Factory Settings for Mixture.... WOW!!!

I just pulled the brass plugs on my 650 and noticed that the factory mixture settings were all over the place.

I had one screw at 1.5, and two at 3 and 1 somewhere around 4 or 5. How is the bike supposed to run properly like that?????

I readjusted all of them to 3 out and now she purrs like a kitten. I am going to plug chop over the new couple of weeks.

 

What model and year is your 650? My 650 Maxim was very similar.

 

I haave never looked at mine. How do you know if it is at a 1.5 or 4? and what is it supposed to be?

 

its a 1983 XJ650 Maxim

 

Count the number of turns it takes to get to the bottom. I have read that starting around 2.5 to 3 turns out, then plug chopping works well.

 

Mine were about the same. 1.5 to 5 turns out!

 

I'm unfamiliar with plug chopping? What is it?

 

THIS IS RICOMATIC'S METHOD.


**"Some of the tuning you need to do you can do without hitting the road.
Put some new Plugs in it.
Lean-out the Pilot Mixture Screws IN ... 3~5 Degrees ... not much.

Run the bike.
Set up an electric fan for cooling.
Rev it up to 5,000 rpm and hold it for 15-seconds.
Hit the Kill switch.
Look at the Plugs.

If you are still Rich you'll see it and hear it.
Based on the performance after Leaning-out the Mixture you'll have to make further adjustments.
Start the bike.
Let it Idle.
Open the Throttle and listen to it coming off-idle.

If it boggs-down before grabbing the Main Fuel Supply ... your still too Rich
If it sputters and coughs ... you have a Lean condition.

You will be tuning to achieve a seamless transition from Idle to when the Throttles Open.
This you will HEAR.
This you will also see as you examine the Plugs.

Plugs that are too clean will require a few degrees of Richness
Too Rich and you tweak the other way.

Hold the Bike at 3,500 rpm.
Listen to the exhaust note.
If the note is unsteady ... (Pop, pop-pop, poppidy-poppity) ... tune-out the miss.
Tweak the Screws a few degrees in each direction until that unsteady note disappears.

Once the unsteady exhaust note is addressed ... you are ready for some road tuning.
BRING EXTRA PLUGS IN CASE YOU FOUL THE ONES IN YOUR BIKE.

Go somewhere where you can do tuning runs.
An industrial park makes a good location.
Run the bike for a few minutes and then do a wide open throttle Plug Chop.
Take the bike right up to high revs ... kill switch and coast to a stop.
If you set up a table with your tools and Plugs you can coast to your work station.

Examine the Plugs.
Closely.
Make individual tweaks to those that ate rich or lean.
Stick-in some cleaned plugs. (Carb Cleaner and toothbrush)

Repeat the run.
Concentrate on getting the Mixture set-up to seamlessly transition from Idle to off-idle.
If it won't "Get-out-of-the-hole" ... make Mixture adjustments to give it enough richness to get going.

After a few runs you'll find Plugs that don't need adjustment and one or two that do.
Make the adjustments to the ones that need the tweak and do further runs.

Before too long you'll fine that you have arrived at where there is no further adjustments to do and the bike is accelerating without delay.

Bring all the tools home.
Ride it.
Do a daily inspection to insure you aren't too lean.
If you get it dialed-in doing Plug Chops ... you'll love the results!
"**

 

This seems like an alternate method to colortune plugs. is this accurate?

 

Yes.

 

Supplemental to Colortuning, actually.

That is tuning for Off-Idle Mixture.
I find that Colortuning gets you a good Idle and not quite enough extra for sustaining the Mixture to Ignition when you open the throttles and the rush of fresh air momentarily is without Main Jet Fuel Supplied.

This Plug Chop corrects the Mixtures so the bike won't hesitate or bog-down when you go to get out of the hole.

 

I'd be suspicious that someone was in there previously if my screws differed by more than 1 turn. It is possible to obtain replacement brass plugs, or at least it used to be.

Be aware that not all of our mixture screws have the same thread pitch. On the 650 the thread pitch was reduced in 1982. So the factory setting on an 80 or 81 is closer to 2 turns out, and the 83-84 are 3ish.

If you've got a bike where some of the carbs on the rack were replaced your mixture screws may not all have the same pitch.

 

Very, very good point.

That's why I have switched from FRACTIONS to DEGREES.
Once you settle-in to where you have a very good Idle and are Tuning for the seamless application of power coming 0ff-idle ...

It will just be a matter of DEGREES that the Screw needs to be turned.
A very small amount.

You can actually go from too Lean to too Rich within a quarter of a turn ... once the Pilot Mixture Screw is within parameters of sustaining Idle but not yet providing enough supplemental Mixture to sustain Ignition coming off-Idle.

I'm presently adding some Richness to my 750 because its getting warmer out and I want it to run a bit cooler.
I added 1.5 Degrees of Richness to the Pilot Mixture Screws and have a great Idle and less power in acceleration ... but a slower burn rate not as hot as the previously tuned-in one with a Leaner, more explosive Mixture.

 

Ok, I have a stupid question regarding the idle mixture screws: Am I correct in my thinking that turning the screws counter-clockwise gives the bike more gas and making it "richer" while turning clockwise gives it less gas and making it "leaner"?

 

That is correct
IN for Leaner
OUT for richer

 

Maybe I'm colorblind but I got my 82 650 Maxim running and used the colortune plug to try and set the idle mixture. I noticed there was a lot of flickering of the cyclinder. Sometimes it would fire brightly and you could hear it in the way the bike ran. Anyways, to make a long story short, I set each cylinder so it fired the same every time it was supposed to, blue like a gas stove burner flame. It ran really nice but you could taste the exhaust if you were within 20 feet of the exhaust pipe. Great throttle response and power. Drove it for 10 city miles on side streets. The bike was nearly out of gas before I started off so I added a gallon of gas. By the time I got back, the tank was nearly empty again. Maybe a better way to set the idle mixture is to use a vacuum gage or better yet the carb sync tool that measures all 4 at once. Get the highest reading at each carb with the smoothest idle when the YICS tool installed? I did tune ups this way on cars and got good results(no YICS tool for old v8 cars). I'm trying this next because the colortune didn't work for me but maybe I'm colorblind.

 

The Blue you get from Colortuning is NOT perfect. It's within the "Window" of Fine-tuning.
Usually, NOT Rich enough to sustain a smooth transition going Off-Idle onto the MainJet Supply when the Throttles are opened.

You are within the Fine-tuning arena if you have the Carbs set-up for gas stove blue.
Now, you want to fine-tune the Mixture to where you have Plugs that show you you are on the money.

If you feel the Bike is too Rich, you'd "Feel it" off-the-line. The transition to Main Jets will be late or not at all.

You have to observe the Plugs very closely, now.
Look at them to see how the Mixture is regulated.
If you find that the Plugs are too dark ... Lean-out the Mixture, some.

If you find a Plug thats too clean, add some Mixture to the Cylinder.

The process of adding Richness or Leaning-out the Hole isn't going to require much of an adjustment.
Probably within just a few degrees. Because the Bike will let you know if you have gone too far or not enough just by looking at the condition of the Plugs.

With BLUE showing during a Colortune, it usually means that you are adjusted for Idle.
Finding the supplemental Richness to the Mixture to carry the acceleration of the engine over until the Main Jet Supply Kick in is the key element in the Fine-tuning.

I doubt if the Pilot Mixtures need much of a tweak.
If you think your bike is a Gas Hog after Colortuning ... you need to look elsewhere, too.

Stuck Diaphragm Pistons not closing fully after throttle closure will waste plenty of gas and give you a false Plug Read for excessively Rich.

See that your Diaphragms are rising and falling without chatter, binding or sticking.
If they are not and you have:
A strong and steady Idle.
Seamless transition coming off-idle.
Plugs that aren't excessively dark.

You are IN.
You're tuned.
Maybe BEFORE you got Dialed-in,, the Bike was running Lean and you weren't aware of it.

 

If I understand correct, to get a good ballpark of where to set your carb mixture screws to factory is to screw them in all the way then unscrew 2 - 3 turns? (82 650 Seca)

 

yes SecaDan, as I understand it 2-1/2 to 3 turns out should be a good starting point.
ideal setting will vary from one bike to the other depending on milage and condition, altitude can also have an effect.

 

My carbs were set to about one and and eight of a turn out when I started "plug chopping"
I thought they all looked not too bad at this setting except number three was very sooty.

I moved the settings out in stages until they are all at about two turns out
except number three that I left at the original setting.
Number three seems to be cleaning up with each run. Darkness and rain put an end ot the tests for today.
Any comments would be appreciated, I may have a float problem or something else with number three.
The problem with number three was a leaking petcock diaphragm. The vacuum line that connects to the petcock is only connected to number three carb.
The low end had improved, and it starts with no choke now. It pulls better from a stop sign now, but I cruise at 100km/hr (60mph) at 5k instead of 115 km/h before tinkering. Hmmmm...