Colortune quirk??

[Super]

Hello All,

I have a quirky thing happening with my attempt at using a Colortune for the first time.

First let me say, I have an 82 GS 750EZ that I got running in early April. I decided it would be a good thing to fine tune the engine not having any maintenance info from the previous owner. I had cleaned and rebuilt the carbs in March and she has been running pretty good since. So I checked and adjusted the valves with the idea of using the Colortune before the Carbtune to synch the carbs.

Well, I was able to get the nice blue flame color on numbers 1, 3 and 4. However, I can't get number 2 to do the same. I can see the spark bright as day, a bright white spark but if I turn the mixture screw out or in several turns, it just stays the same??? Can't seem to get the blue color.

So I rechecked the valves again and they're right on. An opinion was put forth that the coil may be bad but I'm not so sure since the spark is pretty bright. I'm thinking maybe the mixture screw needs to be rechecked. Maybe it's gotten stuck or the spring is hung up. I know I used all new parts when I rebuilt the carbs and she has been running good for 1,000 miles.

I guess I should have left well enough alone but I'm the kind of guy that wants to know that everything has been done right.

Any suggestions?? Or anybody else have this happen? Thanks

[81ZUKI75]

Is the No. 2 pipe getting hot ? Sounds like you've got fire and no fuel. Plugged pilot perhaps?

I have to add this though... I tried the Colortune on both my 750s. The only change I could make to the nice blue flame was if I ran the screws all the way in until the cylinder blacked out .

Good luck.

[waterman]

Are you saying the color stays white or light blue? Thus indicating lean? Or is it yellow indicating rich? If it looks rich, could gas be leaking down vacuum line from petcock into #2 carb body and making the cylinder rich.

If it is lean, I would suspect something is wrong with your mixture screw, most likely tip could be broken and stuck in hole.

[tkent02]

Have you synched the carbs?
That throttle may be completely closed.

[Super]

Just a spark

It appears as just a spark, a bright spark but no real color. Not the bright orange or blue. I'm guessing it's the mixture screw or possibly a blockage of fuel. I so don't want to have to pull the carbs off again!!

I'm going to try unscrewing the mixture screw all the way out and see if I can check there's no blockage or if the spring being hung up.

[Super]

Not synched totally

I bench synched them when I rebuilt the carbs and was going to synch them with the Carbtune after I used the Colortune. I know...it sounds almost Looney Tunes doesn't it?

[Steve]

A closed carb is a likely possibility. Even with as many sets of carbs as I have done, my bench sync rarely is spot-on.

Sync your carbs, then use the Color Tune again.

.

[ddaniels]

If there's no change as you turn the adjustment screw, then most likely there's a problem with the pilot circuit.

[BassCliff]

Hi,

Let's hope the mixture screw tip isn't broken.


Thank you for your indulgence,

BassCliff

[hampshirehog]

Blocked pilot circuit, almost certainly the jet. The colortune comes in to its own here - shows you what's going on inside and I've seen this dozens of times.

[Super]

Thanks for all the help

Thanks Steve, ddaniels, basscliff,and hampshiredog for your help. I'm going to check the mixture screw first, and go from there. Your answers to this problem pretty much follows what I was thinking...or guessing, really. And I just hate to guess at anything. It leaves me open to too many things that can go BAD!!

I will let you know what I find out. Thanks again everybody....this site is the BEST!

[Super]

It's the #2 carb

Okay guys,

You were right. I checked the mixture screw and it was fine. I then hooked up the Carbtune and the number 2 carb was showing NO vacuum reading at all!! Even when I adjusted it all the way out or in....I only got the smallest of movement. SO...the carbs are coming off and will open up number two and see what's going on. This explains why the Colortune wasn't able to get any color at all....apparently no or little gas coming in.

And yes, I did check the number 2 pipe as someone suggested and there was no where near the heat on it as the number one pipe...which was mighty hot.

Thanks to all who offered their help. I will update the results later.

[Steve]

The first thing to check before you take the carbs apart is to see if the tip of the mixture screw has been broken off, not allowing any adjustment.

.

[Super]

Yep..did it

Yep, I followed your earlier suggestion and the mixture screw and tip were fine. Sorry, I forgot to mention it in my earlier post. Thanks for your help.

[Super]

You guys were right..junk in the #2 carb

Okay guys,

My journey with the colortune has been reached. As most of you have suggested, the number 2 carb had some junk in it.

I had pulled the carbs off and checked everything inside the number 2 carb and was about to reassemble it when I decided at the last second to pull the floats off and check the fuel inlet needle valve. Sure enough...a blast of canned air and out tumbles 2 shavings of black rubber!! I had attached a small piece of clear tubing onto the existing black tubing that was on my auxillary gas supply...just so I could see if any junk would flow down into the carbs and catch them before they caused problems. I'm thinking now that maybe I had loosened some shavings somehow and didn't see them.

Anyway...carbs put back on the bike, colortune worked on ALL four carbs and then I Carbtuned synched them. Got them pretty close with the Carbtune. I will button her up tomorrow or the next day. Pretty wore out from this heat!!

Thanks for everyone's help, you guys on this forum are the best!