Suzuki GN250 surges under gas when hot

[tim3151]

Hi.I have a new bike(ghn250e)2007 year with 4500ks on the clock.The problem im having is when i go for a ride the first 20 odd minutes are ok but after that when i put on the gas it surges,splutters,almost backfires.
All i have adjusted is the throttle stop screw yet once i have it idling at a nice level(least i think its right)about 1800 odd,by the next set of lights the revs have gone back up again to about 2500 at idle.
Really would appreciate ANY help at all as need to get some practice in so i can sit my restricted licence,and am at a loss as to what to do.
Is their a air-fuel mix screw that can be adjusted?would that be contributing to the problem?
Thanks in advance for any advice,believe me,I NEED IT.

[spanner spinner]

It is allways difficult to to diagnose running issues remotely but it sounds like from your discription that there is a carb problem with your bike. Due to the time lag that it takes to show up it may be a blocked air vent in the fuel cap. Go for a ride till the problem shows up then wip the fuel cap off and listen for a intake of air into the tank, if you have a spare key take that with you to open the tank so that you can leave the engine running. see if opening the tank makes the problem go away, if it does new fuel cap time (or good second hand one) GN's also suffer from charging issues if the reg/rec is faulty the battery may be starting to either run flat or overcharge, can you borrow a multimeter (or buy a cheepy from one of the car accessories places ie supercheep)and once again go riding till the problem shows up wip the side cover off (or leave the cover at home in the first place) and test the battery voltage with the engine still running don't turn the bike off or a false reading will be displayed. You will also have to rev the bike up to the revs that it usally starts to miss to check the battery voltage at revs as well. voltage should be minium of 13.5 volts maximun 14.9 volts at all revs bike running. if it is neither of these time to strip and clean the carb. a quick check for carb problems is to pull the choke on when the bike is playing up and see if this either makes the problem go away or makes it worse if it does that is pointing to a carb problem BUT carb issues are usally there from the moment the bike is up to normal running temperature ie after a couple of minutes running.

hope some thing here helps.

[scumdog]

Sounds like it may be running too rich when running hot??

[spanner spinner]

forgot to say check the air cleaner is not blocked, or on its last legs.

[Fast Eddie]

I'v had similar issues, mine were fuel starvation problems. the fuel tap/outlet or flow from fuel tank is too slow or blocked. For the first 10/15 mins or so it would have enough fuel in the lines/carbs/floats I assumed but after a bit the limited flow from the tank couldnt keep up and it would start starving of fuel.

good luck with it.

if you want to get rid of your regulator/rec unit and your stator send me a PM haha, girlfriend just bought an 05 gn250 and getting these parts for cheap is proving tough

[JustNick]

I thought any kind of surge from a GN was a good thing?? :innocent:

[spanner spinner]

I'v had similar issues, mine were fuel starvation problems. the fuel tap/outlet or flow from fuel tank is too slow or blocked. For the first 10/15 mins or so it would have enough fuel in the lines/carbs/floats I assumed but after a bit the limited flow from the tank couldnt keep up and it would start starving of fuel.

good luck with it.

if you want to get rid of your regulator/rec unit and your stator send me a PM haha, girlfriend just bought an 05 gn250 and getting these parts for cheap is proving tough

For the reg/rec use a king quad one the only diffrence is the plug body on the end of the wiring and you can flick the connectors out of the body and fit them to your old GN one, R2 do a cheep aftermarket one your local bike shop should be able to help with one or try atv city for a second hand one. one only option with the stator is a new unit or you can get the old one rewound bit it will still cost around the $300 mark to get rewound

[tim3151]

It is allways difficult to to diagnose running issues remotely but it sounds like from your discription that there is a carb problem with your bike. Due to the time lag that it takes to show up it may be a blocked air vent in the fuel cap. Go for a ride till the problem shows up then wip the fuel cap off and listen for a intake of air into the tank, if you have a spare key take that with you to open the tank so that you can leave the engine running. see if opening the tank makes the problem go away, if it does new fuel cap time (or good second hand one) GN's also suffer from charging issues if the reg/rec is faulty the battery may be starting to either run flat or overcharge, can you borrow a multimeter (or buy a cheepy from one of the car accessories places ie supercheep)and once again go riding till the problem shows up wip the side cover off (or leave the cover at home in the first place) and test the battery voltage with the engine still running don't turn the bike off or a false reading will be displayed. You will also have to rev the bike up to the revs that it usally starts to miss to check the battery voltage at revs as well. voltage should be minium of 13.5 volts maximun 14.9 volts at all revs bike running. if it is neither of these time to strip and clean the carb. a quick check for carb problems is to pull the choke on when the bike is playing up and see if this either makes the problem go away or makes it worse if it does that is pointing to a carb problem BUT carb issues are usally there from the moment the bike is up to normal running temperature ie after a couple of minutes running.

hope some thing here helps.
Cheers for that,least ive got a couple good things to go on now,and whatdoyaknow,just happen to have a spare key and limited knowledge of me multimetre.Will give it a good spray of carb cleaner today,and then,6am tomorrow,trials will start.
Will post what develops.

[tim3151]

Cheers for that,least ive got a couple good things to go on now,and whatdoyaknow,just happen to have a spare key and limited knowledge of me multimetre.Will give it a good spray of carb cleaner today,and then,6am tomorrow,trials will start.
Will post what develops.

I dont know,thought there was some other kind of electrical problem also as was a bit tempermental on a few start ups.
So the "trial"got off to a bad start with the bike refusing to start,thought i would put me multimeter on and see what the volts were.Were normal,12.8 or so i think.SO THEN i notice that the negative lead was a little lose.Problems,solved i think.No surges this am.When i bought the bike the + was a little lose but the - was ok.I think it must have come lose the other day when i went for a ride out to phia,with lots of those dangerous corner ruts that want to skid you sideways,as it was when i was nearly home on that ride that the surge problem cropped up.
Might put a little spring washer on it hoping it will grip the allen key screw.
Thanks for all the help,ss cheers,have a good one.