Hello All,
Need some help with a fuel problem. My son and I have been restoring a 1990 GS twin. I rebuilt the carbs (cleaned all of the orifices, replaced the ones that I could unscrew. New float needles and o rings......) After setting the pilot screws to approximately 1 and three quarters out from the seated position the bike will start and run without choke (on a warm day). Once warm the idle will climb (leaning out??) at that point I would unscrew the idle speed knob to try to get a consistent idle. The idle would fluctuate and eventually the engine would die. Would try a quarter turn on the screws either way and still no dice.
It seems like one and three quarters is the sweet spot for starting. Occasionally the bike would run well enough for a spin around the block, but as soon as you would pull in the clutch it would die.
Problem number two. We can't get the fuel from the tank to stop flowing, indicating a petcock problem. Could someone please explain the petcock system to me on this bike? We've gone so far as to install an inline valve to shut the fuel off to the carbs when not running. Not the best idea but we were desperate.
I've worked on a lot of cars and motorcycles in my time (55 years old) and I'm an avionics tech in my day job (28 years). So, technical things usually don't throw me. But for the life of me the fuel system on this bike is beyond me. It is almost June and I'd love to have a ride-able bike for my son. I've read the posts on this forum and have double checked float height etc. If someone would have a systematic approach to trouble shooting this I'd be most grateful.......... :bowdown:
Brian.
1.75 turns seems too little from everything I've read here. I think its more like 2.5 to 3 turns.
Petcock: what position do you have it in?
PRIME: fuel always flows from the reserve line. (bypasses need for vacuum to let gas flow)
ON: fuel flows from main line when engine on (vacuum operated)
RES: fuel flows from reserve line when engine on (vacuum operated)
The Haynes or Clymer manual is mandatory. Any year edition will cover a 1990. (I personally prefer Haynes)
Service manual and owners manuals available various places on-line if you search. The WIKI might have the owners manual. I believe it has a wiring diagram and lots of other really useful information.
The petcock lever is pointing straight down. (short end) The legend with the markings on it doesn't seem to make sense. My son bought it online. 2.5 to 3 turns is something to try.
Makes sense if I'm leaning out and the screws control fuel and not air. :thumb: I remember reading some tips in another Suzuki (might have been 750 or Katana forum) After I followed just a few minor adjustments the engine started. we are close to having a "running" machine :woohoo:
Sounds like it is not a stock petcock. Fuel stops when engine off as down is ON and the fuel is controlled by the vacuum.
Possibilities:
1. Not a stock petcock
2. Fuel hoses connected wrong
3. Petcock no good: stuck open
4. Fuel lever on upside down
The top one had the retaining clip put on backwards (photo from older thread) but in both, prime is up, on is down and reserve is sideways. Fuel lines are reserve on the right (from long tube on tank). Main is on the left and out to carbs on the back. Small hose on back is vacuum to the engine side of the left carb (89-00 models).
IGNORE THE LABELS - from an old thread with a different question.
(http://i1206.photobucket.com/albums/bb442/adidasguy/GS500/Fuel_Valves.jpg)
Thanks adidasguy!
I'm going to print those pictures. They are excellent.
The petcock we have may have been disassembled and reassembled incorrectly :oops:
(I may have done that) :icon_rolleyes:
Here are another couple images that may be helpful...
(http://bbburma.net/MiscFotos/100_1307_FramePetcock_1999_Annotated.jpg)
(http://bbburma.net/Scans/www_gs500_de_HoseRouting.jpg)
Thanks Kerry,
I visited your "general purpose" home page.
Very sweet 500, nicely done!
Brian.
Oh, by the way,
Everyone is very kind here and it is highly appreciated.
In my day job I know it is experience that separates the craftsman from the hack.
I am grateful for all of the experience that is shared here :star: :star: :star:
Quote from: sparks325 on May 30, 2012, 08:43:30 AM
Thanks Kerry,
I visited your "general purpose" home page.
Very sweet 500
Heh. The photo on my home page is of a black '96 that I only owned for a couple years. I sold it to a neighbor kid, who was talking so much when we changed the oil once that we neglected to tighten the drain bolt. Needless to say, the seized engine has been sitting in a tub in my shed for a long time now. He bought a used engine, circa '93, and got it all back together and running again. (Kudos!) The bike went to his older brother and eventually to his younger brother. Recently, the younger bro checked behind him while trying to merge onto the freeway ... just when the car in front of him hit their brakes. "Wham!" I haven't seen the bike, but I hear the forks have a bit of a bend in them. :icon_sad:
After selling the '96 I briefly owned a 2000 ... but my older brother talked me into selling it to him. So, I'm back to just my original yellow '99. I guess I need to take a new picture for my website, but I don't want to shock anyone with my older, er ... "bulkier" look. :icon_rolleyes:
adidasguy and Kerry,
Thanks big time for the info,
My son went for a ride last night (evening.....hopefully not after dark :angel: kids..you know)
for the first time in a couple of months. Of course I had the petcock *&%^(*)^(* assembled in the "not correct" way. Thanks to all of the photos and diagrams it was figured out and reassembled quickly. I had a hand vacuum tester and we were able to test the action with the engine off. It actually works quite well.
There was a fair amount of gas in the crankcase so an oil change was in order.
Cleaned the plugs and mixture screws out to 3 turns. Started and idled nicely.
The idle climbs to about 3k rpm sometimes at a stop, but will gradually settle back to 1.2k rpm or 1.5. Possible float (please comment?) (there are no air leaks between the carbs and cylinders) Other than that it is ride-able. Fork seals are next
Once again, thanks!!! :thumb: :thumb: :thumb: