This is a puzzler!!! We were changing the oil the oil in my son 's K4 750 in preparation for a 2000 mile trip to Texas. We always use Amsoil 20W50 motorcycle oil. The oil had probably 2500 miles on it. There was less than a quart in the oil tank and the other 3 quarts in the sump. I knew that this could possibly be a bad leak stopper valve. We removed the oil pan and the oil pump. Both looked good with not an unusual amount of debris or contaminants.
To be on the safe side I merely replaced the oil pump with another one that I had laying around. It showed less wear and appeared fully functional. I went through it anyway, making sure that everything was clean and functioning. We primed the pump, replaced every thing and spun the engine until the oil gallery filled and the oil light went off. We than buttoned everything else up and started the bike. What happened next is the puzzler! The oil tank emptied accept for about a half a quart. As the engine was running I could see a steady stream of oil returning to the tank at what I assume was a steady flow. Since I knew the sump was now full of oil and the return oil looked a little frothy I shut the bike off. I drained and disassembled again to find that most of the oil was now in the sump.
What the hell is going on here??? He mentioned to me a couple of weeks ago that the tank looked low so he put another quart in. Point is, this has been evidently going on for some time. BTW the bike runs fantastic in all other respects.
This motor was rebuilt 10-12,000 miles ago and the sump was as clean as a whistle, no debris in the engine. There is no blockage of the hoses or oil feed galleries in the engine, The filter bypass is perfect also. The scavenge pump appears to be delivering adequate flow back to the oil tank, it just never seems to fill up. You can see a steady, strong stream while the bike runs. The engine appears to have no performance issues and ticks over quietly and pulls strong. It's last big trip was from KC to the gulf coast back in April, average speeds 75-80 mph. Help! Help! Help! This is ruining a major summer ride.
Bob H.
P.S. I posted this under the general forum also. I'm not trying to over post, this is just the first time I've posted and I'm not sure if I'm getting through. Feel free to respond to banzaibob@bobharvey.com or (816) 587-0006
