Mixture....too rich ?

[NoviceM]

Morris Traveler 1970, 1098cc engine usual SU carb.
Checking colour of spark plugs after a reasonable few miles drive....colour of central porcelain insulator looks fine ( light chocolate/cream). This suggests to me that fuel mixture is correct.
But.....when I start with engine reasonably warm, no choke...the exhaust throws out a distinctive sooty stain on the drive out of the pipe....this suggests that the mixture is far too rich. !
I must admit to being confused. Is it too rich ,?
Any advice greatfully received.

[Andmurph]

Apparently this is quite normal behaviour for Morris Minors.
I have previously posted about the sooty calling card our 1098 pickup leaves every time it is started, regardless of choke usage. It’s embarrassing to park on friends posh driveways. Not because of oil leaks but because of the sooty patch it leaves when you start it.

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[Sleeper]

The fuel mixture does alter during use ... looks a little rich at tickover...you're getting into the black art of needle profiling/changing...

John ;-)

[oliver90owner]

Maybe time for a carburettor overhaul/adjustment?

[Bill_qaz]

Possible valve seal or worn guide oil in cylinder on initial start giving the puff of black soot.
Mine done it since owning but usually only when been parked up for a week. I have a piece of cardboard to stop marking the workshop floor on start up.
No excess oil consumption, starts easily, runs fine, hence C.A.D. solution

[svenedin]

Your spark plugs give you a good idea of the fuel mixture and it sounds spot on.

Due to the design of the exhaust it is absolutely normal for it to have a bit of a smoker's cough. The exhaust has to go over the top of the back axle. This creates a trap for water from the combustion of fuel which mixed with a bit of soot, the exhaust is prone to cough out on start up.


Stephen

[NoviceM]

Many thanks to all folks who took the trouble to post advice, very helpful.