ninjette.org - View Single Post

DannoXYZ · November 18th, 2019, 08:05 PM

The second effect takes place over time when bike is not running and I’ve seen it numerous times.

With petcock not off for whatever reason, combined with leaky float valves, petrol level fills up float bowl and continues to rise upwards. It flows out of jets, fuel-circuits and out into venturi of carbs. It dribbles down throat of carbs and down intake tract of engine.

Due to extreme duration of cams, it’s very likely intake valves will be slightly or fully open. Petrol is much, much less viscous than oil, so it has no problems getting past rings. And since there’s no combustion-pressure pushing rings outwards, ring-seal against cylinder wall isn’t that tight in non-running engine. So overnight, or over course of days, petrol continues to flow from carbs past rings and into crankcase. It continues to rise and displaces air until entire crankcase is full. You’ve got hydro-locked engine because pistons can’t move down and compress fluid.

There’s many cases of this happening, just do web search. I had it happen to my 2008 250. I picked up an ‘86 Interceptor for free in ‘88 because owner though he seized engine. Starter just buzzed and complained. Pushing-starting just dragged back wheel and left skidmark, yup seized engine. I started removing engine to swap in another. When I opened oil-drain to make it lighter, over 3-gallons of oil & petrol mix rushed out and overflowed my 3-gal drain pan.

So yes, leaky petcock combined with leaky float valves can hydro-lock engine. If you’re unlucky enough to have cylinders halfway down, they may be able to complete 1/2 compression stroke and actually ignite. Then they stop suddenly halfway down and snap some rods and shove remnants through side of engine!

November 18th, 2019, 08:05 PM	#17
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	The second effect takes place over time when bike is not running and I’ve seen it numerous times. With petcock not off for whatever reason, combined with leaky float valves, petrol level fills up float bowl and continues to rise upwards. It flows out of jets, fuel-circuits and out into venturi of carbs. It dribbles down throat of carbs and down intake tract of engine. Due to extreme duration of cams, it’s very likely intake valves will be slightly or fully open. Petrol is much, much less viscous than oil, so it has no problems getting past rings. And since there’s no combustion-pressure pushing rings outwards, ring-seal against cylinder wall isn’t that tight in non-running engine. So overnight, or over course of days, petrol continues to flow from carbs past rings and into crankcase. It continues to rise and displaces air until entire crankcase is full. You’ve got hydro-locked engine because pistons can’t move down and compress fluid. There’s many cases of this happening, just do web search. I had it happen to my 2008 250. I picked up an ‘86 Interceptor for free in ‘88 because owner though he seized engine. Starter just buzzed and complained. Pushing-starting just dragged back wheel and left skidmark, yup seized engine. I started removing engine to swap in another. When I opened oil-drain to make it lighter, over 3-gallons of oil & petrol mix rushed out and overflowed my 3-gal drain pan. So yes, leaky petcock combined with leaky float valves can hydro-lock engine. If you’re unlucky enough to have cylinders halfway down, they may be able to complete 1/2 compression stroke and actually ignite. Then they stop suddenly halfway down and snap some rods and shove remnants through side of engine!