Fuel pouring out of Muffler & Air Filter?

[arfstrom]

Hi Guys, Long time no see. Since last year I can get the bike (XS400SH 1981 Special II ((4R4)) to run. now it seems to be spilling fuel out of the carbs and into the both the muffler/Airfilter. since I can feel air being push out the muffler (right side) (Perhaps its not firing) I guess I thought I was leaving the choke on too long.

I am still hoping that the idea of an Italian Tuneup will fix everything. (Drive it faster) (how fast, I dont know, One step at a time.) Other current problems (Charging system, Headlights (same thing)) So I am going to start with the easy one first.
Tobie
XS400 (wifes Bike)

 

[bcware]

If there is fuel coming out of the muffler you've probably lost some or all of your compression; fuel washes the oil off the piston rings. Your crank case may be and probably is also filled with fuel.

You can usually smell the gas if you remove the filler cap. Another sign would be an abnormally high oil level. If it smells gassy or the level is very high make sure to drain the oil thoroughly.

If you lost compression put a tablespoon of oil in the spark plug holes and turn the motor over with the kick start several times. Make sure the bike is upright. You need new oil if it was previously gassy.

Do you have an in-line fuel filter? Do you have a vacuum (oem) style petcock?

 

[OliverB]

If fuel is leaking into the air cleaners when the bike stands for a time you most likely have a leaky fuel tap (valve) and/or float valve leak issues.

 

[bentwrench]

By the way, if you have fuel pouring on your exhaust, probably best not to run it faster. Or possibly at all.

I'm assuming of course that you aren't made of flame retardant material...

 

[arfstrom]

(Insert Bevis n Butthead nerveous Laugh) Fire Fire.....

BC- Everything is as OEM. So the vacum thing is attached. to the Carb boot to cylinder. my wife did notice something more gassy smell. since I was in there though out the process, I am not as senstive to the smell. but I will check.

Oliver? Would a hard ride fix those type of issues? fresh fuel????

Bentwrench Fire fire, hu hu... (I didnt care for the show, but I love the quote)

I just pulled the left side off, and it didn't occur to me to check for oil smell, I am going to get another stator and I will check that then, (maybe sooner)
Thanks guys
Tobie

 

[OliverB]

Oliver? Would a hard ride fix those type of issues? fresh fuel????
Tobie

Anything is possible but I wouldn't depend on it. Pull the hose end off the carb with the engine off and see if fuel drips out of the gas line. If it does, a rebuild of the fuel tap is in order. If the seat in the fuel tap is badly corroded (sealed by an o-ring) , a rebuild might not stop the leak and you may have to replace the tap.

 

[arfstrom]

I found out today after talking to a co-worker, to check for spark. sure enough, I started it up, Sounds Good, then I pulled the boot off the right side plug. No change of sound. I put that back, and pulled the left side off, and it died. So I have new plug wires to replace both of them. (new oil for the Oil change, filter).

Hopefully this will stop the fuel from leaking out the muffler.

 

[tbakic]

if fuel comes out of your air filters check float height, carbs could be overfilling with gas and back flowing out.

could b wrong here but if your pulled the plug on one side and it the motor didnt sound any different then you were probably running on only one cylinder to begin with(the one you didnt unplug) and your carb passage is probably clogged(only one cylinder getting gas, extra gas flowing out air filter) that is kinda what happened to me, fuel pouring out of air filters, as far as mufflers go idk there bro sorry

 

[faber]

I had this problem right after fueling the first time (and have had it in the past). Tap the sides of the carbs with a screw driver to make sure that if the floats are stuck they move.

After that if it's still happening float valve failure, or float heigh is wrong.

 

[cutlass400]

Had this problem too. After a day of riding and parking it in my garage, A few hours later my whole house smelled like gas, not cool. Went to the garage and found a large puddle under the bike. The entire crankcase was filled with fuel and was spilling out of the gaskets. Pulled off the air intake boots and found them filled with gas. It was coming out of the carbs then down the breather tube into the crankcase. The floats are not going to stop the pressure of 2 gallons of gas trying to get in the carb by themselves. The petcock is supposed to shut off fuel when it's not running and allows it to flow when it sees vacuum from the intake (that's what the vacuum tube running from the rubber carb mount to the petcock does). I rebuilt the petcock with a kit from ebay and haven't had a problem since.

 

[faber]

Really if your float valve is in good shape you shouldn't have a problem. You're taking a large volume of fluid down to a very very small hole, yes pressure stays the same but over a much smaller area, so that small amount of force provided by the floats is enough to prevent over-filiing (which is the whole point). Regardless as to whether or not your petcock is bad, you're still going to get overflow if your float valve has failed.

 

[BuchanZig]

I rebuilt the petcock with a kit from ebay and haven't had a problem since.

So this same thing has happened to me and I've replaced the petcock and everything but Im just wondering if there is a more thorough way to get all the gas/oil out of the crank case besides just draining it?

At present I figure Ill just drain it, put in new oil, run it for a minute or two and then change the oil again and filter as well. Sound right? or is there some old trick for this sort of thing?

 

[cutlass400]

So this same thing has happened to me and I've replaced the petcock and everything but Im just wondering if there is a more thorough way to get all the gas/oil out of the crank case besides just draining it?

At present I figure Ill just drain it, put in new oil, run it for a minute or two and then change the oil again and filter as well. Sound right? or is there some old trick for this sort of thing?

i just changed the oil and it was fine as long as you didnt run it while the gas was in the crankcase it should have settled to the bottom and come right out with the oil. If the gas was left in the crankcase long enough it could start eating up the gaskets but it should be fine. Changing it is not a bad idea though. This happened to me at least 3 times before i rebuilt the petcock and stopped it and I haven't had any problems caused by it. After all gas and oil are made from the same thing gas is just thinner and a little more corrosive.