My buddy and I both have 650's his is an 02 mine an 03. We purchased them at the same time. Recently his has started surging at medium to higher speeds. It feels like turning the kill switch on and off, sometimes it happenes very quickly and it's gone other times it can last for up to 30 seconds. I've never had it with mine. Very intermittant problem, than, last night we went for a quick ride, we were at a slow speed, around 15mph and it started backfiring out the pipe. He gunned the engine and ran the heck out of it and it cleared up. We have changed the plugs, drained the carb bowls, checked the fuel tank vent shook down all wiring, we are now out of ideas. Of course the dealer wants it in for "troubleshooting" but he dosen't want to refinance his house to pay for it! Any ideas? Sounds like a job for NYROC

 

Hmm, you got me. Ican only guess. Ya know, we should have a sweepstakes to see whose idea is the reason the machine doesn't run right. The losers chip in and buy the winner a set of tires?


Since you say it is quick, like the kill, and it is intermittent, I have to tell you that it is electrical. Although you have shaken down the wiring, you should take a closer look. Maybe the ignition switch. When you turn the switch, two things are enregized. One contact turns eveything but the CDI on, and the other has a 1 ohm resistor in it to signal the CDI to turn on. You can't hot wire that one. This second contact is the reason why a lot of people can't start their machine when the switch is going bad even though it looks like it turns things on. That might be it.

Or maybe the CDI is going bad.

Or the upside down sensor is going bad.

Or the speed sensor is going bad. It is possible the speed sensor is still signalling the speedometer but not enough to signal the CDI. A holeshot module would help you diagnose this. In fact, a holeshot moodule would be fun to have whether it helps you fix this or not. Get one.

Does pressing the reverse override help? Sometimes the reverse sensor is bad.

 

Thanks for the suggestions NYROC, we were thinking upside down sensor(vehicle down according to the book, same one you are talking about?) also. The bike only has 65 hours on it and they aint been that hard. What will depressing the override button do when moving in foward gears? Didn't even think to try that option, is it a constant input to the CDI when depressed? They(dealer) told him that it might be choke springs but that didn't sound right to me, it happenes way to fast to be a choke problem.

 

ppags,
Please let me know what you find out I also have an 02 650 and it just started to do the surge thing. I've had it as low as 25 and still felt a little surge. But it is most obvious at 40 and up. It feels like I am hitting the throttle and then slightly letting off again and again. Mine also backfired but it has only done that once but thats when the surge problem started.Thanks

 

ppags, I guess that wasn't much of a good thought, because if the reverse sensor was bad you would see a light on the dash. It won't help to press the reverse override unless it is in reverse or if the CDI thinks it is in reverse.

 

any way to check your sliders in your carb? this happened to me and I thought it was electrical and it wasn't it was my sliders were faultly, and the only place the bike runs good is wide open. After a while you might find if you are travelling 20km it will just bog out and die. It will run like $hit then a million bucks and no ryhmn or reason, also I found it would run worse on rougher train.

 

is it possible that the rubber flap under the front plastic is partially obstructing the snorkle ( CISCO 1 ), I forgot about that possibility in our e-mail conversation...WAM

 

newbeatle, no obstructions on the snorkle actually I don't even have the access panel on just to see if it would help.

 

Not sure if it's the same problem, but my 650 did this right from the time it was new. Only @ 3/4 to full throttle and mostly in low gear(higher revs?). After modding the exhaust and installing the snorkle and filter, problem was worse, leading me to believe that it was bogging due to a lean main jet. Switched to 142/145 from 138/142 and the problem went away, plus gained considerable power. Hope this helps.

 

Well, we worked on it all night last night and you guys aint gonna believe what it ended up being! We changed the plugs again, tested the vehicle down sensor, which by the way is a pain in the a-- because you have to take all the plastic off to get to it. Sensor plug had all kinds of crap in it when we unplugged it, so we cleaned it out. We tested the sensor and it passed all the voltage checks so I jumped the cannon plug eliminating the sensor from the ignition. Guess what, you can't do that! The bike would start but would die in a few seconds, lesson learned. Hooked it back up, did a few carb adjustments( even though I never thought it was a fuel problem) and took it for a spin, same damn thing, no backfiring but definately cutting out. Hooked up a volt meter and started looking at voltage with the bike running, it was only 12.1, that is way to low! After snooping around I found that he had hooked up a set of off road lights to an ignition switched wire up front ( brown wire and a black/yellow wire going into a plug ) right behind the steering stem. Not only didn't he know where this wire went too, but it was way too small to power those lights. I disconnected the lights and the voltage jumped up to 13.8, muchas better! Took her for a spin and it was like she was brand new!! I thought my buddy was gonna kiss me! How's that for a painful lesson?![img]i/expressions/face-icon-small-blush.gif[/img]