what story do my spark plugs tell you???

what do you think maybe too rich (these are the outer two plugs 1 and 4)

 

If I'm looking at them right. The left one is to lean and thr right one is to rich. Better get a 2nd opinion though.

 

They both are on the rich side.

 

+1 with Mn-Max, they are both rich. You are looking for a nice even tan on the insulators.

 

Wonder what the other two look like?

 

What I find interesting, is that one plug is clean on one side and sooty on the other.

Mine are kind of like that. They won't seem to turn tan. They either burn a solid white, or if I richen them up slightly, they form a slightly sooty ring around the insulator. The metal electrode remains clean. They're not anywhere near as sooty as these depicted though. My plugs have very low miles. Does it take time for the insulator to turn tan?

 

mine did that till i set the gap correctly at .28 and re-adjusted the mix by doing plug chops now they are all even

worst case your looking at valve seals if it continues after you do the same.

 

Ron,
I thought if it was white like the one on the left it was lean?

 

Interesting. I'll verify the gap and see what's up.

 

midnightblu touched on something everyone seems to forget:

Rich mixture isn't the only reason for sooty plugs. Persistent black soot, especially in only one or two cylinders, generally means it's pushing oil and burning it. It can be valve stem seals, or worn/rusted/clogged rings. You're never going to see tan plugs if you're burning oil.

A compression check should point to ring issues, if it comes out fine then it's probably only valve stem seals.

 

I think those sparks are telling a different story. Right, yep that one is rich, no question.
Left, it's rich around idle but very lean over that. I'm assuming here that the bike was stopped in the regular way (no plug chop) and because of this there was enough time for the ash deposit to build up on the right hand side of the insulator but it wasn't enough to hide the signs of the lean condition on the left.

Let me know that I'm wrong or not please!

 

Compression check was good on my bike so I'm going with worn valve guide seals unless my plug gap is wrong. The (broken) odo on my bike said 50k + when I replaced it. No telling how many actual miles were on it.

 

update guys i went through and colortuned my bike only a few minutes ago ( for the first "true" time) i discovered some things about colortuning:
1. have set of needle nose handy so that when you got to get plugs 2 and 3 out and you get them all the way out and they fall out of the socket into that nice area with lots of hot metal to burn your hands on(the bike should be good and hot when you do a colortune right) you can easeily get your sparkplug out of the hole without burning yourself
2. extensions on the ratchet make it a lot easier
3. colortuning is a lot easier at night you can see the color better
4. there seems to be a large bunsen burner blue section of adjustment so i tryed to pick like the middle blue with respect to how the engine sounds
5. plug chops will be needed for more granular adjustments

in the pic above 4(right plug) was sooo rich it was a yellow flame. the rest where in the blue range

 

This is all very interesting.. I'm going to have to learn all this as soon as I get 3 and 4 to fire up the cylinders... Plug chops.. colortune.. Rich lean.. Whats all this meeean.. man.. my head wants to explode sometime with all the stuff I learn here

 

I don't think it is oil fouled. Oil fouled plugs are usually more shinny. That looks like Carbon to me.

 

The plugs sit in the holes in different angles to the exhaust valves. Mine were running too rich and one side of the insulator was clean. Side towards the exhaust valve. Color tune is a good thing but you must realize that these bikes like lean. So since you are in the middle of the road with the blue color try tweaking just tiny increments the with of a dime towards rich and keep an eye on those plugs. Nice an tan color is your goal. Look down into the plug too to see what that looks like. Go out and put some miles on and do a few plug chops and make note of what you see. If its right you'll see tan

 

yeah i just think it carbon deposits its not slick or glossy its more flat black in color

 

yeah i will do that mn-maxim im in no hurry, i sort of enjoy tweaking it

 

not to hi-jack my own thread but here's some pics of my bike:

and my "you've got to have balls to have this License plate" License plate

 

Hey, that looks alot like my bike.
Are those stock bars?

 

You need have the Carbs PASS a "Clunk Test"

Those appear to be Binding.
Polish the Diaphragm Piston Bores.
Clean with Gray ScotchBrite Pad.

Polish using a Dremel and appropriate rouges.
You are done ... when the Diaphragm is raised and falls without any binding what so ever. NONE. Zero tolerance for binding.

Search Clunk Test and Bore Polishing.
You'll love the results.

 

I love to see these primaily stock XJ Secas still running around, it gives me warm fuzzies.

I wasn't suggesting you are burning oil, I just wanted to point out that carbon soot from oil will make carb tuning by plug read a bit difficult. And deteriorating valve guide seals on a 25+ year old bike shouldn't be a surprise; look what happens to butterfly shaft seals and they're in a MUCH easier environment.

 

etg... wow that looks great, did you ever find out what your gap was when you did the color tune? i noticed you said they are all in the blue on the color tuner but you diddnt say if you got chocolate on your following plug chop. tell us what happened

 

Just a little tip- - get a foot of 3/8 fuel line or old air hose, straighten it with a dowel or pencil, make a half inch cut at the end- - the perfect tool for twiddling your plugs in and out. Remember the anti-sieze too.

Clean looking bike !!

 

no hound i dont think my bars are stock but i love them to death though!!!

 

ok guys i have colortuned the bike and now i have some new pics from my plug chop but before i post these pics here is the info:
temp 42(morning portion)-54(afternoon portion) fahrenheit
Humidity: 57% Pressure: 29.91" (1013.1 mb)
Heat Index: NA Winds: 16.1mph West
Dew Point: 39° Visibility: 10.00
trip: two 35-40 min stints
speed: 60-71mph
rpm: 3500-4500 rpm
interval between trips: 5hrs

let me know what adjustments i need to make to my mixture screws(how much turn)

 

ok guys i have colortuned the bike and now i have some new pics from my plug chop but before i post these pics here is the info:
temp 42(morning portion)-54(afternoon portion) fahrenheit
Humidity: 57% Pressure: 29.91" (1013.1 mb)
Heat Index: NA Winds: 16.1mph West
Dew Point: 39° Visibility: 10.00
trip: two 35-40 min stints
speed: 60-71mph
rpm: 3500-4500 rpm
interval between trips: 5hrs

let me know what adjustments i need to make to my mixture screws(how much turn)

 

You are way lean, turn them mixture screws out a couple of degrees take it for a run & see what they look like then. Post somemore pics everytime you pull them so we can all see where you're at. Okay? Keep tweeken, it will come around.
Gregg

 

You do realize that a "plug chop" only gives you information about what the combustion conditions were like inside the cylinder only in the moments immediately before the plug chop, correct?

 

ok will do that , i will take it out a couple of degrees
also since bigfitz asked what my compression number where ,here they are

cyl 1 132psi
cyl 2 130 psi
cyl 3 125 psi
cyl 4 125 psi

went to my local autozone and rented a compression tester

 

are the compression numbers listed above low????

 

Do the Colortune again ...

Watch the Color
Get into the Blue and keep on adding Richness until you are where the Blue goes away ... ON THE RICH Side.

It's OK to run RICH
It isnt OK to rum Lean.

Running Rich will mean running cool and not having anything harmful happening.

LEAN ... Lean is fun until something really bad happens ruining the engine.
Burned Valve
Burned Valve seat.
Broken Rings
Scored Cylinder Walls
Melted Piston Skirts
Blow-through Piston Crowns
Blow through Piston Crown with thrown rod.
Among other problems.

 

Based on the RPM range you gave us and the insulators looking pure white as an indication of very lean condition I would suggest to go up 2 size with your main fuel jet and do the plug chop in the same RPM range again. I'm assuming you aren't able to change the needle clip position(it's true, when you're using the original needles). But keep in mind, in that RPM range you're tuning for midrange instead of low end / idle. As Chacal wrote: "plug chop only gives you information about what the combustion conditions were like inside the cylinder only in the moments immediately before the plug chop"

To check the idle mixture, you have to do the plug chops around 1500 RPM. Or, just let the bike idle for a minute or two then check those plugs. That's the easiest.

Also, keep in mind your idle mixture not really affects the midrange or top end condition of your mixture. You can run rich at idle / low end but you can run very lean at top!

 

CORRECT!

And such a condition and situation will burn nice little round holes in the top of your pistons.......and that situation can lead to pieces of your con rods, crankshafts, etc. finding a new purpose in life, such as doorsop, wall ornament, or javelin embedded through your rear tire and wheel......

 

so your telling me the only way to get it not running rich on the midrange is to:
1. up main jet size
2. raise needles up

so no matter what i adjust the mixture screws to it will not effect the lean the condition in the midrange, am i correct in that assumption???

i have a stock configuration how can that be???

 

No I told the only way to get it not running LEAN on the midrange is to go up with the main jet size. Raising the needle won't help really.

Yes, the idle mixture condition just barely affects the midrange condition.

How can a stock configuration breath more air? Many small things I suppose and keep in mind, every bike is different.

 

hmm interesting observation i was browsing through chacals parts and i discovered this:

#110: all XJ650 North American models (except 1982-84 Canadian models) and all 1980-82 XJ650 UK/European (4K0) models.

#112: all 1982-84 XJ650 UK/European (11N) models and 1982-84 XJ650 Canadian models.

so that means that us model was meant to run lean for epa regulations so by upping it to the 112's its should eliminate the lean condition on the midrange correct me if im wrong....

other US xj650 owners chime in and tell me if you upped your jets to the 112's

 

I've been fighting a lean condition since I got this bike last fall. (See Pipes Turning Blue thread) I've sealed the boots to the head, repaired the air filter to air box seal, raised the needles .020 and adjusted the float levels in 1 mm increments all to no avail. I've made some improvement but not enough that I feel comfortable with the longevity of this engine at this state of tune. I just received the "Canadian" jets from chacal, thank you sir for all your help and fast response times, 112 mains and 41 pilots. I need to check the float levels one more time and they will be on the bike this weekend. Stand by. I'll let you know what happens. One question, does anyone know what the float drop messurement shold be? How far down should they be allowed to drop when held upright?

 

ETG and Wingnut brings up some good issues, in a round-about way.

Due to differences in the various replacement float valve kits (both in the seat and their needle), I would not make much use of any "standard" float height measurements that are published. Remember, the float "height" is just a measurement that will get you to the proper FUEL LEVEL in the bowl; that proper fuel level (as measured by the "clear tube" method illustrated in the service manuals) is the final goal. A certain "float height" will given you a proper FUEL LEVEL on a particular carb(s), using a particular combination of parts.

The FUEL LEVEL is important because too low a fuel level will result in a lean condition, while too high a fuel level will make the bike run rich.....here's why:

For a particular engine....and here's the part where "every bike is different" becomes meaningful........a particular cylinder will produce a certain amount of vacuum pull on its intake stroke. What determines that amount of vacuum pull? A variety of things: engine size, bore diameter, stroke, intake passage size and configuration, VALVE ADJUSTMENT, integrity of piston ring seal, etc. All things considered, a cylinder is going to pull a certain amount ("strength") of vacuum thru its carbs.

Now, if the fuel level in the carb bowl is "high", this vacuum pulls quite a bit more fuel into the cylinder on each cycle. The high fuel level makes it "easier" to pull the fuel up into the bowl.

A low fuel level is the opposite: that same strength/amount of vacuum is now pulling less fuel into the cylinder.

It's just like you sucking on a straw in a drink cup: you have to draw harder to get the fluid up the straw when the cup is almost empty than when it is full (if you don't believe that this is true, attach a vacuum pump to a straw and see for yourself!).

Now, ADD to the above situation and circumstances the issue with the vacuum diaphram piston unit: it, too, is influenced and operated by the AMOUNT of vacuum that it feels. Less vacuum = less movement. Less movement = the needle not being raised up as high. Low needle = more restriction thru the main jet passage = less fuel being drawn up (a double whammy, that low vacuum condition is........).

This is also why the pistons need to pass----with flying colors----the Rick-o-Matic "clunk test"......any restriction in a piston's movement will restrict the movement of that piston to a given vacuum signal strength.

This is why Big Fitz leads the charge and chants the Valve Adjustment Mantra over and over again: although "vacuum sucks", it's important and it's especially important that vacuum be as equal as possible between all four cylinders. Properly adjusted valves will insure that the vacuum draw is as equalized as possible across all four cylinders.


These little carbs are pretty simple in operational theory: no accelerator pumps, very few circuits, very few parts actually (I think I counted a total of 60 parts total, 45 of which are screws or fasteners of one type or another). The DIFFICULTY with them is that they had better be operating COMPLETELY PROPERLY (internal passage cleanliness, clunk test, etc.), and the fact that there are four of them (let's see, Ferrari's and old tri-power GTO's and Corvettes, and dual-quad Hemi's and Six-Pak Mopars and lots of race engines are the only other motors that immediately come to mind that are multi-carbed, so these little 650cc etc. Yamaha engines are in that same sort of rarefied "family").

The "tuning" process of these engines, if the basics are overlooked or neglected, will harshly PUNISH those who ignore them!


By the way, I think that Canadian models got the #112 mains and #41 pilot jets because of the colder-weather operation issues (cold air = denser air = leaner mixture) rather than the EPA regs issue......but I'm just guessing here.

 

ETG,

My 81 650 has the 110's and 40 pilots in there and it runs fine. I rebuilt the carbs and now I'm working on the valves. I think the guys here may be onto something with the float levels. No matter where you set it dry it always needs to be right at the float bowl screw washer (looking with a clear plastic tube connected to the float bowl drain) If the float level is low thats going to make it lean. So if you can find some clear tubing put some on the float bowl drains and open the drain screws and see where the gas level is. If its right up by the washer it should be ok. You should be able to tune with the mixture screws. Make sure the diaphrams are in good shape (no pin holes) and I'm sure you did the clunk test as per Ricks suggestion.

 

OK long standing question on the idle jets not having any effect on mid and high range. I know Len has said this a few times and I have seen others say it but looking at the carbs there is no off switch for these jets.

So although I concede the effect of that tiny jet gets smaller as gas flow goes up it still is a contributing factor to the air/fuel mix.

What am I missing?

 

Bill....your understanding is correct, but the amount of contribution of the pilot circuit is miniscule compared to the main jet circuit at anything over about 2500 rpms (or under hard acceleration)................

 

but doesnt europe get just as warm of weather as the us at certain times of the year so why do they have bigger jets, the only reasons i could think is THE EPA ????

 

Bill,
You don't miss anything. To understand the effect of the different parts properly in the carbs see the attached picture. (Sorry, I wasn't able to get a larger picture)

 

On STOCK Hitachi's and Mikuni's with Diaphragm Piston CV Carbs:

The Pilot Mixture Screw needs to be adjusted to:

Provide the Cylinder with an Air~Fuel Ratio Rich enough to sustain idle.
Further enRiched to provide: "Supplementary Richness" for Off-Idle Performance.

The Supplementary Enrichment from the Pilot Mixture Screw Provides some Fuel to Mix with the LEAN Intake Air which is introduced to the Combustion Chambers at the Instant the Throttles are opened.

IF >>> There is sufficient SUPPLEMENTARY Richness. The Engine Immediately accelerates without a hesitation caused by an instance of Fuel Starvation. (Hesitation getting out of the hole.)

The Supplementary Richness is also added to the Volume metered by the Main Fuel Jet at Wide Open Throttle to determine the Fine Tuned Air~Fuel Ratio for Mixture Tuning.

The Precision NEEDED in the Adjustment of the Pilot Mixture Screw is within
8 Degrees.

 

Now, if you are running Rich or Lean, what does that mean? Rich meaning too much Gas? And Lean meaning too much Air? If so, which direction do you turn to screw to get more Gas, or more air. And I fail to see what colors on the plugs we are looking at. I'm a total newb to this fine tuning and, while very helpful, this post is confusing because I dont know proper terminolgy.
Also. The term "Plug Chop" isnt very self explanitory. Can someone describe this to me?
-SLKid

 

Thank you gentleman for the charts. Its good information. We have to take a holistic view of the engine"s condition when tuning. This one has had the compression checked, valve clearance optimized, all intake path joints inspected and sealed. The carbs are clean, inspected and pass all drop tests. The only thing I have not checked is the timing which is not easy to adjust so I have assumed it is still at the factory setting. I've been playing with 4 Cly. Yamaha's for a few years now and this is the first one I have had to resort to jet changes to fix the lean condition. I may have given you the idea that I have only been using the float measurements to adjust the levels. I have been using that method as a reference point only. After each tang adjustment the floats have been checked using the clear tube wet method. The different gaskets and float needle dimensions would drive that. Also the 112s and 41 could have been to compensate for the lower average temps in Canada and Europe but I'm inclined to go with the EPA theory.

 

The TIMING is Fixed.
There's NO Adjustment.
As the Ignition Rotor passes across the Magnetic Pickup ... The Duration of the Magnetic Field sends an Impulse to the Igniter which Electronically Advances or Retards the Spark depending on Engine RMP's.

Although some articles suggest "Elongating" the Holes in the Pick-up Coil Mount; that practice is NOT advisable because the TIMING is Optimally Set at the Factory with the Highest Performance Dialed-in.
Adjustment might cause Mechanical problems do to the Dynamic Timing of the Valve Train within the Limits of the Factory Preset.

 

Yes- Rich- too much gas. Lean- Not enough gas/too much air.

Turn the screws OUT (counter-clockwise) for more gas. IN (clockwise) for less fuel. Small adjustments.

Plug colors/Plug chopping- You've seen the photos in the archives. Look at your spark plug tips. The white part with the little metal dot sticking out of it. (the electrode). That white part (the insulator) should be tan. If it's bright, clean, white then you're too lean and will cause ENGINE DAMAGE.

If the tip is black and sooty, then you are rich. If it's black and oily, then you have other problems like worn valve guides or piston rings.

A plug chop is where you ride the bike at a high speed above idle and then cut off the engine with the kill switch and coast to a stop. The plugs are then checked for color to see if a rich or lean condition exists when the engine is run above idle and under load (meaning, hauling your butt around)

 

That's as I thought. The later model XS Yamaha's are that way also. The 78 79s are adjustable but I don't think any of the XJ series is. It's academic anyway as its right on the button after checking it. Good news is that the Canadian jets seem to have resolved the lean condition. I did a shot 20 mile ride and under normal riding conditions and the plugs are running a light tan. That I can live with rather than the scary white I had before. Still can't get the color tune to work as well as it dose on the XS but I started with the mixture screws 2 turns out and it only took a 1/2 a turn either way to find the sweet spot doing it by ear. Absolutely no stumble from idle and the bonsai runs were quite satisfying all the way to red line. I'm going to run it this way for a couple hundred miles and check the plugs again. Think we got it this time. Now to get that blue color off of the pipes.....