Rich at high rpm

85 XJ700. Under no load, it'll rev fine to about 6-7k and then start to sputter and hang and if I keep the throttle nailed, the longer I hold it the worse it gets. Black smoke, wrinkle your nose fuel smell, dark orange flame and then no flame with a color tune. The a/f mixture seems good at idle, nice blue flame, and I just did all my valve shims yesterday, all are now in spec. Carbs were thoroughly completely disassembled and cleaned. New Dyna coils, new throttle shaft seals. I did a bench sync, wet set the float heights, and then running vacuum synced.

Under load, if I nail it, it takes off.......until about 5-5500 rpm. Then the same thing, spit sputter bog, the more throttle I give the worse it is. If I eeeeease the throttle I can get it to maybe 6k rpm in 5th.

One other thing, as I said, I know it's loading up and running rich, I watched it with the color tune, but...after it's warm, it almost exhibits a lean symptom at idle, it wants to hang and idle at almost 2k rpm even with the idle stop screw all the way out. But still loads up and dumps black smoke and runs like crap under any more than light throttle input. Damn near impossible to get her to go over 6k rpm.

Open to any and all suggestions! Fire away and thanks in advance!

EDIT: Forgot to mention, the running rich, exhibiting the dark orange flame and then the flame disappearing under throttle when viewing with the colortune, happens on all cylinders, but is worse on number 4.

 

Stock intake or pods?

If it's stock, then you're looking at float levels or fuel leaking around the float valve seats.

ColorTune is for idle adjusting. You can't duplicate what's happening at high RPM under load in your garage. You'll chase your tail.

Do a plug chop at 6K if you can get there. Maybe it's NOT a rich condition; you could have an ignition problem.

But it does seem like something is still amiss in the carbs. Enrichment plungers not shutting off properly? Stanky old plugged up air filter?

 

Yeah rich gets lumpy up high. I fixed my rich by putting more free flowing mufflers on. You still have to fiddle with the low range but now it's a screamer.

Troubleshoot the problem first as per what fitz said. Floats, or enrichment circuit.

Colortune is only for low RPMs, so pay no attention when it's revving. Be careful, too...they do melt.

 

All right off come the carbs again for wet float levels then. New plugs, get to 5500 rpm, chop. Number 1 looks pretty good, 2 and 3 are pretty dark, 4 is just all soot.

Stock intake, stock muffler. Forgot to mention, new float needles, new seats for them.

compression numbers 140,145,150,153.

Could the possible ignition problem manifest itself only at higher rpm's? If so, what...TCI? I'll ohm out the pickup coils and see what's what with them.

EDIT: I'm bad at remembering everything in one go. New enrichment plungers, because they were a little pitted, and I figure I may as well do this right.

 

You put new plungers and it's still doing it?

 

Make sure the enrichment shaft is able to completely bottom out. None of the fingers which pull up on the needles should be touching them at rest.

 

Yep my first thought when this happened was the enrichment plungers being held up. Not the case, the little forks on them move when i move the enrichment lever before the actually grab the plungers. Also, wet float height is actually just barely not on the low side. The book calls for 1mm below the carb body, +/- 1mm. I'm right at 2mm below on all four. Leveled carb rack fore and aft and left and right both time I've measured them.

With NO FILTER installed at all, for a up and down the culdesac ordeal, there is no change in how it runs. I would think that would lean it out a little, now? In any case, same deal, approach higher rpm's, starts bogging and spitting. Just a touch or enrichment lever makes it significantly worse, so that's another reason I'm sure it's running rich. I'm pretty much at a standstill with this thing...I'm going to do any and all things you suggest, because you all know more than I do. Fire away, my tools are ready!

Cylinder 1 is the only one that wants to play nice! It looks like the most delicious marshmallow every to be roasted on a campfire.

 

By the way, this is my first XJ, my first motorbike every also. I'll admit it's a unique and very cool motorcycle. I've been lurking on these forums without actually posting for a long while, gathering knowledge and doing everything suggested for a 'new to you' bike. Which, by the way, cost me exactly zero US dollars!

 

If it's as simple as ignition, it could also be as simple as loose resistor cores in the park plug caps; or plug caps that need to get a new "bite" in the wires.

Another possibility: a PO may have drilled the jets or done something equally stupid. While the carbs are apart, carefully examine all the components for signs of tampering, and make sure it has the right jets.

I previously mentioned the seal between the float valve seats and the carb body. If that bike has Mikunis there's an o-ring there that may be your issue if you didn't already replace them.

 

The 700 has the Hitachi carbs, which do have the original jets. My father was the previous owner, and it ran great until about a year ago and then it didn't gradually come on, it happened all of a sudden, he says.

New coils, new plug wires, all less than two months old...

I guess I'll go and ohm out the pickup coils now and give this ignition system a why for and a what how. Keep the suggestions coming, I really have no clue what I'm doing, I just have a service manual, and have done all these things from reading on here already. I'm no stranger to engines and carbs, but for the life of me, I can't figger this one.

 

Whoops, sorry. I didn't read carefully enough. "New Dyna coils."

Did it run OK before you installed the Dynas, or was it done along with the carbs, valves, etc.?

What are you running for plugs?

I'm grasping at straws here; it sure sounds like it is indeed "dumping" fuel, but where/why?

 

Have the main jet needles pulled "away" from their plastic head caps? Are the main jet needles (and springs) positioned correctly in the vac piston? Vac piston diaphragm seated correctly into the top of the carb bodies (the small locating "tab")?

Assuming your fuel level really is correct, and your choke plungers ARE seating fully, then it's actually difficult to get these engines to run RICH......especially the 700 air models, they'll jetted pretty lean from the factory.

What happened/service performed/etc. immediately before it "came on" all of a sudden? I mean anything at all, did you change the fork oil, wash the bike, etc.?

 

Battery up to 100% ?
New plugs? Gap correct?
New boots on the wires?

Now, what do you mean by "black smoke"? Black/black, grey/black, blue/black? There are a lot of different blacks, and they all mean something different.

Also, does the smoke happen at idle, 2,000rpm, 5,000rpm, all of the above?

Just for gits and shiggles, when were the valves done last?

The fact that it happened "all of a sudden" points to something breaking, we just have to figure out what it is. It could be anything from a valve, to a wire, to the fuel tank filter.

The more info we have, the better your chances.

 

Well ignition's good. I revved the engine to 8000 rpm with each cylinder's plug wire out and angled against the "nipple" on the plug that it connects to. All the way up to 8k I could see and hear the spark arcing, bright blue. And the Dyna coils are part of the evolution of getting this thing running right again. It started acting up before they went in.

The Yamaha service manual has a little picture of how the fuel should look in the tube if the float height is good - You can see the lip on the carb body, and then the "shoulder" of the bowl with a screw in it in that picture, and the fuel level in the manual is at that shoulder - mine is right at where that screw head meets that bowl, the bottom limit for the float. Am I correct for leveling the carbs both ways when I did this?

As far as I know, nothing happened before it started acting up. Dad lives in FL, I'm stationed in NC, so I'll call him tomorrow and ask him what he did just before that last ride when it started acting funny.

He had never done the valve shims, and the bike has 33k miles on it, so that was the first thing I did. They weren't extremely bad, the smallest intake clearance was 0.76 mm and the smallest exhaust clearance was 0.98 mm. I was worried for a while that he burnt a valve running it like that, but not after those compression numbers I pulled today.

Spark plugs installed are NGK BP8ES, gapped to .030 inches, brand new, just used them for that plug chop earlier today.

What's weird to me is that I know it's running rich, you can see/smell it as well as engaging the enrichment makes it worse, plugs sooty....but the idle, once the bike is good and hot, like to 'hang' at around 2000 or so, until I feather the clutch to load the engine, and then it returns to about 1500. That's with the idle stop screw all the way 'down'. Fully warmed up, but not ran hard and hot yet, it'll idle right on the 1100 mark.

So...any way for me to plug those enrichment circuit orifices completely, just to eliminate that as an option altogether? New needles went in, but maybe I boogered something up, I don't know, that's why I'm here!

Thanks for the input, and I'm all ears still!

 

Everyone else has given you many different ideas... have you tried running with the petcock in other settings? Simple test just to rule that sucker out.

 

To answer the above, the valves were done....tuesday.

The smoke only becomes noticeable at 5k rpm, and in neutral, I have to punch it at that point to get it to smoke, but my dad told me just cruising at that speed he could see it from the exhaust. It doesn't really look grey at all, it just looks black and sooty, like the inside of a fireplace...

I actually have pulled and checked the fuel tank filter for good flow, and I installed an inline filter, a clear one, just so I can look down and see if fuel's flowing. I've never seen the clear inline filter empty, so it must be flowing all right.

And no, the battery is NOT up to 100 percent, it's actually very weak, and I've even had to push start it a couple times. But above 2k rpm or so, I've metered a good 14 VDC at the battery, and all this started when the battery WAS good.

 

Yeah I ran it in prime and reserve, and even ran with the gas cap open on the tank.

 

Carbs church clean? Clunking?

 

The stacks do clunk, and I cleaned the absolute f*&k out of them, but at this point, I'm gonna just tear 'em down and do it again! Off with her carbs!

 

Have you opened where you fill the oil and smelled. Does it smell like gas?

Just a thought.

 

I have and it does not smell like gas, and the level has not gone up any over the last couple months of test riding and tinkering.

 

the Air jet with the larger hole goes nearest the engine

 

I'll check on the air jet configuration. I'm about to go in the garage and tear them suckers down.

Okay so somebody talk to me about YICS. I know the concept behind it, but how great an effect does it have on neighboring cylinders? For instance, the number 4 cylinder is by far the worst off, and number 1 looks pretty healthy. Could the number 4 dump so much fuel that the resulting mixture is draw in by way of YICS into the neighboring cylinders and therefore throw off their mixtures? In short, could ONE cylinder running super rich be the only problem?

EDIT: 210 air jet closest to block on all carbs, 70 air jet toward aft of bike.

 

In regard to your YICS question, yes.

That's why Yamaha specifies that YICS be blocked for both vacuum sync and mixture tuning. (They used an EGA rather than a ColorTune.)

This question generally incites a furor of folks claiming that blocking YICS makes no difference; and we've discussed it until there's no dead horse left to beat. But the science behind it says it's important and Yamaha specified it and it really does make a difference.

The simple fact of the matter is with YICS open, you're going to "see" (either visually or on the meters of the EGA) a combination of the intake charge from all 4 cylinders. If one carb is absolutely dumping fuel, yes it will show up in the other 3.

 

take a look at the needle jet, sometimes called emulsion tube. one end has the main jet screwed into it, the other has a ROUND hole the needle goes in and out of. look to see that the hole isn't worn to a oval shape

 

Needle jet - the hole is good and round, pulled it out, can see through it, and through all the small holes in the side of the tube. Double checked enrichment plunger needle things, they are clean and look to seat right, not bent or anything crazy. The little plastic disc under where the main jet screws into, is that supposed to be pliable, it feels like hard plastic?

 

all the Hitachi carbs i've seen have copper washers under the main jet, i guess that's the same as hard plastic.
how would you feel about getting another set of plugs? at least swap 1 and 4 and see what happens, or put the old plugs back in.

 

I haven't used new plugs since after I did the valve shims, so I guess 4 could be just totally worthless. I wire brushed it real good, but I'll get 4 new ones and see what happens!

Correction, I did use new ones for the plug chop, but then I put the old ones back in. Also, the washer is copper, I suppose it was just tarnished and looked like plastic.

 

Since it "happened all of a sudden" I would focus on anything that moves such as slides and enrichment circuit. As Chacal mentioned, I would really inspect the slides and needles and that whole system. Someone mentioned the looking at the emulsion tube where the needle enters and be sure it isn't worn. The needles aren't rigid and one or more of them may be hanging up.

I assume that you haven't had it running long enough to get mpg reading. Running as rich as you indicate would probably put it in the 20's. What kind of mpg did your dad get before and after the problem started?

 

Dad got in the high 40's, he drove a mix of city/highway. I am getting about 25 right now.

New plugs, did a chop at 5k, can't manage to hold 6k. Ran 5k for about 40 mile, number 1 is good, number 3 is good, 2 and 4 are rich. 4 is by far the worst. Emulsions tubes are good and round, don't look worn, all are clear, including the small holes on the sides. Needles sit in them good like they are supposed to, I revved the engine and watched the stacks all rise and fall as they should, and together....

Something's gonna give if I keep tearing through it all and inspecting stuff like this, I just don't know what. Odds are it will be something that makes me facepalm.

Oh, the plugs are not wet or oily looking, just dry soot, very dark on the number 4.

I know it's not a matter of the enrichment being "on" a little, I rode it today with the cable detached, and the little forks aren't even touching the plungers. I'm thoroughly checking everything I know to check with air/fuel delivery, but this little thing in the back of my head keeps wondering about ignition. I'm wondering, with this being a "wasted spark" system, if number 4 is SO rich, how is it not backfiring on the wasted spark on the exhaust stroke. And both 2 and 4 are the rich cylinders, wouldn't they both be firing at the same time every 90 degrees? Should I start questioning the TCI or that pickup coil for 2/4?

 

Wonder about the pilot screws--any issues there? Where are they set?

 

I pulled them out and inspected, they look fine, as do the little o rings. I went ahead and reset them all to 2 1/2 turns out from gently seated before this most recent ride with no change. Wouldn't that not affect 5-6k mixture anyway?

 

I've been slowly tweaking (thickness of a dime max) my pilot screws to get my plugs the right color, and my mpg has been steadily improving. The pilot system doesn't shut off just because your turning 5000 rpm. As I understand the system, the main jets become more and more dominant as rpm increases but there's always flow through pilot system. As rich as it is running, closing the #4 pilot screw a little couldn't hurt.

 

There is no pick-up coil for 2/4; the pick-up coils, the TCI, and the ignition coils "circuits" are all based on a #1/4 pair and a #2/3 pair of cylinders.

Sooty plugs can be the result of a too-lean condition, also:

Why are my plugs carbon-fouled (dry, sooty black deposits)?:

- Carbon fouling is the result of incomplete combustion----for any reason. It is most often associated with an overly rich fuel mixture (whatever the cause), but can also be caused by an overly lean fuel mixture (or poor spark, etc.) In a lean-mixture condition, most of the un-burnt mixture gets pumped out the tailpipe, but some fuel droplets remain in the cylinder and add themselves to the next intake charge. That's not a very precise way of metering the mixture, so when it's finally rich enough for a spark to ignite, that particular charge may be too rich, resulting in incomplete combustion and plug fouling. So carbon-fouled plugs can be due to rich or lean conditions.......your Colortune spark plug will tell you for sure. If you have a light blue or white-ish flame, intermittent flame, and/or intermittent flashes of yellow within an otherwise white-ish flame, then your fuel mixture is too lean.

And by the way.........if the spark that happens to ignite this overly-rich mixture is the "wasted spark" (which occurs in each cylinder at the top of the exhaust stroke, it will occur JUST AS THE INTAKE VALVE IS OPENING ---- so the backfire pressure wave may be directed back up the intake tract!

 

Well the color's good with the colortune at idle on the number 4, and I suppose it could be leaning out at higher rpm's, although the jet and needle on the slide and everything looks good. I don't know anymore, but I'm gonna keep trying. What would you suggest doing if it was leaning out up top?

 

But I come back to if I ease the enrichment on, just in the slightest, it gets substantially worse....

 

not saying this is right but what if 1 cylinder was lean and 3 were right. by putting on enrichment your hurting the 3 good ones and can't tell what the 1 bad one is doing...........hummmmm

 

If one was lean and three were right I don't think I'd have sooty plugs on more than one. I'm just confused and cattywompus over it right now. I don't really know what to do except take the carbs off again tomorrow, pull them completely apart, clean, rebuild, etc etc. It HAS to be a carburetor issue.

 

Have you synched the engine?

Are the individual carb vac ports (large brass fittings by the idle mixture screw) open to atmosphere or capped off?

 

i'am running out of suggestions and you can't be sure if it's lean or rich yet.
if it's rich:
could the float valve be vibrating and leaking at higher rpm's (that's a stretch)
i'am not familiar with X exhaust but could there be an obstruction affecting 2 & 4, like a loose baffle ?
if it's lean:
are the throttle shaft seals in the right way?

 

swap tci and see what happens.

dave

 

I have synced the engine, and the vacuum ports are capped, the fuel petcock is on the number 2.


I would swap TCI but I don't have one to swap with, and don't particularly care to pay for one until I know it is/isn't the problem.

I have to say, thank all of you for your continued suggestions and help. I'm gonna figger this thing, eventually. I'll just keep working at it and it'll come. I'm too stubborn to give up.

 

The vac ports that I am referring to (just to make sure we are discussing the same item) are the vac port ON THE CARB BODIES on a large brass fitting that is directly to the left of each mixture screw hole at the front of the carb body......I am not talking about the brass ports on the INTAKE MANIFOLDS.

 

Um. The only large brass fitting I know by the mixture screw is the enrichment plunger.

 

Looking forward, there should be a brass port to the LEFT of mixture screw port, tilted towards the back at about a 45-degree angle, coming off a round boss cast into the carb body just below (and to the left) the "flat" top ledge of the mixture screw/choke plunger protrusion........

This is an air-cooled XJ700 motor, correct?

 

Yes, to the left of the mixture screw, at about 45 degrees toward the aft, are round bosses with a black hose coming from them. I thought they were overflow, that is how they've been since I got the bike.

 

Okay, now WHEN did these problems start happening "all of a sudden", were you able to obtain that information from your father; specifically, what service/procedure/event occurred just prior to the onset of these problems?

 

Yes I spoke to him, he didn't do anything before it started acting up. Rode it to work, it was just different, he said. THEN he started troubleshooting, cleaning carbs, yadda yadda.

 

So I've been thinking, should I block off YICS with a steel dowel the right diameter and length to maybe isolate it to one cylinder and focus my hunt there?

 

Shooting in the dark here.... Do your main needles have a point on the ends? Or do they look like they are rounded off or flat? I had a similar issue only to find that two of my needles ends were broken off and not seating at the bottom if the emulsion tube.