Carb problems?

Okay, here's my sad story of woe and despair:

Bought this bike about a month ago, 1982 XJ650J (Maxim) with about 11,000 miles, had sat for about a year. Ran, but was dead the #1 cylinder at idle, would run okay at about 2500+. #1 plug was carbon-black (dry) and barely firing.

Good compression in all cylinders, spark at all cylinders. Pulled the carbs and cleaned very well, using every last bit of advice from here and other places. Polished the slide piston. Cleaned orifices with a single-strand wire. Replaced the idle mixture o-rings and a cracked airbox boot. De-rusted the tank with electrolytic method....that works nicely!.....rebuilt the petcock, added an in-line clear fuel filter, new fuel lines, vacuum lines, and sync fitting caps. Synched using a 4-colum carbtune and adjusted idle mixtures with a colortune plug to the prettiest of blues on God's Green Earth.

Buttoned it up, and it runs MUCH better. MUCHO stronger. Idles fine. Ran half a can of seafoam through the tank "just to be sure".

Now, after three days, we're right back to square one. This is getting frustrating. Okay, here are the symptons:

* Starts right up, cold or warm.
* Idles rough. One cylinder is not pulling it's weight. It's
to be the #4 cylinder (far RH) this time.
* Runs rough up until, let's say, 2500 rpm, then zooms.....really
strong. Once it runs well, it seems to continue running well at
steady throttle. It's only upon low-speed acceleration (or at idle)
that it's to be missing.
* Letting off/closing the throttle results in an immediate decrease
in rpm's, there's no hanging up.

Other observations:

* I pulled all the plugs. All of them look pearly white.....almost like
they're leaned out....including #4, EXCEPT for #1, which was mostly
carbon-black except for two 2mm wide "stripes" of pure white,
180-degrees opposite each other (and perpendicular to the electrode).

* #4 has spark, checked it with the plug out, grounded. Nice blue
spark.

* #4 isn't firing very much, if at all though. Pulled the plug caps
one by one at idle, #4 is definitely the culprit. It just BARELY
affects the rpms when pulled (at idle), whereas pulling the others
(one-by-one) almost kills the motor.

* I drained the carb bowls, twice. All of them were full, both times.
#3 & #4 seem a little low compared to #1 & #2, but not by much.
No crap came out except for the most minor of sedimentation, and
that was mostly from #3.
* I ran a mini-compression check (only plug #4 removed; engine
idling) and it has compression in #4. It "bumps" up on each compression stroke, starting at about 30psi until it reaches about 140psi. I ran a compression check before I tore down the carbs the first time, and all the cylinders were good, around 145psi.

NOTE: a couple of times the bike HAS run on all 4 cylinders (I can
tell), even at idle, and at those times I have to reset the idle speed
down, 'cause it will idle at 1500-1600 after it's warmed up, and each
time I've gone out I've had to re-set (lower) the idle speed, EVEN
THOUGH I NEVER INCREASED IT BETWEEN RIDES. It was
almost as if there was a vacuum leak somewhere causing the idle
to rise........

Okay guys, your thoughts? I suppose I could pull the sync fitting rubber cap off of #4 and spray a bit of gas or insta-start or carb-cleaner or ????? into the fitting to see if that brings the idle up/makes that cylinder fire.

Should I hang the sync guages on the bike and see what #4 is doing?

It seems like carb problems still. I tried tapping on bowl #4 to see if
the float was stuck, but that seems to make no difference. Again,
both times I opened the drain the bowl was full. And the spark plug was
zestfully-clean so it doesn't seem to be loading up. On the other
hand (there are different fingers....ha-ha), I know that cracking the
throttle open brings more air in and can account for an overly-rich
mixture becoming leaner (or being corrected)......so, I'm stuck.

Oh, I also ran some seafoam through the carbs when I first got it
back (after the carb rebuild), that seemed to do nothing.

I tried aiming my propane torch all around the #4 carb while idling
to see if I could find a vacuum leak; no luck (no increase in rpm's).

The in-line fuel filter is clean as a whistle.

Help!

 

1) Swap the plug-in's from the Coils to the wiring harness. If four acts fine and the "problem" is another cylinder -- bad coil.

2) If your bike is a YICS bike -- Pull the YICS plugs on BOTH sides and push-through some wads of carb cleaner soaked terrycloth. (Like you're loading a Musket). Use a wooden dowel or a fiberglass rod to push the soaked wads through there.

3) Pull the left side crank cover and see if there moisture or the face of the crank Rotor is rusted some. Yes? Sand it off with 400 or 800.

4) While you have the cover off ... see if the plate holding the pick-up's is good and tight.

Smells like a problem with the coil or the wire to 4 ... you'll know after you swap the coils around and 4 comes to life and 3 becomes the problem child.

 

Hi Rick, thanks for the help. Yes, it is a YICS engine, and I cleaned the passage with gun cleaner until it was spotless during the first carb rebuild session. Stuck fine pieces of wire up into the top of the passage openings, too, and "reamed" them out. They were pretty spotless.

I just went and pulled the ignition cover, and it's bone dry, and everything
was nice and tight and spotlessly rust-free.

I guess to swap the coil leads I need to pull the gas tank, so maybe I'll do that later, or tomorrow. I was actually thinking along the same lines, first cylinder #1 was bad, now it's #4, and the coil is the common denominator,
but of course the carbs were filthy when we took them down.

BTW, I also pulled the sync cap from the #4 intake, and rigged up alittle tube onto it, and cranked the motor and sprayed a little choke cleaner in there........that cylinder came to life right away. Sounds like a lack-of-fuel issue? Or does carb/choke cleaner ignite even without a good spark?

 

Rick, here it comes.......another really dumb question:

If I swap the lead-in wires to the coils.....so that the current 1/4 coil lead is now plugged into the 2/3 coil (and vice-versa)....won't that throw off the ignition firing? Won't I also have to swap the plug wires to the plugs also....
so that coil 1/4, which now has the lead-in wire from the TCI for 2/3, also have the plug wires hooked up to 2/3?....since this coil 1/4 is now getting the timing signal for cylinders 2/3?

And if this is true, then which plug wires do I need to rotate from/to? Or does it matter? I recall that Yamaha uses a redundant (double) spark system, in that one spark is "wasted" in each cylinder.

If this is a dumb question, please feel free to rate on a scale of 1-10 of dumbness, mainly due to fatigue, not enough rum, and a life spent in the auto biz, which will screw up anyone's mind.

 

I think RickCo was suggesting you just swap the secondary wires on 3 & 4.

 

Okay, help me to understand. The pick-up coil assembly, attached to/at the end of the crank, controls the "timing" of when a spark goes to the individual cylinders.

This pick up coil assembly feeds these signals into the TCI unit. The TCI unit does it "black box" routine and fires off a signal (voltage) to each coil at the proper time that allows the coils to fire, at the proper time.

There are two coils, for clarity I'll call one coil "Coil 14" and the other coil I'll call "Coil 23". Obviously, Coil 14 provides the spark, AT THE PROPER TIME, for cylinders 1 & 4 and Coil 23 provides the spark, AT THE PROPER TIME, for cylinders 2 & 3.

Coil 14 gets it's "timing/when to fire" signal from the TCI via Lead Wire 14.
And Coil 23 gets its signal from the TCI via Lead Wire 23.

If I "swap" lead wires, and plug Lead Wire 14 into Coil 23, won't Coil 23 being getting the electrical timing signal for cylinders 1 & 4, and at the proper time that cylinders 1 & 4 should be firing? (and the same thought for having Lead Wire 23 plugged into Coil 14)?

The actual plug wires are integral to the coils, and cannot be swapped independently of the coil (well, yes, I know they can be, but I'm not going to be cutting open my coils to do so!).

So if Lead Wire 14 is plugged into Coil 23, then Coil 23 is actually getting the "ready/aim/FIRE" signal at the time when cylinders 1 & 4 should be firing. Which seems to me that the plug wires from Coil 23 should now be hooked up to cylinders 1 & 4......to get proper ignition/plug timing in order.

IF THE ABOVE IS TRUE, then does plug wire 2 go to cylinder #1, and plug wire 3 now go to cylinder #4? Or does it matter?

Rick? Nick? Nick, when you say "just swap the secondary wires" are you meaning the "wires to the spark plugs from the coil"? And I assume you mean to swap these wires AFTER I have swapped the lead wires between the two coils? And it doesn't matter whether I plug plug wire 2 or plug wire 3 onto cylinder #1 or onto cylinder #4?

Sorry to be so anal about this, I really want to diagnose and solve these problems, but I don't want to screw anything up even more than it is already!

Thanks.

 

Let's simplify this. If you switch the coil leads on the 1-4 coil you will get the result you are looking for. Remember this system uses the lost spark method. This means that a spark is sent to the cylinders when at top dead center whether on the compression or exhaust stroke. The spark on the exhaust stroke being the lost one. Since 1 and 4 hit TDC at the same time as 2 and 3 are hitting BDC switching the leads between 1 and 4 will work fine. Nick, Rick, feel free to correct or clarify.

 

I'll back you up Max. The swap is a sound troubleshooting technique.

 

Okay, I spent all last night and half of today cleaning the #4 carb. FOund lots of big pieces of something above the float valve, and some smaller pieces and fine sediment in the bowl; the pilot jet was kinda clogged a bit, and the starter jet was completely clogged. Fixed all that. Can't imagine where the junk came from, as I installed a brass-cone see-thru in-line filter in the fuel line after the petcock, and it's clean as a whistle. Some of the pieces of junk were 4-5mm in size, no way could thye have gotten thru the filter........

So I started it up and it still ran like crap, still no #4 cylinder at idle. Took it apart again and cleaned it again, including running a thin wire up through the fixed thin brass tube that hangs down into the bowl. Put it all back together, and it runs a little better, but still no #4.

So now I go to swapping the leads on the coils. Swap them, and it won't fire, at all. Nothing. Swap them back and it won't start. Change the plugs, even though they have only about 50 miles on them. And now it runs fine, idle up to redline.

The plus all looked fine, off-white, except for #1, which was completely sooty black (same as before the first carb rebuild was undertaken). So maybe I fixed #4, but #1---even though it fires---still has some problem. I sunched and colortuned the bike after the first rebuild and everything looked good. Can't understand why #1 is so rich. I'll pit the colortune plug on it again later tonight and see what it shows, maybe pull the bowl and make sure it has the right size jets. What else could make just one carb run so rich?

Okay, I'll report back later........

 

Had to go check out my coils and Yup I goofed, BlueMax got it right, swap the 1 and 4 plug wires as a check.

Here's a cut and paste article on the coils, basically what BlueMax already said.... http://www.geocities.com/MotorCity/Speedway/7795/

There are two ignition coils for the four cylinders. What this means is that each cylinder gets twice as many sparks as it needs, one during the compression stroke for ignition, and one during the exhaust stroke. The only reason for the extra spark is to simplify the ignition system and use two coils instead of four. This is possible because the one and four cylinders and the two and three cylinders move in synchrony (with different valve timing). This is important to remember if you ever connect a tach to the bike, 2000 rpm will read like 4000 rpm.

 

Okay, well I finally got around to checking the primary resistance on the coils and it's 2.5 ohms on the 2/3 coil and 10.5 ohms on the 1/4 coil....so it seems that the 1/4 coil is fried. Time for new coils, and I'll probably get new wires and plug caps, too. Any- and everyone's input is appreciated!

 

The High-Performance "Green" ones that DYNA have seem like a really good deal. You have the option to run different wires. Yellow or Red looks good on the aluminum engine! And, there's no hassle with them. Right out of the box and onto the bike. Baada-Bing ... Baada-Boom!

 

Okay, DYNA green coils and new wires (7 or 8mm copper core?) it is. What about caps......resistor or non-resistor? I'm not concerned about radio interference or anything. I'm using the NGK BP7ES plugs but will probably change to the Champion N7YC. Any "favorite" suppliers or best-price deals? Thanks!

 

If you get the correct wires to fit the coils you have to get the caps that go with the wires, there isn't any choice, they are non-resistor. The wire is generally resistor wire which is fine but I suppose you could probably find copper wire that would work as well.

 

It's soooo nice to see a guy get-out of that damn "Trouble-shooting Mode" ... and, get into that swinging "Tune and Pimp Mode."

There's something about them fine DYNA Red Plug Caps and them sweet-looking and high-performung Yellow Plug Wire that seems to look so phat when you are checkin'-out a bike ... so equipped ... go cruisin' by!

Them Red wires is cool; too. But, they's a huge "I've got this baby on-the-edge" statement happenin' with them Yellow's.

'Siv-ya-no-wha-dime-sane!