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Buell Forum » XBoard » Archive through June 28, 2011 » Consistent Misfire, Backfire, Stuck Idle 5 minutes into ride « Previous Next »

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Lt_adderall
Posted on Sunday, June 12, 2011 - 03:23 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Hi Folks;

I have a 2006 Lightning XB12Ss Lightning Long with 23K miles; only "mods" are K&N Filter and Jardine Exhaust. All preventative maintenance has been performed on schedule. Only "issue" has been a failed stator/voltage regulator at 16K miles that got replaced.

Recently; at highway speed of 70 the engine began to "sputter", lurch, misfire, backfire with a loud "pop" and I could see the variations on the engine speed on the tach. Hit another on ramp, got into my tuck, brought the throttle back to "clear it out" and it got worse. The tach jumped up and down and the bike was like "chitty, chitty bang bang". No trouble codes.

Took it to my local HD dealer and my mechanic is a Buell tech and rides a Ully. Based on the symptoms he replaced the spark plugs and wires, adjusted TPS, ECM shows no troubles with all readings in "spec", he rode it and said it was fine; and I took the bike home.

Rode it again. I let the bike warm up before taking off. About 5 to 10 minutes into the ride; SAME SYMPTOMS appeared! I even got a loud "bang" that flashed the engine oil light and the engine stopped. Pulled over, let the bike cool down and restarted fine. No trouble codes. But really ran poorly as I limped home; the engine misfiring, and spiking in rpm. The other thing I noticed is that when I let off the throttle the RPM"s came down really slow and at some times the engine would "stick" at 2,000 rpm.

Ironically....we have to emission bikes in Maricopa County Arizona; and I ran the bike through in this condition....it passed?

I let the bike sit a week, hopped back on tonight; and got the same misfiring, backfiring, and "twitching" at the tach.

BUT I SEE A PATTERN. Every time I see this happen it happens between 5 to 10 minutes after I start riding the bike.

Tonight the wife ( accompanying me on her XB9X City Cross ) noticed something after I let the bike warm up in dark parking lot. She pointed to the front exhaust header and said "holy shit...its glowing red hot"; she could actually see the pipe literally becoming visually red hot.....like the coils on an oven top. I have never seen this before so I have no clue if this is "normal" and may be a symptom of a problem.

The bike goes back to my tech at HD Monday.

There is obviously something seriously wrong going on with combustion but it only happens, consistently until after I have been riding the bike 5 to 10 minutes; then these symptoms start.

I invite your thoughts!
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Xoptimizedrsx
Posted on Sunday, June 12, 2011 - 04:03 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

classic tps set to high or incorrectly. re-set the tps again by the book.

next take the allen with you on the ride, and ride it a good 15 mins. now stop and adjust Idle at 1000 not 1050 (do not rest tps to do this step just turn the knob).
dont worry about the number your matching the tps to the wear and condition of your bike your weather and ect.

now it will not hang on you. If its doing the issue still you have something else wrong. Keep us posted.

I use to fix a bike a week here till the dealer stopped doing them.

Setting at 5.1 and 1050 is all good on a perfect bike and perfect day in perfect world but that does not exist. use that for a starting point. after the bike is fully warm it needs a fine tuning to be spot on where you bike wants it. this may be 5.1 or it could be less or more.

I have one bike that wants 4.6 and another that wants 5.8 both idle at 1000...
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Syonyk
Posted on Sunday, June 12, 2011 - 10:56 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

If the headers are glowing red, it probably means you're lean as all something or other.

Or timing is badly off.

I'd check for a major intake vacuum leak - something like that can be masked by the richer mixture on startup, then become an issue later.

If your timing has gone wonky or your ignition module is failing, that could also lead to pipes glowing - if it's not firing consistently, you can end up with unburned fuel in the exhaust pipes that burns in there, leading to glowing headers. And, at least over on the Blast forums, "Starts running like crap after it warms up" is almost always the ignition module.
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Syonyk
Posted on Sunday, June 12, 2011 - 10:58 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Actually, scratch intake leak (well, check for it, but... not as likely)

If you're getting the tach jumping around, that implies ignition issues. Either the ignition module isn't getting a solid signal from the pickup, or it's not outputting a solid signal to the tach.

*goes to check his wiring diagrams*
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Syonyk
Posted on Sunday, June 12, 2011 - 11:10 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Ok, I've got an 05 manual, so it's not *quite* identical, but I'm guessing it's pretty close.

At least on the 05s:

The tach signal comes straight from the ECU - it's not interpreting anything off the ignition module.

The input to the ECU comes straight from the camshaft position sensor.

The output from the ECU goes straight to the ignition coils.

So, given the tach jumping around combined with the symptoms you're seeing, I'd guess it's either an issue with the camshaft position sensor, or the ECU.

I know on some bikes, the ECU could crack from loads placed on it by the seat - I've mostly heard of this on the Ulysses, but I believe the Lightning Long is the same frame/seat/etc for the most part.

Pull the ECU, visually inspect for rubbing/cracking/etc. That's probably the easier one to check - borrow one from a similar bike & see if it still happens. If it continues with a new ECU, it's probably a bad cam position sensor, which is a bit more involved to replace, but still not terrible - you don't have to remove the engine to do it, you just need to drill out some rivets and replace them later.
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