My first plug chop story... or what I 'think' is a plug chop

So keep in mind, every so often I am getting 'bogging' reving off idle, and once I reach 2.5k, goes away, and the power doesn't feel 100% there above that.

So, I've been checking my plugs after I get to work, and when I get home lately.

Today - after 20 highway miles, a cruise into town, and about 10-15 seconds idling... they were dark brown. (insulators)
Note- it bogged this morning after a full choke 4 minute warm up. Hit the highway, and after getting off highway to get gas, it cleared up.

Get to work, idle about 15 seconds, and they are BROWN. Ran good all through town.

Fire it up tonight. Run to the bank to make the deposit. Decide to do a mini-chop? 1/8th throttle, 3k rpm killed it and rolled to stop. Flicked kill switch back on BANGGG. Big backfire. WTH?
Check the plugs - black.
OK, so I am rich. Real rich. Like I've been thinking all along.
It acts rich, chokes trying to rev a bit, exhaust is a bit noisier than it used to be, the bogging goes away after some high revs... and Im dark brown. Right? Oh, and my screws are 5-6 turns or so out I think.

So after that mini chop... hit the highway home. 17miles in - decide to try a 6k plug chop, probably 1/4 to 1/3 throttle.
Kill it. BANG. Without even putting the switch back on, I get a backfire. Damnit.
Coast to a stop, whip out the ratchet and mini flashlight.
Pull 3 of 4 plugs... ALL BRIGHT WHITE.

Seriously... c'mon.

What the heck?
Everywhere I search, PLUG CHOP gives me 200 different things to look at, try, explain.... can't get a FLAT answer like
'Idle shold be brown, chop @ 6k should be tan'

I can't find any reasoning behind WHY to do it at certain revs/throttle positioning.

All I want to know really is WHERE/WHEN I really SHOULD be checking them. Because going by my idle colors, I am rich, which to my believe is really what I think I am. But are my plugs supposed to be WHITE @ 6k chop?

I am going to do a second sync tomorrow night, and see how my colortune reacts since this time around...

Sync @ 1500, colortune 950-1050? (RPM)

 

Re: My first plug chop story... or what I 'think' is a plug

Your fist plug "chop" wasn't a chop at all, since the engine came back on...........you are supposed to hit the kill switch, coast to a stop, turn the key off, get off the bike, remove and read plugs.

Turning the kill switch back on re-energized the TCI/Coils/created a spark in the cylinders which were full of un-burned fuel and BANG and so of course the plugs are all very rich and black.

Not necessarily........and this is what I try to stress to people about DOING THINGS BY THE BOOK IN ORDER TO PROPERLY DIAGNOSE SITUATIONS AND HAVE A FACTUAL BASIS FOR MAKING CHANGES....otherwise, you reach incorrect conclusions and go shooting off in every direction and careening through the entire Milky Way before arriving at where you want to be......in other words, the "pinball machine process" of engine diagnosis and tuning.

NOTE TO DOUG AND ALL OTHERS WHO WISH TO LEARN FROM DOUG'S EXPERIENCE: see how quickly the insulators change colors? After one single combustion event......


Your second attempt actually told you something useful....you're very lean at 6K rpms under a moderate load (1/3 to 1/4 throttle, I assume you were "cruising" rather than accelerating at the time?).

THAT bang was probably due to unburnt fuel coming out of the cylinders and exploding in the hot exhaust pipe. It happens.......

That or you have too tight or burned exhaust valves....yikes! Good compression on all cylinders?


Your "chops" after idling for 15 seconds tell you almost nothing, not just because you're idling, but because the engine is under no load, and unless you're aim is to have your fuel mixtures set "perfectly" for an idling engine, then the "at idle" plug chops are not quite meaningless.......they're worse than meaningless, since you'll be tempted to make all sorts of adjustments based on that information which does not necessarily correlate, at all, with the real goal you are trying to achieve.


Your sync needs to be done at idle speed (1100 rpm's +/- 50 rpms), as does the colortune. Note that as you adjust the throttle position screws on the carbs, it is likely that your rpms will change, and you need to re-adjust as you go along (i.e. before you adjust the next "synch" screw). You should have the YICS port blanking tool installed, properly, and engaged, as per the manual. If, after many trials and experiments and etc., you find that some other method works as well, is easier, or produces more successful results, then by all means, follow such "enhanced method" to your hearts content.

In the meantime, follow the recommend procedures, because---assuming that your other engine parameters are okay (valve adjustment, engine compression, carburetor cleanliness, no intake system air leaks, etc.) ----YOU WILL NEVER, EVER....NOT ONCE IN A THOUSAND YEARS, GET IT "WRONG" OR REACH INCORRECT CONCLUSIONS OR RESULTS, NOT EVEN ONCE, when following the factory specifications and recommendations.

One of these days, we're gonna get you a MANUAL!!!

 

yay len! best reply to any post I've done in a month.

anyway, when I said I turned on my kill switch - I meant AFTER I was at a stop with the motor DEAD.
so it WAS a chop, right?

the bang I suspect is just as you say. hot exhaust. my grilzzly atv does it.

my valve clearances were just done... you keep forgetting that

I've looked at my valves via plugholes, they look new, not burnt.

So I'm lean at 6k. so what?
seriously. if I tune to get 6k 1/4 throttle 'tan' whose to say 7k 1/2 throttle won't be lean?

what I REALLY need to know is WHAT RPM AND WHAT THROTTLE to get my dang mixtures right??? That's what I can't get a clear answer out of anyone. What is the GOAL rpm/thottle for 'TAN'?

thanks again len
oh- and as I stated b4, obviously killswitch ob then off is not a chop. lol

 

Re: My first plug chop story... or what I 'think' is a plug

Well, it WAS a chop right up into the moment you turned the kill switch back to on, and fired the mixture in the cylinders ("BANG") and then read the plugs which were black and you concluded that the mixture was rich.......what you DON'T know is what color those plugs were before the BANG......


And speaking of things you don't know............. :lol:

He who knows what he doesn't know is wise.........

Compression Gauges: cheap, somewhat easy to use, non-prejudicial and give you "facts" rather than "opinions". A Maxim's best friend, you could say. Almost better than having a dog.....

 

I don't get how one pop, after I'm stopped, motor dead, and dead for 10seconds... could affect all 4 plugs? why did it pop? I get the one on the highway... but without the motor rolling, why would my plug FIRE?

as for compression- I own a brand new gauge, trying tomorrow. so, disconnect tci and pull all 4 plugs, roll starter over and watch needle bounce?
obviously hot motor.

 

Actually, do it on a cold motor first, then go warm up the engine, and do another one.

Make sure the battery is fully charged, and the throttle held wide open.


It popped because turning the kill switch from off to run opens up the circuit to the TCI and the TCI sends a signal to the coils and the coils fire, and if your cylinders are full of unburned fuel from their last few gulps from the carbs (after the engine had been killed....the engine will still spin over a few revolutions from inertia and sucks fuel in), then that built-up fuel goes bang and being so rich it leaves a nice black coating on the insulators from that one bang........

 

I always thought the firing only went off when the timing told it too? weird.

will the gauge stop at the highest reading, or bounce as the piston goes from 'suck to blow' ?

name that movie

 

If the gauge is worth its salt, it will hold the highest reading, it has an "anti-drainback valve" internally that holds pressure. It's not a vacuum gauge..........!

If it's a movie other than Fractured, No Country For Old Men, or Pulp Fiction, I won't have the slightest idea.......

 

One answer Doug's looking for we havn't really provided; Yamaha has two sets of EGA specs for mixture tuning, one for idle and one for "cruise" which is done at 5K rpms.

 

Uh-oh, Fitz has been studying his Emissions Manual again!

 

Re: My first plug chop story... or what I 'think' is a plug

Out of curiosity... Where does the name "plug chop" come from? I'm no stranger to reading plug color, but I'm unfamiliar with the name "chop".

Can someone please fill me in on the origin of that term?

Burnarr

 

Drag racers would run full throttle and chop the ignition at the finish line.
No idleing or running after that. Then get pulled into the pits.
Since you can't hear knocking over an open exhaust (detonation), they were looking for these TINY little black specks on the white porcelain.

We're just looking for the correct color which correlates to the right A/F ratio (tan) at a particular load/RPM.

Speaking of which, once you are driving under load at 4K RPM or higher you are no longer diagnosing the Pilot circuit. There are 2 other jets and a big needle to look at.

 

Yeah, you caught me. Foolishly studying Yamaha's factory procedures for tuning, I know, I know...

 

Spaceballs! Oh sh!t, there goes the planet.

 

Good catch Storm!

OK guys yes, blah blah tech manual, blah blah drag racing, blah blah...
I appreciate your input everyone, but I still haven't found the answer I need to get it right. I also know AFTER certain throttle, you are off pilot and onto other circuits.

But isn't the PILOT ALWAYS running, and that is what we are ADJUSTING for proper mixture through the entire band?

The one and ONLY question I need answered : WHEN to chop to check for TAN. I need to know how to get the motor running CORRECTLY.
So, how much throttle and what RPM...? That's truly the only question I keep getting other answers to.

Fitz - you said 'one for idle, one for cruise (5k)'

So... with STOCK jetting - they should both be in spec, with proper mixture on the pilot. Right?

So - to get it running properly - do I plug chop @ 5k, FULL THROTTLE, and check.

Right? Is that what I am getting out of this? Orrrr-- is it check at idle, and 5k, and 9k, and 1/4 throttle, and half throttle... blah blah blahhh.

5k plug chop full throttle = the time (rpm) and place (full throttle) to get proper mixture?

 

i'm sure you meant to type "to" instead of "too".

but you're right, the timing "tells" it when to fire. if the motor stopped spinning at exactly the position that it would normally fire next, and the tci is not powered, it will not spark. now put power back to the tci, and add in a mixture of unburned fuel, and kablamo, you've got combustion.

 

Re: My first plug chop story... or what I 'think' is a plug

I also wouldn't be surprised if the TCI fires one spark when first energized... I know that there are other ignition systems that do that - probably as a diagnostic aid.

 

Actually I've heard our TCI ignores the first 2-3 signals, only firing after the crank has spun about 2 turns. Now where did I read that? XJCD?

 

Re: My first plug chop story... or what I 'think' is a plug

Newbie here!!

We only have 2 coils so we waste every other spark.
Don’t we??

Question for dpawl31.
Are you pulling in the clutch (and holding it in) at the same time you hit the kill switch?

Has a throttle shop procedure been posted?

Thanks
albran

 

Yes, pulling in the clutch, KILL switch, holding throttle at same open-ness.

From what I can tell, 5k RPM and full throttle is what I am supposed to do, but I can't get a straight solid answer about the dead-on procedure.

 

Re: My first plug chop story... or what I 'think' is a plug

Doug....what is the sound of one hand clapping?

You're asking a question which is not possible to answer, and you're asking it because you don't completely understand the nature of what the engine/carbs are capable of and what they are designed to do.

TIMETORIDE gave you a hint above.....drag racers read the insulators to check for detonation that would otherwise go unnoticed until they drive over their crankshaft on a future pass (i.e. their engine detonated so badly that it threw the crank right out of the bottom of the engine).

Ever seen a top fuel motor hydro-lock? They shoot the cylinder head 50 feet straight up in the air. Normally those are held on by 16 or more beefy studs.....

Drag racers also check the rod bearings after each run, and if they aren't squished almost to the point of spinning, then they turn up the boost a notch or two.


The point being: different users read plugs in order to get different types of information.

Street vehicles, and in particular air-cooled engines, are probe to overheating (for obvious reasons). Overheating drastically reduces the life of an engine. Continual long-term overheating can be caused by a variety of factors, with low oil levels and lean fuel mixtures being the main culprits.

So.........if you want your engine to last long happy time, you set the fuel mixtures to give you a slightly rich mixture, mainly as a precautionary measure.

Such a setting will NOT give you the best power or acceleration performance. "Rich" cools the combustion temperatures slightly and tends to slow down the combustion rate within the engine.

Due to the "dumb" nature of carbs (as opposed to fuel injection), it is not possible to maintain the same fuel-air mixtures at all throttle openings, under all conditions. When you crack your throttle wide open your engine gulps a bunch of air (goes lean) and only a few fractions of a second later does the fuel supply "catch up" with the increased air flow and return the mixture to a more-or-less proper ratio.

How do you plan to typically operate the bike? would be a good starting point to determine where and when to do plug chops. If you are typically going to be running wide open at 5K under hard acceleration, then do it there, and adjust your jetting to get a nice tan color under those conditions. It will probably run way too rich in almost all other situations, but that is the trade-off that is a fact of carbureted life.

I would think that for the best mix of performance and durability, you would test for typical cruising conditions.

And what you'll then find, is that the factory specifications and settings/jetting is what you'll end up using. They didn't just "guess" at what size jets, needles, vacuum piston weights and springs, etc. to use.

If, on a stock bike, and with stock jetting, you find that your plugs are too light or too dark, it is usually an indication of some type of problem within the system......vacuum leaks, plugged jets, etc.


The stock idle mixture screw (i.e. the pilot fuel circuit variable flow adjuster screw) can be successfully set with a colortune plug because:

a) it's a variable setting, and.....
b) the pilot fuel circuit is active during the transition from idle speed to off-idle speeds, and perhaps up to 2000-3000 rpms under some conditions.

A colortune cannot be used for anything but the idle mixture setting.

Reading plug insulators after plug chops is a second-hand way of being able to see the combustion conditions inside the cylinders (just like a colortune plug does) at other speeds and engine loads.


You're heading into driving yourself insane on this subject because you're trying to achieve "fuel mixture nirvana" across the entire spectrum of engine conditions via the "reading of the tea leaves" (in this case, tea leaves being plug insulators) and you'll never accomplish that.


If your intake and exhaust are stock, and your jetting and needles etc. are stock, and you have properly adjusted valves and good engine compression and properly functioning ignition system, then set the synch and adjust the idle mixture screws with the colortune and be done with it. If your plugs are black all the time or lily white then you probably have a problem within your carbs that needs to be remedied; no amount of plug chops will ever solve that issue and tinkering with a broke system due to small bits of erroneous data will only make things worse, and much more time-consuming and expensive for you!

 

Re: My first plug chop story... or what I 'think' is a plug

hi guys,
Good read one thing I think has been over looked though. Doug you say your mixture screws are 5 to 6 turns out? :? I thought 2 to 3 is the norm for stock bikes. That may be one reason your plugs look rich.

 

Re: My first plug chop story... or what I 'think' is a plug

Completely? No. Generally, and with enough to know what I am trying to explain... yes.

... Point observed?

Hmm... here's my breakthrough tonight.
For a month - I've been getting hints and getting told to do plug chops for proper mixtures etc.
Due to the inadequate descriptions of people on this site, and my idiocy of not being descriptive enough (hah! I think I over describe 200% of what I write here...) anyway...
I was under the assumption that CHOPS were for MIXTURE checks, that were ADJUSTABLE via the PILOT SCREW!
NOT for jets and jet tuning!
Now, that alone is my dumb fault.

You ask, why would he think the pilot plays any part in higher RPMs?
Because I have been told, once again - on here, by SIGNIFICANT individuals, that the PILOT CIRCUIT plays a role in the entire power band.

So - with all the talk of chops and mixture - I believed it was all based off the PILOT MIXTURE SCREW.

Well, let's see - the first sync I did, was followed with a colortune.
Now, it did not go all that well. The colors were all blended, had to take the screw nearly out to go yellow. But somehow managed to get it idling good. I have tweaked them here and there since, and got the idle a tad better. Got the plugs (AT IDLE!!!!) to be dark brown instead of BLACK.
See here is where some confusion lies - when folks on here talk PLUG COLOR, they are only talking about idle colors, correct? Or are my plugs- with stock jetting, airbox, exhaust, proper valve adjustments, and compression... supposed to be WHITE if I do a CHOP @ 5k?
Something tells me NO. And if so - I need to know WHY, and what CIRCUITS I need to look at - but why would ALL 4 be white... could ALL 4 carbs be non-fuctioning in the exact same circuits...? I find that hard to believe...

SO!!!! My problems thus far - have finally been answered, once again by the great Len - albeit not exactly the way I expected, but described enough to give me an epiphany (chops=jetting, not pilot mix!)

So from here on, I will resync tomorrow, lean my PILOT out a bit since I am brown at idle with spots of black. We'll see how the idle works out.

After that, I need to find out if white plugs after a chop on stock - everything.... are ok or not.

I will say - I do believe that after all these miles since getting her running again, have helped. The cylinders look much cleaner (no more carbon all over the crowns) and it's running decent, most of the time. Seems to be dependent on weather mostly? But still needs a sync and more tuning.

So - now that' THAT is all cleared up... with stock EVERYTHING, and the motor specs (valves etc) set properly - SHOULD MY PLUGS BE WHITE AFTER DOING A 5k CHOP?

 

http://www.angelfire.com/fl4/pontiacdud ... plugs.html

Very good read.

Also explains the 'soot' around the base ring, being that the air/fuel mix is rich (as yamaha intended) and that that is OK for me!

So much for 'ignore everything on the plug except the insulator'!

Can't wait to look at my ground straps to see how my temps look.

 

Doug; Yes there is some good "spark plug theory" in that article. However, the VERY FIRST LINE STATES "This is valid for track only (not street driving)"

You do want some tan on your insulators; it does take a while to get a good color built up and get a good "read" and doing WOT 5K plug chops only tells you what's going on at 5K on WOT.

Personally I prefer to check them occasionally after returning from a long ride (homebound commute, 63 miles is usually good) so I'll simply hit the kill switch as I'm coming up the street at about 4K on half or whatever throttle and give 'em a read. Or do an occasional "cruise" chop, running down a deserted stretch of road at 5K/60mph, NOT on WOT just at a "normal" throttle opening, and have a look.

chacal's right, you can drive yourself crazy trying to find Nirvana...

Now read my post about the breather hose...

 

Mark down the exact angle position of your screws.
#1.(/) #2.(-) #3.(\) #4.(|) That's your recorded baseline.

Turn all 4 Counter clockwise an EQUAL amount and ride again. Write down your impression of any bog, throttle transition, overall "pull". This is your seat-of-the-pants dyno session. Read the plugs.

Turn them out a bit more, ride, read, record. Keep going until it runs bad.
Fill a whole page with notes.

Re-set to baseline, go "IN" that 8* , repeat as above. Fill another page.
After studying all your notes, you should be able to get the EXACT setting that you want.

 

It takes me a week of riding around on the (only 2 carbs) Norton with a screwdriver in my back pocket to "evolve" a good idle.

TIME is right. It's an evolutionary process.

 

Hi...I'm going to revive this thread because spark plug reading is confusing me. I finally did some plug chops yesterday and saw lots of white, and even some black speckles! 8O . It was late yesterday, so I went home and made some adjustments. Today I do some on the way to work, and get a white, with maybe some tan "arc" on the top of the insulator, but the insulator below the threads is BLACK and sooty. So is the "base ring" (the metal on the bottom of the threads that the electrod is welded to) for 1, 2, and 4. #3 still had too much white. How am I supposed to read this?

To do the chop, I was going approximately 50-55 mph on a flat road in 5th, grabbed the clutch and hit the cutoff switch (in that order) and coasted to a stop.

My setup is a stock airbox with paper filter, plumb quick intake boots, Bike tire tubed and RTVed intake boots, new intake gaskets, 4-2 MAC? exhaust with straight through perforated and packed baffles. I have fully rebuilt the carbs and cleaned the pilot circuit very well, and know that I can adjust by colortune at idle using the pilot screws. But the screws are all 4-5 turns out. Float heights set to spec using clear tube method.

 

Re: My first plug chop story... or what I 'think' is a plug

Hilarious! Just read this whole thread. I've been there.

 

With your open exhaust you probably need to go up 1 (or more) main jet size/s.
And/or maybe shim your needles.

Here’s a link that talks about shimming the needles.

http://www.xjbikes.com/Forums/viewtopic ... eedle.html

albran

 

i've been thinking about this, and thought this might add some perspective:

in my seca 750, the stock pilot fuel jet is a 40, and the stock main is 120.

the pilot jet feeds into 3 ports in the carb throat, one of them is in front of the butterfly and flow to that port is controlled by the pilot screw. the other 2 are right at the top of the butterfly (when it is closed).

the main fuel circuit opens and closes when vacuum pulls up the needle - kinda like a continuously variable pilot screw.

anyhow, at idle, the mains are closed and you are running off the pilot circuit only, so the pilot screw can adjust 33.33% of the fuel flowing in to the cylinder (maybe 100% if you consider the butterfly blocks off the other 2 ports)

at half throttle, the needle half way opens up the main circuit so it's like having another pilot circuit with a size 60 jet. now the pilot screw only adjusts 13.33% of the fuel going into the cylinder. (1/3 of 40 divided by 40+60)

at wide open throttle, the main circuit is opened up and you're using the max flow through the jets, so the pilot screw adjusts 8.33% of the fuel going into the cylinder (1/3 of 40 divided by 40+120).

*disclaimer - these figures probably aren't exactly right and are for illustrative purposes, heck - i didn't even take into account the different size air jets - i'm guessing that the larger pilot air jet skews the percentage adjustment even smaller at off idle - but, like i said, that's a guess.

anyhow - maybe someone will read this and a light bulb will go off or something. i like it when that happens.

 

I agree skeeter, and I think that's why my plug chops aren't going so well. I think the base ring and lower part of the insulator are black since I've been trying to over compensate on my main circuit using my pilot circuit, and when I do a plug chop run, I've usually been riding around at low throttle, then get it up to speed for 20-30 seconds and stop the engine...and the base ring and deep insulator must be colored from the earlier running, and the insulator tip from the running right before shut off. Heck, if the chops are working for other people (and I'm using the recommended NGK plug, like I assume everyone else is) then it has to work right :roll: ?

I think I'm going to have to increase my main jet and maybe even my pilots, since I'm 4-5 turns out on them. I just compression tested the motor and everything checks out (140-150 between the cylinders) so I didn't kill my engine yet running lean (it was good while it lasted ) but now it's time to tune this thing up right. I'm also not sure if the plumb quick intake boots are creating a problem, and I'm thinking about changing them out with the proper ones...but it's so expensive :evil:

 

Continuing Skeeter's theory:
But first: I'll use Skeeter's disclaimer: I'm no expert EITHER...just asking.

Could carb tuning nirvana be a three-step process like syncing them?

At idle, the only "active" fuel source is the pilot circuit. If you do a plug chop after an extended idle wouldn't you be able to see how close the pilot mixture screw is to perfection? (assuming of course your sync is dead on)

Once you set this, DON'T TOUCH it since theoretically it's correct and doesn't have that much effect on the higher rpm anyway.

Then do a "mid range" chop. It would be difficult to adjust this area since there isn't an easy adjustment. I have Mikuni carbs so there are few jets I could mess with. I would have to either adjust float levels a touch or shim the needle or potentially add a bit of weight to the plunger I guess.

At WOT you could obviously change the main jets (and tweak float levels) to give you the read you are looking for. I'm sure the main jets would affect the mid-range but with some experimentation you could get close.

As mentioned in early posts, if you chop at WOT and show lean, adjusting the pilot screws could easily make you very rich at idle and potentially foul plugs sitting at a stop light.
The opposite would be giving you a very lean idle which would probably hang and give you little engine braking.

And I'll use Skeeter's disclaimer: I'm no expert EITHER...just asking.

 

yeah - i think. they do call it the "idle" screw.

you already mentioned this, but i think the main point is that you can either set your idle screw for a perfect idle, or use it to compensate for less than perfect jetting and needle(s) (a little bit, anyway) for off idle situations - but the trade off is that you'll sacrifice perfection at idle.


skeeter - became enlightened upon realizing that true enlightenment is not achievable.