B5: engine sputter/hesitation

[mattsz]

Not sure how else to describe it.

I took a ride yesterday, everything started out fine.  I knew I was going to need gas soon, and sure enough, the low fuel light began to illuminate briefly when braking, or stopped facing downhill, the usual thing, for me anyway.  I had to ride about 18 more miles before a chance to stop for gas.  At this point, the fuel light still had not come on steady.

As I slowed on a level stretch to stop for gas, I shifted from 5th to 4th gear, and the engine started to sputter and skip a bit, very briefly, with no response to throttle blipping (why does that always seem to be the gut response to engines misbehaving?  "Give it more gas, that'll fix it!"  ). It did this two or three times in a short interval, and when I pulled into the pump, and put it in neutral, it was idling fine, but when I twisted the throttle to run the speed up it would sputter lightly.  Back down to neutral, fine; rev again and it sputtered.  I did this for a minute or so, and I observed that while the bike was sputtering, the neutral light and the red "Royal Enfield" always-on gauge indicator light actually dimmed slightly "in time" with the sputtering.

I filled up, and rode a bit more, 1/4 mile maybe, and it began happening again, again in 4th gear.  I experimented while at about 30-35 mph and shifted between gears: 3rd gear, no sputter.  Back to 4th, sputter.  5th, no sputter, but the engine lugged so slowly that I couldn't really tell.  Back to 4th, sputter.  Back to 3rd, no sputter.  4th again, sputter.  3rd one more time, but it did sputter a bit this time.

My buddy and I stopped for lunch to think about it, while our bikes cooled down for about 40 minutes, but we couldn't come up with any obvious quick-fix scenarios, so we decided to head home on back roads to avoid traffic.  All the way home, the bike behaved perfectly.

As you all know, I'm new to this whole business, but based on what little I do know, and based on what I've learned about these bikes here on the forum, this shouts electrical fault to me.  The barely flickering indicator lights are the red flag - if it were any other type of fuel or mechanical problem, wouldn't the lights stay bright if the engine were sputtering within rpms well above idle?  Also, the 4th-gear-only thing suggests to me an engine-speed vibration-related problem - can that be anything other than electrical?  I also know that there have been some wiring chafing problems amongst us here.

The fuel was low when the sputtering started, but I've ridden with less fuel (according to the indicator) with no trouble, and of course the problem continued after I filled up.  Fuel flow could be the culprit, but what about those lights?  A dirty or fouled plug would be a constant problem, at idle as well as at speed, yes?

Any thoughts?

[jartist]

Start with the simplest things first. A few ideas:

1) Water in the gas?- fill up the tank and add a little seafoam.

2) Throw in a new spark plug

3) Check battery voltage

4) If these don't work. Check wire routing especially where the sharp bends are in the headlight and battery box and grease the connections.

5) I forgot about this one and should be before 4. Some people have had the sidestand kill switch be activated by bumps or vibrations, especially at speed. You'll find the connection on the wire about six inches from the stand. You can simply disconnect the sidestand and see if that works.

[GA-DK]

I think you are right on track with your thinking and analysis.  It is probably a partial short of bad connection aggravated by vibration.  I would remove all covers, put bike on center stand, start engine, then examine wiring, and switches.  Look for movement of anything that will effect idle.  If you find it, be sure to post solution for others.  GA-DK

[JVS]

3) Check battery voltage

5) I forgot about this one and should be before 4. Some people have had the sidestand kill switch be activated by bumps or vibrations, especially at speed. You'll find the connection on the wire about six inches from the stand. You can simply disconnect the sidestand and see if that works.

I would check these two first

[mattsz]

Would water in the tank cause a problem only just before empty?

Spark plug is easy to check, but it seemed to be so RPM dependent.

Battery voltage is fine, such as I can check it at idle and "at speed" with the bike stationary.

My side stand has been disconnected for quite some time...

[Arizoni]

Sounds like a loose harness connector someplace.
The wiring harness is being excited by the frequency of the engine speed and I can just picture one (or more) of the partially connected connectors moving and making and breaking contact.

I'd start with the bundle of snakes in the headlight casquette.  Especially the wires connecting the ignition switch.

[gremlin]

the run/stop switch on the right handlegrip meets the vibration & circuit power requirements of your trouble description.

[mattsz]

the run/stop switch on the right handlegrip meets the vibration & circuit power requirements of your trouble description.

Interesting.  The right side of the handlebars vibrates more than the left - the mirrors told me that...

[Ducati Scotty]

Maybe interesting, but not unique. Lots of these bikes vibrate more on one side than the other.

Scott

[barenekd]

When mine was running like that it, was the sidestand switch connectors coming loose. Got them on tight and never any more problems.
Bare

[mattsz]

Well, boys and girls, how about an update?

This problem appeared again.  It got to the point where the bike would only run with the lights off - as soon as I turned the lights on, it would sputter and spit.  Lights off, smooth operation.  But it didn't last - soon, I stopped at a light and the bike died.  Key on only, full power available.  Run switch on, bike died.  Switching the run switch on and off turned all the power off and on.  Finally, nothing.

I found an empty lot, and went right for the battery cover - and can you guess?  Of course you can!  The strap connecting the ground wire to the battery was broken.  I removed the broken fitting, and screwed the wire right to the battery terminal to get me home, with no further trouble.

Everybody reading this - I don't know why they use these crummy fittings, but I think they should be replaced as a preventative measure.  New owners, replace them before they break!  It isn't hard, and it isn't expensive.  Don't get stranded - especially on what will likely be the last nice riding day of your year...

[gremlin]

Glad you found & fixed your gremlin.

[mattsz]

Thanks, Gremlin.  And, yet another hearty thank you to everyone here who made sure I would know to look for that broken battery lead in the first place!!!