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Join Date: Nov 2007
Location: Chandler, Arizona
First things first. Unless you live at the north pole, you should be using 20w50 oil. 5w40 is to thin to provide protection for the bearings under load. It has a very low film strength compared to a heavier oil. I can't remember exactly how much oil I put in my Vulcan 750, but it seems it was very close to 4 qts. On the centerstand, you should fill it up VERY SLOWLY until it just touches the top of the sight glass (not the line cast into the case next to the sight glass) If you think you have too much oil in it, siphon out some until you see a tiny little bubble at the top of the sight glass, and leave it there. You will notice that when the engine is running there is no oil visible in the sight glass. That's because the sump is mostly empty, the oil is circulating throughout the engine. What happens when you put too much oil in an engine is the crankshaft will hit the oil in the sump. The engine will feel sluggish and very low on power. And it will blow oil out the breather. The first thing I would do is drain that 5w40 out of it, and fill it to the proper level with 20w50 oil and see what happens. If there is still a problem, it is not likely oil related. Also I always use Emgo oil filters on the VN750. I won't use anything that says K&N or Fram on it, though I don't know if there is a problem with K&N oil filters or not. Fram oil filters are junk.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike