Morris Minor Owners Club

Lately my car has started running a little rough on idle. It seems to vibrate more and makes the exhaust shake. I’ve checked plugs and their not fouled but sooty. All cylinders seem to be firing and there’s seems to be no loss of power when driving. I’ve recently replaced oil filter, sump and rocker gasket. Could someone advise on a sequence to follow to check for issues, I know there’s the carb and distributor alterations but don’t know where to start being a novice.
Thanks in advance

First thing to do is to try cleaning the plugs with a soft brush and check the gap (25 thou) and see if that cures the problem, at least temporarily. If so, check the plugs again after a couple of runs. If they are sooty again, it could be that the mixture should be weakened slightly, or the air filter is choked, or it may even be an ignition issue....although if you have not been fiddling with the ignition settings, I don't see why that should suddenly be a problem.

Before looking at settings on the engine, just check that the exhaust mountings are both OK (middle and rear) and that the pipe is not loose at the manifold (check when cold to avoid burn injury). Also, is the engine steady bar in place between the back of the head and the bottom of the battery box?

If those are all OK, then check that the jet is returning to its correct position after the choke has been pushed in. If you look underneath the carburettor whilst an assistant pulls the choke knob out, then you will see the jet move down. When the knob is pushed in, the jet should return all the way up until it is seated against the adjuster nut.

Does it run smoothly if you very slightly increase the idle speed?

Even checking the tailpipe colour, after a good run, should give some indication of running rich. Plugs should be clean after a good run, not fouled in any way - soot or otherwise.

A rocking/shaking engine could be because the idle speed is too low. Cleaning the plugs may improve the running temporarily but will not solve the problem. Sooty plugs (after a reasonable run) is an indicator of something amiss with the fuel/air mixture.

If this problem arises only at idle there is the possibility of fuel bypassing the float valve to a small degree, but more likely it is a simple maintenance issue.

Hello both
I’ve removed plugs and brushed, checked air filter and also choke as instructed. Little piston does return when pushed back in. Manifold seems firm and exhaust along its length has very little play. I started from cold and as you can see in video no problem. The second video shows it running a few minutes after starting, as you can hear it appears a little rough. I don’t know what I’m hearing I just know it doesn’t sound as good as it did? Any thoughts? Links to video below
https://share.icloud.com/photos/08eMmI2 ... pivLOxCDaw

https://share.icloud.com/photos/031NK9D ... dnoSIEjO3g

https://share.icloud.com/photos/0b7adiU ... BQFvzIff3w

One small observation - when you pull the choke out, give it a quarter turn clockwise so it holds position rather than sliding back in as demonstrated in your first clip.

All
I also adjusted the tappets using a feeler gauge, I followed instructions as per manual. It ran great afterwards although they didn’t really need adjustment, I just did it while replacing the gasket. I’ve done nothing else to the engine. I’ve checked plugs with multi meter also, all good. Any pointers appreciated.

From the videos attached is there any advice on what to look for?
As said was running fine and slowly started getting rough. Hadn’t noticed any loss of power but haven’t been out this weekend for fear of doing harm. The plugs were sooty and have recently reset tappets which was fine immediately after. The choke is returning the piston fully.
140 views on the videos! Is there anything more I could share which may help analysis?

Thanks in advance

That's a very rich and fouled plug, clean and wind the mixture nut up half a turn.

You will always have sooty plugs if you just start it on choke and don't push the choke back in and then go for a good run. Clean the plugs again, check the gap is correct and then get going for a good run on a nice bit of open road. Then, without letting the engine idle overmuch, stop the car and check the plugs again. If sooty once more, weaken the mixture as advised and try again.