 per 2bushes and 2 screws so £16 for two sets.
A sticky float valve will cause too much fuel to flow. My 1.6 Morris Marina once reached indicated 100mph flat out down hill past Rownhams Services on the M27. The SU carburettor fitted has a fuel overflow "overboard" , so I ended the journey with fuel pouring over the exhaust area (away from the plugs). The float had gone down all the way, and jammed in 5mm of rust in the bottom of the float bowl.
I had the same happen to an old Allegro of mine (Vanden Plas 1500 for the pedantic). My father had blocked up the overflow with blu-tak...Because it was leaking. Did NOT last long. Managed to put the fire out unfortunately.
float bowl should have a retaining clip which sits in the groove. you could test the float in a jar of water to make sure it floats and has no holes. also the needle valve should have a washer under it to adjust float height.
We came across one at Techenders where the clip had been placed under the hinge instead of on top. Coupled with a jammed metering valve and a stripped screw on the float chamber cover. The inside and outside of the carb were wet with petrol. It arrived at Techenders and died in the field. Next day it wouldn't turn over as it had locked up with petrol in a cylinder and the oil was mostly petrol. Some work with poking the valve , reassembling the carb properly , fixing the top with a long screw with a nut on it, and an oil change and the bus drove home.
As you see above this isn't the carb off my bus. I just fitted a duff float to demonstrate a problem. Seems to run much better now.
