Hello again, OK so been having some trouble with my gs500e, stalling and spluttering.

This morning I got it started but noticed that it was only firing up on the LHS cylinder (RHS cold).

I removed the plugs and checked and it was sparking fine on both cylinders.

But, I have only been testing it recently with quite low fuel level in the tank, with petcock on "reserve".

So then I filled the tank up about halfway, and its started fine and tickover was fine too.

So I'm thinking it must be a fuel flow issue, like the one described here...

http://gs-500.info/index.php?title=GS_geht_nach_Vollgasfahrt_aus

This is what I originally thought the problem was, because it was originally only at higher speeds (+60mph),
but more recently at lower speeds too.

I reckon its the petcock diaphragm or vacuum leak, but would that cause only one cylinder to be running?

Thanks.

both bowls feed from the same T , so it shouldnt affect only one carb fuel delivery.

petcock vaccum port connect to left carb so this could affect only Left side.

disconnect the vaccum hose from the petcock and block it, leaving it connected to carb, leaving petcock vaccum port without hose

try on PRIME

if it fails  and you checked spark plugs andf ignition is working in both cylinders, clean carbs

also check for vaccum leaks on carbs

and check the simplest way to see if gas is getting to carbs, open drain screws of the bowls , you can connect a hose and see how fuel comes out.
if you have gas in bowls and still problems, jets are clogged

I just noticed that the pipes on my bike are wrong way around compared to the blue and red pipes on this diagram - I wonder if that could be the problem? I will have to swap them around and see what happens. Also the pipes look too narrow - it was very difficult to fit them on the fuel tap (on tank) nozzles. I should replace them with larger inner diameter pipes. (http://gs-500.info/index.php?title=GS_geht_nach_Vollgasfahrt_aus)

http://gs-500.info/index.php?title=Benzinhahn_und_Schlauchf%C3%BChrung

interchanging res and ON isn a big deal, and its easy to check each hose,  You shouldnt be running from reserve all the time, is dirty gas.

Got the pipes swapped over yesterday, and it seems to be running OK now.  the pipes are tight fit, but dipping the ends in hot water really helps to get them on. Thanks for the help and advice, much appreciated.

what is the actual height of the on/reserve level in the tank - can you tell by looking at the filter (in the tank) whether its above/below the "ON" level. I have been having further issues with the bike becoming 'boggy' (fuel starvation) at speed when the fuel is low. Started running it on reserve, and switching to ON when not in use.

You can leave it on reserve wen parking, both RES and ON are controlled by the vacuum switch.

what is the actual height of the on/reserve level in the tank?

Cant understand totally

It is 3 or 4cm , look at the fuel pickup screen of the tank petcock.it has 4 "windows" the first bottom 3 are for reserve. Then you have the bottom of the tank near the carbs ,on the sides that hug the frame, i would call them the fins or "wings" that are somehow a dirt trap by gravity,in the lowest part.only way to use tath fuel is to dance the bike while riding,and it has a sediment/grime risk

thanks - that makes sense.

I have been testing my tank at very low levels of fuel and it seems to be about 1cm deep at the top of the bottom window (on the plastic filter), where the ON level runs out. I don't know if mine is modified or non-standard but that's what I found. I have been running it around the block a few times (in the 'ON' position) and waiting for it to get 'boggy' then switching it over to 'RES' while riding - so I have tested that a few times. I have been looking into the tank with a torch to see what level its at in the tank.

I have already swapped the pipes over to the correct positions as described here... https://gs-500.info/index.php?title=GS_geht_nach_Vollgasfahrt_aus

Also it surprised me how long it takes for the fuel to run through when the bike is on tickover. If I switch it from RES to ON (while on bike is on tickover) and wait for it to run out - it took about 7 minutes! I thought it would run out of fuel much quicker than that, but thats what happened.