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SU adjustment.

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Rubber hose will get you very very close.
 
Steve_S said:
Rob, you been workin' on that virtual B again? Nice sig!
Click to expand...

yeah, I've picked it up again. However, I didn't start over from "scratch" this time. I went back and looked at all the different models I had and started working with the one that was 'the best of the bunch'. I'm modeling the interior right now. I was gonna ask you for some shots of the '65s steering column pretty soon. I don't need them 'just yet' as I'm still tweaking the seat, but I'll probably need some within the next week or so. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
It'll help more to see how it fits in the dash. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

I'm taking my time with this go. So, it may be a while before I need any reference pics. When's the next gathering? /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
 
Thats a fine idea! one colour tune for each carb!

I just had a go, never used one before, I knew she was running rich so I weakened her off.

The adjusting nuts could be turned by fingers, which I thought a little odd, especially as so many folk talk about the adjusting spanner. There certainly was not enough resitance in the nut to make me think it was acting on the spring. I screwed the nut up the jet until I could not do it with fingers anymore and would have needed a spanner. I guess it has come up against the spring.

The colour tune showed a light blue colour in both number 1 and number 4 so I guess its close.

She is now idling smoother and no black smoke, I went for a quick blast, about a mile, came home and pulled number 1 plug, the very tip has started to lighten in colour.

She might not be spot on but she's a lot closer.

I might experiment tomorrow with the lifting pin:-

If the engine speed increases, the mixture strength of the front carburettor is too rich.

If the engine speed immediately decreases, the mixture strength of the front carburettor is too weak.

If the engine speed momentarily increases very slightly, the mixture strength at the front carburettor is correct.


Thanks all.
 
The adjuster may indeed be as easily turned as you describe. It ~should~ have some amount of resistance from the spring to keep it located. I'd say if the mix was adjusted to *just* blue, you've got it spot-on! Well done! /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif
 
piman said:
Hello all,
i have always worked on the principle of the same number of colourtunes as carburettors. Don't forget that there is a balance pipe between both carburettors and so there is some interaction, i.e whichever cylinder is drawings draws from both, but not equally I suppose.

Another factor that upsets a colour tune is if the engine draws in oil at idle, (worn guides\seals) that cylinder will always be rich.

Alec
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So you put a colortune in #1 and #3, and then do you tune the front one and then the back, or tune them at the same time, like lean/rich one flat up front, then same thing in the back?

I was always taught that whatever you did to one, you needed to do to the other within reason. They might be one or two flats off or something like that.

Two colortunes sounds like a neat idea, but i may be too much of a cheapskate to do it.

Thank you,
-Bill
 
Durn, I'm too much of a cheepskate to buy one. I just use the methoid in the manual, you know, lift the piston.
 
Lifting the piston is more useful than a color tune, imho. Those things haven't worked properly in 20 years, thanks to modern fuels. They are especially useless in older cars.
 
Ethanol will save th' planet, then.
 
Steve_S said:
Lifting the piston is more useful than a color tune, imho. Those things haven't worked properly in 20 years, thanks to modern fuels. They are especially useless in older cars.
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The problem I have with just lifting the piston is that I rarely, if ever, get a textbook response.
 
There is some amount of "back-n-forth" when doin' dual carbs, but nothing daunting. Get a good balance of air draw between 'em at tickover (500~750 RPM) then fuss with the pins or ColourTune. Then back to idle speed/balance for final adjust. I've not had a problem using the ColourTune gizmos in any of the older cars, from MGs 'n Triumphs to V12 Jags. The "lighter" fuels may be a different story but I haven't had any issue. :shrug:
 
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