Colortune??

[Bob_Irwin]

the carbs on my sprite need adjusting as the last thing in my tune up. Considering using a colortune. Do they work better than the old fashioned way? I so, do you use one or two? Thanks

 

[jlaird]

The old fashioned way works just fine and surely is cheeper.

Balance em and use the lift the piston trick.

Should take a few min at best.

 

[spritenut]

I have a colortune, everytime I use it and set the carbs per the instructions, the car runs lousy so I have to readjust the carbs by ear. It may work great on a single carb car or even a dual carb car with a true 2 port intake but the stock logg intake on a Spridget makes the colortune see fuel from the "other" carb.
It does get the carbs close

 

[Sarastro]

I got a colortune and used it once. Everything went fine, or seemingly so, but I got the thing clearly too lean. I haven't gone back to experiment with it again, but I intend to. I think it's always a good idea to have some kind of clear, objective measurement, rather than to depend on artistry. But I'm a technogeek, so whattaya expect?

That said, it's the old story--it takes a little skill to do the lift-piston trick, but it works fine once you figure it out. A lot of things can give you an incorrect result--for example, lifting the piston too much or getting one carb too rich and the other too lean. That 1 mm lift that the books recommend is probably on the high side; you just nudge the thing a teensy bit. And, you have to adjust the carbs together--you can't risk getting one a lot different from the other. It's probably easiest if you start with the carbs clearly too lean, which is very easy to detect when you lift the piston--the thing nearly stalls. Then, as you adjust them ritcher, you can see the change easily.

 

[racingenglishcars]

I think a colortune gives a good indication of a stochiometric mixture, as per instructions, but unfortunately the car doesn't run best that way. Older engines, especially with carbs and worse, with siamese ports, work much better with a slightly richer mixture.

 

[bugimike]

As far as tune-up tools, I agree with everyone else about "the old fashioned way". Other than a length of hose to listen to the hiss, a tool I have found helpful is a Unisync (not sure of that spelling) which will equalize the air intake fairly accurately!

 

[jlaird]

To do it right a Unisync is mandatory. Ear is ok for quick and dirty by Unisync puts em spot on for balance.

 

[Sarastro]

Yes, definitely, the unisyn is one of the greatest tools ever invented, in my book. I never was able to sync those puppies by listening to the hiss at the end of a piece of tubing--for one thing, it depends a lot on EXACTLY where, at the carb intake, you place the thing. But with the unisyn, it's trivial.

 

[recordsj]

I haven't been able to find any info on this "lift the piston trick" I have been seeing in this post and others. Can you fill me in on the details of this?

by the way, I have a 1500 midget with a signle weber dgv carb. Does this method relate to this kind of setup?

 

[regularman]

I got the Weber but I am interested in that color tune. I would love to see one work. I bought a gunson gastester for $$$ and hope it helps me a bit. I know mine is rich and I want to lean it out a bit. Mine had the weber when I got it so I have no experience with dual carbs on a car. I have fooled with them on bikes but I am told that the SUs work different than motorbike carbs. I remember the minis had just one of those and I put oil in it from time to time, but never touched it. I am happy with the weber, it got 37 on the highway just the way it is and had plenty of power. I just want to see if I can lean it a bit, I can smell the richness at times.

 

[recordsj]

I have a 1500 midget with a signle weber 32/36 dgv carb. I have the colortune, but noticed it doesn't do much better than tuning according the weber tuning specifications (see link below).
www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm

do you know of anything of the "lift the piston trick" that has been talked about? Do you know about which applications it works with?

 

[bugimike]

Most all of the SU carbs. Not Webers!!

 

[regularman]

I have a 1500 midget with a signle weber 32/36 dgv carb. I have the colortune, but noticed it doesn't do much better than tuning according the weber tuning specifications (see link below).
www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm

A weber is pretty easy to get the idle mixture and idle speed set good, but those screws only help at idle. When you get into how rich it is when driving down the road, then its all about having the right jets. I know mine is rich. I forget the numbers on mine and plan on taking the top off to get those and then order some that are 1 and 2 sizes under and see how that does with the gastester and performance wise. jets are not expensive to buy if you know which ones you need. ebay jets This guy sells them or you can find them locally. Its like the instructions say with the idle jet, look at the screw turns and see if it is good enough. I'm concerned with my primary jet. That is the one used the most while driving. the secondary only kicks in when you are at full pedal or close to it and that is good enough for me if its a bit rich. I like Webers myself.

 

[racingenglishcars]

I think really the secondary kicks in at the transition point, and that's somewhere between "lightly pushing" the pedal and a "little bit down". That is to say, not as much engine speed defined, and more throttle position defined. You can see the main jets deliver fuel when looking down the carb and steadily revving. Running rich on the main jets gives little more than worse gas mileage. Of course WOT needs a richer mixture.

 

[Dadandson]

What would be the best resource for learning the nuances of an SU carb? VB offers a video and there is a book titled "SU CARBURETTOR TUNING TIPS & TECHNIQUES BOOK". Are these good resources or am I missing something?

 

[Pythias]

try here first ..
https://video.google.com/videoplay?docid=-1412933522016810360.

do a search for university motors on youtube!

 

[zblu]

Tried a colortune about 15 yrs ago, another one of the interesting might be's!, always been interested in the vac systems they used to use to tune honda 4 m/c's, seems a better method!

 

[Sarastro]

The book, "SU Carburettor Tuining Tips etc." is largely for rebuilding--lots of good diagrams, disassembly/assembly instructions, and so on. A better book, for tuning, is Hammill, "How to Build and Power Tune SU Carburettors," Veloce Publishing, Speedpro Series. But there is so much info on the web, and in the BCF Wiki, that you really don't need a book. There are even videos on YouTube (search "University Motors").

 

[regularman]

Tried a colortune about 15 yrs ago, another one of the interesting might be's!, always been interested in the vac systems they used to use to tune honda 4 m/c's, seems a better method!

You mean a carb synchronizer? Is there ports to attach them on SUs?

 

[zblu]

No, but the concept appealed