Hello all,

Its been a while, the GS has been pretty reliable since it had some major surgery last year. However,

Riding to work this morning, (after it has been stood for about 6 weeks), it started first time, ran nicely on choke and away I went, Knocked the choke off at the usual point, and all was still well.

20 minutes after this, she sharted coughing and popping when I gave it some beans, and was struggling to idle. I could rev her at lights fine, but as soon as the engine was under load, the popping and coughing was back.

Does this sound like fuel starvation to you gus, or am I barking up entirely the wrong tree?
Do you think a carb strip and clean is needed?

It just baffles me as she was fine when she was cold, and for about 15-20 minutes she was running like she should, why would it only start when the engine was hot?

Any help appreciated........

Turn the fuel valve to Prime when riding, if the problem goes away, then yeah, it could be fuel starvation.  Possibly a vacuum leak on the way to the fuel valve?

Stock fuel tap is gone, its a simple on/off/res tap on it now. (I have had that problem in the past).

I did switch the tap to res when it started acting up, but it made no difference. (the tank is full). When I had the trouble with the fuel tap, it was acting up at high revs, now its acting up when I am pulling away, fine if I can keep the revs up.

Tank Vent Clogged (FAQ section has a how to clean)
http://gstwins.com/gsboard/index.php?topic=41061.0
If this is it, popping the fuel tank will cure the problem for another 20 minutes or so (at the current fuel level.) As fuel is used, if the vent is clogged, a vacuum builds in the tank and fuel does not flow well. Popping the cap relieves the vacuum.

Can't swear that's your problem, but it fits the symptoms well. Popping the fuel tank will either confirm or deny (it gets better for a while, or it does not.)

My theory:

Crap in the float bowls.  While riding (during warm-up) it was just floating around.  Eventually it found it's way into a jet.

I am gonna go with a clogged Jet (prolly the pilot) with a potential vac leak. The starvation thing normally doesnt affect idle. When I had the starvation issue the thing would just putter out while I was riding.

Quote from: DoD#i on April 09, 2010, 07:13:38 AM
Tank Vent Clogged (FAQ section has a how to clean)
http://gstwins.com/gsboard/index.php?topic=41061.0
If this is it, popping the fuel tank will cure the problem for another 20 minutes or so (at the current fuel level.) As fuel is used, if the vent is clogged, a vacuum builds in the tank and fuel does not flow well. Popping the cap relieves the vacuum.

Can't swear that's your problem, but it fits the symptoms well. Popping the fuel tank will either confirm or deny (it gets better for a while, or it does not.)

I think this is correct

You guys have it covered pretty well; how about water in the bowls.  Metal fuel tanks suck.

prs

update time, Sorry its been a while.

Tried riding it home with the tank cap open, no change,
Took the carbs off, no crud in the bowls or jets, all clean,
Checked the diaphragms, they are good,
Checked the intake manifolds for leaks, all good.
Checked fuel lines and filter, all good.
Good amount of flow from the tank.

put it all back together and still running crap.

Turns out the rubber cap on the right hand carb (as sitting on the bike) was split.
The one on the left carb used to do the vacuum for the fuel tap, but had been blanked off with some tube and a bolt. So i did the same to the other one and she is running well again.

Thanks for all the help guys.