Loss of power and stall

[alnmike]

One two occasions I've had a loss of power on my GS650L.

The first time I was on the highway going 70, (without the engine fully warmed up) the engine would fit and start from full power to about half power with a constant throttle position. Eventually the "half power" time got longer and longer and after about 3 more exits I couldn't keep freeway speed anymore and had to go a max of about 45 on the nearest off ramp I could find. When I got to the stop sign at the end of the off ramp the bike stalled despite my best efforts and I pushed it out the road and the bike wouldn't start again. After calling work and telling them what was happening I tried again and it started right up. I took surface streets the whole way just in case and it never did it again. Even on the way back from work on the highway.

Until the next time about a month and a half later. Last night I took it out on the same stretch of highway near my house (not fully warmed up) and it was doing the fits and starts again but not long enough for me to loose too much speed. I got off the highway again and it stalled as I stopped for the light at the end of the off ramp. I waited and waited and it never would start again so I push started the bike (the battery had died from so much cranking) and kept the engine at a minimum of 4k rpm to keep it from stalling the 5 minutes back home.

The bike is in good shape as far as oil changes and those simple things and from just a visual inspection through the gas cap, rust is not obvious in the tank. I'm at a loss, hope you guys can help!

 

[almarconi]

My first thought would be the petcock, is it original?

When was the last time the valves were adjusted and the carbs cleaned?

There is a whole lot more to bike maintenance than oil changes.

 

[Flyboy]

Had a GS850L that would do something similar, if you rode it hard on the freeway for any period of time, it would run out of fuel and die, the only way to get going again was to take off the tank cap, and blow into the tank, sort of pressurising it, then it would start straight up and go fine.
So it would seem, there was a problem with the tank venting, thus creating a partial vacum restricting the fuel flow, by opening the cap, you were equalising the pressure and she was good to go again, so maybe a blocked breather in the cap, or a faulty petcock, that was not keeping up with demand at high power settings.
But she would run all day everyday riding normaly, so maybe start by checking those two things.
Hope it helps.

 

[tom203]

Sounds like fuel starvation , so check tank vent and petcock as others have mentioned. If the bike has sat for long while, there could be a scum buildup on petcock filter blocking flow at low fuel levels at random times.Visually check fuel level to ensure the fuel gauge is somewhat accurate as tank runs down. Moving to prime position would allow quicker carb refill if it happens again and save lots of cranking!

 

[Big T]

Do you have a fuel filter in the gas line? If so, remove it

As others noted, take off your gas cap and check the vent

If it runs fine most of the time, but starves for fuel on the freeway, something is impeding your fuel flow

 

[alnmike]

Update, took it out to determine if it was a fuel vent/cap issue. It is not.
Its prefect above 5k rpm, it just doesn't have any torque below that.
After my clutch cable broke, I replaced it. Ever since, its been having this fueling/valve problem. Today it refused to start till I put it in first, and then it started and kind of pulled forward, the clutch lever doesn't fully disengage anymore I guess. (Thought I adjusted it properly).
I also had new intake orings put in a while ago and right before I did that I took apart 2 of the carbs (the ones I didnt strip out) and they looked clean.


How many hours would it take a newby to adjust the valves. If its like 30 hours, I might as well push the bike off a cliff and get a 250 ninja lol.

 

[ardbeglily]

Alnmike, a valve adjustment would take a noob about 60-90 mins if you have the tools and shims on hand. I can loan you the ProMotion tool and the shims I have when you are ready. You should also join the Shim Club, Ray is very helpful and patient.

 

[Steve]

How many hours would it take a newby to adjust the valves. If its like 30 hours, I might as well push the bike off a cliff and get a 250 ninja lol.

Nowhere near 30 hours (at any one session), but if you have to order shims, it will take a few days for them to get there.

Between the service manuals and other tutorials posted on BassCliff's site, there should be no problem adjusting your valves, as long as you know which end of a screwdriver to pound on.

If you are mathematically-challenged or simply want an easy way to figure out what shims you need and a method to keep track of what's in there, I invite you to follow the suggestion at the end of my sig.

.

 

[BassCliff]

Hi,

It took me longer to take the pictures and write the guide than it did to actually adjust my valves.


Thank you for your indulgence,

BassCliff

 

[Guest]

Classic petcock symptom

 

[alnmike]

Lol, sorry, just a little frustrated and jumpy, my last day off was whatever the last holiday was

Anyway, I was in the middle of reading Bikecliff's guide when I decided to check back on this thread.
Going to order a new petcock tonight, and ardbeglily, ill take you up on that offer, unless the tools are less than $50. It would be a good idea to just buy them for the next time I have to do this.

Edit: Any way to check the petcock before spending $70? Im also going to sync my carbs when I do my valve adjustment, cant wait to build a manometer