I have been working on a 47 Knuck that was recently rebuilt. The engine is leaking oil badly from around the rear head. We've made a restrictor to limit the oil to the top end but it still leaks. Any suggestions as to what to look for?

WD4ITY

 

Since oil to the top end returns by vacuum to the bottom end make sure the pushrod tubes are sealed tight Other than that check the oil lines that wrap around the tin valve cover boxes Sometimes the braze cracks and as you know the valve covers are prone to leak due to the type of gaskets One more thing the oil isn't trapped in the rear pushrod tubes due to a blockage in the lifter body ? Good luck

 

Had the same problem many years ago and found that I had a cracked vavle cover next to the frame. I concluded that vibration was the source of the problem. I changed the cover and contact glued a small strip of 1/16" rubber between the two. That turned out not to be the problem although it was a good idea. The rocker arm shaft was worn enough to where the rockers would rotate higher and bump the cover on the inside. Over a period of time (I had overhauled that motor four times in 20 years of riding) the stress crack developed. Let me add some more information since I've been riding the old hogs for many years. Your heads, being iron , need as much oil as they can receive so don't restrict your oil flow to the heads. Something else to look at is restrictions in your oil returns . You have about 25,000 miles before an overhaul IF everythingis new andclose to factory spec. Other wise ride safe and change you oil every 1000 miles. Your 61 year old knucklehead is the coolest one on the block believe me .Hope this helps , Mike