So I've had issues with floating idle on this bike pretty much since I bought it (it was in rough shape.) I rejetted, turned out the idle screws, and pretty well got it under control.
Last year, I advanced the ignition 5 degrees and started running premium. The idle started floating again, this time only after I'd been on the highway awhile, running at 70 MPH. The engine felt subjectively hotter (which makes sense with the ignition advance.)
I just reversed the change, putting ignition back to stock. Bike idle isn't floating anymore. I'm tempted to throw a CHT on the bike and see if I can make it repeatable.
Is it possible that the idle on these bikes could start floating when the engine hits the high end of it's operating range? This would explain accounts of members that only have floating idle after 30 minutes of riding.
Mechanically, how would that work? Also, I dont have my manual on me (at work right now) so does it list the normal ranges for temperature operating ranges?
I've experienced the same time of symptom and also had my bike mysteriously shut off on me under the same circumstances. Couples cranks to clear the cylinder and she was back up.
Curious to see how this pans out...
My son tells me that the floating idle issue with his bike gets worse the longer he rides it. I took it out the other night around the neighbourhood and the problem didn't start to get really noticeable until after 12-15 minutes of riding. I was home by then so I don't know how bad it gets with a longer ride.
I've noticed it before on bikes with rubber manifold boots. I believe it's the rubber that gets small cracks and the heat expands the rubber, causing those small cracks to swell.
Quote from: NickyNumbers on October 27, 2011, 01:40:31 PM
Mechanically, how would that work? Also, I dont have my manual on me (at work right now) so does it list the normal ranges for temperature operating ranges?
I'm not sure what the mechanism is. I'd thought valves, but really seems more likely carb related.
There's no listed operating temps on these bikes, so everything would need to be an A-B comparison. I just know that mine gets worse as it gets hotter, and several others have reported the same experience.
My experience indicates that the ignition module may be at fault - circuits within control timing/dwell, and may be affected by heat, especially in older units. Designers provided two relatively large heat sinks, but since the whole assembly is encased in rubber epoxy there's no air flow and therefore heat builds up the longer you ride. You can feel the outer plastic get slightly warm after riding about an hour.
Also, electronic components sometimes degrade with age - for example some types of capacitors, etc.
Changes in ignition timing will cause rpm variations at idle for any vehicle I've ever dealt with, as well as overall power/fuel economy .
I've run several different modules on my bike, and each has it's own 'style' , anything from hunting idle/occasional backfire, to excellent performance, to un-rideable total failure.