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Proper use of the Gunson Colortune

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Bob,

Many, many thanks! Thank you for the very complete instructions, which along with the good input from others gives me an excellent idea of how to go about using this neat tool. I know this information is going to be of great use to many.

George,

When you say a greased o-ring, do you mean a greased fiber o-ring or a rubber one. I would think that a rubber one might, because of the heat, melt into place.

And what kind of grease do you use?
 
Well folks.... what am I doing wrong?

I set up the colortune today following the good instructions I received in this forum.

No matter how lean I made the mixture, the colortune remained yellow. I could never get blue or whitish blue at all -- just yellow.

The colortune itself became as fouled black (no oil) as the spark plug.

I have long had a suspicion that the folks in the shop where I had work done on the car (engine rebuild, etc.) put in needles to make the mixture rich. I don't know if this actually happened or if it might have an effect on the colortune.

Perhaps I'm just doing something wrong.

BTW -- the "odd" thing is that when I adjust the mixture using the lift the pin method, I can get the carbs to work correctly. If I raise the plungers just a moment, the engine doesn't speed up or slow down as it would when the carbs are out of adjustment.
 
A handful of Q-Tips and some mineral spirits will clean the ColorTune "window".

As for the "no change" with the adjuster, look to your choke linkage. Be sure the jet is moving up all the way as you turn the adjuster and not being restricted by the choke stuff.
 
I took my TR3 into a mechanic and when it came back, it was running too rich. I found out that the 13/16 nut above the brass nut was too tight, and kept the choke on. After loosening it, the choke was working. Try taking off you pistons and see if the choke is working properly. You can pull the choke cable and look down where the needle was. It should be going up and down.
 
The jet seemed to be moving up and down, but I will take a closer look. and I'll take a look to see if the choke is being kept on. I don't think those things are happening, but I'll check.

I am inclined to take a look at the pistons and the needles to see what has been installed. Is that a useful thing to do for analyzing this problem?

again, however, I get good results from the push the pin method. Could it be that the shop has set the mixture rich to increase power on the road? The idle is a bit sloppy, but on the road the car runs smoothly and has plenty of power.
 
Usually when the mixture readings don't make sense, it turns out that the problem lies elsewhere, like valve lash or valve/ignition timing. Even the 'rich' needles should be adjustable for correct mixture at idle (they are "rich" because the mixture goes richer at mid and high throttle).

Another possibility is worn jets, which can really screw up the mixture curve.
 
Randall,

When I had the engine rebuilt, the carburetors were not rebuilt (much to my surprise). So they have some age on them.

The valves were completely replaced a year ago, and adjusted just a few days ago.

So, I'm thinking that the carbs need some work.

I have been studying up on this procedure for many months and, when this driving season is over, I am going to give the rebuild a try. My sources of information range from John Twist videos to the very detailed Moss video on "The Overhaul, Tuning & Maintenance of SU Barburettors" and service manuals. I have the Moss rebuild kits. It all looks straight forward as long as I keep all the components in correct order. It should be as easy as falling off a roof... hmmm... and perhaps with the same consequences.

My dilemma is this: The car is clearly running rich... but it performs well on the highway. I can clean the spark plugs from time to time and go on enjoying the ride... Or I can try to get it right and possibly drive myself crazy trying... I suspect that others among us have suffered from this passion.
 
I had the same problem with the Herald. After I re-adjusted the float so that I wasn't flooding the carb, I was able to tune it in properly.

So, if you cant get blue, for some reason you have to much gas.
start by checking: choke for sticking, float for correct level, fuel valve (may not be closing?), piston not going moving up and down smoothly (stuck to high?) needle not centered and sticking?..


After solving the floats problem, at idle, or at steady rpm, the flame is blue, and when I give the throttle a quick push the flame turns yellow (rich) for a few seconds. Just what it is supposed to do. More to the point, drivability is MUCH better.

Good luck
Yisrael
 
Yisrael,

Good advice. I will start a systematic investigation of all those potential problem areas and see if I can narrow it down.

I am inclined to come back to my original suspicion, however, of the valves for the first cylinder. The reason for this is that the spark plug for that cylinder is consistently fouled, but all the other plugs are perfect. That means that something is affecting that cylinder alone.
 
Poolboy,

That is not something I have done... but I had a thought this morning that I should have done so. I'll try it today. In the past, whenever I have pulled the plugs, the number one plug has always been soot-covered and the other three have been in proper condition. Which clearly indicates that the problem is confined to cylinder #1.
 
I've been wrestling here with the problem of number one cylinder consistently having a soot-covered spark plug while all the rest have been clean. That is what I found whenever I returned to my garage and pulled #1 plug.

I asked a friend about this and he suggested the following procedure. He said that I should take the car out on the highway, run it at 3000 rpm for about a mile, shut off the engine and pull off the road, and pull the #1 plug. He said he would bet a buck that #1 would be as clean as the others.

Guess what.... he won his buck!

What the heck is going on?
 
So #1 has either an ignition or mixture problem, only at idle. Didn't you say before that #2 had low 'dry' compression ? I'll bet it's leaking in some fashion that is messing up the mixture for the next cylinder in the firing sequence (#1).
 
Randall,

No.... #2 is doing just fine -- good compression. No problems with it. How can #1 have a mixture problem at idle if #2 shows no evidence of it? Aren't they served by the same carburetor?

Of the two possible problems (ignition or mixture), it seems like mixture can be eliminated. That leaves ignition, but I am getting good spark in that plug.

The "fouling" that occurs, seems to be at idle, as you suggest, or if I slow down and stop just before shutting the engine down. If I idle a bit before shutting down the engine (as I pause to open the garage door) or if the engine struggles a bit going up my driveway, chances are that the engine will diesel a bit when I cut it off. Someone has suggested that the position of #1 close to the radiator may have something to do with this (???) More mysterious things have occurred with this car.

Poolboy,

What is an "ethnic tuneup"?
 
LexTR3 said:
Randall,

No.... #2 is doing just fine -- good compression. No problems with it. How can #1 have a mixture problem at idle if #2 shows no evidence of it? Aren't they served by the same carburetor?
Click to expand...
Yes, but that isn't all there is to mixture. For example, at low rpm, the airflow through the carburetor is not smooth, as cylinders #1 and #2 together only draw air at every other crankshaft revolution. If something happens to actually blow a bit of air backwards through the carb and then suck it in again, then that bit of air will pick up a triple load of fuel as it goes past the jet three times. Also, the fuel/air mixture gets mixed with whatever is leftover in the cylinder from the previous firing, so if something were preventing the cylinder from scavenging properly (getting rid of as much exhaust gas as possible), the result won't burn as well. Things like this are part of the reason that engines with wild cams don't idle well.

Of the two possible problems (ignition or mixture), it seems like mixture can be eliminated. That leaves ignition, but I am getting good spark in that plug.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]What is an "ethnic tuneup"? [/QUOTE]
He means "ethnic" as in "insert ethnic slur here". But it's a common effect for running the engine hard to help clean up carbon and other deposits that build up under light or no load. Kind of like the difference between a gentle rain falling on your lawn, and spraying it with a stream from a hose nozzle.
 
Perhaps a "poor man's tune up" might be a better description, the kind I, as a college student, used to give my Bugeye
 
Ed I just finished testing the carbs with the color tune and had no problems. I first set the carbs the old way (by the book) then checked with a color tune I borrowed from a friend. No adjustments were needed so I skipped step 1 and went to step 2 and 3 and found that no adjustment was needed. If any thing they may have been a tad on the lean side. I will take the car for a short drive after the storm clears and take a look at the plugs. I would rather have the car on the rich side.

As for the worth of the color tune I don't think I would buy one. If all else is working as it should be the carbs are not that hard to adjust. Good luck with getting yours right you have lots of good information on this topic right here.

One last thing, I was setting the carbs on my TR6 after repairing the float vent valve on one of the carbs. I was having some hard starting problems when the car was hot. As for now the car starts as it should when hot. I'm keeping my fingers crossed that this problem has been cured.
 
TR3driver said:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]What is an "ethnic tuneup"?
Click to expand...
He means "ethnic" as in "insert ethnic slur here"...[/QUOTE]

You guys can call it an Italian Tune-up -- I won't take offense. Had Fiats for 35 years alongside my TRs.
 
Randall,

What causes the blowback? And is there some way to check if this is what is happening? I can live with #1 fouling at idle or no load as long as the things are corrected when I run hard. As long as it is not doing any damage to the engine.

Keith,

Glad the Colortune worked for you. As I said, it didn't work for me on #1, but I suspect it would have worked fine on #2, 3, and 4. I didn't try that, but will. Despite the rich mixture indicated by the Colortune, I was able to get things right using the push the pin method, and perhaps that's all I really need.

I am coming to the conclusion that it is time to rebuild my carbs. With some luck, that will solve much of the problem.


"Ethnic tuneup"

Ha, ha. I thought it had something to do with engines hanging in trees in front of house trailers while the car was up on cinderblocks..
 
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