What's the order?

So, seeing lots of sync, colortune, rebuild, clearance posts.

What is the proper order for a carb overhaul/ recomission project on an XJ?
I'm guessing here:
1) rebuild carbs/ bench sync/ dry set floats
2) valve clearances in spec
3) new plugs
4) wet set floats/ re-install carbs on bike
Now, what is next?
Colortune then vac sync?
Or visa versa?
Anything else?

 

vac sync, then colortune and then vac sync again..

 

Maybe mix in some plug chops, too, since Colortune is only going to take care of idle, unless you have a dyno you can run on while Colortuning.

 

After returning the carbs to the bike, and if everything was done correctly, the bike (although expectedly "cantankerous") should be rideable enough to run 10 miles or so to get it fully warmed up for its initial vac sync, with YICS blocked if applicable. At this point the mixture screws are still at 2.5 ~3 turns out.

Vac sync. Use a house fan ("box" fan) to blow air over the motor.

Then set the idle (after removing the YICS tool if used.)

Ride the bike a bit; double check the sync if the idle still hangs. Look at the plugs (obvious issues will reveal themselves.)

THEN ColorTune. Again, best done with the bike fully warmed up, and YICS blocked if applicable. I recommend a pair of reasonably high-quality "light duty" welders gloves for handling hot plugs. Anti-sieze compound is your new best friend as well, just go easy and don't get it all over the ColorTune (don't ask.)

 

Dang, you guys are quick! Quick like an XJ in the power band range!

1981 non-YICS XJ 650
I did the vacuum synch, but did not do the ride and recheck. . .
Mixture screws are set at where the 'old' ones were:
1 = 2 and 1/4 turns out
2 = 1 and 3/8 turns out
3 = 1 and 1/2 turns out
4 = 1 and 7/8 turns out

Need to re-do vacuum sync after another ride. ( Is the fan really necessary? The first go round with vac sync took about 20 minutes - figure second time would be less)
Need to colortune - noticed that # 3 and 4 plugs have a little black soot on the bottom of the thread ring of plugs.
Is the only place to get the Gunson Colortune is on-line?
Autozone, Napa, etc. do not appear to carry it.
Len have it?

 

The mixture screws were set at the factory to keep the EPA happy, and only "matched" the cylinders when they were new.

Once the bike got a few thousand miles on it, you cleaned the carbs, adjusted the valves and set the float levels, the original mixture settings became moot. No longer applicable.

The book actually specifies a "base" setting for the early 650's mixture screws-- at 2.5 turns out.

I'd set them there rather than the original settings. It will make the next steps easier.

And yes, the fan is necessary. Think about sitting stopped in traffic for 20 minutes...

Auto Parts stores will look at you like you're from Mars if you ask for a ColorTune. I believe Len carries them or they're available all over the web.

Your sync and the accuracy of your float levels are more important right now.

 

I got mine from Len.

The gunson factory or whatever is somewhere across the pond.

Ebay maybe.

 

Yes, they're in the UK.

(I think I got mine off Amazon, before I joined XJBikes.)

 

Shot an email last week to the Morgan Co. on this very topic. Here is their response:

"Hello Joseph

Thanks for your airmail.

Yes this is the way to do it. Colortune first then Carbtune.
I know some people who are very fastidious would do Carbtune first then Colortune and then Carbtune again but I don't think that is really necessary.
Please get back to me if you need more information.

Best regards

xxxx xxxxx"

So basically it does not hurt to carbtune first and colortune second. But you would have to carbtune again if you change any of the mixtures settings. No big deal I suppose. I have always done the colortune first. And have been doing it that way for the past few years. So when there were so many people that did it the other way, like you, I wanted to know for sure.

 

Yamaha's EGA manual (they didn't use a ColorTune, they used an EGA) specifies that the sync be done first. That's what I've always gone by; mixtures last.

 

That's interesting. So two varying authoritive points of view. My Z1 manual indicates to adjust the mixture before balancing. I know, its not an XJ. But that shouldn't matter. What does EGA stand for (Electronic Gas Analyzer)? Or Exhaust Gas Analyzer? Either way, the color tune is a type of gas analyzer if you think about it. Just gives the results visually instead of by some other means. Weird thing is, my Yamaha manual doesn't even want the dealers to touch the mixtures. They are factory set. This is due to EPA regulations of that era. As you stated before. That is only when the bike is new and they make that statement to cover their butts from the EPA at that time. They have to be changed when modifications or changes in engine with time dictate it.
But my thoughts are, when you change the fuel mixture, you possibly changing the vacuum on that cylinder. Changing the RPM's possibly. Thereby changing the balance of the bank of cylinders. Thereby, requiring final balance after mixture settings. That is why it makes more sense to me to balance at the end.

 

I never suggested that the sync shouldn't be revisited after fine-tuning the mixtures.

EGA=Exhaust Gas Analyzer (circa 1979.) That's what the little plugs on the bottom of the stock head pipes are for. And yes, we're using the ColorTune to provide a visual substitute.