more colortune carb tuning

Well the xj is running, and reasonably well. But the colortune plug colours tell me things are not tuned. Also I've some sooty and some white plugs.

I've
- cleaned the carbs and set float levels so that the fuel is at the level where the washer from the bowl attachment screws joins the body of the carb. (one is 1mm below this, so where the washer meets the screw head.

- re-shim'ed the cams, all were about 10um too small a gap. I've gone for the wider end of the range. (Haven't re-measured since re-shim'ing, I guess this would be sensible, it's probably a little more top end rattly than previously.)

- balanced carbs (non-YICS engine) using the home made oil-manometer method. (worked ok, although they were never entirely stable and tended to wander a little after setting.)

Runs much more smoothly with power from low revs and non of the over-rich, stalling when warm issues. Even delivery up to 90mph at which pint I decided that was enough for now. I have a new high frequency vibration in my right foot but probably less on the bars, go figure !

BUT
No 1 cylinder is blue and however far I turn in the screw the flame stays blue. (this one has the lower fuel level)
No 2 cylinder seems right at 4.5 turns out, but doesn't seem a very precise adjustment.
No 3 cylinder is orange and stays orange (this is the higher fuel level)
[No 4 cylinder shall remain untouched since I've trashed the adjustment screw head then broken off a hardened steel screw-extractor in the middle of it !]

Questions:
- Do I need to isolate the vacuum lines as for balancing ?
- What is the 'default' number of turns out for the XJ600 ?
- How accurate do you try to be ? Good to a half-turn ?
- Using the centre stand and chocking the front wheel as high as I can still doesn't bring the carbs entirely level, but close. Does this matter ?
- How accurate do the float levels need to be ? I'd say they are generally on the low side of Haynes suggested levels.

Sorry for so many questions !!

 

A half a turn would be 180-Degrees.

The optimum Air-Fuel Mixture is within a small window of LESS than 10-Degrees.

I think its closer to 5-Degrees.
Certainly NOT a whole half a turn.

You can be Lean ... IN ... and too Rich within 10-Degrees.

 

Blimey! I can't see that getting that kind of precision with a colortune at all.
Even on the 'good' cylinder it seems to go
'bright orange'
'weaker orange'
'orangey blue'
'sort of invisible or is that blue'
'oh yes that's definitely blue'

over about two or three turns.
Any thoughts ?

 

Colortune is not that accurate and is more marketing then truth.

The more accurate way to see the relationship between your mixture adjustments and ignition spark is by exhaust temperature.

I used a infared heat gun and teperature mapped each cylinder before and after adjustments. When evrything is right, and the planets align. The 2 outboard cylinders, 1 and 4, will run about 220 deg F and in 2 inboard cylinders, 2 and 3, will run about 30 to 40 deg f hotter. I found that #3 was running about 40 deg f cooler then 1 and 2?

I measured the resistance in the plud wire to the coil and compared it to #2 which had the same length wire. #3 had high resistance. Therfore a weaker spark. I had a spare set of coils and used a wire from them. The cylinder came back to life.

Your best bet is to measure your plug aires and test the coils. These coils loose their efficiency as they get older and if your bike ever sat outside for any length of time. I would replace them outright.

Hope this helps.

Dodger62

 

Dodger62 I'm in agreement with you. There are too many variables.

The Colortune Plug offers a Shortcut to finding the tuning range that you do with the thermometer.

With the VISUAL ELEMENT of seeing the color Blue in the Plugs Window ... the Tuner can quickly find the area where the Air~Fuel Mixture is best set to initiate Fine Tuning.

You can do it BY EAR ... But, the most convenient method is to watch the Glass in the Plug turn Blue.
That's a darn good place to be rather than guessing ... 3-Turns Out!

But, the Optimum Mixture may need to be a little bit more Rich than the Colortuner brings you to.
Might be the other way; too.

But, the bottom line will be how HUT the MIXTURE will BURN.
More AIR ... a Hotter Burn
More Fuel ... a Cooler Burn.

But, I won't slam the ColorTuner ... It finds the 5-Degree range the Pilot Mixture Screws need to be adjusted too for strong Idle and Off-Idle performance.

Quicker than the Old School Method of doing it buy Ear!

 

Try using the colortune at night (dark area)....the blue color becomes extremely visible.

 

Hmmm, I don't think that this addresses the issue of one orange and one blue cylinder,wherever I set the adjustment.
-Could that really be down to a 1mm difference in float level ?

Also,
- what device would I use to try the temperature method? and
- would I be aiming for the hottest possible setting ?

Thanks

PS Coils and HT leads are new, as is pick-up so definitely a carb issue.

 

1mm too high a float level could cause fuel to leak by the float valve and give you more fuel than you can tune out. A choke plunger not fully closed will do the same thing. Of couse the float level may not the problem, it may simply be that one float valve is not seating. In that case it may seat in time or you will need to pull the carbs and polish the seat with a wooden nonpainted golf tee. All this makes the colortune seem inaccurate. I assure you that it is with properly cleaned and functioning carbs. It is telling you now that the carbs are out of tune and that something is wrong with fuel mixture controls.

 

It sounds to me like you need to resolve other issues before getting those carbs tuned in. Get your floats set right, and correct across all 4 carbs. Fix the bad screw and give the whole thing one more good clean.

Start with a good situation, not a mess.

 

I'm surprised. Here I thought everybody else worshipped at the Altar of Gunson, and now I'm seeing that I'm not the only one who doesn't think the colortune is the final word in tuning.

 

Well I'm getting good at popping the carbs on and off anyway ! It is at least going great compared to when I started this whole palava 3 weeks ago.

 

Quick reminder of original questions:

- Do I need to isolate the vacuum lines as for balancing ?
- What is the 'default' number of turns out for the XJ600 ?
[strike]- How accurate do you try to be ? Good to a half-turn ?[/strike]
- Using the centre stand and chocking the front wheel as high as I can still doesn't bring the carbs entirely level, but close. Does this matter ?
- How accurate do the float levels need to be ? I'd say they are generally on the low side of Haynes suggested levels.

 

Well as your question hasn't been answered, let me open myself up to public ridicule for getting this the wrong way round, but shouldn't you be turning the screw out to get a richer mixture - if you screw it in it will be blue all the way until there is not enough to ignite ??

 

Yes. if you are refering to a YICS tool. The carbs need to be isolated so they don't pull air/fuel from another carb via the YICS port. If the XJ600 doesn't have a YICS port then I am not sure what you mean.

2.5

1/4 turn

no

+or- 1mm

 

Setting the carbs with temperature? I never heard of that. How do you do it? Where do you take the temperature? I would like some details on how to do that. Maybe a picture with a arrow pointing at the spot on cylinder #1 and cylinder #2. What are the options? I know that a heat gun is one. Can you do it with a thermometer?

 

I can see the thermometer working-out.

You'd NEED the Exhaust Temperature of a Cylinder known to be at the right Air Fuel Mixture after tuning.

Then with the I-R Thermometer, you could get the temperature of the exhausts to match after doing some tweaking of the Pilot Mixture Jets!

I don't have an I-R Thermometer ... But, I'm wishing I did have one about now. I'd like to get the Mixtures squared-away on my 900 before anyone comes to look at it!

 

I've never done it, but the way my 750's been behaving, I was considering taking the laser-based temperature probe we have at work and pointing it at the header pipes. That's where I'd think to do it, anyway...

 

I think you´re right on this one, Greg..

- can´t we get this cleared once and for all, X-perts please 8)

 

Idle Mixture Screw = Pilot Circuit Screw = Enrichment Screw (they're all the same thing, just called by different names depending on who, when, where, the weather, and what who had for lunch that day):

IN (clockwise) = LEAN
OUT (counter-clockwise) = RICHENS

 

Thanks len - you´ve eased my mind

 

We are refering to a gas analyzer. There is a screw on each of the header pipes down near the bottom where the analyzer probes attach. On the drain plug there is a phillips head screw that is removed and the temp probe attaches there. It uses co and hydrocarbon emissions along with temp readings to bring the carbs in tune as well as emissions standards. Mostly available at large shops since the units are expensive. There are some smaller versions available for home use but even they are $400 to $600.

http://tinyurl.com/4h9b3s

 

Dodger62 / BlueMaxim --- Are we talking about two different things?

Dodger62 appears to be using temperature only to adjust the carbs.

BlueMaxim is talking about a gas analyzer. The one temperature sensor is used only to correct the gas reading by correcting for temperature.

What I am interested in is the temperature only method. Has anyone done this? Does it work? What is the procedure?

Note – A cheap Chinese $40 infrared gun is available at Harbor Freight.

 

I have one of the IR temp. meters and I tried it on my exhaust pipes but it's not accurate enough to tell anything besides if the cylinder is firing or not since the reading changes a lot if you move it around and aim at different spots.
They use the exhaust temp. method on airplane engines and race cars but to get a good reading you have to insert a thermocouple into the exhaust.
Then if you knew what to expect you could use it for tuning except I think it changes more with engine load than it does with the mixture.
You can find the thermocouples and gauges on ebay if you want to try it.

 

I still think that theres some merit to Exhaust Temperature measurement to determine Mixture.

It would be within a "Range" though. Probably bike to bike; too!

I know a Lean Mix burns hotter than a Rich mix. How much is the question.

Certainly, you'd get a "Notifying result" if you took the reading right at the first bend coming out of the Head.
Putting it into practice by knowing what the Temps are are the factors missing at the moment.

 

Thanks for clarity BlueMaxim.

I do have a phillips screw on the right hand side of the engine at about YICS level, but I'm fairly sure it's not YICS. It isn't marked on the side of the engine casing under Yamaha amd the Haynes manual doesn't mention anything about it. Also there are separate balance tubes from the nipples on the cylinder inlet rubbers which are all T'd together and then connect up to the petrol stop-cock. I guess they wouldn't exists if it was a YICS.

To balance I used these nipples and blanked off the two I wasn't using. I wondered if I needed to repeat that for tuning the idle screw ?

 

Sync Number Four to Number Three ...

Sync Number One to Number Two ...

Sync Number Two to Number Three ...
One is married to two and goes along for the ride.
Done.

 

I have thought about the IR temp method. But it only gets you in the ball park.
Other factors can throw off readings, right?
Like:
Wind blows and cools off one of the pipes.
One header is thicker(or thinner) and radiates heat less or more effectivly.
The IR guns, I ASSUME, would need to be vissible down to the thousands(and also accurate down that far)

The cost of a ColorTune. ~50 bucks
Cost of IR ??????
I would personally choose the CT.
BUT the BEST way to really know whats going on is plug reads.
Those buggers will tell you whats going on.

 

TWO DOWN.... I now have two carbs in range and even though the others were set at equal float levels one is very rich and the other is very weak, so off with the carbs again and tweak the floats some more. I can't believe they design them to be this sensitive to float height, it seems like madness.

 

Welcome to the world of motorcycle carbs!

 

I was just reading through this post and something jumped out at me.

You said that all the vacuum nipples were teed together and hooked up to the petcock?

Someone else needs to chime in, but if you don't have a YICS, I don't think you would want that?
I believe it would promote "cross-talk" between carbs and upset the sync...but again I'm not familiar with this particular bike set up.

 

When synching I isolated them.

I was previously wondering whether this would screw up the idle screw tuning but nobody seemed to comment so can't be a problem I guess.

 

It will if the sync causes the Butterlfys to open. The Idle will get faster. As you sync you have to adjust the Idle and keep it at the basae rpm you are working at.

I always sync at a little below 2,000 rpm. I want to be sure that they are all pulling the same at off idle; too.

 

I think I understand.
When synching there was about a 6 inches of oil pressure difference between each pair from the state they had been in previously. It took a tiny adjustment to synch and this barely changed the idle. This should be ok, yes ?

 

hi, a few words to interduce myself.. i am Pete and live in the UK in a small town cauld Alnwick. hobby is rebuilding unloved unwanted bikes. the latest is a (1993 XJ600s Secca)

been reading the posts on the carb / colortune question, i have the luxury of a well equipt garage, i have a exaust gas anlizer which i have used on my other bikes and my car; this has been usless as ii have been unable to find out what this bike should be

Newbi Pete

 

I set my pilot screws 2 1/2 turns out as default. I get an orange/blueish color, and I don't get any color change with more than 2 turns in or out. What does this indicate? Can my float levels be too high? Or is something else amiss?

p.s.

Oh, and my plugs are black with carbon.

 

Orange is rich. Turning the pilot screws out richens the pilot mixture; in leans it out.
Check your float levels. I suspect that they are indeed set too high.