'81 XJ550 idles then spills oil/gas EVERYWHERE. Any help?

I bought this bike August 2016, a 1981 Yamaha XJ550. It is my first bike and I had a great time with it until winter set in. There are times the bike has sit in freezing temperatures under a waterproof bike cover for a month at a time with a full tank of gas and seafoam (is that how I should store the bike?). I would take the bike out every now and then to make sure it was still in working order. I took it out a month ago without any problems until recently...

I went out one day and the bike was turning over and would idle for a short time then stall out. After keeping at it for a while (and killing my battery), I got it to idle but as soon as I pulled the throttle the bike would stall out again. Then suddenly I noticed copious amounts of a gas/oil mixture pouring out from underneath the bike. I tried troubleshooting where the fluid was coming from and removed the air filter, then started the bike up again. Once I got it to idle, I pulled the throttle and found that there was a stream of the gas/oil mixture squirting from the carbs to where the air filter is located. I pulled the battery and got it on the charger, then cleaned the air filter with soapy water and let it dry out. The next day, I reinstalled the air filter and tried to get it to turn over. Lots of ignition action but no idle. I removed the air filter and tried starting it again to see if there was gas/oil squirting and all in a sudden the bike backfired with a loud POP that sounded like a shotgun going off. I thought maybe the bike was sucking too much air so I put the air filter back in and tried again. With the air filter re-installed, the bike backfired again with a loud POP, this time with a flame of fire coming out of the exhaust. Then the bike started smoking as if it were on fire.

1st Repair Attempt - Replace Spark Plugs
I got online and researched the symptoms and found some info that suggested to replace the spark plugs. So I went to the store and got some NGK replacement plugs and installed them. The old plugs were completely black. I also noticed that I was suddenly extremely low on oil (since I guess a bunch of it squirted out with the gas/oil mixture?), so I added 2 quarts. With the new plugs in and oil added, I turned it over and SUCCESS! The bike hesitated at first but by carefully applying the choke I was able to get it to idle. I ran into the house and grabbed my helmet, thinking I would take it for a test run around the neighborhood. As soon as I hopped on and pulled the throttle, the bike stalled out again, just like before. I got the bike to start back up and idle with the choke, pulled the throttle and---nothing---stalled out again. There was a noticeable loss in power when I pulled the throttle. Then I heard what sounded like a waterfall, looked down at the ground and once again, more gas/oil was pouring out from the bottom. I was back to where I started and very frustrated.

2nd Repair Attempt - Clean Carbs
After doing more research and watching a bunch of your videos, all signs were pointing to carbs carbs carbs. So I pulled out my iPad and with my carbs removed, followed your careful instruction side-by-side as I watched you explain how to clean the carbs. I probably spent a total of 2 hours just cleaning the carbs (4 hours total with removing and reinstalling). I surveyed the function of the carbs butterfly valves, choke plungers, and diaphragm slides after cleaning:

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I'm new to motorcycle mechanics so I wasn't exactly sure what I was looking for, but everything seemed to be functional. I was proud of my work and ready to re-install and get back on the road. The next day, I pulled the recently replaced spark plugs and found they were black yet again after the 1st repair attempt failed so I cleaned them with a brass wire brush and carb cleaner. The black plugs with zero miles on them made sense to me as during the 1st repair attempt I was backfiring a lot. Then I put the carbs back in. I got the bike to fire up, and the same exact thing is now happening... the bike only idles with the choke and as soon as the throttle is pulled the bike dies. I let the bike idle for about 5 minutes thinking maybe it would run better after the engine is warm. With the engine warm, I was able to turn the choke off and get the bike up to 5,000RPMs. A few seconds later, another waterfall of a gas/oil mixture was at my feet.

Searching various threads and forums online, the potential issues I've found are:

1) One or some of the floats are stuck open (even after cleaning?)

2) The crankcase is full of the oil/gas mixture (possibly caused by either a failed petcock or by leaving the petcock on prime and the engine was flooded with gas?) and needs to be emptied then refilled with oil. After draining the crankcase, it will no longer be overflowing with excess fluids.

Any advice?

 

Fuel leaking past float needles. Don't bother with just cleaning. 30 year old rubber parts need replaced.

http://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/

http://www.xjbikes.com/forums/threads/the-secret-life-of-carburetors.14751/

 

first adding 2 quarts of oil is excessive



check your inbox I have 2 files uploaded on rebuilding and cleaning your 550 carbs


sounds like your oil was blowing out the overflow breather tube into the airbox then out the drain


also when first filling the carbs you may want to tap on the bowls with a screw driver handle incase floats were sticking

 

Thanks for your reply (and the inbox files)! I added 2 quarts of oil because it spilled 2 quarts out when it was leaking everywhere as originally described. I tried the "tapping on the bowls with a screwdriver" trick and that didn't work. I'm not sure what you mean when you say that oil is blowing out the overflow breather tube and into the airbox then out the drain. What would cause that to happen? And why would my carbs need to be cleaned again after I had already done it? Are you suggesting they weren't cleaned properly? I don't understand how a little varnish deposits would cause all of these problems.

 

where was your oil leaking from?
the motor is sealed except for the crankcase breather tube which connects to the air box.
unless seals at shifter and output shaft are leaking
are you using the sight glass on the clutch cover to check your oil level with bike on center stand?

your oil leaked out because
1 the crankcase filled with gas
2 due to internal pressure caused by piston blow by the rings,

the carbs have 3 circuits in them
enrichment (choke)
Pilot jet
Main Jet
all need to be removed and cleaned.
it is likely that your needle valves which are connected to the floats are not sealing properly causing flooding out of the air jet at intake side of carb or at main jet slide needle. or possibly out of the 2vent holes you see when looking at back of carbs.

you will also need to check the wet set of the fuel levels.
look at this link for cut aways of the carbs and the tiny passages that need to be cleared

Something New, Something Naked

 

if the floats are leaking or not doesn't matter because the fuel petcock is. if the fuel shut-off actually shuts the fuel off, all that will happen is the line will drain
past a leaking float and you might never notice that.
the job of the floats and needle valves is to keep the gas at a level the carbs can work at. so if the valve goes "open to closed to open" or "open to leak to open"
doesn't matter just so the fuel level stays right while it's running. once the bike is off the petcock should shut the gas off.

 

I had that issue years ago with my xj550. It was a faulty petcock. Vacuum side was pulling gas and dumping a full line of fuel into the one carb. New petcock solved the issue and has been good ever since.

 

About to either rebuild or replace my petcock---any advice between the two?

 

Rebuild takes more time, but is less expensive.

This is a two-player party though. If the float needles were not leaking the fuel would never get into the carbs, even with the petcock left on prime (full open all the time).

 

Well, friends... I have an update. I brought the bike to my local mechanic. He rebuilt the carbs by replacing the float bowl gasket, float needle, and float seat. We found aftermarket K&L parts on eBay for $80 (set of 4). He was able to preserve the main and slow jets--he thought it was best to keep them OEM since they weren't badly worn. The bike runs like a charm now. Thanks for everyone's input and feedback!

 

Wait! Don't do that . . .

Nor that!

Well that is good news - we (they) are always here to help out.

 

To winterize you need to use a fuel stabilizer like Stabil ... Seafoam will NOT stabilize the ethanol we are stuck with after as little as 2 weeks on non use gas will break down and turn the inside of carbs to peanut butter it will gum up the passages , when this happens it means a FULL (read church of clean) tear down and soak . Spray cleaner will NOT work in most cases . For overhaul kits use xj4ever ... he has the butterfly seals , and CORRECT needle and seat kits . some of these K&L kits are a "Universal" type might work, might not. I highly recommend the solid brass tipped needle over the vitron tip , 2nd season since church and have not has to touch carbs.

 

Keep an eye on things. He did not replace the throttle shaft seals, or the fuel rail o-rings. Both are old, and will eventually fail (much sooner than you might think).

 

That is why as the original owner of my XJ550 it has only seen one tank of alcohol/gas mix, when I had no other choice on the road. It was only in the cycle for 2 hours as I went down the road.

The dealer warned me, never use "gasohol" as it was called back then as it would destroy the rubber parts and gum up the carb. Using straight gas has helped me avoid all kinds of problems with the carb seals, rubber gaskets, etc.

 

Oooh boy----/ hopefully you don't have more issues .......

 

My point does not matter if you run non alcohol fuel or not you need a fuel "stabilizer" Seafoam is a good product , I use it too ... BUT I do not rely on this over the winter, I use a mix 50/50 Marvel mystry oil/Stabil the oil keeps seals from dying out .

 

That's why I use premium gas, no ethanol in chevron 94 for storage and still potent after 3-4 months with fuel stabilizers. They use a separate nozzle at the pumps for 94 unlike lower grades that "may" contain ethanol

 

the pumps say UP TO 10% you're only going to get 10% when ethanol is cheap and crude is high, follow the money