I just had a mechanic mate take my bike for a ride.

he reckons I have a fuel delivery problem.
he reckons that the whole 4 cabs are losing power and said it's either fuel deliveryor carb. levels.

I am going to try a bike ride tomorrow with the vacuum disconnected as we took the fuel tank off and found that fuel could flow with the tap turned off.

Also, should there be a hose running from the tank underneath center back?

 

Don't understand 'underneath centre back' - running from the petcock/tap to somewhere ?
Mine has 3 hoses from the petcock - one fat fuel hose, one skinny vacuum hose, and one other -drain hose ? seems to serve no purpose - can't find where to connect it anyway !

 

I rode it again today, about 6,800 rpm is played up, It may have been a little better today with the vacuum hose disconnected.

One thing I did was slowly eased off a bit at the 6.8 and it still played up all the way down to about 6.2 then it was good, if I eased it up, it was good to about 6.8rpm.

So I have a thick fuel line connected, Vacuum hose disconnected from the back of the engine and a screw in the hose to block it. (this is the hose that goes to the fuel tap)
On the bottom of the tank, there are two pipes that look like they could take a hose, big one and a small one, both are disconnected. (no hoses I found to plug them into)

I did about 10k's (10/2+10*10% = 6) 6 miles and didn't run out of petrol (with no vacuum hose)

 

'Screw in the hose to block it' ......?
Did you remember to block the outlet for the vacuum pipe at the carb as well ?
There's a drain hose on mine which comes out next to the fuel filler cap, and runs down into a central rubber 'boot', which is an overflow....that's the only hose outlet from the tank, other than the tap....

 

I don't have a vacuum from the cabs.

I have a feeling that all my hoses are all Fuked up, can some give me a run down of what and how all the hoses should be for my 94' please. (the manual is no help)

 

These are pics from my backup set, which should be the same for your bike.....??
pic 1 is the vacuum hose connection to the side of the carb from the fuel tap, NOT the engine
pic 2 is the hoses -viewed upside down- one goes from tap to main fuel inlet (fat bugger) skinny bugger is vacuum line
other two are drain hoses. I looked up the schematics too - not much help there
I'll see if I can blow up the schematics and get a better idea.......
Tell me if this helps you......

 

Checked the schematics again Mark - 90 carbs - mine- and 93 carbs - yours -seem to be a bit different....You don't perhaps have a cracked fuel line or something which is causing your problem - a split in the fuel line would allow air in, and probably give you grief ?
Sorry mate, best I can do .......frustrating, buggermedead !

 

Mark - these photos from mine - 1990- from old carb sync photos - might add to your solution..

"Also, should there be a hose running from the tank underneath center back? " This photo - hose as above shown from top left is overflow hose from filler - drains to ground on RHS of bike.



Hose from rear of petlock above is the vacume hose - gose to side of #1 carb as on next photo...

 

Thanks, Shadow1, Naga_Thai
My cabie's are different, no vacuum on the left of 1, black plastic tops on top of the Cabs, and I have a choke mechanism not seen on your photos.

I think the tank photo would be right and show how I should do my top vacuum part.

 

Try these - from straycat & Gonzo...