2009 crf450r fuel in oil

[Lead Head]

The fuel tank is above the injector. Fuel will make its way through the pump's rotors and into the line. Fuel doesn't need to be pressurized to flow through an injector. I've played around with injectors before and the will flow fuel just by gravity feed. (was experimenting with fuel injecting a small briggs and stratton and I noticed the engine was still running with the fuel pump off)

Automotive fuel pumps have a check valve in them. It only allows fuel to move out, but not back in. Why? Because the pump's rotors/gears/whatever can't form a perfect seal. Without the check valve, whenever you turned your car off the fuel pressure would drop to zero as it flowed back through the pump, and the next time you go to start your car it would take a while as it would have to build fuel pressure again.

[gotwings]

Well, I can tell you from personal experience that this doesn't happen with the Honda system. No fuel gets through the pump, at all, period.

So, I say again, the crankcase cannot fill while the bike isn't running.

47 p.s.i., or no. It's only a couple of ounces of fuel in there.

Ring seal is the issue.

Either that, or aliens are putting fuel in your crankcase oil.

[pace]

I tend to think you are correct about ring seal being the issue in many of these cases. My bike only experienced fuel in the engine oil when new (< 4 hours) which was when I was riding in cooler weather in the spring.

[MELK-MAN]

Losing sight of the real problem. WHY is there so much fuel present in the first place, enough that it fills the crank case.

[Wayward Son]

if the oil capacity is under 700cc's how much fuel do you think it takes to over flow out the fill hole? looked at the dipstick on a 09/10 crf? how many times of the injector bleeding off whats in the fuel line do you think it takes to over flow the fill hole? less than you think.

people are confusing the normal fuel smell the oil gets thru the combustion process vs the overflow issue.

its 2 very different things.

[CRFPOOR]

My 09 leaks every once in a while. I check the oil after every moto and you will know if it's leaking right away, while unscerwing the dip stick it starts pouring out. I just put a new injector in while I han the engine apart putting in a new top end and the first ride it did it again. My 2010 crf250r has never done this, I am stumped. Can a petcock be installed in the line of is the pressure too much for hose clamps??????

[MOTOPHILE]

Interesting thread. So this "ring seal" issue only happens to 09 Honda 450f's? Doesn't seem likely. If so why? Could it be that some of the fuel pumps don't seal well when not operating? That in conjunction with a bad 09 injector causes the overflow? Did anyone ever measure the volume after draining? Seems like if it were that bad of a ring seal issue that there would be a noticeable decrease in performance...

[Wayward Son]

its not ring seal.