blowing oil/petrol through air filter box/xj550

noticed petrol tap leaking? went to start bike and would not so checked spark at plugs ok after numerous attemps to start i take out plugs and they are dry,no petrol getting there,take out air filter and leave off cover, bike starts,but sounds rough then a flush of oil/petrol comes flying out?bike will only start now with cover off and only for a few secounds/ where is the oil coming from?could it be that when attempting to start,starter moter was constantly running for along period of time as bike would not fire up, any suggestions?

 

Pretty common problem geo...

#1. You either have a faulty petcock or you left on "PRI" not "ON".

#2. And, you have one or more carb float valves stuck open. BOTH problems should be addressed (rebuilds).

Willing to bet if you check your oil level, it's over filled because gasoline is leaking past your floats and filling your crankcase...DO TRY TO START YOUR BIKE UNTIL YOU CHANGE THE OIL AND FILTER...bad things can happen.

 

thanks for quick response, have ordered new fuel tap repair kit,will check carb float valves,i think i also left petcock on pri,and will also drain oil and get filter. could this all been caused by faulty/leaking petcock?

 

I guess the best way to answer is it could be a two pronged problem.
#1 No matter what you are likely to have a leaky needle seat in one or more carbs. This is the main problem which should be remedied by a carb cleaning/overhaul.
#2 If you left the petcock on "PRI", you may not have a petcock leak as "PRI" is a constant flow situation. If it is leaking in the "ON" position (can check by just pulling the line off while not running...if you see no leak leave it overnight with some sort of catch can...if it holds, no need to rebuild) a rebuild is in order.

Lastly, you must replace the oil and filter if it's contaminated...I would check this by opening the oil fill cap and smelling the oil...if it smells like gas, don't hesitate to change....just remember, until you fix the leaky float, you could very well refill the crankcase with gas all over again.

 

NO. A petcock issue only "enables" it.

You have one or more stuck, dirty, worn or mis-adjusted float valves in your carbs. The float valves in the carbs are what control fuel flow AT the carbs. If they were working correctly even leaving it on PRI would cause no problems.

While a leaky petcock should certainly be dealt with, the real issue is your carburetors.

Get a service manual, you have some work to do.

 

First off apologies if this is a load of crap as I'm still learning about the XJ

My goldwing did that when I overfilled the oil but that has a crankcase breather that fed back into the airbox for emission control

 

Not "a load" overfilling the oil certainly can do it too; and it also pumps into the airbox, plus the carbs and usually all over the ground too.

However, if the crankcase wasn't simply overfilled by the owner, the carbs dumping gas into the crankcase will cause an "overfill condition" and then the gas/oil mixture pukes out.

Very common with the XJs since their carbs are located well above the motor, especially compared to the GW.