Fuel in oil system

So I just got an '82 XJ750 Maxim project. I got it real cheap and not running. I was told that it ran before it was parked. I charged the battery so I could find out what happens when I turn the engine over. Note: the gas tank was empty.

What happened: A fuel oil mixture started gushing onto the floor of my garage.

Upon inspection: The fluid was being pumped from the gearbox into the carburetor manifold and spilling through the airbox onto the floor.

Upon further inspection: My bike does a neat trick! You can put fuel in the tank and drain it right out of the oil drain.

Questions: WTF? Does anybody have any experience with this? Did the guy who sold it to me neglect that it ran until he creatively re-plumbed the bike? When do I cut my losses?

Thanks everybody!

 

BBucket:

You've just experienced a common XJ event.

Either your petcock has been left on "Prime", which should never be used except for the initial filling of the carburetor float bowls after they've been run dry, OR

you have a malfunctioning petcock in need of repair.

When the petcock is set on "Run" or "Reserve", it should only flow fuel when the engine is running.

To check this, set the petcock to "Run" and unhook the fuel line to the carburetors.

If fuel runs/drips out, your petcock is not working properly and needs repair/replacement, which is not exceedingly expensive.

Search the archives for "petcock" and you'll find plenty of previous posts.

Good luck!
Herb

 

BBucket:

Sorry -- also wanted to clarify that the fuel is not being pumped from the crankcase to the airbox, it's actually flooding the carburetor floats, with some then running backwards into the airbox, and some forward into the engine.

Herb

 

Actually the fuel oil mix could be pumped into the airbox via the crankcase vent tube if the crankcase is overfilled with the fuel oil mix. Still not a real big deal. Fix the petcock and then start rebuilding the carbs. For the fuel to leak out of the carbs it has to get past the float valves. Since the bike has been sitting up I suspect the float needles are dried out and need replacement.

 

Blue:

Thanks for correcting my oversight. I failed to note in BB's post that it first occurred when he turned the engine over.

Regards,
Herb

 

Time to yank the carbs, fuel petcock and oil filter. Clean all 'till shiny, replacing little rubber bits (yes, this will cost you a bit of dough, but not badly). See Rick's guide in the forum section for help. Install parts and new air and oil filter. Replentish oil. Give her a crank and see what happens. Be prepared to change the oil again in a few hundred miles to flush out the junk.

 

Don't get overwhelmed.
Don't try pulling the Intake Manifolds. Don't risk breaking a Cap Screw.
Push the Rubber Air Box Boots back-in to get room for carb removal.
Go slow.
Have fun.
Make it Go fast again.

 

Yup the first time that i took off my carbs i pulled the manifold boots off, got lucky of having all of the bolts come out just fine. then putting them back on i found that i did not have to take them off at all. now it only takes me mear mints to take off and put back on.

 

Wow! Thanks for all of the great input. I'll see if I can breathe some life into her this weekend. I'll let you know.

 

SHE LIVES AGAIN!!!

Thanks again.

 

*Every time you take off your carbs, you find a short cut. I takes me about an hour to remove the carbs, change an intake rubber, put the carbs back on, hook everything back up and synchromize them. I did it the other day and was on the road in an hour!
I think the first time I took them off,iti took me all day to remove, clean and put them back on. I think I can do it with my eyes closed now! >PD<

 

They're on the right track, the reason your airbox and engine will get flooded with fuel is your float needle's little rubber tip is failing to seal in the needle seat in your carb fuel bowls. Yes petcocks need a cleaning and their rubber seal replaced after many years, but the petcock is not what causes this.

If your float needle and seats are working properly you could hold 20 gallon's of gas over the carbs with an open feed line going to them. The idea is as your float raises to the desired float level, the needle pushes into the seat and seals off the gas flow, no matter if there is gravity open feed, or closed off by the petcock. Closing the petcocks will help it not drain your tank into the engine through an open intake valve, and airbox, but you still have a problem with the float needles.

Goodluck