Carb tuning with a Colortune, help please!

[djg42]

Hello,
I got a colortune to help in rejetting my bike. Testing the idle mixture is simple enough, but how do i use the colortune for midrange and full throttle?


I went up a few sizes on the mainjet. My idle is good blue color, but when i give it 1/2 to open thottle the psark turns pure yellow. Does this mean the main jet is too big? I havent done anything to the needle yet.

I read this on another thread,

"tuning in the needle part of the circuit with a colourtune you'll need to disconnect a sparkplug and hold the throttle around half - three-quarters open. (If you dont pull a plug it will rev its nuts off)"

any help would be greatly appreciated!! thanks,
DG

[sam78gs750]

Yellow flame=too rich. So yes, your main is too big. Go down a size at a time until you get a nice blue flame on the mains. As far as removing a plug (other than the one you're replacing with the colortune?) for the needle circuit, I never heard of that. I'm curious why you would need to do that as well....

[djg42]

thanks i wasn't sure if all throttle ranges were supposed to burn blue.
i was lacking power in mid and full range, so i figured i was lean- could a rich condition cause poor acceleration too?
THANKS!

[TiberiusM]

Theres a guide on the Morgan page here http://www.carbtune.co.uk/colortune.html

Its a scan of 4 pages from the instructions maybe? Can be kinda hard to read
Page 1
Page 2
Page 3
Page 4

So according to those, you should have a slight yellowish color midrange....if I'm reading those pages correctly

[ddaniels]

Do any U.S. guys order and use this Colortune? What's the price of it? I don't know the conversion from Euro's. Is there a place in the U.S. to get it?

[djg42]

i got mine on ebay-it was used and missing the mirror so it was only $15, when i looked there were plenty for $45
if you see one missing the mirror its worth itt, you can use a any old mirror.
Has anyone used the colortune to jet there carbs? Can you give me some advice? I though it was running lean but the spark is yellow when i give it throttle??Thanks,
DG

[bwringer]

A Colortune is great for getting adjustments and jetting fairly close, but you still have to fine-tune by test riding to see how the engine performs under load.

Also, the directions mentioned that you should not use the Colortune plug for extended periods at high rpm. What exactly that means in terms of time and RPM limits is hard to tell.

[djg42]

is it correct that when you open and close the throttle up to 4000 rms, the spark should be yellow, not blue?
at high revs what color should it be?
Thanks!

[chef1366]

Colourtune is a good tool to get you in the ballpark with the idle.
That's it

[sam78gs750]

is it correct that when you open and close the throttle up to 4000 rms, the spark should be yellow, not blue?
at high revs what color should it be?
Thanks!

if you snap the throttle open to the needle or main and release, it will and should be yellow (rich) for a moment, when held there it will turn blue if you have the right needle settings and jets in.

Also, the directions mentioned that you should not use the Colortune plug for extended periods at high rpm. What exactly that means in terms of time and RPM limits is hard to tell.

open the throttle to needle circuit, look at the color then shut the throttle. twist the throttle again to the main jet. 2 seconds at each is more than enough to tell where you are at. adjust needle/change main jets as needed. When it's burning blue on all circuits, do plug chops on each circuit to confirm under load.

A Colortune is great for getting adjustments and jetting fairly close, but you still have to fine-tune by test riding to see how the engine performs under load.

Agreed. revving on the stand is a good indication of where you are at, but plug chops should still be done to confirm. Colortune works best for setting idle circuit. On the needle and main it saves you from having to do plug chops at every step of the way.

[Danjal]

Ive seen the color tunes, but how exactly do they work?

[sam78gs750]

Ive seen the color tunes, but how exactly do they work?

you take your spark plugs out and replace them with the colortune plug one at a time (or if you want you can buy 1 for each cylinder but I think that would be unnecessary expense...). It has a clear "window" at the top of the plug that allows you to see inside the combustion chamber. You start the bike and adjust your air/fuel mixture by what color the flame of the igniting vaporized fuel mixture is inside of your engine. Yellow flame=too rich, White/blue white=too lean, Bunsen Burner Blue=just right.