I was playing with my '96 gs500e on a long, abandoned straightaway, trying to max out the speed... got it up to just under 120 (like 115 mph but we'll round up ), still had a little torgue to spare but figured I'd back off since my helmet was buffeting a little...  the problem being... the bikes transmission seemed to no longer function.  I rolled off the gas without using the clutch, and the bike, of course, started to slow down, just as I'd expect it to.  I hit 90, 80, 70, 60... I started giving it some gas to stabilize the speed at 55 but the engine just wasnt making any noise at all, no matter how much i twisted the throttle i couldnt hear any signs of compression from the engine...   at about 45 I pulled the clutch in and tried revving it... no joy, no signs of life at all from the engine.. 35.. 20.. 10... I pull over to the side of the road...the engine is completely stopped.

I think "oh, crap, oh crap, oh crap, oh crap. . . I've killed it..."   and try hitting the starter a few times.. i can hear the starter moving something but i cant hear signs of combustion...

so i flip the bike to the off position, thinking i maybe fried the electrical system and the spark plugs arent getting any electricity (does the bike have magnetos?)

so i sit for a minute trying to figure out what i should do... I'm on a bridge in the middle of nowhere with no traffic in sight. . . but i really dont want to call someone to tow my bike somewhere...

so after about a minute of thinking, i try starting the bike again.  it immediately kicks on...

I give it a few experimental revs and it responds completely normally...

I took it waaaay easy going home and had absollutely NO problems at all.

no problems since.

so the question is.. what do YOU think happened?

my best guess, after thinking it over, is that keeping it at WOT for the minute of so i had it flooded the engine.. the mixture was too rich and when i dropped the throttle to slow down it drowned itself.  the fact that i havent looked at the air filter since purchase might lend even more credit to this explanation, as airflow might be slightly restricted to the engine, enrichening the mixture even more.

any other ideas?  should i get a shop to look at it?  I've put about 80 miles on it since and have had no problems.

thanks

http://gstwins.com/forum/viewtopic.php?t=19375&highlight=fuel+starvation+high+speed

Almost the exact thing happened to me today with my '05.   I was on I-95, doing 80+ mph for about 5 to 10 minutes and felt the engine miss a few times, then it got real bad, so I squeezed the clutch and pulled over.   The engine died completely before I got stopped.     I had half a tank of gas, and the petcock was in the correct position.   I couldn't find anything loose or broken, so I got back on and it started right up.   I tried to get it to do it again, but it ran just fine.   :dunno:

Fuel starvation at high speed is apparently a common issue for GS's.

you didnt flood it, you leaned it out.. the float bowls were empty.. and didnt filll back up..

well then.. sorry i started a new topic.. wish there was a way to combine this thread with the linked one.. I searched for fuel rich high speed, not fuel starvation.. thats why i didnt find it  

ummm... oh yeah, one thing i forgot to mention, is this was on the tail end of a 5 hour ride, meaning that the bike had been running at about 65 mph for 4 hours, and no problems.

also, my bike really hasnt been looked over since i bought it. I know that the previous owner possibly didnt take the greatest care of it, it sat for several months at a time unused, and the oil was only changed every 4 to 6 thousand miles (which, to me, means 6 thousand). . .

luckily, I am a big do-it-yourselfer... and I like tinkering. and I have boucoups of time off.  so I'll clean out the tank and screen, play with the petcock... get a new air filter (even though it seems there was no correlation to this problem why not?), change the oil (hasnt been done for two years... only 400 miles, according to the previous owner, but after two years no good reason not to anyways. plus i dont know if he changed the oil filter and stuff)

the bike has 11 grand or so on it. I dont want to shell out the money for a dealership to do a tune up (200 would be reasonable, but as it sound a thorough job can be around 800)  but i guess i can check the valves and stuff, also... consider that clymer manual ordered...

hrmm i have an 05 i bought back in nov. and have had no problems with it .. i hop on the highway and do an hour run at about 80-90 and have no problem .. yet ..

I didn't read the responses but I bet someone has said it already...  your carbs couldn't supply enough fuel.  This can be caused by a gas cap not venting as well as it should - but won't show itself until really high fuel consumption

Quote from: sgaterboywell then.. sorry i started a new topic.. wish there was a way to combine this thread with the linked one.. I searched for fuel rich high speed, not fuel starvation.. thats why i didnt find it  

ummm... oh yeah, one thing i forgot to mention, is this was on the tail end of a 5 hour ride, meaning that the bike had been running at about 65 mph for 4 hours, and no problems.

also, my bike really hasnt been looked over since i bought it. I know that the previous owner possibly didnt take the greatest care of it, it sat for several months at a time unused, and the oil was only changed every 4 to 6 thousand miles (which, to me, means 6 thousand). . .

luckily, I am a big do-it-yourselfer... and I like tinkering. and I have boucoups of time off.  so I'll clean out the tank and screen, play with the petcock... get a new air filter (even though it seems there was no correlation to this problem why not?), change the oil (hasnt been done for two years... only 400 miles, according to the previous owner, but after two years no good reason not to anyways. plus i dont know if he changed the oil filter and stuff)

the bike has 11 grand or so on it. I dont want to shell out the money for a dealership to do a tune up (200 would be reasonable, but as it sound a thorough job can be around 800)  but i guess i can check the valves and stuff, also... consider that clymer manual ordered...

Yeah, the float bowls dried up. Davipu was telling me he had this problem when he went 90 for any extended period of time. Talk to him about what he did to fix it.

This happened to me exactly once.  The GS was between 700-1000 miles old, and I was heading back from visiting relatives...on the highway, at night, probably going 80 (indicated).  I had been underway for about 15 minutes.  IIRC, I took my hand off the throttle momentarily, then when I tried to open it up again I got no response.  When I looked down, the tach was reading 0 (which I thought was extremely odd because the clutch was engaged and the wheels were turning).  The first thing I thought was that I hit the kill switch when I put my hand back on the throttle, so I flipped it to the other position, realized it was now in the off position, and flipped it back to the run position.

I pulled off to the side of the road and pondered for a moment, since I was still about 45 minutes from home.  I double checked everything, put the sidestand down and back up again, then tried to start it.  It fired up just fine.  

The rest of the ride went without incident, I later realized that it wasn't the kill switch or the sidestand switch, since the bike would have restarted almost immediately (it was still moving, in gear), and eventually settled on the fact that it must have either been an ignition problem or a fuel delivery problem.  The thing that still has me perplexed is the 0 tach reading.  

I've put a few thousand miles on it since then and have not had a repeat.  I was routinely commuting an hour+ (each way) at similar highway speeds until the snow came, so if it was a chronic problem I most likely would have experienced it again.   :dunno:

thanks for all the responses.  I'm just happy that it wont cause any permanent damage to the bike.

venting the fuel tank a little more seems like a decent idea.

get on a diet. the gs engine got tired of hauling your big butt in the road and had to take a break, thats all.

I had to run my '92 in PRI on long freeway trips (shorter trips around town were fine with just ON). Since I'm not mechanically inclined, I left it to the Baby G's new owner to fix this problem (yup, he knows about it, and the Baby G is already giving him headaches with the carbs, etc! :lol:).    :mrgreen:

Its the POS petcocks. The one on the tank is  hard to get it completely open. The main one is vacumm operated and also has a tendency to deteriorate and stop opening completely. Also at WOT the amount of vacumm being pulled is reduced because its breathing thru the carbs mostly. This closes the petcock valve enough to starve the carbs of fuel.

Most racers remove all this crap.

Quote from: JamesGIts the POS petcocks. The one on the tank is  hard to get it completely open. The main one is vacumm operated and also has a tendency to deteriorate and stop opening completely. Also at WOT the amount of vacumm being pulled is reduced because its breathing thru the carbs mostly. This closes the petcock valve enough to starve the carbs of fuel.

Not dismissing that people do have problems with the petcocks, but the symptoms I had were different than the common fuel starvation issues people have described (which seems to happen on throttle).  I think it's more likely that the high vacuum in the intake manifold with only idle throttle caused an overly lean (and non-combustible) mixture...the same deal that causes exhaust popping on deceleration.  There was a great discussion about this a while ago...ah, here it is.

What I took away from this was:  don't chop the throttle from high speed/high rpm (a.k.a., high fuel flow) to idle.  Dunno if keeping the throttle cracked slightly is the trick, but I haven't had an issue since.

And vacuum in the tank ...
Cool.
Srinath.

Sorry but reciprocating engines and carburators don't work like that. CV carbs are "Constant Velocity" in that they are self correcting for mixture. They put out a consistant fuel amount governed by jetting depending on the demand from the engine (the vacumm pulling air thru them). Unless something is wrong with it, or jetting is screwed up, there is no point where the carbs "go lean" just because engine rpms and throttle position aren't at a certain alignment.

But that doesn't relate to sgaterboy's problem which is a classic example of a the carb's fuel supply not being able to keep up with demand while haulin' ass, but then running fine once it was able to catch up.

Quote from: JamesGUnless something is wrong with it, or jetting is screwed up, there is no point where the carbs "go lean" just because engine rpms and throttle position aren't at a certain alignment.

That's not exactly true.  If you open the throttle suddenly, the carbs will go lean, because the gas has more inertia to overcome than the air, which will rush in almost instantly.  It will self adjust, like you mention, as the gas catches up to the air, but it's not instant, which is what causes hesitation.

Probably not exactly what you're talking about, but I thought I'd point it out.

I don't mean to derail... but you went 120 on a naked bike? Holy cow! I took my '02 gs5002 to 80 and was scared!

Then again, I'm somewhat a wimp

That is both a limitation of both crank inertia and the CV slide (flat slides don't have that problem) retraction time.  The mixture hasn't really gotten leaner, its just the air hasn't gotten to the engine yet.

Quote from: JamesGBut that doesn't relate to sgaterboy's problem which is a classic example of a the carb's fuel supply not being able to keep up with demand while haulin' ass, but then running fine once it was able to catch up.

I don't understand:

Quote from: sgaterboyI rolled off the gas

Why would the fuel supply not be able to keep up when the throttle is closed?  The fuel supply was keeping up fine with the throttle open, why would there suddently not be enough fuel at lower throttle?

Forgive me, but your statements seem to imply that what happened to me just isn't possible, and I find that very confusing...but I'm not a mechanic.  I just don't see how closing the throttle would starve the carbs where WOT didn't.  I don't see how there could be "something wrong with it" on a nearly new, unmodified engine (in my case) and not have any subsequent symptoms (unless it magically repaired itself while I wasn't looking).  I do know that other reciprocating engines deliver fuel to the carbs differently at idle, cruise, and WOT settings, but I know more about aircraft engines than motorcyle engines.

Maybe it's just one of the mysteries of the universe that I am not destined to understand.  I stand by my conviction that 'carburetor' is French for "don't touch it".

Quote from: JamesGThe mixture hasn't really gotten leaner, its just the air hasn't gotten to the engine yet.

If the air hadn't gotten there, that would make the mixture richer, wouldn't it?

Sorry...I'm probably being daft, but I'm just not comprehending what you're trying to say.