Gunson colour tune

[ttwlr]

Anyone use these ?
Just bought one on eBay. Looks an old one going by the box

Screenshot_20251116-195108.png (2.55 MiB) Viewed 68100 times

[Bill_qaz]

Svenedin is your man I'm sure he'll be along when he sees your post

[King Kenny]

I used one years ago, but it was not as easy as the instruction say. Nowadays I can tune my Traveller by ear. These may be helpful to a new owner and are probably better than nothing.

[svenedin]

Bill is right. I do like the Colortune. Using one of these does enable one to get the mixture very close very easily. Then the lifting pin and great care can get the mixture even closer. When I was little, people would know "a bloke" who could whisper a carburettor for a pint or two. The difficulty is that the A-series will not run happily with a bunsen blue flame. The mixture needs to be a bit richer. There is also a difficulty in that the mixture is not perfectly even between all cylinders. It is even more difficult if you have a PCV valve because the burn colour is affected by a spray of atomised oil. It looks like a background burn colour with fireworks. I have only once taken my Morris on a rolling road. It was tremendously accurate at idle but not at load. At load it was weak in terms of mixture.

Stephen

[ttwlr]

Bill is right. I do like the Colortune. Using one of these does enable one to get the mixture very close very easily. Then the lifting pin and great care can get the mixture even closer. When I was little, people would know "a bloke" who could whisper a carburettor for a pint or two. The difficulty is that the A-series will not run happily with a bunsen blue flame. The mixture needs to be a bit richer. There is also a difficulty in that the mixture is not perfectly even between all cylinders. It is even more difficult if you have a PCV valve because the burn colour is affected by a spray of atomised oil. It looks like a background burn colour with fireworks. I have only once taken my Morris on a rolling road. It was tremendously accurate at idle but not at load. At load it was weak in terms of mixture.

Stephen

They Do look good especially for me as I've never tuned a car before, I see a few people on YouTube talking about them and thought I'd keep a watch on eBay for one, some sell very high in price, but was lucky to get this one as I went up on a buy it now for £39 and nothing is missing.
Not found a video yet showing you how you tune carb, just seen flashing blue light.

[geoberni]

I always used one decades ago, so looked for one on ebay.

The one you've got looks good as new; they usually don't come with the bottle of cleaning fluid or it's empty.

I found the mixture on Basil was way too rich, it runs much nicer now, with less soot out of the rear....

[ttwlr]

That's good to hear Bernie,
Mines bound to running ritch, and yes, I've not seen one with bottle, add said hardly used it.
Can't believe how much some sell for on eBay one I was watching went for £77.

[Sleeper]

Re ... " the cleaning fluid" , is it Acetone??

Thanks

John ;-)

[ttwlr]

Thanks John

[svenedin]

I've actually still got the same Colortune kit that I have had for 36 years.

Many people say that you don't need a Colortune because you can adjust the mixture using the carburettor lifting pin. That is true but not all carburettors have a lifting pin and it does take practice to use that method. The Colortune is much easier I think. Just make sure that you release the choke cable pinch bolt before adjusting the mixture. If you don't, the cable can prevent the jet moving properly with the adjustment.

The "perfect" mixture is bunsen blue. That mixture is all of the fuel being completely burnt but our A-series engines were not designed to run quite so lean so some trial and error is needed. Heading towards a whitish blue flame is much too lean and the engine will run too hot. Conversely, a yellow/orange flame is much too rich but you would probably also notice that the exhaust is black and sooty and smells of unburnt fuel. A slightly yellowish blue seems to be just about right. If your engine burns oil then it will interfere with using the Colortune because it will tend to make the flame yellowish. Obviously warm then engine up to temperature before setting the mixture.

If inquisitive you can try the Colortune in different cylinders and you will notice that the mixture is not quite the same in all cylinders so it is always a bit of a compromise.

The main reason for getting the mixture right is to get the engine to run the best it can and not waste money by having a mixture that is too rich. All that achieves is sooting up the engine and pumping unburnt fuel out of the exhaust!

Stephen

[ttwlr]

Thanks Steven, I think mines running rich going by what you put.
But will be interesting to see what it does.
You have had yours a very long time, I bet your a master at it now, I remember people in 80s saying they just had the car colour tinned.
What is it you turn on the carb, is it just the brass Nut ?

[brixtonmorris]

Its great
I have used it for 40 years and on hundreds of minors.

[svenedin]

Thanks Steven, I think mines running rich going by what you put.
But will be interesting to see what it does.
You have had yours a very long time, I bet your a master at it now, I remember people in 80s saying they just had the car colour tinned.
What is it you turn on the carb, is it just the brass Nut ?

The SU HS2 has two nuts underneath. The top one (nearest the body of the carb) is for centring the jet and should not be touched. The lower one is for adjusting the mixture. Usually it can be turned with the fingers but if needed there is a special SU spanner for it. The adjustments from an engine that is running quite well to a well tuned engine are small, possibly as little as half a flat or one flat. Absolutely spot on is a fraction of a turn and takes patience. Remember though that all this does is get the mixture correct when the engine is idling. In theory with standard needle (AN for a 1098) the mixture is then correct throughout the rev range but that is not always the case. The only way to be sure throughout the rev range is to have the car tuned on a rolling road. If it goes well from simple idle mixture adjustment then a rolling road is not necessary. In my case, with a rebuilt engine, I could get the idle mixture perfect but higher up the rev range the mixture became too lean. A custom profiled needle determined by rolling road test was the answer. An engine that can be set to a good idle mixture but then runs too rich higher up the rev range suggests a worn needle and or jet.

Stephen