I have a rather newly purchased 1991 gs500e so I am not yet familiar with all its quirks. This is my first bike. The carb was cleaned and adjusted and all the worn parts were replaced by a suzuki dealership. However despite this it looses power and eventually stalls at highway speeds (65-75mph). I am assuming fuel starvation, and I am hoping it can be fixed by cleaning the fuel line and or fuel tank. Any hints from vet riders would be helpful. Thanks, thas all folks.

Hi there,

I too have a 1991 GS500E and had the same problem, which was quite scary on the Interstate.

You probably will need to replace the frame-mounted vacuum petcock and I'd replace your hoses, too. See the posts for the whys and whats.
Here are previous links about this, as well as my posts on the subject.

http://gstwins.com/gsboard/index.php?topic=19375.30

http://gstwins.com/gsboard/index.php?topic=20287.0

If you need more help, just ask!

Best wishes,

Todd

First off, just try running it with the petcock on prime.  Low fuel flow through the vacuum-operated petcock is often the culprit.  Before replacing the petcock, it's worth taking it apart and cleaning it out.  I found a fair amount of crud in mine.  You'll probably also want to give the carb a good clean.  While you've got the carb apart is a good time to rejet.  Yes, even with stock exhaust.  Also, while you've got fuel lines apart, put in an inline fuel filter (mentioned here.  I found that to be a big help.  There's probably crud in your tank that's ending up in the carb.

At the very least, I'd recommend cleaning out the system, and installing the inline filter.  Good luck.

Thanks yall. I'll start with switching the petcock, and if that doesn't work I'll replace it and the fuel lines, perhaps install a filter.

oooh...that happened to me once and i was flying down the carpool lane here in ca...yup check fuel lines for sure, check the rubber diagphram in the carbs some time its old and torn you lose vacuum.... and also my GS didnt like being shifted to 6th and staying there while in the freeway.....everytime i had a stalling incident i was in 6th....so stay in 5th..the shaking from the high revs help the gas flow....i think 

Quote from: poormanracing on January 10, 2007, 09:45:54 PM
oooh...that happened to me once and i was flying down the carpool lane here in ca...yup check fuel lines for sure, check the rubber diagphram in the carbs some time its old and torn you lose vacuum.... and also my GS didnt like being shifted to 6th and staying there while in the freeway.....everytime i had a stalling incident i was in 6th....so stay in 5th..the shaking from the high revs help the gas flow....i think 

5th on the freeway: Alleviate the problem? Possibly... Accelerate wear on internal components? Yes.

Just use prime. (Remember to turn it back when you park)

See also: Converting petcock for non-vacuum operation.

I had a problem just like that.  What helped me get over it was doing a few things.  I went to a Pingel petcock, removing the factory petcocks on both the tank and frame.  New spark plugs.  And shimming the needles on the carbs.  But I think the needle change was the real improving factor there, the other things were done in the name of maitenance (plugs) and reliability (Pingel).  My bike is also non-stock, what has been done to yours?  An exhaust system or changing away from the inlet airbox may make these changes more needed.

Quote from: CirclesCenter on January 10, 2007, 10:50:41 PM
5th on the freeway: Alleviate the problem? Possibly... Accelerate wear on internal components? Yes.

accelerate wear?...pssh...ive checked the rpm vs. mph chart here in gstwin....even in 4th you can run 90mph with the redline just starting...5th good 7k-9k rpm...not too bad....6th is like 4k-5k.....5th you can accelerate on demand as well....but what do i know right

Quote from: poormanracing on January 11, 2007, 08:43:19 PM

Quote from: CirclesCenter on January 10, 2007, 10:50:41 PM
5th on the freeway: Alleviate the problem? Possibly... Accelerate wear on internal components? Yes.

accelerate wear?...pssh...ive checked the rpm vs. mph chart here in gstwin....even in 4th you can run 90mph with the redline just starting...5th good 7k-9k rpm...not too bad....6th is like 4k-5k.....5th you can accelerate on demand as well....but what do i know right

shut up you lucky bastard.....

and give me your NSR.

maybe the hoses were routed incorrectly? that's what happened to my bike

Quote from: poormanracing on January 11, 2007, 08:43:19 PM

Quote from: CirclesCenter on January 10, 2007, 10:50:41 PM
5th on the freeway: Alleviate the problem? Possibly... Accelerate wear on internal components? Yes.

accelerate wear?...pssh...ive checked the rpm vs. mph chart here in gstwin....even in 4th you can run 90mph with the redline just starting...5th good 7k-9k rpm...not too bad....6th is like 4k-5k.....5th you can accelerate on demand as well....but what do i know right

Ok I know that you aren't going to notice, but you are wrong.

So for the rest of you here's why I am right, and you shouldn't run your engine at unnecessarily high rpms.

Piston speed is measured in Feet Per Minute. (At least in the US, probably Meters Per Minute elsewhere.)  Now every piston has a given stroke, which in the case of the GS is 56.6mm, or  2.228 inches. Now for each revolution it must complete this distance (stroke) once up, and once down. Giving us  4.456 inches of travel per revolution.

Now in 4th at the 11,000 rpm red-line of the GS500 (As PoormansRacing recommends.) you are completing that distance 11,000 times per minute. Giving you a piston speed of 4084.67 FPM.

At that speed you have 7658.75 G's acting on your pistons. Stop, wait, let that sink in 7,658.75 G's. Done? Ok. (That's a peak load BTW)

Now just for simplicity's sake I'm just going to half that (I.E. shift to 6th and do about 65~) and also I'm really tired of doing math. You can guess what would happen a 3/4th's and so on.

At 5,500rpm you have a piston speed of 2042.34 FPM.

At that speed you have 3829.38 G's acting on your pistons. (Doesn't that number give you a whole new respect for your motor? Keep in mind this is just from spinning that fast, this does not include combustion forces.)

So obviously higher RPMS increase loads on your engine. Hence they shorten engine life.


Now as to Distance traveled by YOU on your bike Vs. Distance traveled by the pistons.

At 60~ mph (5,500 in sixth give or take a margin) Your pistons are traveling 2042.34 FPM, and at 60 mph you are traveling 5280 FPM.  A ratio of 2.585 : 1

Now at 90mph and 11,000 rpms Your pistons are traveling 4084.67 FPM, while you are traveling 7,920 FPM A ratio of 1.939 : 1

(Yes I realize I am totally disregarding combustion forces at the moment, but for the current discussion they are irrelevant as we are talking about a flat stretch of road with no headwind. Granted they would play a large part but that is a lot of math that would only FURTHER prove my point. Especially if we include valvetrain dynamics...)


So let us say we both go on a journey. PoormansRacing on his 11,000rpm 90mph ride and me on my 5,500 rpm ride. Covering 90 miles.

PoormansRacing's pistons will have traveled 245,080.2 feet. Experiencing 7658.75 G's

My Pistons however will have traveled 183,810.6 feet. Experiencing 3829.38 G's

Now that result is doubly in my favor! We will both experience those peak loads (respectively of course) twice per revolution! So not only are my pistons experiencing less load, they are experiencing it less times!

(If you disagree with me I recommend taking remedial math classes.)

(No seriously, I'm not joking.)

CC... if you weren't a man, I'd love you!

You should have seen my thread about Nitrous on the Camaro forums.

You would have cried.



BTW back to the topic:

Don't listen to less informed parties.
Try PRIME on the freeway.
Clean out Carbs.
Replace parts as necessary.


(In that order.)

Lets go play some blackjack, CirclesCenter. 

so all those time i was wearing out the purple monster  ......i guess those thieves deserve her more...

I almost tore down the tank and fuel system, then discovered that the fuel shuttoff under the tank was not properly aligned to fully open. This could be a common situation, because anytime you remove the tank or shut it off, you run the risk of not opening the valve completely or, overshooting the "perfectly inline" configuration of the valve, thereby reducing peak fuel flow. This will cause it to starve at high speed.

I had that problem a couple of times.  I think the posters at the beginning of the thread were correct.  When I took the suggestion to switch it to gravity feed it solved the problem.  Matter of fact, I rode like that from then on, just remember to switch it back to the normal position when youre not riding.  Anyway, that solved the stalling out problem...try it...there isnt a simpler fix for the problem.