fuel problem continues grrr

[hdavy]

After about 15 mins use engine won't idle properly and eventually stalls. Given a blast with open throttle will go but will not idle at reasonable revs. Eventually won't run properly at all. (1098 with regular carb which has previously been OK for 12 years). Mixture setting seems quite correct.
Fuel pump filter clear and always seems to be fuel in float chamber. So far have tried spare pump, new electronic pump (hopeless) and refurbished standard pump. Have blown down fuel line. No fuel intake leak. Revved engine with finger over carb air intake to increase pressure through jet which have done successfully before on other cars.
None of this cures problem. Looks as if it's not a pump problem but some fuel flow between float chamber and jet. So what next? Dismantle float chamber/jet. Ugh.

[charlie_morris_minor]

sorry forgive me if you have already been asked this in a previous thread.. but what is "reasonable revs" and what is the problem is it dying at tick over or running lumpy / hunting.

i had a problem with a carb that worked fine until i cleaned it and the lite oil i had put in to overcome the dirty carb for a few years was now to lite.. changing back to the correct oil corrected the problem

[hdavy]

Charley reasonable revs I call roughly between 800 and 1500. Not really lumpy. Just stops suddenly. I use the recommended light oil in the dashpot. What do you use?

[panky]

It seems to be happening once the engine has warmed up - is the choke sticking on, does the piston slide up and down easily and land with a gentle thud indicating it's down properly. Alternatively it could be running very lean, try turning the jet out a couple of turns just to see, you can always put it back.
For info I've been using EP90 in the dash pot, but I've got a HS4 fitted to a different head.

[hdavy]

Panky. The piston slides and clicks down very well. I have altered the mixture both ways. Stuck.

[panky]

I notice you said it was hunting, this suggests to me a weak mixture and to check for air leaks - manifold, vac advance line. Does it make any difference if you pull the choke out when it's struggling to tick over.

[charlie_morris_minor]

I notice you said it was hunting,

i think that was in my question trying to get more of a description ..

have you tried checking the piston drop when the problem occurs i.e. when the engine is warmed up.. the problem i had was that when everything was cold it worked fine in the garage and during the quick spin i took the car on after the carb rebuild but when it was all warmed up properly, after a good run, the piston was not damped properly and rather than slowly close it just fell like a stone .. it was fine when revving up and running but as soon as i took the foot of the accelerator it would die changing the oil to the recommended oil fixed it straight away.

have you looked at the electrical side of things.. condensor / coil etc ( over to you Roy ) in case it is something breaking down when getting hot?

[bmcecosse]

Plugs may be oiling up. What plugs are in ? I suggest Champ N9Y will be suitable
I doubt my engine will idle for 15 minutes.... Are the plugs wet / oily when it does this?