Hi all,

I wrecked my GS around 3 weeks back but since have replaced forks, front axle, top and lower clamps/steering stem whilst also fitting a few mods while I'm at it. Been riding for 4 days again now and the bike feels and looks amazing however today when I was starting her up after work I had a bit of a problem.

She started first time with choke on full no problem, but after around 40 seconds or so, still on full choke and letting her warm up a little because it was 6 degrees, the  revs started dropping until the engine died. Started her back up and the same thing happened unless I held the throttle at a constant 2-3k rev range. I ended up just setting off with the choke halfway and then turned it off after a minute or so and had no problem whatsoever riding home.

What could the problem be? I've browsed the forum and can't find the same issue anywhere. Any advice would be much appreciated

I'd like to just blame the cold if you had no further issues, all kinds of weird things can happen in sub freezing.
Carbs misbehaving?  Fuel valve misbehaving?  Battery misbehaving?

Rubber basically turns to plastic when it gets extremely cold, the membrane in the petcock could have been stiff and providing a weak fuel flow.  Bike burns through the bowls and incoming fuel can't keep up with demand so it slowly loses momentum and comes to a halt.  By the time you fire it up again it had filled back up, rinse and repeat.
Cracking the throttle leaned it out enough for the bike to keep up with itself until it got good and loose from warming up.
It's a possibility, not saying it is what happened.


When riding in cold conditions I would usually call the bike ridable at half choke and switch it all the way off another few minutes on the road, so that's not unusual to me.
I wouldn't worry too much about it if it was a fluke, but definitely follow up if it's repeatable.

I'm guessing he meant 6C and not 6F which would be 42 degrees F.  Which is still a tad chilly for the cold natured hussy the 500 can be.  I always let mine warm up for 10ish minutes before riding when it dips into the 40s and upper 30s.  Although that can be a pain if you're in a hurry.  Other than that, I cant really offer much input here other than to say that they seem to run a bit funky in really cold weather unless adequately warmed up.. but yeah,  if it was indeed 6 F,  hahah  that's crazy cold and i'm surprised the bike would even start in the first place.  Good luck man!

Quote from: SirHansford on December 03, 2016, 09:24:40 AM
I'm guessing he meant 6C and not 6F which would be 42 degrees F. 

Didn't even think that, I always forget we're a multinational forum...

Well, I would be insane enough to ride in weather that cold, I figured I wasn't alone 


There's a lot of things it could have been.  A sticky needle?  Fuel filter element got a minor clog?  Moisture in the fuel? 

I'll still say to mention if/when it happens again.  If it's not repeatable then it may just have been temperamental that day.

Thanks for all the replies guys! Yes, I meant 6C .Apologies for not specifying that.

Had the same problem today. Managed to get it started after some fiddling with the idle adjuster screw and the choke but took me a good 15 minutes. Today it was 0C when this happened though. Took her for a good ride after and no issues. Idles at 1.3k as usual and sounds healthy.

Heres a video of what is happening if it can help anyone pinpoint the issue. It's not my bike but it's basically the same issue in that on full choke it hangs at around 3k revs and slowly drops until it dies unless i keep a steady throttle. After some fiddling about and numerous start attempts with different idle mixtures and abjt of throttle, choke on full revs the bike to 4k revs and warms up moderately fast. I have recently fitted a new slip on with no baffle which may be amplifying the problem?

Video : https://www.youtube.com/watch?v=teSisYeHJpQ Makes the exact same sound at the beggining too unless i apply some throttle to get her started. I'd say around 10-15 attempts where the choke on full revved to 3k and unless i held the trottle, the revs would drop until it stalled.

"and slowly drops until it dies" Does she do this cold but run fine after warmed up a bit? How many miles on her and have you done a valve clearance check to make sure they're not tight?  as far as the exhaust with no baffle, i've read that a baffle is needed in most cases because it gives the back pressure required to run smooth, but i don't know if this is always the case or would cause your symptoms but its something to consider. im sure others are far more qualified than me to help but thought i'd toss out what i could.  keep us up to date with your progress and best of luck to ya man!

Quote from: SirHansford on December 05, 2016, 01:26:50 AM
as far as the exhaust with no baffle, i've read that a baffle is needed in most cases because it gives the back pressure required to run smooth.

These aren't 2-stroke engines, so back pressure is not needed or wanted at all.

But what needs to be done if a better flowing exhaust is put on is a rejet, and if this wasn't done it'll be running lean.
I don't think it would be the direct cause, but it's certainly not helping.

I think it could be something as simple as the idle is just set too low, or way too lean.

What are the mods you have done?

Of course when my bike had low compression due to bent valves it would die if you started it cold and let it idle, but it would run on the road fine as long as you nursed the throttle at stops to keep it from dying if you were stopped for >1 minute or so. The "tight valves" may be somehow related to the problem. Who knows. Lots of stuff got fixed on mine between then and now so it's hard to say exactly what the cause of the poor running at idle was.

Quote from: mr72 on December 05, 2016, 09:11:34 AM
I think it could be something as simple as the idle is just set too low, or way too lean.

He did mention idle is set warm at 1.3k, so I don't think that's it.

But I'm willing to guess a lean condition caused by the aftermarket exhaust is a contributor.  The jets aren't doing much if anything at idle, so I'm less inclined to blame them than I am to blame something fuel related.  But especially with cold, "thick" air I could see it adding to the issue.


"Fiddling with the mixture screws" is not something I'd go about doing in this situation, but if you did get it to start by doing so it does sort of support this hypothesis that you're leaned out from the exhaust and it's causing a no-start when it's really cold.
After running it go ahead and pull a spark-plug and see what color it is.  If you parked it after your last ride and haven't tried to start it or anything since you can pull it now.
White would indicate leaned out, black is fouled, brown is healthy.


But I think something larger is at play here.  Usually running lean will still run, but that slow drop in RPM until stall screams "fuel delivery" to me.
Try this, next time it's having trouble keeping an idle going set the petcock to "PRI".  It's actually mentioned in the video description.  If he had lost fuel in the bowl in the time it was sitting and he was trying to start it without proper fuel level I could see it behaving like that.  But yours being repeatable makes me think it could be a petcock issue.

If no change, try tapping on the sides of the bowls with the handle of a screwdriver.  If any needles or floats are stuck it should free them up.