A question only a GS500E god could answer!

[Kaanan]

     I am new to GS500E's, and really all motorcycles for that matter. And I am having the damndest problems with it already. Let me explain.
     First off, the throttle response in the low rpms is horrible, you twist the throttle and it takes a few seconds for any reaction, but in the mid and upper range the throttle response is fine. Even after reving it a few times, when the RPMs fall to idle, and I give it another quick twist there is no lag.
     The second problem with it is when I am at highway speeds and put the clutch in, the RPMs don't fall immediatley. If the bike is at 5,000 and I put in the clutch, it will drop to maybe 4,500 and take about thirty seconds for the bike to wind down to 1,200. Does that mean the engine is still getting gas with no throttle?
     The third problem, and this one is really serious. I was on the highway going eighty in rush hour traffic, and out of no where the bike starts sputtering. My first thought is "great, out of gas" so I take the first exit I see and look in the tank, it looks like there is about a gallon left in there. (But I did the JB weld trick with the petcock, so I have no reserve now.) So I figure that was the problem, gas 'er up and get going on the highway again. No more than five minutes down the road it starts to happen again. Luckly I was by an exit again, but this time I couldn't keep the engine running. I put the clutch in and it died. It took about two minutes of turning the engine over, both with the choke on and off, to get it running. So I park it at a gas station and just let it run for about five minutes. Everything seems fine so I get back on the highway and the five minute trip to my final destination goes by without a hitch. My buddy and I sit down and eat for about fourty-five minutes and hop back on the bikes. The twenty minutes of highway travel go by, like before, without a problem. We take our exit and do some city driving for about ten minutes and then it happened again. Only this time it was dead. Five minutes of turning it over, checking for spark and gas, which by the way the plugs were dry, so it was not getting gas. Damn. We were stranded for about twenty minutes before some good samatarians came by with a pickup truck and offered us a ride to the gas station. We get the bike in the back and take the five minute trip, unload it and it fired right up. Long story short it died a few more times on the way home, but none were as serious as the former.
     I'm dumbfounded. We just rebuilt the carbs, did the petcock trick and still it seems there is a fuel delevery problem. So we replace the only fuel hose with some more heavy duty stuff. The inside diameter is the same, but it is thicker, because we think maybe one of the lines is kinking. Except new when we fire it up, it's still lagging in the lower RPMs. But now our new problem is backfiring.
     CAN ANYONE PLEASE HELP! I have searched and searched, but no one seems to have this exact problem! Any help is going to be much appreciated. Thank you all for your time.

[JeremyP]

Sounds like you are running LEAN. (also the GS is notorious for not having instant throttle response in the low rpms, if you want instant keep it right around 5k)

and your other problem, if it only happens at high speed, then it is "high speed fuel starvation". you might want to check the job you did on the petcock

GOODLUCK!

EDIT: oops lean not rich 

[ben2go]

If you modded the petcock to eliminate the vacuum part,you should still have reserve.You are only eliminating the vacuum action and turning PRI into an off.The rpms hanging is a lean condition.This could be dirty carbs,bad jetting,vacuum leak,or air leaks around the air filter,air box or air box connections to the carbs.The constant dying along with the other problems usually means they're some blocked passages in the carbs.I've also had bad plugs and weak ignition system do the same thing.

[ben2go]

Valves out of adjustment can have wierd side effects on the carbs.

[GSnoober]

What jetting are you using? Next, which air filter and exhaust? What condition are the carb boots in? If they're leaking air, that will cause the engine to run too lean, even if the jetting is correct...

The low RPM lag, backfiring, and "hanging throttle" problems you've mentioned are ALL classic signs of jetting that is TOO LEAN. Don't expect some magic fix for this until you've got the jetting dialed-in. Most people tend to think of "stock" as "perfect", but that isn't even CLOSE to correct. "Stock" means that is the best engineering compromise the designers could make to sell the motorcycle in a given market; here in the US, we get LEAN carbs and JUNK front and rear suspension, while the rear disk brake is a bit of overkill... a drum brake would work just fine, and save some weight, but "real" sportbikes have discs on both ends, including the GSX-R line, so Suzuki wanted to keep discs in the family..

Have you looked at the spark plugs? If they're not sooty, then you're NOT running rich; if the insulators are clean / white, you're TOO LEAN. If they're chocolate colored, then you're in the ballpark with the jetting. If they're BLACK or oil-fouled, bad things are happening, and you need to stop running the engine until you figure this out...

Answer my questions about your jetting, filter, carbs, and plugs, and maybe we can help you nail this down.

[ohgood]

Welcome, if you haven't been already.

ANd congratulations on finding two of the biggest faults of the gs right off the bat: Lean and Fuel Starvation.

Both should be easily fixed. Have you adjusted your valves yet ? what's your milage ? Do the valves (unless you have definite proof they were done) before you go messing with the carbs. yes, you're lean, if it's stock. yes, you likely have a small vacuum leak if the revs come back slowly. yes, you can find most of the problems easily.

do a search for 'float height' and it's another easy thing to check out, a little more difficult to actually check.

good luck, post your findings

[GSnoober]

Float height checks: First, on the GSTwins website:

http://gstwin.com/float_height_check.htm

and the same article on the website of the author (Kerry, one of the moderators here):

http://www.bbburma.net/FloatHeight.htm

If one site is down, you have an alternative webpage available.

Kerry' s homepage; some good information there, so check it out:

http://www.bbburma.net/index.htm

[yamahonkawazuki]

regarding the valve adjustment, ( if needed) here is kerry in all his glory walking one through it. ( i believe on ( ed_in_az's)(former member of this forum)bike


http://video.google.com/videoplay?docid=-2015554469142545363&q=gs500+valve&total=3&start=0&num=10&so=0&type=search&plindex=0

[Kaanan]

     The valve adjustment was the next thing I was planning on doing. I did find a lot about the float height adjustment, I'm assuming that has something to do with running rich/lean? Also, would the high speed fuel starvation really make my bike unstartable for ten minutes? I figured after sitting a few minutes it would start right up? And if I understand correctly, would buying the next size up in jets solve this problem?

[ben2go]

Did you try to run the bike on PRIme?The petcock is restrictive and not meant for riding.That could cause upper rpm lean conditions.Before I learned about the mod for no vacuum,I drilled out the petcock prime outlet.It's best to do the valves and then tune the carbs.

[Kaanan]

     I live in Green Bay, WI and it is raining and 35 right now, tomorrow is going to be snowy hell, but the next day is going to be quite nice. I plan on doing the valve adjustments then, and working my way from there. Wish me luck!

[ben2go]

gooder luck

[Kaanan]

     I guess it also should be mentioned that, in the first hundred miles or so, when she was working, damn was it fun! I really do enjoy the bike. Even working on it, so far has been very easy and even quite enjoyable. I am confident I can have all the troubles worked out in one, maybe two good days of working on it.
     I also want to again give thanks to everyone on this site who have helped me. It means a lot and it's nice to find these helpful forums, especially thanks to everyone for being so kind.

[yamahonkawazuki]

anytime man, our pleasure 

[Kaanan]

UPDATE: I just checked the valves and the spacing is fine. I'm both relieved and frustrated. I just also took apart my carbs and everything appeared to be working properly. I took the air filter off and the valves were sliding properly too.
     So if I was running rich/poor, how would I adjust the mixture?

[Kaanan]

     Also, I know I mentioned this but I am not sure if everyone cought it. I did block off the petcock (one hole on the selector controlled by the knob and the vacuum hose outlet) and I understand that means it could not be a cause, right?

[ben2go]

     Also, I know I mentioned this but I am not sure if everyone cought it. I did block off the petcock (one hole on the selector controlled by the knob and the vacuum hose outlet) and I understand that means it could not be a cause, right?

When you mod the petcock you should have on,res,and prime should become off.Setting mixture is a trial and error thing.The mixture screws are next to the float bowls pointing down.If your carbs have never been adjusted then there may be brass caps over the mixture screws.Second pic on this thread mixture screws are #2. http://gstwin.com/rejet.htm

[Kaanan]

     So can I just adjust the screws while I am doing my float height check, until it evens out? I am running very lean on both carbs.

[ben2go]

     So can I just adjust the screws while I am doing my float height check, until it evens out? I am running very lean on both carbs.

Yes.Just set the float height first.

[Kaanan]

     So this is whats up guys, I took than damn petcock off my bike after realizing it was the root of all my problems. Homestly, the gas merly trickled out! And I replaced ot with two valves and a T. It flows about four times better. I have yet to put everything back together, but I did hook all the gas lines up and the float heights are both correct now.