Colortune Diagnostic Colour Chart

Hi All, apologies in advance if this already posted elsewhere. I thought it probably must be, but I've searched for it and couldn't find it, although I found some very good articles on carb cleaning by Rick. Maybe I just struggled because of the mixed spellings of 'colour', I don't know, but back to my request:

Does anyone have a copy of the colourchart that they could post or send to me ? (post as in post here - I don't need your only copy !)
I've bought the kit and adjucted it until it's rich then backed it off until it's blue, but feel that it's a little richer than I want it. The black and white instructions mention bunsen blue, but my bunsen flame burns with two colours (inside and outer flame) and don't know which they mean.

I'd like to be able to try and do it by the instructions before I try my own method.

Thanks.

 

There is no color chart but your setting is very close. I always tune to rich which is a yellow flame then turn the screw in until the yellow is gone and I see blue. Then I turn back out until there is just a hint or tinge of yellow. At this point the adjustment is done in 1/8 turn increments. The first blue you see after yellow is bunsen blue.

 

Well that would be fine, but some other posts have said that this setting will give CO levels of about 4.5% (which my exhaust tester agreed with) whereas we should be aiming for about 1%.

Hopefully this will give much better mpg with acceptable throttle response and performance. Or am I off the mark, here ?

I haven't done enough mileage on it yet to see what difference tuning has made - I want to do a few more before I check it again.

 

Actually there is a color chart but I never used it after I found out I want the flame to be blue. There's a range of only about 1/2 turn either way that goes away from blue to yellow for too rich or nothing and it cuts out for too lean so the blue in between is easy to find.

 

BTW, it's impossible to get a reading of just 1% because the engine won't run that lean. You'd have to install a catalytic converter to get that so stick with 4%. Either way, it won't increase your mileage unless you just idle all the time and don't go over 5 MPH.

 

To get the best mileage on the highway with acceptable performance you have to adjust the pilot jets, tapered needles and main jets so you get a reading of around 4.5% at all speeds and throttle settings. If it's much above 4% and too rich you will be wasting fuel and if it's lower you run the risk of causing engine damage so you'll have to strap on the exhaust tester and take it out on the highway or run it on a dyno to check it. Or you can do what I did and install an O2 sensor in the exhaust manifold, put a readout on the fairing to indicate the mixture and then adjust the carbs to always keep the reading in the green on the center of the meter.

 

Then this is an invalid topic. The colortune is not made for such precise settings. You need to set the carb with a bridge four gas analyzer. Only it will tell you when "your" bike is at such a setting. You are dealing in specifics which are specific to your bike it's carbs and it's valves.

 

From using the Colortune I saw some different shades of blue, including one that was quite vibrant. From an aeshetic point of view, it would be satisfying if this were the colour to aim at.

Some people have said that the change occurs in only a few degrees, but from using it it appears that 1/8 turn is still a fairly small increment.

I have a Gubson 'professional' gas tester, but I also have a 4 into 1 exhaust. I can set the carbs and then check afterwards, but not each pot individually. CO levels were much higher after I had adjusted the carbs: 2% ->4.5% which is not the sort of change I was hoping for.

I'm asking after the colour chart because I want to get it right and because there are references to it all over the web.

The second hand colortune I bought had black and white instructions that just said 'bunsen blue and that if it gets too lean it is blue/white. Sorry, but I don't think it's 'invalid' - this is EXACTLY what the colortune is made for.

If there's no chart available I will just lean each pot out by 1/4 turn (screw it in) and see if response is still good.

 

greg in london:

The Colortune Plug isn't a Precision Instrument. It only provides a peek at what the Power Stroke burn is looking like at the time of Ignition.

That the Makers want you to Dial-in the "Blue" Color when adjusting for Idle makes for an interesting argument.

WE don't want to have our Bikes adjusted for an Air-Fuel Mixture that will be best to get the Machine to Idle. We NEED a A/F Ratio slightly Rich to provide a small measure of Fuel to sustain RPM's as the Throttles are opened and the Rush of Fresh Air is introduced to the Combustion Chamber.

That can only be accomplished by Tuning the Pilot Mixture a small Percentage Rich.

Without the small Percentage of Richness added to the Fuel Stream the Combined Pilot Mixture Supplement and Main Jets Fuel Supply would be Lean. A condition that would cause a great many problems if the Mixture is Lean during Mid-range and Wide-Open-Throttle operation.

I contend that this Supplemental Richness is NOT available when the Colortune Plug is displaying a Mixture that is burning "Bunsen Blue."

After weeks of Tuning for the best overall performance AND attempting to find a Mixture that is best for the longevity of the 750 Engine ... I am
still adding Richness to the Pilot Mixtures once set by Colortuning ... Increasing the Richness while Monitoring the burn by visually inspecting the Plugs at intervals of a few days of riding.

After my most recent adjustment to the Pilot Mixture Screws to add yet some increased Richness to the Fuel Supply ... I am confident that the COLOR of this most recent tweak is outside the ratio that would show a Blue Flame.

The Condition of EACH bike is different.
The Condition of EACH CYLINDER is different.

The results of Colortuning are therefore limited to the One Cylinder being tuned with the devise and limited to that one Cylinder.

The results are not Scientific in nature and a "Chart" would be simply colorful. Not useful with regard to what to expect from its looks.

 

4.5% sounds about right, that's what I usually get.

 

I hate it when you get to the stage where you've asked for advice/help and then end up arguing with others when they say something that you don't like, so I'm going to try and be really careful not to upset anyone.

There are, however, a few different opinions going around and it was partly as a result of recommendations that others have made on this site that I have invested in both a 14mm colortune and 12mm colortune (arrived today). If the view is that they are not that accurate after all, a bit of debate may inform anyone else who is thinking about buying one. [Damn - did that sound sanctimonious - I didn't mean it to.]

I'm a firm believer that any tool used with thought can give useful results and while you can only get fully accurate results with a gas analyser (lambda sensor or whatever) attached to each exhaust port (which is not practical with a 4-1 exhaust), something like a colortune gives real time direct information on what is happening inside each cylinder at the time that you're testing it.
Now clearly if you're testing at tickover, you are only getting information about the pilot jet and not about mixtures throughout different throttle openings and the rev range. Changes to the pilot air/fuel mixture which affect the mixture throughout all throttle openings. [This is because the pilot jets continue to supply fuel as the throttle opens - and slightly more as revs rise, so this fuel is ADDITIONAL to that supplied by the jets and needle.] The % of the total mix affected by the pilot jet gets proportionally smaller as revs rise/the throttle opens, as the main jet/throttle needle will provide MUCH more fuel.
Yamaha/Mikuni/Hitachi have designed their carbs with this knowledge in mind and have selected jets and needles which will function well in conjunction with a correctly set pilot mixture. In other words I'd be very surprised if anyone burnt a hole in a piston as a result of wrongly setting the pilot mix - moving the needle down a couple of notches, used a blocked main jet or radically changing the airbox/exhaust set up maybe, but not the pilot mix.
Note - follow Rick's advice on carb cleaning (other threads) and all your carb circuits should be working effectively - otherwise blocked airways will upset the mixture in unexpected ways - or not.
So much I know already.

The Colortune shows in colours what is happening inside each cylinder. I'm not sure that it is fair so say that this is not precise - I can't see that it can do anything other than give true information, except that you should be aware that the engine might react differently on a different day, when weather/dampness/temperature/location of the neighbour's cat might subtly affect conditions. Those variations will be small, however. After all, we're talking INSIDE the engine here and those few ounces of aluminium hammering up and down dozens of time each second will put up with no nonsense. There may be a difference cause because the colortune is a different shape to the sparkplug and drops compression slightly, as well as not projecting the spark tip right into the combustion chamber, but we have to take it on faith (and the recommendation of lots of XJBIKES posters) that the error is small at tickover.

Setting the mixture to where it is too rich gives us a yellow flame and then leaning out the mixture (if that's the right phrase) gives us a point where the colour changes to a pale blue. Beyond this there is a vibrant blue and then a whitish blue if the mixture is progressively weakened further.
The yellow/blue changeover is the richest mixture Gunson say you should use (which would give max power), which seems reasonable, but for economy and clean running we may want a slightly leaner mix.

The new set of instructions say that the change point is at 4.5%CO and that engine revs will fall when CO levels are down to .5%CO (a very lean mix). Modern engines should be set just abobe this at 1%CO, older engines set halfway between, which I guess would equate to 2.5%CO.
Except that we can't measure CO levels for individual pots - well I can't anyway, which leaves a number of ways of proceeding:
* Arbitrarily choose a recognisable colour - the 'vibrant blue' and set to that on the basis it's somewhere between too much and too little (but a colour chart would have been nice)
* Set to the changeover and then turn each mixture screw back in by small increments until performance/tickover suffers, using it for a few days to identify any problems (including plug chops)
* Set to the changeover, then weaken the mixture of each cylinder, but test with the gas analyser (although I don't have confidence in the readings from this yet) until it reads about 2.5% - unless it won't tickover happily at this level.
The last two assume that each cylinder will react in a linear way to adjustments to the pilot screw.
I'm working on the basis that, despite what some posters have said about making adjustments of only a few degrees at a time, 1/8 or 1/4 turn increments will be okay (nothing else would be manageable).

I'd prefer to go for a specific colour, but would like other views on it. Rick, the second sounds the OPPOSITE of what you're saying - have you gone for the 'Gunson richest' mixture and then gone richer again - so that if you tested again you would have a yellow flame ? If so what results are you getting.

Apologies for the long post.

 

First a few points, just a year ago we had an XJ burn a piston because of a clogged jet. So a lean mixture will do damage. While the colortune is a fairly precise instrument I don't think it would be practical to try and correlate the color to a CO emissions amount. But it may be worth a shot despite all the variables of fuel blend/grade, spark quality, compression and atmosphere. I don't know of anyone who has but then I hadn't heard of a colortune color chart until now and I have been involved with XJ sites since the mid '90's. Somehow I missed that entirely. It would take a gas analyzer and about 5 to 10 bikes to compare data and form an opinion.

 

When I bought a Colortune in the eighties it came with a colour chart of sorts. Googling for it I found a colour chart for the other diagnostic tests - opening the throttle, mid range etc - but not the one I was hoping for. Most of the reviews/write-ups refer to a colour chart though.
There isn't one on the 12mm Colortune which came today, either.

Mind you, I'm well aware that after being sent to a printers the colour print would change, same when it is scanned and again when I print it out, but I should get an indication of what I'm looking for when I'm looking at the plug tuner.

On your holed piston: was it a blocked pilot jet or another jet ?

PS - if anyone around London does fancy having a gas analyser shoving up their exhaust - particularly in the next few days while I'm on holiday - I'm sure we can lay on a cup of coffee while the gadget does its magic.

 

I can scan my color chart and send it to anyone who wants it if you send your email address but you are never going to get the CO down to 2% no matter how long you look at the blue colors!

 

Here we have to meet a minimum of 5.5% CO on the emissions test every year. As long as I can come in under that I'm happy.

 

Hi ArizonaStever - yes please send me copy of the chart - I'll PM my email (although it might be public anyway).

I don't know if I'll get it to 2% or not - I'm aiming at better running and economy, not a number, but I do like to know how to do a job properly.

Oddly enough, before I began 'tuning' I had a figure of 2%, but that was with the outer two pots running fine and the middle two so weak as to not show a flame, so two pots were practically contributing fresh air !

 

Greg, I know you are trying to save fuel but making the bike run way too lean is not the way to do it. It has to have the correct amount of fuel to run properly, no way around that unless you invent a new type of engine. One way would be to block off 2 cylinders but by cutting off most of the fuel you will make it so difficult to start and hard to warm up that you will end up having to use the choke all the time the engine isn't hot and use a lot more fuel than you would have before. Have you heard the term Cold Blooded that refers to an engine hard to warm up because it's too lean? Also, if it's so lean that it misses, your HC (unburned hydrocarbon) output will go way up because it won't be firing every time. Just keep moving and try not to idle much!

 

Steve ...

You were sweating the Arizona Inspection for awhile.

Did you manage to get the bike through and what did you wind-up doing?

 

I haven't got my 1100 to pass yet. I still need to adjust the valves and replace the cam chain then hopefully it will be OK. In the meantime I got out my SR500 to use again. It gets over 60 MPG!

 

It was a main jet and yes I understand your point about the pilot jet not being alone in fuel delivery. While it would be harder for a pilot jet to hurt the engine and probably couldn't have done that specific damage we still like to err on the safe side. Too much heat is not good for an air cooled engine at any speed.

 

Lean is Bad.
Too lean and it leads to a myriad of problems caused by heat.
Warp, burn-through, burned valves and seats, piston slap and more.

I always caution those who have done a Complete Carb Cleaning including removal of the Pilot Mixture Screws to not become addicted to the way the Engine will run on the Lean side.

Although it will sustain a steady and constant Idle and put more power-on than before ... the Lean Condition will contribute to a breakdown in short order.

 

Steve, thanks for the charts.

Lean burning has always been a bit controversial. When I was learning about bikes, the maxim was always to err on the rich side to avoid holed pistons etc. This was in the days of Bonnies, GT380s and other bikes which seemed quite susceptible to mistakes.

The problem obviously is heat generation. One point which is sometimes forgotten is that the problem is cause by one or two cylinders running leaner than the others. Under load, the throttle is opened wider than would otherwise be needed to obtain the desired power. The leaner burning cylinders will generate more heat than the correctly carburetted cylinders with all the dangers that entails.
If you do not run at full throttle, you will not be in danger. That's why the manufacturers used to suggest alternate needle positions for high speed or gentler touring. For max power, let's be honest, we're not concerned about economy.
At idle speed, we're concerned about an even tickover so we don't stall the engine at the lights. We won't generate enough heat to cause problems (unles something else is seriously wrong).

Japanese bikes these days (so I understand) are meant to run comparatively lean. How that relates to older bikes is a point of conjecture, but I'm not aiming at a super lean engine. I just want to have all the carbs set up to run cleanly and if I know I've achieved that, I don't need quite such a big safety margin as if I'd done it completely by ear.

I don't think that the XJ750 is as liable to danger from overheating as my old GT380 which had three sets of points where the timing could wander, or old Brit bikes with tappets closing up or coming loose.

Keeping it in context, Rick, just how rich do you reckon you're running now ? Is there really that big a difference between hat we're aiming at ?

 

There's a pretty narrow window in the setting of the Pilot Mixture Screw that determines the transition from Lean to Rich.

Once the Bike is tuned for Idle I'd say that the whole adjustment for a Mixture that can be too Rich to ... to Lean is within an eigth of a turn. Certainly within 5-Degrees or so.

I'm doing the settings like they are separate with each one feeding its corresponding Cylinder.
I recently added Richness because after a Plug Inspection the Ceramics were too clean for their own good.

I added two degrees.
I'm running these two added degrees for a day or two ... but, not today or anytime soon ... the weather is quite bad.

I still have a very strong and smooth Idle.
Throttle response if accurate and immediate.
I might have found the place where I am going to leave them alone and accept the condition they're at right now as "Optimum"

I will put some time on this new setting to be sure that the burn isn't too Lean. But, as opposes to most other 750's, I have the added cooling of a sizable Oil Cooler to bring down the operating temperature a bit.

 

A range of 1/8 turn sounds possible for a range - but that's 45 degrees. If the weather holds out I'm going to be doing some more fiddling over the next couple of days, but Thursday the boat tickets to Dieppe are booked and we'll be having a long weekend at the 24hr Le Mans races.

Last time we went we ran out of petrol on the run into the town and following the diversion, so we're keen to optimise mpg - and will have a full spare can as well.