gsxr 400 gk73 carb advice

[p0gue-mahone]

Hi
I have bought a 1990 gsxr (none runner stored 5 years) which is in very good cosmetic condition but has carb problems,
on inspection 2 of the diaframs are split and one needle has worn through and snapped off(luckily it fell straight into the emulsion tube.The remaining needles have signs of wear.
So do I attempt a refurb or look for a second hand set, bearing in mind that I dont know the condition of the engine (it turns over when pushed in gear) but I have never heard it run.
Also a manual wiould be great if someone could point me in the right direction.
Cheers Ste

[Variablevalves suck]

Hi,
There was a manual available to download via the banditalley site (after signing). Its worth sorting the carbs if you can as you never know the condition of what you buy as all sets are going to be 20 years old. Wemoto do diaphrams and i think NRP can get parts or you can go factory pro. O'rings i can supply.

[p0gue-mahone]

I have now refurbished the carbs with a parts from another set of carbs and O rings from Variablevalves
But it still wont start.
The only time it will run/cough is when i either squirt some petrol down the carb throats or cover the throats while cranking the engine.
the carbs are being fed via a pop bottle and tube so no tank feed issues and there is a good spark at each plug.
If anyone can answer some of these questions it would be appreciated.
Does the airbox have to be on for the intake air to be pressurised or should it start without it ?
Does anyone know what the cylinder compression should be?
i will also need to know where the timing marks are and any other info would be a big help.
cheers Ste.

[M1KE]

Having the airbox on is a vital part of these bikes running well with standard jetting.

[p0gue-mahone]

http://i612.photobucket.com/albums/tt20 ... e/gsxr.jpg
http://i612.photobucket.com/albums/tt20 ... thight.jpg
http://i612.photobucket.com/albums/tt20 ... /carb2.jpg

I have now managed to upload some pics and am slowly making progress with the bike.
It now starts and seems to rev up to 8k smooth enough but is still being starved of fuel higher up the rev range.
The next step is to try dropping the needle clips 1 position (its central at the moment)
The problem initially was the float hight's,although I set them to 15mm (see pic for method) the bike would not run at this setting and i had to close the tabs until 13 mm.
The question I need answering now is
In the pic of the carberettor throats there are two small jets circled.
Why is fuel bleeding out of the jets on 1 bank of carbs.
Cheers in advance for any help.

ps Is the bike a gk73 because it has the single exhaust?

[Variablevalves suck]

Hi,
Its a 1989 RK model, looks very tidy. The hole on the left/center is the main air jet and the one on the right is the pilot air jet, so the left feeds air to the emulsion tube and the right feeds air to the pilot screw, if you got fuel leaking out i'd say the float valve is not sealing and the carb is flooding over. It may be worth resealing around the airbox where the carb rubbers/mounts fit in as these leak air with age and can make the bike not rev smoothly.

[GSXR400GAZ]

try setting the mixture screws back to factory settings: 3.5 turns out.