Colortune proceedure, just checking?

[Sundowner]

Tomorrow I'll be having a final shot at setting up the HS6's on my Sprint. They were rebuilt a few years ago, but with very little use since. There are no vacuum problems. Sports air cleaners fitted.
I've used Colour tunes before, but only in single carb situations, never for multiple carbs, so please tell me if this angle of attack is wrong (or not)......

I warm it up thoroughly and separate the two HS6's.
I throttle the rear carb back completely and set the front carb so the engine is idling around 1,000RPM.
I insert the Colortune into #1 and proceed to set the front carb's mixture.
I shut down the engine, move the Colortune to #4, shut down the front carb, set up the rear carb as before and adjust accordingly, so that it matches the front carb.

Should I repeat the procedure with #2 & #3?, or will the above be good enough for everyday driving?
I have a Unisyn for balancing the airflow..... I've got that bit down pat.
Is there anything else that I should attend to?
Cheers,
Rob

[xvivalve]

Unless you have a different colourtune to the ones I've seen, the depth of the spark plug tube on a Sprint prevents its use...

Have you seen this?

viewtopic.php?f=30&t=33689

[SprintMWU773V]

The tool usually comes with an extension wire which I have successfully used on a Sprint engine. Whether I've ever actually found a colourtune useful is another debate. I have one but I have found that actually you can easily be miles out and still achieve a good blue flame through the window as it were. Personally I've found a gas analyser more useful and provides some useful numbers when setting up for the emissions test whereas a colourtune is really just a shot in the dark. You don't need one to figure out if you're running too rich or too weak, your nose will tell you that.

[Mad Mart]

You can use a colortune kit on a Sprint and I have done a few times. But I agree with Mark, not the best results, but better than nothing.

[Galileo]

I've had no problems with using a Colortune but it's the newer version with the slimmer body. Though you can't use the mirror tube properly you can balance it on the wire. I've always struggled with twin carbs and the gas analyser on it's own...

[Sundowner]

I've had no problems with using a Colortune but it's the newer version with the slimmer body. Though you can't use the mirror tube properly you can balance it on the wire. I've always struggled with twin carbs and the gas analyser on it's own...

I too have the newer/slimmer version.
But since you've had no problems, could you confirm that the steps I mentioned in my initial post are suitable please? Or perhaps share the procedure you use?
Cheers,
Rob

[Galileo]

Fairpoint, that was your question after all.

I guess with Colortune it's the old maxim of I would not start from here if I was you, differing fuel mixes including ethanol nowadays mean they're probably wrong anyway but in the absence of an o2 sensor in each exhaust port then they can be a guide. When I set carbs I do this:

• Slacken off the throttle link.

• Colortune in cylinder 1, set carb so it's leaning towards the richer side in colour.

• Repeat for cylinder 4, I'm really more interested that the colour is the same in both cylinders than the precise shade.

• Balance the carbs and then use the gas analyser for the final adjustment moving both jets the identical amount.

• Tighten back up the throttle link

• Go for a drive ensuring that I 'make good progress' and judge results.

Proper mechanics (and my dad) sniff the exhaust have a listen, and then do some sort of magic, I need gadgets...

[Sundowner]

Thanks Galileo,
It would appear that I was on the right track.
Now to get out there and get it done so that I can watch the F1 boys qualifying in the wet this afternoon.
Thanks again,
Cheers,
Rob

[Sundowner]

After a couple of hours mucking around I've found that Colortune's aren't good on Sprints.
I went through a process as I listed above, but even though the "indications" said it was right, the car was idling very lumpily and obviously rich.
So I reverted to the old tried and proven method and again I have smooth idle, and crisp throttle response.
As I mentioned earlier I have used Colortune's on single carb engines with much success, the last being my Mk1 Zephyr, but they do display misleading colours in the Sprint.
Cheers,
Rob

[Galileo]

I completely agree, use as a method for balancing the A/F mix but not for setting it overall.