Colortune Help!

Okay, I'm having a little trouble tuning my XJ700. The Gunson Colortune won't ever turn orange. It's blue with the mixture screws all the way in and nearly all the way out.

The color changes a bit as I open up the screws and it flashes orange as the engines sputters and pops more. So I've sort tuned it by finding the place where the sputtering and popping stops.

Obviously that's not very accurate. As a result, the bike takes forever to warm up and bogs down when I accelerate too fast, also there is still some sputtering and backfiring.

Also, it warms up backwards from what I would think...when it's cold it idles very low and stalls easily. Then the idle rises as it warms. Shouldn't it idle high when cold and then drop down?

Any thoughts?

 

What have you done to the bike/carbs already? is the bike warm + the enrichment circuit off?

 

I've overhauled the carbs. I believe the bike is warm. Enrichment circuit off.

 

The idle will get higher as the engine warms, at which point you back off the enrichment circuit ("choke"). A fully warm engine should idle at ~ 1100 RPM (check your manual for the exact idle spec).

If you were working on a car engine, with an automatic choke and fast idle on the carb linkage, you would be correct in thinking that the idle will drop once the engine is warm. Your motorcycle has none of those things.

 

Clean the ColorTune Plug.
Use Dish Detergent and Kit Brush.
(Or Q-Tips)

Some "Early ColorTune Kits" come with a flimsy H/T Lead that Arcs.
(They sent me a well-insulated H/T Lead when I called and complained.

Wrap H/T Lead with 2 Layers of Vinyl Electrical Tape.
Shrink Wrap.

Inspect "Choke Plunger"
Straighten-out Bent High-hats after Heating.
Roll Plunger on Pane of Glass.

Inspect Plunger Lifting Forks for synchronized movement and any binding.

 

okay thanks,

Just took it out for a ride. I don't think I'm letting it warm up enough. after 15 minutes of riding it idled at an even 1500.

I haven't been using the choke to start it. The choke just kills the engine right now. I'm assuming it floods it out. some more tuning is needed...

 

Did you check the condition of the o-rings on the mixture screws ? Just wondering - if they perished and died a little air could be getting in. A finger over the end might be enough to tell you.

 

Here is a guide I found on using the colortune. This assumes that you have checked that it is functioning properly as suggested by others. Seems that you may be a bit lean. Are the float levels set properly?

Color Tune Guide

 

Is there a possibility that you have the jets reversed?

 

To address the last three posts:

o-rings are new on the mixture screws. There is a chance they are not sitting correctly. I will check that.

Float levels have been quadruple checked. They are good.

Funny you should say that. When I first finished the carbs I followed that Haynes manual which reverses the air jets. Wouldn't fire at all. Switched them following chacal's instructions and checked the fuel jets just to be sure.

And now an update: This thing runs great when properly warmed up. There's spurting, bogging down, and backfiring at low RPMs when it's still a little cold. 3000RPMs in 3rd and 2nd is a smooooth ride....So some of this is "user error". I'm gonna try the colortune again after riding for a good 15 minutes.

 

XJOE550

That chart is super helpful. Thanks so much!

 

Cool chart, but I've never heard some of those terms before. I'm assuming that "fixed choke" means bikes where the choke is either on or off, like my dirt bike, and "variable choke" means it can vary in the range of fully open to fully closed. So our XJ's have variable chokes, right?

 

Yes, I found it confusing at first glance. And although some great information it could have been organized better. But for the most part. You have the three test.
So for the first test you follow the instructions on the left side section. And start yellow (rich) and go lean until you get a nice bunson blue. The color strip they provide for that test is what you should experience as you proced with that first test at idel. You only have to worry about the trouble shooting section for the first test if you run into issues. The trouble shooting guide that pertains to our bikes is the (FIXED choke or carburetor with seperate idle circuit). Since our carbs have a serperate idle (pilot) circuit from the choke circuit.

It is confusing, because our chokes are variable chokes. But that is not the section of the guide that I think you should to follow. Use the one that states "seperate idle circuit".

 

It's actually because our "chokes" aren't true chokes at all but rather enrichening circuits.

A true choke is a secondary butterfly for closing off airflow to create a rich mixture for starting. Our "choke" is simply a passage that is opened to dump additional fuel into the carb. Variable, yes; "choke" not so much.

 

My take, after reading those Instructions, is that the terms, and other language used in the directions, is meant for tuning automobile systems.

A Fold-out pamphlet came with mine.
Doesn't resemble that one.

 

Mine will idle at 1100 after just two minutes of riding. When it's colder out (40* or below) I'll let it run for about 5 minutes before taking off, but I still have to cut the enrichment after 2 or 3 minutes.

There are a couple things I suspect, both to do with flooding.

1. Could be the enrichment plungers/o-rings/orifices. You should be able to turn the screw in and get zero fire when looking through the Colortune. The fact that you can't get to a point of white or no fire make me suspect something is up with the plungers or the plunger mech. the lifting arms have been known to be put on upside down (done it myself).

2. The fact that it bogs down when going with throttle up leads me to believe the float heights are wrong or there are a couple sticking floats. But like I said in #1, this could be from the enrichment plungers also.

Do us a favor, check the color of your spark plugs. I suspect they are pretty black.

 

Spark plugs are all black. Of course. It's flooding, I know this. Double checked the mixture screws and choke assembly. Everything is correct. Fuel level is spot on in all four carbs.