Odd mechanical thing happened on the road this evening

[rodekyll]

I got the tank and fairing on the trike and naturally had to road test them.  Since the final paint portion started the trike has only been started to move it in and out of the Quonset hut (light is better outside).  It was running a little ragged when I first started out -- more feedback from the floorboards than I'm used to, and not quite the pep.  No problem -- I'll just get it outbound and open it up a little.  So I did.

I was cruising about 65 for a mile when there was suddenly a series of very loud backfires.  There was no associated engine behavior -- just the backfires.  Very loud, and a series of maybe 10.  Then some more.  Like gunshots.  At first I thought it was someone alongside the road doing something, but the sound was moving with me -- definitely coming from my trike.  It must be exhaust?  After a quick glance to verify voltage, oil pressure and temperature (good on all) I shut it down and coasted to a stop.

I did a quick visual -- nothing hemorrhaging, no bad smells, no smoke.  No manifolds blown off or mufflers missing.  I toggled the main power and checked for sparks or other indicators that I'd pinched a wire or knocked a coil loose in the recent construction -- nothing apparent.  I thumbed the kill switch -- nothing unusual.  Fuel pump grumbles and my fuel pressure gauge comes up normal.  So I cautiously start it up.  It's running hot, true, and normal.  The vibration is gone and it steps out lively.  I turned it back to the barn anyway and paid close attention as I ran the 8 miles back home.  Nothing unusual.

Any idea what could cause such dramatic and repeated backfires?  Short of sucking a valve, I've never encountered that, ever.

[pat80flh]

Maybe a failing ignition switch? Losing, then regaining power to the ignition system?

[Aaron D.]

Sure sounds electrical-bad ground to something in the ignition circuit, like a tach or other sensor.

[Mike Tashjian]

I added a circuit to my 02 Stone(in 03) and removed the battery terminals.  Best I tell the computer did not like the momentary interruption and acted exactly as you described.  Took me a few rides to figure out, I had no idea what happened.  Removing a  battery terminal seemed to reset the computer and I have never had another issue.   Mike

[RinkRat II]

 Could be either : A)  It was thanking you for the new paint.
                            2)   Sidestand switch ghost
                            C)   Neither of the above 
                             4)  Electromanetic flux from the Borealis

      Paul B

[pehayes]

Ragged running at first, flooboard feedback, lack of pep.  Are you sure you weren't just running on one cylinder?  If so, the second cylinder was pumping raw fuel into your exhaust system.  Once the second side starts to fire, the result is big explosions to clear out the exhaust system of unburnt fuel.  Did you feel any extra power surging just prior to or during the explosions?

Patrick Hayes
Fremont CA

[LaMojo]

Probably carbon in the combustion chamber coming loose and intermittently shorts out a plug. 

[Farmer Dan]

Gremlins get my vote.  Nobody ever gives them the credit they deserve..

[rodekyll]

Ragged running at first, flooboard feedback, lack of pep.  Are you sure you weren't just running on one cylinder?  If so, the second cylinder was pumping raw fuel into your exhaust system.  Once the second side starts to fire, the result is big explosions to clear out the exhaust system of unburnt fuel.  Did you feel any extra power surging just prior to or during the explosions?

Patrick Hayes
Fremont CA

I think it was hitting both sides -- just not really well.  I suspect the ten or so starts over the month had something to do with it too.  I only moved it ten yards each time.  It could have accumulated some raw gas in the mufflers from that.

No, I felt nothing at all different immediately before or during the event.  I could not even feel the backfires.  They were quite audible, but did not affect the engine.  No surging, no cutting out, just ragged running -- almost like bad gas.  And once restarted all was good.  I went back out at midnight (trying for some darkness so I could aim the HID lights) and ran out the entire road system with no hiccups whatsoever.

The trike goes on the barge for the USA tomorrow early AM.  If I've got a problem here I'd like to know what it is before I launch.  Like I said -- I've never seen or heard of this before.

[normzone]

" The trike goes on the barge for the USA tomorrow early AM. "

GO [RODEKYLL] GO !

[Arizona Wayne]

The distributer jumped a tooth 'cause 1 of those gears is worn out, throwing all your timing off. 

[Groover]

Probably carbon in the combustion chamber coming loose and intermittently shorts out a plug.

This sort of along the lines of what I was thinking, but more of a bridged fouling plug. Happens a lot on 2-strokes (in my experience) from loaded low-end (very rich), but can't say I've seen it on a 4-stroke.

Sounds a lot how you described with a erratic misfires and banging. Sometimes they clear on their own with more throttle, sometimes they'll completely foul out. Though they still run, the performance does drop considerably when that happens (which doesn't sound like your case). Many times it would happen with a brand new plug (the image is the closest thing I could find online)

[oldbike54]

 Fellas , I haven't seen a properly tuned fuel injected bike form anything more than a light layer of carbon , especially with the removal of lead from gasoline . 

 Dusty

[rodekyll]

Yeah, I've taken 30,000 mile plugs out of my efi bike and gotten them mixed up with the new ones.

I'm thinking it was my battery cutout switch.  It sits directly under the lid of the fuse box.  When I slapped the lid shut before the ride I might have touched the cutout button.  The odd vibration* might have rattled the button and interrupted power (doesn't explain why the dash lights styed on, but . . .   and then opening the fuse box to check things after shutting it down, I undisturbed the button.


*remember the 15-sec rule on efi bikes -- where you toggle the kill switch and then wait 15sec for the ecu to settle down before starting?  This bike has always run better when I count to 15 after turning on the ignition.  When I started this ride I backed out of the carport.  I have to shut down the engine to change direction because the trike has no clutch.  So I've been practicing doing a forward/reverse/forward procedure in the fastest possible manner to save time.  I went from reverse to forward in just a couple seconds -- not enough time to re-zero the ecu.  It may have been punishing me for that quick shift by running ragged.  The minute or so that I spent checking things out by the side of the road may have been the time it needed to reset itself.  So when I restarted it was smooth again.

But that's all I've got right now.

Aimed the headlights last night.  Yeah.  I do indeed own the night.  I never thought I could use sunglasses at night, but with these lights I could.

Got a few pics today.  I'll post after the trike gets on the boat tomorrow -- too much left to tinker on it to take the time now.

Keep the speculation coming, gang -- someone is going to figure it out for me.  :)

[acogoff]

     Primary wire to coil crimp on terminals deteriorated or not slid onto the male blade properly(done this one myself, had it between the plastic and the terminal instead of engaging the female part properly) DUH.

[lucky phil]

It had been running on 1 cylinder for a period of time ,maybe intermittently due to an ignition problem ( which explains the rough running) and built up unburned fuel in the exhaust which caused the back firing.

Ciao

[rodekyll]

     Primary wire to coil crimp on terminals deteriorated or not slid onto the male blade properly(done this one myself, had it between the plastic and the terminal instead of engaging the female part properly) DUH.

That's a realistic possibility and I'll check on it right away.  It fits the scenario.  I did intentionally disturb the coils when I put the tank on.  Maybe I got a wire loose or touching.

Phil -- you're probably right about the sequence of events.  I'm trying to figure out why that sequence came to be and how to make it not happen again.

[jackson]

From reading the symptoms, I was thinking electrical; coil, spark plug cap, bad connection somewhere along the electrical ignition path, etc.  Then, I read the post from acogoff where I think he hits the nail on the head (or very close to it).  Hope you find it quickly.

[Chuck in Indiana]

Well, it's an ignition problem for whatever reason. No spark for a couple of revolutions then spark and bang. Repeat. Something's loose somewhere. <shrug>