Well left carb sucking air...
That o-ring under the plastic cap where the vacuum spigot is, is missing its o-ring or has a bad one... "Professional carbs cleaning means these are all missing" usually...
Cool.
srinath.

Nope the two o-ring seals are fine.

I had the bike in pieces again with a bike expert. The suction is fine.

The problem is when high revs for long time and then close throttle the engine dies. He thinks its because no petrol in float chamber. I've checked petrol flow from tank and ok, I connection the tank directly to the float chamber petrol tube and that didn't solve it either.

I'm stuck. I HATE the GS500.

I am no expert but from reading thru various posts in this forum I would suggest checking the float levels. Sounds like they're WAY too low.

Did you cover just the little air jet hole or the whole venturi?
Assuming that you have the carbs properly assembled and the pilot mix and sync correct, I would guess  float level or intake valve clearances.

Either way, fix your attitude first. If you think your GS is bad, wait until something goes wrong on that SV.

cheers  

Quote from: ManixI am no expert but from reading thru various posts in this forum I would suggest checking the float levels. Sounds like they're WAY too low.

To adjust the float height you have to remove the bowl from the bottom of the carburetor.
But you can CHECK the float height without taking anything apart.  See my Float Height Check page.

EDIT: Changed link from sisna.com to bbburma.net

Quote from: KerryTo adjust the float height you have to remove the bowl from the bottom of the carburetor.
But you can CHECK the float height without taking anything apart.  See my Float Height Check page.

I've got some similar issues I've been trying to sort out that I think are float height related.  So about the U-tube checking method (like Kerry's):  

I noticed that the fuel level in the tube varies depending on how much the drain screw is opened.  If it's just cracked opened, the level is lower.  As I slowly open the screw more, the level rises.  After a full turn or two, it levels off - but at that point fuel is leaking out of the screw.  I figured wide open is the correct way...  But, I wonder because when I set the level w/ the carbs apart, it's off when I check it this way w/ the U-tube method.

Thoughts?

Thanks.

There is a point that the level is stable and fuel isn't leaking... 1-2 turns. Also if it leaks you might want to check the o-ring or get a hose that fits better. Small openings are ok you just need to wail a while...and that is a pain I know sitting on your hunches.
Cool.
Srinath.

Quote from: seshadri_srinathThere is a point that the level is stable and fuel isn't leaking... 1-2 turns.

Thanks, Srinath.  So if the screw is just opened enough to let fuel into the hose, it's not enough, but if fuel is leaking out of the drain screw opening, it's too much.  Hmmm... that seems a little tricky, cause it's hard to see when the fuel starts to leak out of the drain screw.  I'll give it a go.

Quote from: seshadri_srinathAlso if it leaks you might want to check the o-ring or get a hose that fits better. Small openings are ok you just need to wail a while...and that is a pain I know sitting on your hunches.

I'm not sure I follow this part.  The "leak" comes from the drain screw opening itself, not the tube or drain hole (tube fits snug, no leak).  I didn't think the drain screw had an o-ring?

Isn't there an O-ring there... I dont remember... or have too many carbs confused. Mine and Gino's and rashads and DonD's have never leaked even at 3 turns out on the drain. So somehitng isn't right.
Cool.
Srinath.

Quote from: seshadri_srinathMine and Gino's and rashads and DonD's have never leaked even at 3 turns out on the drain. So somehitng isn't right.

Hmmm... well, I figured it was somewhat normal that it would leak at the screw.  My (possibly incorrect) logic:  The drain screw closes the drain hole w/ the taper at the end of the screw.  Once the screw is opened (taper backed out), fuel gets past the taper and drains out the drain hole.  But also, once backed out, the fuel seeps into the threads of the screw/screw hole and it leaks through.  I don't think there is an o-ring to prevent such leakage.  I seem to remember this is how the drain screw works... but I'm not certain.

JamesG is right, the SV will be a bigger prob to fix when it goes bad. Right now thats not the problem though .

I didn't know the drain screw had three settings, i've always had it screwed in as much as it would go. Hmm.

Things have changed a little since my last post. The acceleration is fine, idle will only die when bike has been at high revs for over 4 seconds (ie drained fuel in float chamber?). I'm going to check the float heights as suggested thanks.

JamesG, my intake valves have never been checked for a long time (10,000 miles +), but then I'd have more problems than just the idle dieing sometimes wouldn't I?

Lemme try the drain screw's and get back. Otherwise I'm looking at float height problem I hope.

Also, choke tends to kill the engine instantly after its been running for a little while, and placing my hand over the whole air intake on either (not just one as in my first post) carb causes the engine to die without revs going up.

OK one valve bing a little open due to clearance being too small will cause it to run bad @ idle mainly. Mine had a exhaust valve that was open... and it defintely made its idle a mess, however intake being open will blow pressure back into the intake and my cause your vaccum caps to fly off. Set the valves before trying your carbs. Exhaust valves aren't as important as intake (in terms of effect on idle) BTW mine would get better when it got hot... cos valve clearance goes up when hot letting the valve close... but depends on how much it was tight.
Cool.
Srinath.

The bike idles fine, its only when its been running and then de-rev and the engine dies, regardless of hot or cold. Don't think valves can have that effect.

Attaching a clear tube to the drain screw tube to check float level is an awesome idea.

Here's my update:

Attached tubes to drain and checked floats, they both have good levels of petrol in them.

Question. If you cover the air intake a fair bit with your hand should it get covered in petrol residue?

I am completely knackered if the valves are ok. In that case, my GS500 is to undergo painful torture.

Cover intake and hand gets soaked in gas... Normal.
OK  Your valves may still be to blame, but please check if the cables (choke and throttle) are letting them close fully when you let go. Also is the problem worse when you turn left or right.
Cool.
Srinath.