GSX750 Starts fine but will only run on choke.

[mike mock]

My GSX750 Starts fine and runs sweetly for the first few seconds, but will only run on choke, then it gets hot and dies.

If I try the throttle it dies.
Ive cleaned the carbs, jets, blown them through, and they are well synched.

Fuel is fresh, vacuum tap works, air filter clean, plugs new...etc..

Anyone got any ideas please?
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Mike

[RhynoCZ]

Are the jets stock sizes? Is the air filter there and functional, any air leaks before the carburetors (airbox). A huge air leak = a lot of air, would explain why it only runs with choke, that makes the mixture alright enough for the engine to run, by reducing the amount of air coming into the engine.

Did you clean the idle jets, as well? How did you balance the carburetors, when the engine runs only with the choke?
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[mike mock]

Standard jets, and exhaust.
Just checked the air filter and box. All seems fine.
Nicely screwed in, snug.
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Mike

[RhynoCZ]

When you took the carburetors apart, did you take out the mixture screws and if so, when you put them back did you tune (turn) them according to what the service manual says?
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[mike mock]

Yes. 2 1/4 turns.
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Mike

[RhynoCZ]

Well, the last time I experience poor running (choke only, with backfiring into the airbox), all it took to fix was a yet another clean up and reassembly. The idle jets were still not perfectly clean, although an air compressor was used to blow through them.

Does the engine run smooth, all 4 cylinders?
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[garth]

Have you ever had it running correctly?

What are the diaphragms like?
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You ain't a has been if you never was

[mike mock]

Just taken them out for a look. They seem fine.
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Mike

[mike mock]

Sorry, yes it was running well, The tank had rusted, so I resealed it etc. and it has run well since.
Then it just started doing this weird choke issue thing..
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Mike

[jaffa90]

"""""""Then it just started doing this weird choke issue thing.."""""

The choke (jets) sound ok to me, try to find why it won`t run on the pilot jets.
Is there room for an inline filter inbetween the tap and carbs?

[garth]

Checked the bowl or gauze on the fuel tap?

Checked fuel flow of tap?

Tried running on aux tank?
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You ain't a has been if you never was

[Fizzer Thou]

It sounds as though the inlet manifold 'O' rings are split,allowing too much air into the engine.Running with the choke on allows more fuel in to compensate a little.

Not sure which model of GSX750 you mean so I found this as a guide

https://www.fowlersparts.co.uk/parts/4514505/gsx-750hfgh-h-1987/cylinder-head

Part #24 on the fiche
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