GS500 Throttle response/Back/Misfire?

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GS500 Throttle response/Back/Misfire?

Hi All,

My Suzuki GS500 commuter workhorse has started to develop a little hiccup (mainly starting from cold, but has happened after a good long run).

A few time, when opening the throttle, the engine seems to die/take a while to respond and is sometimes accompanied by a small *pop* (not really a backfire). Not the ideal situation to be pulling out of junctions from.

I've google'd it and have got suggestions from carb diaphragms mobing to dirty plugs. Anymore more expert advice would be gratefully received.

Thanks in advance for any help

Popping could be either a loose or kinked breather pipe usually petrol tank or engine.The throttle reponse could indicate a possible pinhole with carb related rubbers, either the tops of the carbs or the rubber between carb and cylinder head. Could either be a tiny hole or rubbers arent correctly attached. Is it more of a sneezing noise when you start it up?

Unfortunatly your description covers a myriad of possibles. Such as from Carbs to dirty plugs to coils breaking down to dirty fuel to dodgy HT leads etc etc I could go on but boring people is what I am good at. Has the bike been serviced? Carbs balanced, cleaned recently? Bit like looking for a needle in a haystack of needles. The workshop techs appreciate that this is not what you want to hear. But you need to be a bit more specific which is not easy we know. For example popping means burning fuel in your exhaust that has not been burnt in your combustion chamber. This suggests misfiring on a cycle which could mean bad plug dodgy HT lead and so on. See what I mean.sorry to be Doctor doom but more info is needed.And also what the bogwog above said.

First and simple check to do before you start stripping any components.It could be something as simple as water in the fuel floating around in the carby bowl's.Drain carby's into glass and see if there is any water or dirt in the system.If there is, then it's probably in the tank too.Drain and flush system and fill with clean fuel.Depending on how much junk comes out,you may have to clean out the carby bowls and blow out jets.


hi i have Suzuki GS 500 '94 and on the left bank the spark plug is black and on the right hand side the spark plug is golden brown the bike idle's perfect but miss fire's if i rew up to 5000 rpm and feels like runing only on the right cylinder but it runs on 2 cylinder's if i take the HT leads off any side it still runs the same ,but if i run it on the left bank only it idles 750 rpm and the other side only it idles 1200rpm .dose it mean my carb's need to be syncronices?

Sounds like you're checking the right things but you need to be a little clearer about the results!From the spark plugs it sounds like it's not firing properly on the left hand cylinder.Are you saying it miss-fires at and above 5000rpm, or miss-fires up to 5000rpm then runs OK? And is this with it on the stand, or out on the road?From the HT leads it sounds like you're saying:take the HT lead off the right side and the idle drops to 750take the HT lead off the left side and the idle is still at 1200.That does sound like the left side isn't firing properly, but if with the left side unplugged it still idles at 1200 rpm then it sounds like the idle speed is set very high anyway - possibly to compensate for another problem.BUT, you also say "if I take the HT leads off any side it still runs the same", which goes against the 750rpm / 1200rpm thing. So which is it?The reason I'm being pedantic is because it could be a carb problem, or an ignition problem. If it is a carb problem then unless the synchronisation is a LONG way out, I would have suspected something else. How long has the problem been going on? And how suddenly did it start? Pop back with some answers & then we'll start with cheap & easy tests / fixes & go from there.

Hi. Also have a similar ish problem with a GS500E. Starts easy on choke & runs with choke off for a while then becomes erratic at which point cold fuely air is being blown back through left hand carb. finally exhaust gets smokey then the engine dies.. filling the airbox with thick smoke.. 'new' spark plugs are both sooty.. Valve clearances are all nicely towards top of tolerance ie 0.06-7mm when measured cold.. new plugs. Compression is a little low but is consistant between cylinders & adding oil to the bores makes no difference to the compression..

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