xj 650 won't start without help

Hello
A friend just got a 1981 xj 650 that was sitting for 10 years.
It is in good shape and the bike runs great when running.
The carbs where pulled and cleaned and the floats where set to 15mm
the petcock works and carbs are getting gas but the bike would not start.
this is where I enter the picture. I removed the carbs and blew air through all passageways and reassembled. Primed and no start. So I get some gas and put some in the air box and the bike starts and runs. It runs great idles perfect and you can shut it off and it starts up like new several times. Let it sit overnight and it won't start without gas in the breather.
Why is this happening?

I want to help my friend but I don't know why this would happen.

The float level could be wrong as someone else did that and told me that is what he read on some website. 15 mm?

So what do you think is the problem ?

Thanks

 

The pickup tubes for the choke are clogged. Most likley the orifice in the float bowl is clogged. You are basicly manually choking it when you put fuel in the airbox. Pull the carbs again and clean. You will need a small piece if wire to clear the hole, I pull a single strand from a small wire brush and use that.

 

I thought of that but when it starts the choke seems to work. On 3k off 1200 rpms. So it must work right?

 

Not necessarily, its adding extra air to the intake and making it run faster. Its possible some of them work. I would say at least two of them are clogged. Two or more clogged starters will make a cold engine hard or impossible to start.
Since that bike sat for 10 years its best to go through a few things.
Valve adjustment
Entire brake system, shoes and pads inspection.
Clutch
wiring connections
Make sure its safe before oy ride. Just because it works now does not mean it is safe to ride.