Greetings All, having just got my car back on the road and taking it out to reduce the 'running in' milage at every opportunity I was rather miffed the other day when I noticed that the engine has begun to run slightly 'off tune'
It starts well but on tickover when warm, just hunts and misses slightly from time to time. Rather than a nice smooth purr
Now, I run a Weber 30DGF on a low level alloy manifold that has always performed well - the plugs (NGK BPR7HS) show good clean colour, but the exhaust is slightly sooty
The colourtune shows a picture of nice even mixture at tick over with the addition of the odd flash of rich mixture in time with the hunting. It also indicates worn parts (diaphragm and metering needle/jet) the funny thing is that this must all be happening with only the primary choke open, with both chokes in operation the engine pulls well and runs if anything slightly lean as it pops back on overrun hence the clean colour on the plugs. I have a service kit for the carb and will change everything and try again, but I do wonder if the overall tune of the engine is in some way producing the symptoms, but the cam is not too wild - yet
I'm also sorting the upgrade to the carb department with a Solex C35PHH which seems to have just about the ideal choke/venturi combination with 35mm choke and 31mm venturi for this size of engine. It will also be a jump from the Weber 30 DGF with only 23mm venturi, I'll keep an update with pic's as I progress.

Ian.

Not had much time to really get into the overhaul of the carb, but have managed to remove it without dropping any nuts or washers - bin there - done that
One of the stud nuts is very close to the choke mechanism and can be a faff to get off with the rocker box in place (not going to remove it as it's not leaking)
I found the kit on ebay at a reasonable price and I'll list the parts as I strip it to get a record of all the E-tubes and jets etc plus any damage and/or worn parts.

Ian.

It's a fixed jet carb, so you can't alter the running mixture unless you change jet sizes. Hunting on tickover is often a sign of a weak mixture, and this can be adjusted with the slow running mixture screw.

Sooty exhaust is normal.
When we had leaded fuel, the exhaust was grey, which was actually lead deposits, not a sign of correct running. With unleaded fuel, no deposits, so we just get the soot. Normal.

portland_bill said:

It's a fixed jet carb, so you can't alter the running mixture unless you change jet sizes. Hunting on tickover is often a sign of a weak mixture, and this can be adjusted with the slow running mixture screw.

Sooty exhaust is normal.
When we had leaded fuel, the exhaust was grey, which was actually lead deposits, not a sign of correct running. With unleaded fuel, no deposits, so we just get the soot. Normal.

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Thanks Nigel, Appreciated I'll bear this in mind when I service the carb.

Ian.

Greetings, I have started the strip of my Weber 30 DGF 1/252 and will start a more appropriate thread to deal with it all.

Ian.

If you feel the need to clean any jets, do not poke wire down them, it will make the holes bigger. These are precision holes, as the mixture depends on that. Old toothbrush bristles can be good, they don't do any damage, but don't lose them inside. Carb cleaner sprayed the opposite way to the normal fuel flow should clean them out fine.