Gunson Colortune exprience?

[canuck750]

A fellow vintage enthusiast brought a Gunson Colortune kit to a recent vintage bike gathering. His experience with it on old British twins sounded promising. I went ahead and bought one on Ebay and plan on trying it out on Eldorado and V7 Sport.

http://www.ebay.com/itm/181958396786?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Anyone have experience with a Gunson Colortune, got any advice, tips?

[HardAspie]

I remember those. My wonder was this: do they allow adjustment for different spark plug simulation or does one use them as they are and hope that combustion with actual plugs is correct?

[SED]

My sense is that it is pretty good for idle mix and gives you a way to confirm your carb settings. 

I had one from years ago that finally got used on the LM to fine tuned my idle adjustment.  It confirmed my other adjustments and was a more sensitive to mixture.  My recollection is that best idle is slightly richer than Gunson (Bunsen) blue. 

Not sure it can show the true mixture at hwy speed because you could only rev the engine with the bike on the center stand (or rollers).  It would be impossible to read while riding (i.e., engine under load) and don't know if the mixture changes from no load to loaded.

Interestingly I only used it once, felt it confirmed what I was doing, and have used the standard Guzzi idle adjustment method ever since. 

Also had a friend who bought 4 so he could put one in each cylinder of his British sports car.   

[PeteS]

My experience is like SED's. Its very useful for setting idle. Also it helps see whats happening just off idle if you are experiencing hesitation. They don't recommend using it much over 3k rpm or you risk damaging the quartz window. It comes with an aluminum o ring. You don't want to torque it in or you will crush the o ring.  Also be careful with the ceramic standoff for the high tension lead. It will last if you take some precautions. Mine lasted some 30 years.

Pete

[Chuck in Indiana]

If your ignition system is up to snuff, they work fine for idle mixture. If you have weak ignition, it'll say to make the idle mixture super rich and make your pipe blue in a heartbeat. Don't ask me how I know. 

[guzzisteve]

I've been using these to set idle mix since mid 70's. Go from overly rich to lean for best results. Leave a tinge of orange in the bunsen blue for best burn. Very slight amount of orange.

[canuck750]

Thanks for the advice

[lazlokovacs]

my experience on the lemans was that 'best carburation' as measured on an electrical tacho, was quite a fair bit richer than Bunsen blue..

[Wayne Orwig]

I would put the $$ toward a Gunson Gastester.

[canuck750]

I would put the $$ toward a Gunson Gastester.

Are these straightforward to use?

I have never seen or used one, but it looks pretty interesting and could make use of it on a number of motorcycles.

[80CX100]

I seriously considered getting a set of colortunes when setting the carbs up on my bike,, read a lot of mixed reviews, and some horror stories about the threads not fitting the spark plug holes exactly and causing some problems.

Can't remember where I read it, but I learned that I could use my homemade manometer, vacumn gauge, made with a yardstick,vinyl tubing & tranny fluid(will use thicker 2 stroke oil next time) to set my air screw mixture perfectly for the highest idle,,, did that,, then set idle, balance,etc,, went through the process 2-3 times,,, she ended up running very sweet after all that,,,

I don't regret not getting the colortunes,,,fwiw ymmv

Kelly