do these symptoms suggest I need a valve adjustment? Edit: or bent valve?

[Rudemouthsky]

-Constantly fouling vertical cylinder plug (black)
-Runs particularly poor at high speed (misfire, popping) --     Improves short term with a new plug
-Backfires through pipes upon shut down (bang-flame) not sure that is technically referred to as a backfire..)
- Black exhaust smoke from the offending cylinder pipe.

Thank you...

[ducpainter]

The valves would have to be so tight that it affected compression. How long since the last adjustment?

Can you do a compression or leakdown test?

Sounds more like a carburetor issue to me.

[koko64]

Gotta agree with DP.
I replied to your other thread. A valve adjustment is a good baseline however to even everything out before a carb tune. How long ago is a good question.
Could be too lean up high and too rich down low. With your mods your carbs need a tune.

[memper]

What set up you got internally on your FCRs? (floats/clips/jets/air screws)

Are your filters dirty?

How long has this been going on?
 since fiddling with the carbs?
 since changing to flat slides?
 since new exhaust?
 out of the blue?

[Rudemouthsky]

"What set up you got internally on your FCRs? (floats/clips/jets/air screws)"

Fuel mix screw: 3/4 turn
Slow air  1 - 1 1/2 turns
Float ht 9 mm
Main jet 155
Main air jet 200
Slow jet 60
Needle EMT
Needle clip 3rd pos.



"Are your filters dirty?"

Filters are clean.

"How long has this been going on?
  since fiddling with the carbs?
  since changing to flat slides?
  since new exhaust?
  out of the blue?"

Pretty much out of the blue. But here's something I just realized;

I noticed the engine running rough and misfiring a bit out of nowhere a few weeks ago. Traced the problem to a loose fitting spark plug cap. I replaced the entire wire and cap with cheap AutoZone 7mm wire and a generic cap. The cap only fits my plug with the metal "head" that you normally unscrew and remove left intact. Could this cheap auto parts store wire possibly be the cause? I can't see imagine why or how it could...

Koko: the Dyno was just a power run, nothing more. If I scanned and posted the results would that help you help me in any way?

[koko64]

Its worth a look at that dyno run. If there is an a/f trace on it even better.

Your special exhaust may be asymetric enough to affect fuel requirements for each carb.

Definately could be an ignition issue with one cylinder. Cables, plug, etc.

One cylinder may have valves out of spec.

What are the two plugs colors?

[Rudemouthsky]

Its worth a look at that dyno run. If there is an a/f trace on it even better.

Your special exhaust may be asymetric enough to affect fuel requirements for each carb.

Definately could be an ignition issue with one cylinder. Cables, plug, etc.

One cylinder may have valves out of spec.

What are the two plugs colors?

Offending cylinder: black, burned looking plug. Other plug is light gray.

[Rudemouthsky]

ah, there is an A/F read out...is this legible if you zoom in or do I need to properly scan it?

[koko64]

Got the pic ok now. Yep. Go to 160 main jets for sure. It's too lean at WOT where the peak power should be.

Now to sort that fouled plug issue. I would change plugs and check all ignition wiring again. I would prefer to run the same plug wires on each cylinder. Is the fouled plug wet or dry?

Interesting to hear from members who have these types of exhaust and if they needed different slow jets for each cylinder. I 've never dealt with those pipes.
I would check carb synch and ensure your valve adjustments are ok.

[Dirty Duc]

Which plugs are you running? If you have resistor plus and resistor wire, you will have issues  IIRC, almost all modern autos use resistor wire.

[Rudemouthsky]

Which plugs are you running? If you have resistor plus and resistor wire, you will have issues  IIRC, almost all modern autos use resistor wire.

I am using R plugs, the Champion RAHC (cross reference to NGK DCPR8E). Using the cheaper Champions bc of how fast I go through them. I am def becoming more suspicious of my wire, just ordered a pair of NGK CR5's.

Fantastic deal on em' right here btw...http://www.summerlandautosports.com/shop/item.aspx?itemid=2483

[Rudemouthsky]

So I took my bike into the shop for a valve adjustment prior to my Mexico ride (both cylinders need it). I had not yet installed the main jets. Got a call yesterday from them, they say the vertical coil is causing an intermittent misfire. (I had told them about the fouled vertical plug and asked them to investigate). I brought them replacements Chris Kelley had sent me (thanks Chris!!!) and asked them to also perform another dyno run, this time with the new coils, and attempt to improve the HP. (they are being extremely stubborn about this for some reason) I pointed out how the A/F numbers from the previous run looked way too lean at WOT according to multiple experienced techs, and his response seemed to make sense...paraphrasing here;

"Where the measurement is taken will affect the A/F read out. In your case, it was taken at the end of the exhaust, this is why it appeared lean. Only the tech performing the dyno run should speak to the results, as only the tech knows where the measurement was taken"

- Is it common for a coil to act up intermittently, and only cause a misfire at a certain RPM range? 

I would still like to get more top end from this motor, but they seem to feel the jetting is fine. So it looks like I'll just pay them for the valve adjustment and have a go at it myself. I'm curious about the old coils, going to send them back to Chris and see if he's interested in testing them.

[Dirty Duc]

"Where the measurement is taken will affect the A/F read out. In your case, it was taken at the end of the exhaust, this is why it appeared lean. Only the tech performing the dyno run should speak to the results, as only the tech knows where the measurement was taken"

First, did they say what kind of dyno and measuring they are using?

If they are using a wideband O2, unless you have an exhaust leak, I call shenanigans for several reasons.

1: If they were getting reversion from the outside air, they wouldn't have been able to tune it reliably at all.

2: If the numbers are consistently off for a given distance from the exhaust valve, how does the tech know how much to "fudge" the numbers to get a "good" AFR?  Did they measure your exhaust (not somebody else's that kind of looked like it).

3: Again I cite Brad Black (although I paraphrase), "Customers like the response from a Duc that is tuned a little richer on the dyno then common wisdom would suggest." (no FHE on this here, but if the trace on that dyno sheet is at all representative, you should have a "flat" spot between 6500 and 7500 rpm... and looking at the trace a little closer, I shouldn't be surprised it feels slow.  14.5 is a good part throttle cruise AFR, not a good WOT power AFR)

4: If your coil was intermittently malfunctioning (which I'll leave on the table for more experienced people to talk about) then the AFR trace should have shown some obnoxious fluctuation (unless they turned up the automatic smoothing too high, see point 2)

The point of a dyno is to get relatively scientific numbers so you can usefully change things to make it better.  If you can't show the customer scientific numbers, then you probably don't know what you are doing, and I wouldn't trust you to tune my lawnmower.  And that is why I prefer to break and "fix" my own toys.

[ducpainter]

First, did they say what kind of dyno and measuring they are using?

If they are using a wideband O2, unless you have an exhaust leak, I call shenanigans for several reasons.

1: If they were getting reversion from the outside air, they wouldn't have been able to tune it reliably at all.

2: If the numbers are consistently off for a given distance from the exhaust valve, how does the tech know how much to "fudge" the numbers to get a "good" AFR?  Did they measure your exhaust (not somebody else's that kind of looked like it).

3: Again I cite Brad Black (although I paraphrase), "Customers like the response from a Duc that is tuned a little richer on the dyno then common wisdom would suggest." (no FHE on this here, but if the trace on that dyno sheet is at all representative, you should have a "flat" spot between 6500 and 7500 rpm... and looking at the trace a little closer, I shouldn't be surprised it feels slow.  14.5 is a good part throttle cruise AFR, not a good WOT power AFR)

4: If your coil was intermittently malfunctioning (which I'll leave on the table for more experienced people to talk about) then the AFR trace should have shown some obnoxious fluctuation (unless they turned up the automatic smoothing too high, see point 2)

The point of a dyno is to get relatively scientific numbers so you can usefully change things to make it better.  If you can't show the customer scientific numbers, then you probably don't know what you are doing, and I wouldn't trust you to tune my lawnmower.  And that is why I prefer to break and "fix" my own toys.

I'm going to 'distill' these comments to...

[cough]bullshit[cough]

[brad black]

if they're getting a lean reading due to the sample tube location they need to do something about the sample tube.  introducing error into an experiment is not what you generally set out to do.

i'd still be running 165 or so anyway.  and smaller pilots.