hs4 rebuild

[dorisandjack]

evenin' all! not long fitted my hs4 only to realise it needs a rebuild kit, I did buy one an it turned out to be wrong so time to fork out for another, I was wondering what the difference (if any) is between the black and red jets available, I'm running a new AAU as well

[bmcecosse]

One will be for the waxstat carb - but sorry I don't know which..... I'm sure Burlen will guide you. Why do you think the carb needs an overhaul ? What's wrong with it ?

[dorisandjack]

well it's an old carb anyway but when I kill the engine it's chucking a bit of fuel in still although the mixture is correct, I would assume a worn float needle?

[bmcecosse]

" it's chucking a bit of fuel in " - what does that mean ? The fuel pump keeps ticking ??? Is the float bowl vertical ? Yes maybe it needs a float bowl - but that's not an overhaul kit! If it's working, best to leave well alone. You didn't come back to say which inlet manifold you are using.....

[dorisandjack]

as in it'll keep running or at least trying to for a few seconds after turning the ignition off, yes float bowl is verticle and its a mini three branch with the inlet built in

[chesney]

Running on isn't carburettor related. Generally something glowing red hot in the combustion chambers, such as carbon build-up, exhaust valves overheating (poorly adjusted?), advanced timing, or potentially a weak mixture (though I've yet to experience that). Think about the principles, when you switch the ignition off, there's no more spark, so nothing to ignite mixture. There may be mixture continuing to enter the chambers by the suction of the falling pistons in cycle, but there is 'nothing' to ignite it, so not fuel related. In this case, something is igniting the mixture (which is being drawn in by design).
You can buy anti run-on valves, but try merely mask the problem. But it isn't over fuelling causing that.

[dorisandjack]

ah yes that does make an awful lot of sense, which way do I twist the dizzy to retard timing?

[chesney]

To the left, though it isn't necessarily the timing, that's just one cause.
I would use the manual adjuster on the dizzy first.

[dorisandjack]

righto! next question.. hahah, where's the manual adjuster?

[panky]

Thumbscrew on the top of the metal body of the dizzy

[bmcecosse]

Oh dear - running on is usually caused by RETARDED ignition timing. Certainly not a carb problem.......cancel the overhaul kit....

[chesney]

Could it not be argued that pre-ignition caused by over-advanced timing could be heating the exhaust valves past their usual 'threshold' perhaps? (Intrugued as I was enlisted to solve running on on a friend's Minor that was running way too advanced, retarding the ignition eradicated all trace of running on).-

[bmcecosse]

Probably could be either way - but usually hot running is attributed to retarded - advance = pinking and holes in pistons......

[chesney]

Looks like I got there in the nick of time then!
Thanks for the info.