GSF250 runs on 3 cylinders after getting a thrashing

**Joe Harvey** · 18th September 2011, 21:30

Hey guys Im new to your site and stumbled across it googling problems with my gsf 250 bandit 9

0, a little about myself... names joe and Im a learner rider bought a bandit to learn on and do my licences on, bought it off trademe real cheap without seeing it or riding it.. big mistake

.. anywas bike started of with a little miss down in the low rpm witch was a bitch coz it would hesitate wen taking off from traffic lights and i would almost get run ova by cars behind me!! so i took it to a bike shop in new plymouth and they cleaned up my carbs.. bike ran mint for about 100 ks and started doing it again.. took it back and they did my valve clearances... the miss down low rpm range got better but then wen i gave my bike a good thrashing it would drop a cylinder on acceleration but would come right again if i took it real easy... so i took it back to the shop again... they test the coils and re wire the bike to the book.. i get the bike back and take it for anotha ride... same thing again it drops a cylinder wen i give it a good hiding... so i take it back again.. they cant fault it and say its probly my cdi unit.. so i take bike home and put a new cdi unit in!! still drops a cylinder wen i thrash it... does any1 have any idea wot the problem could be? im about ready to push it off a cliff

as its driving me nuts and costing me alot of money... im thinking its a coil my self as it seems to drop a clylinder wen hot... any help would b great

.. cheerz joe.

**tigertim20** · 18th September 2011, 22:08

hey man, firstly welcome to KB. dont take anything too seriosly, and most importantly, dont feed the trolls!!

As for your bike. testing electrical components is frankly a fucking cunt, many electrical issues are sporadic, which means that they are running fine when you test them but fail later on. The issues occurring during harder riding could be caused by heat affecting components, or electrical load causing issues as well, that could be down to a regulator, a stator, or a CDI.

Just to be sure though, (its unlikely but worth a look anyway) Take your spark plugs out, and have a look at them, they might be half fucked and due for replacement. Also check for an oily residue on them, a slight gasket leak somewhere could be causing aminor oil leak into a cylinder, that at high RPM increases in flow size enough to stunt the spark of the plug in that cylinder.

My suggestion to you is this.
1. Buy a box of piss.
2. Offer this box of piss to any KB member with a similar bike who is happy to help you out
3. go to see this KB member, and basically use a process of elimination by swapping components between the bikes, and going for a quick hoon between each change to see if you can isolate the problem causing compenent
4. drink the box of piss with your new KB friend, get drunk, bang his missus, get punched and told to fuck off
5. order your new parts, and tell your mates the black eye was totally worth it.

**F5 Dave** · 21st September 2011, 12:41

Originally Posted by Joe Harvey

. . . ! so i took it to a bike shop in new plymouth and they cleaned up my carbs.. bike ran mint for about 100 ks and started doing it again.. took it back and they did my valve clearances... the miss down low rpm range got better but then wen i gave my bike a good thrashing it would drop a cylinder on acceleration but would come right again if i took it real easy... . . .

Could be several things. Obviously changing the plug for new ones & replacing the filter if paper, or cleaning if foam is a good start to eliminate issues.

But from what you have written above makes me think it isn't the coils or stator breaking down as usually they get hot & they play up. That being said I'd also measure the spark plug caps to see if they are ~ 5-8k. Find a mate with a meter. If it is getting better if you take it easy it sounds to me like a fuel delivery issue.

ok lets talk old suzukis & aside from electrical gremlins they are also famous for silt from the inside of the tanks. Fine rust particles build up in the carb & block the pilot jets. This silt is so fine it gets through any sort of fuel filter.

First thing people do is fit a fuel filter. As I said it strains the big bits. But it also can cause a kink in the fuel line that will restrict the flow of gas to the carbs. You can get right angle filters that may help. This would mean when 'thrashing it' the fuel supply wouldn't keep up.

The proper thing to do is to seal the tank with a propriety sealer like POR & wait for it to harden properly. Then check that the tank breather hasn't become blocked, as this would. . restrict the fuel flow to the carbs especially blah blah, you see where I'm going with this.