Hi,
I've found that when I drive my GS at 160km(100mph) or above for to long it starts getting fuel starvation.It starts to splutter and loose speed. If you slack down for a couple of minutes you can go back up to high speed but only for a while then the same thing happens again.
I've checked all my fuel hoses and they seem fine.
I also checked the float levels with the pipe method and they seem to be inline with the gasket as suggested on this website.
Does anyone know what it could be. I'm thinking of setting the floats higher but I'm afraid it might then start overflowwing and it's quite a mess if you start getting fuel in your oil. Maybe I should try lifting my needles but I don't think that will help,
Help?
try it with the gas cap open, then try it with just the on line from the tank directly to the carbs. cap the res off. and report back here.
You're lucky, mine does it at 85..
3 miles and its *choke* *choke* **DIE**
My 98 does it too. I noticed that when I cruise on the highway at high rpms and speeds, it starts to chug and act like there is fuel starvation. I am not sure if there is a problem with the vacuum or what, because I can reach down and turn to prime (which I believe is gravity fed) and run at the high speeds and rpms with no problems.
I forgot to mention that I'm already running on prime. Minde also only makes it up to about 85mph if the tap is in on position so I usually drive on the freeway with it in the prime position but it gives the same symptoms.
I'm gonna try the cap story and see if that makes a difference cause I remember that one of my friends had a similar problem at low speeds after they resprayed his bike and it turned out that they clogged the breather pipe on the tank with paint.
1->If this solves the problem what should I do ? Where does the tank breathe?
2->If it doesn't work would it be ok for me to try and set the float levels 2 or 3 mm higher or should I try lifting the needles one notch (currently in centre position)?
My wife and I have come to the conclusion that its a good European bike, where you have short quick runs. Its probably good in big cities like New York and Chicago too. Here in southwest America where everything is long stretches of turnpike for hundreds of miles, the GS may not be such a great bike due to this fuel starvation problem.
The WRX bike will *probably* go up for sale shortly after I get the paint done.
A friend of mine does about 190kmh (about 120mph) without any troubles (on prime) and it's a '96 model so it shouldn't do that
Quote from: gerharddvsA friend of mine does about 190kmh (about 120mph) without any troubles (on prime) and it's a '96 model so it shouldn't do that
Mine is a 96..
I wonder if it has to do with the bigger carb jets..
Does your friend have a stock exhaust?
I haven't opend the carbs myself but from what I can see, everything is stock including the exhaust. Her brother has also got a GS500E with stock exhaust but it was rejetted and it can do over 200kmh(125mph) which I don't think is too bad. If I could just get hold of the mechanic that did that job and find out what size jets he used and if there was any other mods done but I still have to sort out my original problem.
Quote from: gerharddvsI haven't opend the carbs myself but from what I can see, everything is stock including the exhaust. Her brother has also got a GS500E with stock exhaust but it was rejetted and it can do over 200kmh(125mph) which I don't think is to bad. If I could just get hold of the mechanic that did that job and find out what size jets he used and if there was any other mods done but I still have to sort out my original problem.
That may be the answer then..
Odds are, with a stock exhaust, it has not had the carbs altered.
The smaller stock jets may not require the fuel feed that the larger ones do..
I have 150 mains.. The stock mains are 122.5..
That might solve your problem but my bike is still stock jets (122.5) and stock exhaust. Still original after 80K km on the clock but quite sure this is gonna change after I do my long awaited rebuild :)
In the mean time I still have to solve my problem cause it's getting a bit annoing that a chick is driving faster then me all the time :)
Check the fuel tank shuttoff valve. It has to be completely open. This caused problems for me twice, once when I failed to open it completely after a tank removal, and the second time I turned it past its fully-open position. The little screwdriver slot on the valve needs to be totally, 100% in-line with the pipe coming out of the tank (i.e. vertical).
My bike is all stock 95, w/ 950 miles on it. and I also have fuel starvation. Mine starts as low as 50 MPH !!! Its driving me crazy! I am trying new "bigger" fuel lines and a high flow fuel filter as soon as I get time to install it.. Ill let you know if it does anything :thumb:
(I also run on prime always, as I have the vacuum line disconnected)
By the way, this is a problem Suzuki should fix. This is most annoying, because I can't see the damn valve and the slot is cut at an angle so a screwdriver doesn't even work well.
The simple fix would be to turn the valve around so the slot is facing left, so you can see it and turn it easily. The only reason I can think of they did this is to discourage people from doing tuneups & air filter changes.
Keep your fuel lines as short and straight as you can get them..
Quote from: MountaineerBy the way, this is a problem Suzuki should fix. This is most annoying, because I can't see the damn valve and the slot is cut at an angle so a screwdriver doesn't even work well.
The simple fix would be to turn the valve around so the slot is facing left, so you can see it and turn it easily. The only reason I can think of they did this is to discourage people from doing tuneups & air filter changes.
If there was a kit that eliminated that valve and included a fuel quick disconnect, how much would you pay for it..
My father-in-law owns a machine shop and is always looking for little parts like this to make..
Is it worth a hundred bucks to you?
:lol:
Quote from: gerharddvsIn the mean time I still have to solve my problem cause it's getting a bit annoing that a chick is driving faster then me all the time :)
This is what I can't understand! Since this is such a well-known problem, and so many of us have it, WHY hasn't it been fixed at the manufacturing level yet!? :x
pandy :dunno:
Quote from: MountaineerBy the way, this is a problem Suzuki should fix. This is most annoying.
My old GS400 retained the fuel supply hose and vacuum hose on the tank valve instead of a frame-mounted valve. So the tank shuttoff resembled the pri-on-res valve on the GS500 frame. You could remove the tank after you pulled off the hoses, as long as you were not in "pri."
Faxxxy, I'm going to try to remove the tank as little as possible over the next 10-20 years. I plan to keep the bike 'till I auger in, since the last one gave me 27 years. I might take a look at the valve clearances every couple of years, maybe clean the K& N filter as well. No reason to touch anything under there anyway. Unlike most of the people on GSTWIN, I lost my interest in serious wrenching a lo-o-o-ong time ago. Now I just want to ride. The GS500 is as reliable as a brick shithouse, unless you decide to monkey around with the carbs.
I think what needs to happen is Suzuki reconfigure the tank fuel supply so that one can see and turn the tank valve with the seat off. Maybe they could stick a special tool in the tool kit that allows one to reach the *&^&^$^%# tank valve without inducing a hernia, charlie horse or heart attack! And send that tool out to all current owners!
Basically, for all of us, it doesn't seem as though there's a golden rule that Solves The Problem. We each just try different things until we find what works for us!
pandy :cheers:
O well Lets hope I find the problem cause I'd rather be riding it each weekend then trieng to fix another problem. This is only supposed to happen with the old bikes. Thats why I paid more and got a GS500E and not a GS550 but anyway somebody has to get the dud bike else somebody else gets it. I should just do a rebuild and get done with it cause oil consumption is a Buddha Loves You. Unfortunately it's my only transport so I can't afford to have it standing for months. Plus Suzuki spares like pistons and stuff are quite expensive around here but the saddest thing of all is that nobody on this forum lives in South Africa so I'm pretty much on my own :( but I have no intention of selling my bike. I'll fix her even if it takes forever to solve all the problems :)
Quote from: gerharddvsO wel Lets hope I find the problem cause I'd rather be riding it each weekend then trieng to fix another problem.
Buy a Honda... :lol: :mrgreen: :thumb: :cheers: ;)
:o
Ban him!!! :P
pandy :mrgreen:
Quote from: FaxxxyBuy a Honda... :lol: :mrgreen: :thumb: :cheers: ;)
So did you very carefully check to make sure that the tank shutoff valve is fully open? That means the slot in the valve is vertical.
Quote from: gerharddvs.... have to put the bike on prime at high speeds cause the little vacuum pump can't supply fuel fast enough. ...
there is no pump - gravity feed only
Quote from: mjmQuote from: gerharddvs.... have to put the bike on prime at high speeds cause the little vacuum pump can't supply fuel fast enough. ...
there is no pump - gravity feed only
This is a question I've had for some time. So the vacuum to the petcock just, what, opens a valve?
-Gavin
Quote from: gavinQuote from: mjmQuote from: gerharddvs.... have to put the bike on prime at high speeds cause the little vacuum pump can't supply fuel fast enough. ...
there is no pump - gravity feed only
This is a question I've had for some time. So the vacuum to the petcock just, what, opens a valve?
-Gavin
Exactly. In the "ON" and "RESERVE" positions gas can only flow if the engine provides a vacuum to a rubber diaphragm in the petcock. This pulls the diaphragm back (OK it is really atmospheric pressure on the other side that pushes the diaphragm) opening a passage for fuel to flow. If the vacuum hose or diphragm have a leak, or there is crap inside the valve area of the petcock then it will not open fully and you have gas starvation at high speed. Check by turning the petcock to "PRIME" which does not use the diaphragm - if that fixes your problem, then you know it is the vacuum line or diaphragm or crap in the frame mounted petcock.
If it does not solve your problem, then check the tank mounted valve - it is fully open when the slot is inline with the outlet and totally off when it is turned 90 degrees. If that is OK it may be crap on the screen inside the tank - empty the tank and take the tank mounted valve off - clean the screen and re-install.
This morning I tried driving with the fuel cap open but it still does the same.
I'm in the process of reassembling the bike cleaned all the hoses including the tap on the tank and the one with the vacuum but it seems they were all fairly clean. It did seem that the float levels were very low which by the way wasn't detected with the pipe method which I'm never using again in my life, (waste of time) I set the float as fairly high but so it doesn't overflow thru when I tilt the bike. If I still have fuel starvation I don't know.
Interesting it seems I've still got 120 main jets in my carbs and 40 pilots.
What is a reasonable size I can make the main jets without having to change the stock exhaust and where can I buy them maybe on the web (remember I'm in South Africa so they have to be able to ship to me)
Anyway I'll be testing it tonight and I'll let you guys know whats the verdict on the original problem.
I tested it his morning and it's working. I can average at about 160-170kmh for long period without any problems and on long stretches if the road isn't uphill I can drive 180+ kmh, no problem. :)
I have developed another problem and that is that my clutch is going. When the bike is hot it starts slipping but from what I hear it's not diffecult to replace and you can do it in the frame but that's another project for another day.
...
early this morning (2:30am) I warmed up the bike (gs500f 2005) for about 2 minutes, then I started riding normally in 1,2,3rd gear until I got to the freeway (empty at the time).
I had 163 miles on the tank, so I figured I still had some 20 more to go before refueling (I average 188mpg), so I get on the freeway and start accelerating.
Some fool tries to pass me while im still accelerating and I let him know that I mean business by leaving him behind and reaching 90mph.
30 seconds later, when the guy is just a speck in my rearview mirror, the bike starts to sputter, I figure it's the fuel and switch to reserve and the engine dies :bs:
I'm like, "what in the name of lucifer!"
I pulled over, try to start the bike, switch to 'normal' (not reserve) and it just wont go.
Take key out, wait a second, put key back in, push starter, and it works.
I start to accelerate my way out, and after reaching some 75mph, the engine dies again :dunno:
Pulled over, repeat procedure, no go. repeat, nothing.
Finally it works, I go to my destination slowly (as in 45mph), get there, leave bike sitting for about 4 1/2 hours, go back to bike, switch to reserve, turn bike on, warm up, go to gas station, fill her up, accelerate to 80mph on freeway, and everything seems ok :?
How can I go from getting 188 miles per tank to 166 miles? is it because before I was only doing 61mph and now I go well beyond that? (75-90mph)
Mileage can easily vary by 30~50% based on how you are riding/driving any vehicle - and speed is one of the big variables in the equation.
im on a '93 and getting the same problem at just about any speed. All it takes is the bike to run for a bit. 20 minutes or so. I had it in 2 diffrent shops, both spent a number of hours but didn't charge me cuz they couldn't figure it out. they got it running better though. Then I had to go and play with it, i didn't do anything other than take the carbs apart to see for myself. Everything seemed fine so i put it back together and now i'm back to where i started. So when anyone figures it out, please post what you find.
This is now starting to happen with my '97 GS. Fuel starvation of some sort at 85 mph. Yeah, it's annoying. I think, more importantly, it's down right dangerous. Driving these SoCal freeways at 85 with extremely dense traffic around you and all of a sudden you drop 20 mph for no reason. Now you need to dodge traffic (which wont slow down of course) from in back of you. It's nuts and it's at the point right now where I'm actually driving my car to work this week. I'm going to be going through all of these previous posts tonight to see what I can take care of this coming weekend.
My commute is 27 miles each way (most of it on the freeway). I make sure I am on prime for my commute and I have no problems (most of the way running 70mph +). I to have noticed that when it is time to switch to reserve it seems as thought I still have a few gallons or gallon (it looks like alot is still in there). I can only get 2.5 to 3 in it though. :dunno_white: :dunno_white:
Quote from: mjm on July 23, 2005, 08:19:36 AM
Quote from: gavinQuote from: mjmQuote from: gerharddvs.... have to put the bike on prime at high speeds cause the little vacuum pump can't supply fuel fast enough. ...
there is no pump - gravity feed only
This is a question I've had for some time. So the vacuum to the petcock just, what, opens a valve?
-Gavin
Exactly. In the "ON" and "RESERVE" positions gas can only flow if the engine provides a vacuum to a rubber diaphragm in the petcock. This pulls the diaphragm back (OK it is really atmospheric pressure on the other side that pushes the diaphragm) opening a passage for fuel to flow. If the vacuum hose or diphragm have a leak, or there is crap inside the valve area of the petcock then it will not open fully and you have gas starvation at high speed. Check by turning the petcock to "PRIME" which does not use the diaphragm - if that fixes your problem, then you know it is the vacuum line or diaphragm or crap in the frame mounted petcock.
If it does not solve your problem, then check the tank mounted valve - it is fully open when the slot is inline with the outlet and totally off when it is turned 90 degrees. If that is OK it may be crap on the screen inside the tank - empty the tank and take the tank mounted valve off - clean the screen and re-install.
I think mjm is on the right track here. In the fuel system circuit there are two items that seem like the obvious bottlenecks; the carbs and the petcocks. If the carbs have been recently cleaned / rejetted then they're probably not the problem. It seems much more likely to me that one or both of the petcocks have accumulated some sludge in their passages that would restrict the flow of fuel at high speeds. Try removing, disassembling, and cleaning the cocks and see if you still have problems.
Hi,
You are all wasting your time the fuel starvation is on all the GS500s I suspect it was designed like that as some kind of speed or ref limiting mechanism. The only solution without modifying your bike is to put it on prime before you get on the freeway.
In the racers corner (http://www.gstwin.com/racers_corner.htm) they show a way of replacing the whole system with just a fuel cut of valve because apparently this bike has too much plumbing and I agree. Down side to both of these methods is that you loose reserve.
I usually keep an eye on my trip counter because I know more or less after how many miles I run into reserve. I was thinking of trying to modify the stock petcock in some way. Maybe drilling the whole behind the diaphragm to let more fuel pass but I'd rather find an extra one and play around with that.
I've found that if you set your floats a bit higher you can go a bit faster before fuel starvation One of my friend removed the floats completely when they were dyno tuning it. In this case the petcock regulates the flow. Just never put it on prime!(it tends to dilute you're oil:)) It then runs like hell but it's very heavy on fuel. Wouldn't recommend it unless you're into drag racing:)
Somebody mentioned to me that the old Suzuki 650 Katana had the same problem. Apparently they solved it by using the petcock from some Kawasaki (don't know which model). This petcock apparently had a larger diaphragm. I don't know if there's any truth to this maybe somebody knows?
I suspect most of these problems are related to water in the gas, caused by normal condensation; here are some suggestions on how to deal with this problem...
Drain your gas tank COMPLETELY into a suitable container; try to get every drop out of it. Then, remove the fuel chicken assembly (number 1 in the drawing) and fuel filter assembly (number 9 in the drawing):
http://www.psndealer.com/fiche/images/Suzuki/1997/Motorcycles/2104_34.gif
Next, flush the tank with some fresh gas (filter it through cheesecloth or a CLEAN disposable rag if you want to try to re-use it, to filter out the CRUD). Try to flush all the nasty junk out of the crap pockets while you're at it...
While you're doing all that, the gas you recently drained from the tank will be floating on top of the WATER that was sitting in the bottom of your fuel tank. Condensation causes water to form on the inside of your gas tank; the more air space in the tank, the more chance for condensation to cause problems such as many of you are experiencing. I don't have the time to explain the science behind this, but read this thread by V8Pinto (Topic: water in the gas) for more information:
http://gstwins.com/gsboard/index.php?&topic=20114.0
Then, read this one by red_phil:
http://gstwins.com/gsboard/index.php?&topic=13730.0
Read the entire thread, including the reply by scratch...
You have nothing to lose, and you just might solve most of your fuel-related problems by flushing your gas tank, and cleaning the fuel filter; also, make sure to check the HIDDEN "on/off" valve at the base of the fuel filter unit (number 9 in the drawing). You normally can't see the on/off switch unless you lift (or remove) the gas tank; check to be sure the valve is OPEN ("ON"). If the slot is VERTICAL, fuel will flow; if the slot is HORIZONTAL, fuel flow will be blocked. Use a large, long-shanked flat-blade screwdriver to turn the valve to the full-open (vertical) position, if it isn't already in that position.
Lastly, you can put a few ounces of rubbing alcohol, Heet, Dri-Gas, or any similar alcohol-based product into the gas tank, which will help you compensate for the effects of the condensation, but I don't think you should make a habit out of it. Gasoline is formulated to burn at a certain rate, and alcohol burns much faster; too much alcohol will probably lead to other problems down the road, since it will attack the various rubber parts and other components it will come into contact with on the way to the cylinders to be burned... you'll be much better off in the long run if you drain the tank, flush the crap pockets, and get everything set up properly BEFORE you develop holes in your gas tank (caused by the collection of condensation in the crap pockets, which are the lowest part of the fuel tank).
Hi all,
This is a very common GS500 problem -- and is caused by fuel starvation due to poorly designed or undersized vacuum petcock components.
Cal Amari, this is probably not condensation in the fuel, this is a GS500 weak point, but your suggestions are certainly relevant in other cases.
Here is a previous thread:
http://gstwins.com/gsboard/index.php?topic=20287.0
Here was my input from that thread:\
Hi there,
My 1991 GS500E had the same problem a few years ago and after much trial and error, the only thing that fixed it was buying a new replacement Suzuki petcock (the frame mounted petcock on the left side that has the lever for ON, PRIME and RESERVE). Apparently the rubber diaphragm inside the petcock degrades over time and causes the problem, which doesn't allow the vacuum petcock to flow fuel as it should.
I bought my petcock from a mail-order dealer in Pittsburgh, PA, for about $50, which was $25 or so less than the local dealer.
I'd go with a new one like I did and not try for a used part, which at some point will likely have the same problem as yours does now.
I also recommend replacing your old fuel lines at the same time to get rid of one more variable and potential trouble spot. Get 1/4" black rubber FUEL line at a local auto parts place. Be sure it is marked for FUEL and NOT for VACUUM. Fuel line is made of special materials with nylon webbing to add strength. The fuel hoses do deteriorate over the years and they are cheap and easy to fix, as well as an important safety issue. Use small hose clamps and all connections on the new hoses and you will be in good shape.
There is also a second petcock on the GS500 as you probably know, but that one is a simple fuel shut-off under the tank. There is no vacuum mechanism on that petcock, just on and off, but you have to be sure it is fully ON.
Read through the boards and do a search on fuel starvation and you will see this issue come up often for our beloved GS500s.
If you need more help or advice, just ask! :)
Good luck and I hope you get it sorted out.
Yours,
Todd
I would suggest cleaning the petcocks before spending $50 on a replacement part. When I bought my GS it had been sitting for over a year. The gas left so much sludge in the tank petcock (shut-off valve) that it would no longer flow until I cleaned it out. Here's a picture:
(http://img.villagephotos.com/p/2006-1/1133557/tankpetcock.jpg)
The yellow plastic piece is what actually flows or cuts off the gas. On my bike both passages in this piece were completely clogged. On your bike maybe they're only partially restricted, which would result in fuel delivery problems.
I had a 93 GS with 150 main jets and I never had any starvation problems, and I maxxed my GS out atleast a few times. I had the stock lines and the what not, just something to go off of, maybe try to rejet, really makes the bike run better. You might also find some unexpected things too when you in there.
PS. dont go to 150's though, thats with a K&N and V&H exhaust.
Quote from: boosdad on February 07, 2006, 06:52:51 PM
I have noticed that when it is time to switch to reserve it seems as though I still have a few gallons (it looks like alot is still in there). I can only get 2.5 to 3 in it though. :dunno_white: :dunno_white:
I have that exact same problem... I'll try cleaning the petcock today, though. I'm going in to put in 135 mains, 37.5 pilots (woulda got 40, but those were out of stock, it was 37.5 or 45). I also got 127.5 mains in case 135 leaves it too rich. UNI filter in the stock box with a V&H exhaust, BTW...
I'll see if this fixes my problem. I had my bike up to 90 today for a short stretch, and was holding 80 for a good while with no problems. It only acts fuel starved when I've got about 100 miles from a full tank of gas.
I also noticed my tank mounted petcock shutoff valve is facing the left side of the tank, whereas everyone elses faces the right... Kinda convenient, I think, but obviously the PO messed with it a bit...
Quote from: Queso on June 23, 2006, 03:06:18 PMI also noticed my tank mounted petcock shutoff valve is facing the left side of the tank, whereas everyone elses faces the right...
Interesting.
Do the fuel hoses "cross over" each other between the tank and the ON/RES/PRI switch? If not, then the ON position will drain all the way through your REServe fuel, at which point the RES and PRI positions will do nothing (because they're incorrectly attached to the ON hose).
Quote from: Kerry on June 23, 2006, 03:55:57 PM
Quote from: Queso on June 23, 2006, 03:06:18 PMI also noticed my tank mounted petcock shutoff valve is facing the left side of the tank, whereas everyone elses faces the right...
Interesting.
Do the fuel hoses "cross over" each other between the tank and the ON/RES/PRI switch? If not, then the ON position will drain all the way through your REServe fuel, at which point the RES and PRI positions will do nothing (because they're incorrectly attached to the ON hose).
Yeah, according to the clymers diagram, I got all the tubes going to the right places.
Are you talking about THIS diagram?
(http://www.bbburma.net/Scans/Clymer_FuelSystem.gif)
When the tank-mounted petcock is mounted correctly -- long tube in FRONT -- the hoses should NOT cross over each other between the fuel tank and the ON/RES/PRI switch. If the tank-mounted petcock is mounted backwards, the hoses SHOULD cross over each other.
So I ask again:
Quote from: KerryDo the fuel hoses "cross over" each other between the tank and the ON/RES/PRI switch? If not, then the ON position will drain all the way through your REServe fuel, at which point the RES and PRI positions will do nothing (because they're incorrectly attached to the ON hose).
Here's an old post (http://gstwins.com/gsboard/index.php?topic=12790.msg107879#msg107879) which may explain things a tiny bit better. :dunno_white:
I had my bike on the interstate for a total of about 4 hours today, all over 80 MPH and none of the dreaded fuel starvation.. guess I'm just lucky! yay!
*knocks on wood*
My bike did fine even at 100+ mph until I got to 116 miles from a full tank, then it acted like it was out of gas... This after running perfectly fine for over an hour at 85-90. As I slowed I downshifted, kinda bump starting before stopping, and it got me to a gas station - for another 2.5 gallon refill :mad: I'm going to do some extensive fuel system work over the next couple weekends. I want to get at least 200 miles out of a tank before I have to refill. I can make it that far if I don't use freeways, but I go on freeways all the time, so... Gotta fx itl
In regards to that post - I'm not actually running out of fuel. There's plenty left, I just can't use it at high speeds for some reason. I can't ride to even near actually needing reserve because it cuts out with over a gallon left, and switching to RES doesn't help... Yet I can start it back up with no problem to get to a gas station.
I had cured the problem completelly.
Had it exactly as the rest describe, which I couldn't live with. It is plain dangerouse for the bike dying while going 80 mph on the fast lane. So I redid the fuel system.
1) Modifyed petcock. Probably the most important step.
Petcock on our bikes is a disaster. It is poorly designed and is notorious for failing.
Here is the picutre of a gunk I pulled out from the vacuum line of the petcock:
http://culbertfamily.com/jenya/gs500/petck_dirty.jpg
Having that gunk in there would mean not enough pull on the diaphragm, hence not enough fuel flow.
However, simply removing the gunk would fix the problem only temporarely. One ought to wonder as to where all that gunk came from. I can't think of anything, but from the fuel. The diaphragm in my petcock was undmaged, no holes, nothing, which can only mean that the diaphragm leaked the vacuum around its edges.
I tried to assemble the petcock together many times, even making new gaskets for it and checking it for a vacuum leak with a pump. I could never get it hold the vacuum.
All that lead me to a decision to convert petcock from automatic vacuum operated shutdown to a manual fuel cut off, the way it is described in details in the following post with few pictures of mine:
http://gstwins.com/gsboard/index.php?topic=19363.0
2) Drained the tank and checked tank petcock. In my case, tank petcock's fuel filter was in the absolutelly clean condition, so doing all that was just for the peace of mind.
3) Replaced all fuel lines. I went on the large size of the inner diameter of the line by using 5/16 hose.
http://culbertfamily.com/jenya/gs500/petck_connected.jpg
4) Completelly disassembled carbs, soaked everything for a day in the carb cleaner, blew with an air compressor, assembled and tuned both idle mixture and synchronization.
I haven't had a slightest sign of the fuel starvation since. And I normally go 80mph all the time. Occasianally, bringing it up to over 90.
Jenya
I took out my petcock and took the screws off the back, but it was stuck together som'm fierce, and I didn't want to ruin the gasket without a spare. I'm going to try all that to a slightly lesser extent... I like those fuel lines you got, I'm going to be replacing mine soon. Do you have an additional fuel filter in any of those lines? I noticed an extra one on my bike...
Quote from: Queso on June 25, 2006, 10:04:28 PM
I took out my petcock and took the screws off the back, but it was stuck together som'm fierce, and I didn't want to ruin the gasket without a spare.
Keep in mind that it isn't possible to get any replacement parts for the petcock, including the gasket. I ended up cutting a new one myself.
Stock configuration doesn't use any fuel filters other than the one inside of the fuel tank. However, I installed a fuel filter into the line going from the petcock to carbs. I kinda felt that it may be a good idea, considering that I used JB Weld to modify the petcock and thought it would be good to prevent some of the dust that may still may be loose from traveling into carbs. I went to the auto parts store and looked at their non-paper filters. Actually, I didn't just look at them, I opened every package very quietly, so that store employees won't notice, and blew through all of them to find the one with the lowest resistance.
Jenya
Quote from: mjm on July 23, 2005, 08:19:36 AM
Exactly. In the "ON" and "RESERVE" positions gas can only flow if the engine provides a vacuum to a rubber diaphragm in the petcock. This pulls the diaphragm back (OK it is really atmospheric pressure on the other side that pushes the diaphragm) opening a passage for fuel to flow. If the vacuum hose or diphragm have a leak, or there is crap inside the valve area of the petcock then it will not open fully and you have gas starvation at high speed. Check by turning the petcock to "PRIME" which does not use the diaphragm - if that fixes your problem, then you know it is the vacuum line or diaphragm or crap in the frame mounted petcock.
If it does not solve your problem, then check the tank mounted valve - it is fully open when the slot is inline with the outlet and totally off when it is turned 90 degrees. If that is OK it may be crap on the screen inside the tank - empty the tank and take the tank mounted valve off - clean the screen and re-install.
I was getting the typical fuel starvation. On the highway at 70 MPH the bike felt like I was running out of gas. Sometimes I got around it by downshifting and giving it some more gas. A couple of times I pulled over, turned off the bike and started back up again. In addition to that, it just felt sluggish in general.
I'm glad I found this thread. I tried putting it on PRIME today and went on the highway again. I had absolutely no problems. I could even accelerate in 6th gear - obviously not quickly, but it was possible. So my next step will be to take out the frame-mounted petcock, try and clean it up and at least replace the fuel lines.
It's definitely good to know that it's not the carbs and something fairly simple.