sync or colortune - what 1st?

[Hawkins]

10 characters

[GARTHXS]

colourtune

Sync then adjust mix and sync again

[GARTHXS]

colourtune

Sync then adjust mix and sync again

[65oldsboy]

Sync then adjust mix and sync again

It's like déjà vu all over again.

[Hawkins]

thanks, that's what i thought.

[dbeardslee]

Hawkins - Garth is correct - synch, colortune, synch. I even go as far as to check the synch in between each carb adjustment to make sure I have an even draw across all four carbs when adjusting the mixtures. To be accurately adjusted all four carbs should be within 2 cm of vacuum of each other.

When I colortune mine (or anyone else's) I adjust the screws out until the flame color is completely yellow. Then I bring the screws back in until the color changes completely to blue, and then I go 1/2 turn in from there. That works real well, but it took some playing around to figure that out. The thing to keep in mind with the colortune is that, while it shows you the color of the burn, it's not showing you on a 'real' spark plug. If you do it by the colortune directions you would stop when you get bunson blue, but by trial and error (and some comments from other members) I found that resulted in a rich condition. Put the additional 1/2 turn on them and they should be pretty perfect.

On the colortune, it doesn't take very long to get the adjustment right, and you don't want to leave the plug in a hot motor too long. For me, once I've got the colortune in with the motor running, it takes less than 30 seconds to adjust the screw. There are some plastic parts that could conceivably melt if left in contact with a 250 degree motor too long - at least that's what the manual says. I always let mine cool off a little bit in between carbs. The time it takes me to clean the old plug, install it, and recheck the synch (taking my sweet time) has been sufficient for me. Also, make sure you have a fan blowing across the motor while doing these operations so it doesn't overheat. You'll also need a dental pick, or a suitable surrogate, to fish the brass washer out of top of the number 2 & 3 cylinders after removing the colortune. That thing almost always stays put. And lastly, wear gloves - those little buggers get hot.

[Hawkins]

Thanks guys. I couldn't get the bike to run good at all with the colortune. Could these coils be putting out more juice than the colortune is gapped to handle??

Anyway, exhaust smells rich at idle, so I backed the screws into 1 turn out.

After the engine gets hot though, the idle speed is high and it takes a long time for the engine to drop revs, which indicates the idle mixture is lean?? I checked for vacuum leaks with propane, but couldn't find any.

Could weak charging/battery cause the rich smell at idle, and when i compensate for that my mixture ends up being too lean for driving conditions? Last time I checked (couple days ago) I was getting 13.5 volts or so at approx 3500 RPM. I'll again when i pull the seat, and check the idle voltage too.

Thoughts anyone?

[dbeardslee]

Hawkins - The colortune will work fine with the green coils. It's normal for the idle to increase after installation - use the idle adjustment screw (the big one in between carbs 2 & 3) to adjust it down. Set the carbs properly with the colortune as outlined above. If you start monkeying around with the mixtures after colortuning you kind of defeat the purpose. Also, make sure the engine is at full operating temperature before adjusting. What are the particulars of your setup - modifications, jet sizes (both main and pilot), and float heights?

[Hawkins]

Ok, if it worked for you it should for me. Then again I'm rushing a job you shouldn't rush! I'll try again.

Float height - can't remember, but it was working fine. I had em set to spec last time I did it.

Stock airbox with new K&N filter

120 mains

42.5 pilots

mixture screws out 1 turn

Green Mikes XS coils, new iridium plugs gapped to 0.040"

thanks for the help.

[dbeardslee]

Hawkins - The 80 SG was jetted at 120 mains on 1&4 and 125's on 2&3, so if you've got 120's all the way across I can't see that making it run rich. Floats should be set at 23mm for 80/81 carbs. I'd check the float height and make sure they're set right. I use a combination square as a guage. I set it one mm more than the measurement I'm looking for, and adjust the floats until I can only see about 1mm of light between the cast iron part of the square and the top of the float. That's with the end of the 'ruler' part flush with the gasket surface. I like the combination square because the thickness of the ruler just fits between the raised part of the gasket surface and the side of the flange. You don't want your gauge to actually touch the float as it's very easy to depress them and not notice. Whatever you use has to hang over the float or you won't get a good measurement. Also, measure from the gasket surface with the gasket removed. I'd check that first as incorrect float height - specifically too low when measured with the carbs upside-down - can definitely make them run rich.

[79XS11F]

Because the adjustment of both will have an effect on the other I do both twice. I sync, color tune, re-sync and then correct the color. If the color is way off I will even sync them again. When set up with vac gages and color plugs in place it's not a big deal to do it as many times as is necessary to get all cylinders running and burning the same.
Rob

[Hawkins]

She's running pretty decent there now, not perfect but ridable amd not lean enough to do any damage. For some reason I can't get the bike to run good with the colortune plug, so I've just set the screws to be on the rich side if anything.

Actually 79XS, I bought this bike when I lived in Ottawa 10 yrs ago. Lots of good roads in that area. Since I moved back to sea level I've struggled with these carbs. Maybe it's time to admit I can't tune a bike!??

Thanks for all the help dudes. I'm heading out for a 6h run to my hometown tomorrow, 27 deg and sun forecast. I'll do some chops along the way and post the results whenever I get internet again.