Colortune

[cadetchris]

literally just discovered these and they do seem a very good idea.

are they worth the money or is it best to rely on ear and experience when adjusting ones carburettor?

[bmcecosse]

Don't waste your money....... No need with an SU carb - lifting the piston tells all.....

[cadetchris]

thought so, clever idea though

[peterpimlico]

"Lifting piston tells all ....." Please tell more?
Regards .... Peter

[chrisd87]

There's a small pin on the underside of the carburettor that's used to lift up the piston a fraction of an inch. You want to get it so that when the piston is lifted, the engine momentarily speeds up a little, then returns to normal idle speed.

Although I've got a colourtune (was given one), I tend just to use the plugs as an indicator of the mixture strength.

[dunketh]

I have one in a nice black box.
The fact it never leaves its black tells you all you need to know about it.

I actually find an exhaust tester a great way of setting idle mixture.

[bmcecosse]

Idle mixture is easily set 'by ear' - with the lift pin as a check. However - it may bear very little relationship to the overall running mixture, which is checked by inspecting the plugs after a decent run - not after pottering around town.... Colourtune has no sensible use on a car with SU carb(s).

[peterpimlico]

Maybe I should be asking this question under another heading..... Tuning!...... So, I lift the small pin and adjust until more revs appear, then look at the plugs after a longish run and the plugs will look like ??????????? Sorry, I'm a little confused! Not your fault of course, but could you please explain in more detail the best way to tune a carb?
Regards ....... Peter

[bmcecosse]

Engine needs to be hot - so after a bit of a run. Lift the pin slightly and if the engine revs up noticeably, it's too rich - so weaken it slightly and try again. Correct setting is when nothing much happens when you lift the pin...... Plug colours - correct is light beige, too weak is white, and too rich is brown-black.....

[peterpimlico]

Many thanks for that information.
Regards .......... Peter