Gas from the breather

Just got my XJ900 running for the 1st time in 8 years, cleaned out the carbs and its starts easily. When I put it to prime on the petcock and leave it, fuel pumps out of the breather tube, why is this please?

 

Prime permits gas to free flow. It is used only until the carbs fill with gas, or until gas stops flowing through the glass fuel filter.The "on" setting allows gas to flow only when the bike is running.

 

sounds like a float valve or float level issue. If the valves are in good working order, your carbs should not leak a drop even with petcock set to PRI. Most common cause is gunk buildup and/or wear of the float valve assemblies. either way, the carbs will have to come off.....

 

Carbs are off, also the starter motor as it seems to have seized. You are supposed to be able to turn it when its off the bike?

 

yes it should turn - you can also test it with a charger or car battery. Red to the stud the wire came off and black to the casing.

 

I have stripped it down, the brushes are very worn, motor turns when powered but when I add the gearing it won't, gears look OK

 

AHH, good old ebay, replacement motor fitted for £20

 

Whilst I had the carbs off, I checked them over. Did the clunk test OK, set all the float heights, refitted today.
Bike starts instantly, revs up OK but slow to rev down again. It idles alright.
If I rev to 3k it takes 2 secs to go back to idle.
Any ideas? Cheers

 

you could have throttle shaft seals leaking air, sticky throttle cable, hanging throttle slides, or worn diaphrams, or it could be your idle set too fast. what rpm is it idling at? should be around 1000 give or take a few rpm

 

Idles at 1000rpm, diaphragms looked fine, very good condition. Throttle cable is OK, would the throttle shaft seals leak after mucking around with the carbs, I didn't touch them?

 

Did you take the carbs off the rack?

 

9 years of none use can harden any rubber seals let alone its been 21yrs since the bike was produced they are just small o-rings in there.