The same problem, time and time again...

[Method]

Ok right this is the only place i havent tried for advice yet.

Probably a bit silly, considering the callibre of some of the people around here so here goes:

Basically my bike seems to have had this, or a very similar problem since ive had it.

Its an intermittant fault that just keeps coming back randomly.

What happens is it appears to be running seriously flat and it wont idle. Below 4k rpm you need to keep revving the engine to get it to still fire, but when it gets about 5/6 rpm it runs allright again and the power flies (well as much as a restricted GS500 can).

Upon removing the seat there is a small puddle of fuel in the bottom of the air box.

Upon removing the airbox and running the engine there is a blowback from the carbs. You rev it up and the carbs blow crap loads out the back (towards where the airbox would be.. so that explains the puddle). When you rev is slowly through the range it doesnt appear to blowback / blowback as much, when you blip it or rev it relatively quickly you get a crap load of blowback.

My plugs are totaly black, and the exhaust is popping at the back (excess fuel i imagine).

Now i have tried multiple things to try and sort this out, ive even fitted a different set of carbs on it.

Float bowls move up and down fine, they are set at the correct level.

I have adjusted the pilot screw to where the haynes says it should be, and also tried in a load of other positions.

Airfilter is fine as i replaced it a week or two ago from one at the BMF.

The problem, as i said, is intermittant and just seems to come on randomly. I can never seem to get to the bottom of it.

So if you think you have an idea, could you please just throw it into the air (how ever silly), you might just suggest something i havent thought of / done allready.

Theres a pint in it for whoever manages to get my bike back on the road, and a box of chocolates / another pint / coke if it stays running for another 3 weeks afterwards! (eg the problem doesnt come back) !
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Full Test Dec 04... Suzuki GS500 Jan 05... Suzuki SV650 Mar 07... Gixxer 6 K5 May 08... Oh and my 'Rado
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[veeeffarr]

Transcript FTW

tR says (14:00):
is it running on both cylinders?
Method says (14:00):
yeah
Method says (14:00):
its rough on the left mind
Method says (14:00):
im running rough on the left
tR says (14:00):
have you had the carbs balanced?

[TheDonUK]

I have this quite regularly too on my GS Method. Redex Petrol additive seems to clean it up for a while... prolly a carbon build up somewhere...

[finpos]

The blowing back of fuel is the thing you need to be concerned about. May happen sometimes, but that sounds excessive. Would seem to indicate that the inlet valves are not closing in time/properly.

Milage/last time valve clearences were looked at?

finpos.

[Trixie]

Sounds like the bike is running too rich as well (i.e. too much fuel, not enough air) - probably as a result of the fuel in the airbox?

Silly question - but are you running standard jetting?
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Dead nobodies in company cars...

[Ichy]

Could be worn valve springs, at higher revs they might be struggling to shut the valves fast enough.

I'd check valve springs, valve timing and clearances first, balance the carbs next and finally check the ignition timing and advance.
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[ZRX61]

Do a leak-down test. Possible buggered inlet valve.