Morris Minor Owners Club

Today I tried out one of those Gunson CO testers on my wife's Moggie. Trouble is I have no idea what would be a good CO % value for a Morris Minor. The European emission standards aren't any help because they specify grammes per kilometre. You can read on the internet that 0.5% is a good value for a computerized vehicle, so I was shocked when the Moggie came up with 4%. Not that the equipment inspires much confidence (sorry Gunson) but it does prompt the question what percentage value you should achieve at idling if the car is properly set up. Can anybody shed light?

4 % is very good for an old A series. There is of course no need to worry come MOT - the requirement there is 'visual'.....

never bothered me

Nor me... no point setting for idle as the engine isn't working then. Err on the side of rich.

Exactly - it's the working CO that will tell you how it's running. But in fact - best guide for that is plug colour after a good hard run.

Thanks to all for constructive feedback. Worth mentioning that MOT emission test (for modern cars) is done at idle. Having re-adjusted the mixture to get a low reading on the Gunson has definitely improved the running of the engine. Plugs were russet brown before and just a tad lighter russet brown now. Just a question to bmcecosse. Why do you say that 4% is a good value? Is there some reference material out there?

For an A series - 4% is a very good result!! Some Minis have to reach that standard. Modern cars of course are ZERO.

Also, modern cars don't have carbrettors to wear and fall out of adjustment causing mayhem with these readings...