Author Topic: Fuel in crankcase  (Read 1828 times)

Dirty Steve

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Fuel in crankcase
« on: March 01, 2015, 10:28:34 PM »
Hi all...
I have a '75 CB 750 and, as the title suggests, I'm getting fuel in my crankcase. (I've hardly ridden it, by the way, and don't think I've done any damage yet.) I've replaced all the float valve assemblies (Honda brand) and the floats are adjusted and bouyant. It seems to be happening while it's running because it runs very poorly at all RPMs. It blows white smoke (not terribly noticeable), fouls the plugs, and spits soot and gas out of the drain holes in the exhaust.
And for some reason, the overflow tubes don't drain the excess fuel from the bowls, even though I made sure they were clear.
Anyway, any wisdom on this subject would be greatly appreciated!

buggiebuggie

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Re: Fuel in crankcase
« Reply #1 on: March 02, 2015, 09:08:42 AM »
You have a stuck float valve or you don't have them adjusted properly.. Did you adjust them off the bike and upside down for height above the carb body or just give it the old "eyeball" while holding them upward?

Dirty Steve

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Re: Fuel in crankcase
« Reply #2 on: March 02, 2015, 05:35:22 PM »
I had the carbs out and measured the height in millimeters above the body (26mm).
Isn't the excess gas supposed to go out the drain hose before going into the intake? I made sure they were clear.