Topic: fuel overflow into oil res:

[turnenwheels]

 Hello, Got a CB750K4.  Quetion is why do I get fuel overflowing into my oil res?  Second do I need to adjust the air flow?  I live at 3600ft.  elev.  That's for your help.

[Mark M]

Can't work out what you meal by 'oil res' but any fuel overflow will be due to float problems in your carbs. either the floats are being obstucted (or leek) or the needle valves arn't seating properly. The needle valves are the likly problem. They can be worn out/damaged or cloged with crap from the tank. If the bike has been standing for any length of time, show me one that hasn't, then it will probably be rusty. Clean out the tank/Carbs and fuel line then fit a fuel filter to prevent reoccurence. If you tank is badly rusted it will need treating.

If your lucky it could just be a one off bit of grit in the fuel line - a sharp tap on the relevant float bowl may clear it. But chances are you will need to stip it all for a good clean out. 

[eldar]

The only way I know of for fuel to get into the oil is inside the cylinders. If you are draining fuel that badly you need to replace your float valves and turn your petcock off whenever you stop the bike.  You also need to clean out your overflow tubes sine this very problem is what they are supposed to prevent.

[Gordon]

Second do I need to adjust the air flow?  I live at 3600ft.  elev.  That's for your help.

I live in Denver, and the only alteration I had to make when moving here was a slight adjustment of the idle mixture screws to lean it out a bit.  Since you're way down there at 3600ft, you would probably only need a very minor adjustment if any at all.  Check the plugs and see how you're running.

[TwoTired]

It is common procedure to turn the gastank fuel petcock to off when the bike is parked.  Mark M has already addressed the float bowl system, and fuel supply as the first areas to investigate.  But, at the bottom of each float bowl is an overflow drain tube which connects to a stand pipe inside the carb bowl.  It's function is to drain off fuel when the float bowls are overfilled, so the fuel doesn't flow into the intake runners, to the cylinder, past the rings, and into the bottom of the engine to polute the oil supply.  You should check the tubes and the stand pipe for blockage that prevents them from proper function.

[turnenwheels]

Thanks for the help, I'll give your suggestions a shot and get back to you.