suzuki gs 650 gt 1983

stony · L Plate Warrior Joined: 05 Jul 2010 Karma :

I'm at my wits end. Bike going like a mouse's heart. Took her out for a good one and 120 miles later she cut out. Loss of power and no rev above 4k rpm. On attempting to restart she spluttered then died.
Got her home.
Good spark on each lead. No airlock in tank and ran alternative fuel supply to prove cock and vacuum. Drained all carbs, no sh1t in the juice.
Bike now starts but wont rev above 5000. Ticks over fine. If I rev her she dies at 5000 but spray aerosol in airbox and she revs freely. Def a petrol prob or the lack of. Have blown out the fuel line to carb with compressed air and emptied carbs through vents.
This is something simple that I am overlooking.

ANY IDEAS??????

Odie · World Chat Champion Joined: 24 Jul 2004 Karma :

Try blanking off the vacum take-off, mate had the same problem, turned out that the vacum hose was dragging fuel down and into the inlet.
Also, due to age, check the diaphrams in the top of the carbs, they are prone to cracking.
____________________
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radical · Spanner Monkey Joined: 02 Jul 2010 Karma :

Op check that your tank breather is not blocked, confirm this by running the bike with the fuel cap open.

stony · L Plate Warrior Joined: 05 Jul 2010 Karma :

Tank vent ok. Ran bike on alternative fuel tank with vacuum blocked off. Still same

radical · Spanner Monkey Joined: 02 Jul 2010 Karma :

Op can you see if the slides are opening fully via the airbox ? has a choke flap possibly jammed one of the carbs? Have you tried revving the bike directly from the throttle arm on the carbs to check for cable damage?

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

radical · Spanner Monkey Joined: 02 Jul 2010 Karma :

Not sure of the choke operation on this model but if the choke flaps were closed I would say that would stop the bike from revving, has a choke cable or linkage broken causing the choke to be permanently on?

stony · L Plate Warrior Joined: 05 Jul 2010 Karma :

Thanks everyone for the replies. Carbs are (seem) ok, 1 and 4 diaphragms ok. This problem manifested at 80mph on a motorway. Choke operating ok. I t seems like fuel starvation but I have good fuel flow.
I haven't taken of the carbs yet as the airbox looks like the bike would need an epidural to get it out from behind the carbs.
Does anyone know where a manual could be downloaded??
How is the fuel from the fuel line delivered to the 4 carbs on this model (hidden under manifold).
ALL INFO GRATEFULLY RECIEVED

radical · Spanner Monkey Joined: 02 Jul 2010 Karma :

Not sure how the fuel is delivered even though I used to own one, could i suggest that you open the drain screws on all four carbs then turn the petrol tank tap on and just watch each drain as the fuel runs out into a container, just to see if fuel starvation is the problem or if the problem is isolated to just one or two carbs.