colortune not responding to changes?

[crowdpleazer]

I recently got a 1981 GS850G with Mikuni carbs. It needs a little work but nothing major other than maybe carb issues. Checked valves and they are all within spec. Playing around I got it to run fair but not right. I have to play with the choke some to keep it running. I have a colortune and when I put it in cylinder 1, it has a small blueish purple spark. When I turn what I thought was the mixture screw (center top of each carb near intake boots) the color of the spark stays exactly the same. I guess that is not the right adjustment? Its the only adjustment there other than idle speed. What am I doing wrong?

Ps a friend has a balancer with 4 mercury tubes that I can borrow. I havent borrowed it yet but plan on it soon.

Any help is much appreciated!

[tom203]

Barn find that beens sitting ? - head to Basscliffs and follow the carb cleaning tutorial. No shortcuts, or the colortune and sync tool will likely be as bewildered as you!

Try this courtesy of Mr. Nessism

http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

Edit; Head to page 1 of the pdf if it loads oddly- my computer skills are limited!

[almarconi]

That is the correct screw to adjust. It may not be working if the carbs are clogged up. If you need to add choke for it to idle then I would imagine the carbs are dirty. When was the last time they were cleaned? The colortune also takes a little getting used to, make sure you are in a dark enough area that you can see the window on the plug. The correct color looks like the flame on a gas stove. You will have a very hard time seeing it in direct sunlight. The change is also not immediate, you should make small adjustments on that screw and then look at the window. You can also adjust each carb by the highest idle method but until they are clean your wasting your time. If the carbs are clean, they should be able to hold an idle once the choke is off. It may be lumpy because the carbs are not synced but you should be able to hold an idle.

[crowdpleazer]

I was really hoping to not have to take the carbs apart as I may be selling the bike come spring... But its hard to sell an old bike that doesnt run... Nice tutorial by the way. Thanks!

[almarconi]

You can sell it as a non runner, just don't expect to get much for it.

[crowdpleazer]

You wanna make an offer? new rear tire, new front brakes, farring and windshield, luggage rack and back rest, good title, have spare clutch and more.

[almarconi]

I need another bike like a hole in the head. Three bikes, four cars..I've got enough stuff to wrench on. I really don't ride enough anymore to justify more than one bike.

[Steve]

Don't worry about the color not changing.

A couple of years ago, TheCafeKid and I were tuning up a bike the Simon Kuether had bought. I had borrowed a Colortune, knowing that this project was coming up. Saw all the colors change BEAUTIFULLY, just as they should. I was impressed.

Took the Colortune to my house, put it on my wife's bike, turned the screws and saw ... NO CHANGE. Well, not quite NO change, but very little. What happened was ... as I turned the screw in to lean the mixture, the flame started getting a little more erratic, then finally going out completely. As I turned the screws back out, the flame started to come back intermittently, then more steadily, finally a right proper steady flame. Moved the Colortune to the other cylinders, same thing.

Just to be sure, I tried another bike. Same results.

My conclusion? The Colortune will work quite well on the VM carbs, but not so well on the BS carbs, which were on all the twins and then on all the fours from '80 on.

.

[azr]

One thing I like to do with the colourtune on my VM carbs is listen to the changes. The colour does change indeed but at the same time you can see the spark arcing inside the colourtune you can also hear it arcing. It's very easy to hear and once you have a nice smooth sounding arc it's basically tuned.

[almarconi]

I've used it on both my KZ and GS, the KZ has keihin carbs and the other mikuni BS and I can get a color change on both.

[crowdpleazer]

looks like ill be ripping the carbs apart tomorrow. they are quite clean on the outside and the last owner said he just rebuild them so they probably are messed up.......

any suggestions on what kind or brand of dip to get for the carbs? and where to buy?

[Steve]

Most of us use Berryman's Carb Cleaner Dip or Gunk Carburetor Parts Cleaner.

Look for either one at your favorite auto parts place or Wal-Mart.

Expect to pay about $20-25 for the can (you only need one can). That same can will last for MANY sets of carbs for several years.

While you are doing the carbs, it also makes sense to get new o-rings for the carbs and the intake boots, along with stainless screws to hold the intake boots. You can get the whole package for less than $25 from cycleorings.com. Mr. Robert Barr runs that little service, he is a member here. I also had the pleasure of meeting him at the Brown County Rally in Indiana last spring.

.

[BassCliff]

Greetings and Salutations!!

Hi Mr. crowdpleaser,

Here's your S.W.A.G. Follow the steps in the maintenance lists in order to have a safe and reliable motorcycle. Happy New Year!

If you are here you probably have a 30 year old motorcycle that needs about 20 years worth of maintenance. You'll find all kinds of helpful tips, procedures, manuals, etc, in the links below. Let's get started.

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please Click Here For Your Mega-Welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[crowdpleazer]

Thanks everyone! I have rebuilt many weedeater and pushmower carbs and a couple Holley cars. This is the first motorcycle one. Stuff is much different in these! But I think I am on the right track now. #1 is soaking in Chem-Dip right now. Cant wait till the snow is gone and its not blistering cold so I can ride.

[Steel Toed Tank]

Don't make plans on selling it yet, when you ride it you'll see why.
Good running GSes are AWESOME!