I have a 1908 yamaha xj 650 maxim and i cleaned the carbs and reasembled fine, but when i hooked up rubber gas line to main feed between first and second carb the gas leaks out pretty fast. is there a small o rong in there? that maybe deteriorated?the rubber is good its leaking where the pipe goes into carb.

The only vacumn lines on a Maxim 650 is the small line from the fuel petcock that turns it on when there is intake suction. It can be connected to any intake manifold But is usually connected to cyl. # 2 left to right. The 4 vent hoses to the carb tops just hang down the back of the motor.

Spray starter into the carb intake with no choke, if she runs for a few seconds then you know its fuel starvation
clean jets & airways & blow through with compressed air

I'm guessing that the fuel block you refer to is the inner side of the petcock assembly. If this is so, the larger line is the fuel supply and connects to a swivel pipe in between two of the carburetors and feeds all four through internal piping. The second smaller hose is a vacuum line to operate the petcock and runs from one of the rubber carb mounts to the petcock. My 85' model also has four vent hoses running from the top front part of each carb back and down between each one. I hop this helps.

There are two lines coming out of the fuel petcock (shut-off valve). The small diameter one is a vacum line that connects to the top of the rubber intake located between the carb and the engine head. you should notice that all four intakes have a vacum port in this location and they should all be capped excet one - usually #2.

The second line of the fuel petcock is the larger diameter one, and is the fuel line. Make sure you install an in-line filter if it has been lost. The fuel line connects to the carb on a pipe that feeds all four carbs. The pipe is located on the lower portion of the carb, down by the float bowls. There will be a connection port between #2 and #3 (right in the middle of the carb assembly). It will be difficult to see when everything is assembled and even more dificult to reach.

yes, the breather line hooks to the petcock on the line facing the back, the fuel line hooks to the larger one. the line from the breather is actually a vacume line that turns on the fuel, without it you will not get fuel out of the petcock unless it is in the prime position.

# 1carb left 0.04+or-0.04 inches mm 1.0+or-1.0 # 2 carb right 0.08+or-0.04 2.0+or-1.0 hope this gets you there

You need to replace your floats in carbs, problem solved

you will never have gas coming from the shifter, gas only goes from the tank to the carbs then as a vapor into the cylinder for combustion. if it is gas on your shifter then it is dripping from somewhere or maybe your carb overflow tube which will exit under the bike at rear of engine. if this is the case then you have a sticky float in the carbs. turn off fuel tap and it should stop. but if you are in the USA get some Berrymans B12 fuel additive and double the dosage and run bike til hot then leave to stand overnight. this should break down any gum/varnish which is making the floats stick. if it don't then run it again and do the same. if all else fails you will have to remove carbs and take off the float chamber bowls and clean them with carb cleaner

so you have a hole in your tank somewhere. or leaky fuel **** gasket. firstly you need to find the leak. or is your gas just flowing right thru your carbs and out the overflow? shut off fuel to eliminate carbs. if it stops leaking then its probably gummed up carb floats. use Berrymans B12 fuel additive this will work into the carb and hopefully break down the gum. or strip and clean them by hand with a good spray carb cleaner. or remove air cleaner and spray directly into carb and let sit for a few days.
if it's a gas tank leak then you will have to get it lined, (liquid sealer) so long as the hole is not too big. if it is then drain and dry the tank, get it welded professionally or patch it with a filler or fiberglass and then get it sealed, i used my local radiator repair shop to het mine done.