How to fix oil leaks on 47 FL rockers.

[aben]

I would like some guidance on the best way to fix oil leaks on 47 FL rocker boxes, I don't know exactly where it is coming from. I have checked the timing on the breather valve and made sure that the small return lines are open. It smokes and stinks from oil leaking onto the exhaust pipes. Any suggestions would be welcome.
Ben

[knuckleheadtim]

You should start with the simple things first. Check the oil pressure with a gauge. Many of the aftermarket pressure relief springs are too heavy and cause too much oil to be delivered to the top end. You should have 30# max when you rev the motor while warm. Next, check all of the corks on the pushrod tubes for a good seal. The return system relies on crankcase vacuum passed through the lifter blocks to pull the oil out of the valve tins into the rocker boxes. Any leakage will cause serious oil buildup in the tins. They are NOT oil-tight, and shouldn't fill up to the point of leaking. There are numerous other possibilities such as worn rocker shafts (or early slotted ones designed to operate with a 6# oil pump), cracked tins, lack of vacuum and failed guide gaskets. Also, make sure the oil isn't blowing back from a leaky feed line.

[Steve Little]

Everything Tim said and check if the engine has Eastern lifters.
Eastern make good parts, but they made a batch of lifters a few years ago that had an extra hole incorporated into the design. This extra hole has caused no end of grief for so many Knucklehead owners.
The hole negates the timed vacuum to the rocker cover and the cover fills with oil and will run down onto the exhausts.
Before solving this issue on my bike, I couldn't go for a ride without someone in a car pulling up beside me and asking if my bike was on fire.
It has been said that Eastern were contacted about the issue, and their reply was that they will do nothing until their current stock has been sold.
To be fair to Eastern, this was a couple of years ago and may have been resolved now.

[aben]

Thanks Tim. What would you think about putting a restrictor in the feed line to compensate for some of these causes ? I will ask Steve this question too.

[aben]

Thanks Steve. How do I identify Eastern lifters ? What do you think about putting a restrictor in the feed line to lower the volume of oil to the rockers ?

[Steve Little]

Thanks Steve. How do I identify Eastern lifters ? What do you think about putting a restrictor in the feed line to lower the volume of oil to the rockers ?

A quick description of a lifter would be (working from bottom to top) the axle / roller area at the bottom, the main cylinder of the lifter, and the reduced spindle area at the top of the lifter, which has an internal thread for the adjuster to screw into.

Eastern lifters have a hole drilled into the radius corner at the base of the adjuster spindle. The hole was about 1/8"
This can be seen when you lift all of the pushrod covers and roll the engine over to bring each lifter to the highest point.
Look down the bore of the lifter block.
If it is an Eastern lifter, you should see a hole drilled into the area I have described.
When repairing this problem on my EL, I experimented by blocking one hole at a time. I then took the bike for a short ride. Each time, the rocker covers would fill and then push out past the sealed gasket. When I plugged the last hole, I rode the bike and no oil. I was so happy, I jumped on the bike and rode an hour into Melbourne and back home. Not one drop of oil came out past the gaskets that had previously leaked.

The reality is, if you are working on your bike with the tanks off, you can remove all of the valve covers, start your bike and the oil should be sucked back into the engine.
The valve covers are only there to stop water and dirt getting in.
1936 and 37 knuckles didn't have dust covers.

A couple more causes of your problem are
over oiling with an S&S oil pump.
Mislabeled cam cover gaskets from James a couple of years ago.
These gaskets don't seal the vacuum hole when the cam cover is fitted to the case.

[knuckleheadtim]

Good info Steve (as always). I would not under any circumstances restrict the oil flow to the rockers. If you have loss due to worn parts in one area, you will starve other areas by restricting flow. With some patience and sleuthing, you should be able to narrow it down. We can work with you if you keep feeding good information.

[aben]

Thanks Tim.
Ben

[aben]

Thanks Steve,
Ben