Help with colourtune and carb settings

[Guest]

My bike is a 1979 Suzuki GS1000E with the 28mm VM slide carbs.Just fitted new fuel screws set initially at 1.25 quarter turns out on each of the carbs. I have set the air screws at 1.5 turns out. Have synched the carbs and look good and even. Bike starts fine, have tried slowly turning the air screws for the max rev technique, but have to be honest there is no pickup in revs. So fitted the colourtune plug to observe the flame colour and manipulated the air screws to give a blue flame which turns out to be 1.5 turns out. Is this the right technique please. Any advice on using the colourtune would be appreciated.

[tkent02]

Try the fuel screws about 5/8 - 3/4 turn out.

[hampshirehog]

I'm surprised your air screws are showing blue at only 11/2 turns out with your fuel screws 11/4 turns out. Are these the new 'long' fuel screws from Z1? The might have a slightly different taper on them to original.

[gs79]

Thanks for the reply TK, just for info, I am running a Vance Hines 4 into 1, with bellmouth carbs, and dynojet stage 3 kit

[gs79]

Hi Wally, yep they are the Z1 fuel screws my friend

[chuck hahn]

yes...turn them in ( the bottom ones ) to about 3/4 to 7/8..no more is needed. THEN you do the colortunes to see what going on...and you want to see the color at around 4,000 RPMS as well. Be advised that from idle to a quick run up youll notice that the flame will go yellowish orange then smooth back to the blue...thats whats normal as the carbs suck in bunches of gas to get the engine revved up...then it will settle back as the system balances back out.

[gs79]

Righty oh! will turn the fuel screws in to just over 3/4 and check with colourtune, particularly from idle upto 4k,. So is the adjusting of the flame colour done with the fuel screws or the air screws.

[hampshirehog]

I'm going to go against what the others are saying - just to confuse things. Your Colortune won't lie to you - blue is blue.

Up your tickover a bit (you can just hold the throttle open a tad rather than screw the adjuster in) and take a peek at the colour. If she starts to rev too high pull a plug lead or 2 off to keep things under control. If the colortune stays blue you're ok.

Then take her out for a test run. No opening the throttle more than 1/8th (mark it with tape so you can see it). If the pilot circuit is tuned in you should have a nice colour on your plugs.

[hampshirehog]

So is the adjusting of the flame colour done with the fuel screws or the air screws.

Both. In effect out on the fuel screw richens the mixture and out on the air screw weakens it. The idea is to get the airscrews 1 - 2 turns out and even(ish).

[chuck hahn]

Actually HAMP, there are 2 colors of blue in a cylinder..one being the type of blue you see when you light say a propane torch and then there is a brighter..almost whitish blue. The propane blue is perfect fuel to air mixture. the whitish blue is a way too lean blue..so your statement blue is blue is incorrect.


You adjust the flame with the mixture screws on the side of the carbs. Turning them IN richens the mixture and turning them OUT leans the mixture. Turn them in till you see the yellowish orange and then out 1/8 at a time till you just see the flame is blue..then just you run up the RPMS and observe the flame as you go up. Do fine adjustments as you see necessary. The videos Ive watched say around 4,00 because 3 to 4000 is an "average" cruising RPM under most cases..not all though.

[chuck hahn]

Again Hamp..getting all the mixture screws to 1 to 2 out is a misnomer...each cylinder will requires its own setting based on the ACTUAL color of the cylinder. I have had some as far in as 3/4 of a turn in and the flame was perfect..others as far out as 2...so you really need to set each cylinder as it is showing you its needs



Best way to remeber which way turning the screws effects the fuel mixture is to use this saying..

remember the word ENRICHEN..now replace the E with an I and you get INrichen.

[gs79]

Thanks for that, have had the colourtune on all four pots and registers blue from idle and upto 1/8 throttle remains blue and same upto 3500 revs, so I guess I am not to far away.

[hampshirehog]

You are right about the blue Chuck - I was being a bit casual.

I was disagreeing with you ref the fuel screw settings because normally at 1/14 turns out he would be having trouble getting the air screws set within range. That makes me think the taper on those new fuel screws could be different (I haven't come across them yet so I'm just speculating).

[chuck hahn]

Depending on what color it turns AFTER 3500, youll just adjust it another 1/8 turn on the screw..if it goes whitish bright blue then youll turn it INricher and if it goes yellowish orange youll turn it OUT to lean it just a tad. It takes some fiddling but youll find that sweet spot your looking for.

[Steve]

The settings used will vary a bit from bike to bike, but there are some "ballpark" settings that will get you started.

For a bike with stock airbox and exhaust, start with the fuel screws (on the bottom) turned out 5/8 to 3/4 turn, start with the air screws about double that.

For a bike with pods (or your bellmouths) and a pipe, start with the fuel screws about 7/8 to one full turn out, and the air screws again about double that.

Further tuning with the Colortune will be with the air screws. Turning them IN (clockwise) will richen the mixture, turning them OUT (anti-clockwise) will lean the mixture.

I agree with hampsirehog, I am surprised that you are getting decent color with the mixture that rich, but, like was said, "color is color".

I will disagree, however, that all the settings should be even. There will be slight differences in the manufacturing tolerances of each carb and all its parts, so don't get stressed if one carb has the air screw out 1 1/2 turns and another one is 1 5/8 turns. Just do what is right for that carb.

.