Topic: Leaky and Smoky

[bkalasin]

Did a patial rebuild on my '72 CB750 some time ago (rings, gaskets, and seals) due to compression issues. Am now blowing what looks and smells to be gasoline from #3 tail pipe directly onto my rear wheel. After several minutes I also get smoke where pipe #3 attaches to the engine itself. Thought I had set the valve clearences properly but she doesn't sound overly efficient either. Is this my problem or do I have other gremlins? Do the rings need to seat? Carbs?- I did open them up and clean them. Why only one pipe blowing gas? Anyone care to tell me where I should start?

[Clyde]

I had a similar problem on my K0, where the 3 and 4 pipes were blowing fumes and gas.  The solution was to balance the carbs and the problem disappeared. The slides were much higher than those on 1 and 2

[bkalasin]

Appreciate the information. However, upon further inspection, I noticed that the gas is NOT coming from the pipe. Rather there is a drip from the overflow pipe to the oil tank that was routed in such a way that it dropped immediately into the end of the tail pipe and turned into a fine mist coating my rear wheel. Re-routed the overflow pipe but the gas is still blowing onto my wheel and wet, sticky substances coating your wheels are a little disconcerting. So my question is now "Why do I have gasoline in my oil tank?"

[kghost]

Could be carb sync, but I am more inclined to think your carbs are leaking and filling the engine with gas.

[pmpski_1]

kghost - What do you mean by that? How\Where do the carbs leak?

[TwoTired]

Okay, here is how to get gas in the oil supply.
1- Fuel in gas tank
2 - Petcock on or leaky petcock valve
3- one or more carburetor float valves leaky or other wise unable to stop flow from tank.
4- overflow stand pipe in carb bowl plugged or tube attached underneath carb plugged.
5- Fuel spills into carb bore and intake runner.
6- leaks past intake valve into cylinder.
7- leaks past piston rings and drips to bottom of engine.
8a- dry sump engine has scavenge pump, sucks fuel into oil tank.
8b-wet sump engine now has gas in the oil sump.

[kghost]

There ya go, TwoTired answered that.

[pmpski_1]

Thanks, makes sense. I guess my brain was a little fried last night. Long day at work