View Full Version : Knuckle Rocker Seals

Bill Pedalino
03-07-2010, 05:19 AM
I'm having some trouble with (I think) rocker box leaks on my '47 FL. I've always installed the rocker seals (the ones that the rocker arms pass through) with the beveled side facing out (toward the left side fo the bike). I've been installing these seals like this for many, many years and have never had a leak or any other problem. However, this one, because it's my own, is giving me trouble.

As the parts books don't show the factory's preference for installing these seals, I thought I would ask. Has anyone had a problem with these seals leaking when installed with the flat side toward the right side and the bevel facing the left ??


Chris Haynes
03-07-2010, 11:42 AM
I have a box of genuine H-D seals. There is no beveled edge on them. Both sides are flat.

Bill Pedalino
03-07-2010, 04:43 PM

You're correct, the HD seals were square on both sides. The aftermarket seals have a bevel - even the better ones like James. I always assumed that the bevel was to make it easier to stretch them over the right-side arm of the rocker arm.

In any event, I'm thinking that it doesn't make a difference what side the bevel faces, as long as the inner and outer circumferences offer a seal between the rocker box and the rocker arm and the edges of the upper and lower cups/covers press into the side of the seals. I usually use No. 2 permatex on the outer edge and white lube on the rocker arm surface of the seal and I put a little No. 2 onto the edges of the cups as well.

This has ALWAYS worker for me. But this one leaked profusely, as I used old, badly bent valve cups that I worked very hard to straighten and I even replaced the return lines. I was intent that these cups shoulf not fall into the 'For Sale' box at Oley. I concentrated on the upper surfaces of the cups which were really bad and I reshaped them. To my delight, they do not leak at all. This is a small victory, as they were really distorted and bent up. You reallly can't tell that they've been worked on from the outside when installed. Unfortunately, I did not pay attention to the bottom surfaces of the cups and that's where the leaks ocurred - three out of four leaked. Badly. I've since corrected this and all bottoms are flat.

HOWEVER, after disassembling the heads I did notice some oil on the head castings below two of the rocker seals. I wasn't careful enough during disassembly to notice if it was there before disassembly, or if it dripped out of the rocker cups when I took the heads apart. That's why I'm questioning myselfe.

THEREFORE.... I'll just re-seal everything and that SHOULD correct the problem.

03-07-2010, 08:52 PM
between the cover and the head did you put 2 gaskets under the intake and 1 under the exhaust? also i usually bolt the two halves together and touch them on the sanding disc to square them up. i know the quad seal is usually thick enough to compensate for the irregularities but some times there is a sharp edge especially on the aftermarket covers and it cuts a groove in the seal and makes it a little porous at the contact area. i wish someone made good cups that when assembled they resemble the top end of a pushrod tube for more contact surface

Bill Pedalino
03-09-2010, 10:42 AM
Yes, I do use the Two/One gasket configuration.

The facing off of the seal-ends of the upper/lower cup assemblies is a good idea - I'll start looking at that. Especially as these original cup/covers are becomming more and more disfigured.

03-09-2010, 01:34 PM
Usually any leakage in this area is caused by a lack of vacuum in the cups or excessive oil feed, not a poor seal. It would be virtually impossible to have an airtight oil cup, and in the case of the intake cups, a small bleed hole is added to eliminate vacuum from air pulled by the guides from fighting the suction pulling oil from the cups through the tubes.

If you are leaking oil, I would check the following:

1-Do you have the correct rocker shafts installed? Early shafts have a groove milled into the length and must be adjusted to limit oil feed to the cup end. These are used in conjunction with the early oil pump spring that limits pressure to about 5 pounds. The late shafts need the higher pressure pump to deliver enough oil to the cup end.

2-Are the shafts or rockers worm? If so, oil will feed to the cups faster than it is removed.

3-Are the valve guides reasonably tight (especially the exhaust)? If the exhaust guides are worn badly, you could build up pressure in the cups and force oil out everywhere.

4-Do you have tight springs and good seals on the pushrod tube? A Knuckle will leak in, not out if the pushrod tubes aren't very tight. They are ported to crankcase vacuum which is used to pull oil from the cups into the rocker boxes through the small tubes.

My guess is you are trying too hard to stop the leak instead of making sure you don't have excessive oiling or too little vacuum. If you set up a pressurized oil tank and connect it to the rocker box feeds, you will see that there is a very minute amount of oil reaching the cup end of the rockers. The seals on the rocker box end are mainly to isolate the low pressure (vacuum) in the boxes from the atmospheric pressure in the cups. Thus, they need to be fairly tight on the rocker arms.

Steve Little
03-10-2010, 10:54 PM
Knuckleheadtim. youve got a PM.

04-05-2010, 08:42 PM
Bill: I installed the repo rocker seals with the bevel inside the rocker box or to the left. I did this so that the tins would have an even contact as they are never perfectly positiond toward that big donut. It would then be the same as the original non beveled seals since the inner side does nothing but sits flush against the retainer/stop washer.....Joe

04-08-2010, 09:05 AM
I just did a top end on my '41FL. I did all of the seal stuff(as people posted) and now have a different problem. I am fouling out the spark plugs with oil. Valve guide/valve clearance is at factory specs. Rings are new and sized to bore. I have the oil pump set to specs. It appears as if I have too much oil in the valve tins and it is not being sucked down the tubes. Any ideas would be greatly appreciated.

04-08-2010, 11:09 AM
motorpickle i have ran into this problem before and on one motor it turned out to be the motor seal being worn out so the crankcase could,nt form a vacuam. another thing you can consider is a 106-5070 high evacuation breather gear from s and s i,m going to put one in a 38 motor i,m putting together to see if it works as good as i,ve been told it does. hope this helps.

04-08-2010, 02:12 PM
Did you make sure your push rod tubes have new corks or silcone seals thoughout? The oil returns down the push rod tubes and if there is a vacum leak there then the oil can't get back to the bottom end to enter the scavenge cycle.

AMCA # 12766

04-09-2010, 09:12 AM
Rollo: new seals throughout. That's why I am cornfused. I blew out all return lines on the tins with compressed air. Same with the passages in the rocker boxes. I get good pressure and oil out of the chain oiler/breather tube. Still looking for the problem......

04-09-2010, 08:35 PM
There are some after market lifters from Eastern that have a small hole toward the top on the shoulder, they prevent oil returning from the rockers. It has the same effect as a poor seal at the rocker cups and/or pushrod tube. If you are unsure you need to pull your lifter blocks to identify this
Hope this helps

04-09-2010, 08:41 PM
I intended the above reply to Bills issue, not Motorpickle, oops

04-09-2010, 08:44 PM
There are some after market lifters from Eastern that have a small hole toward the top on the shoulder, they prevent oil returning from the rockers. It has the same effect as a poor seal at the rocker cups and/or pushrod tube. If you are unsure you need to pull your lifter blocks to identify this
Hope this helps

Bill Pedalino
04-25-2010, 07:53 PM

I have several intake valve cups and one has the small vent hole near the rocker box, two others don't. Was the vent hole a factory and/or dealer modification that came later?

Quite honestly, I've ever paid attentionto these holes until I had this leakage problem - in my OWN machine, of course.... I'm not sure about whether or not I should drill the holes in the cups that I'm now installing, as they don't have them. I understand the point about possible conflict in vacuum through the valve versus that in the return tube during the intake stroke. It seems logical and if logic this doesn't fail me, it would seem that venting to the atmosphere should not cause any harm in the intake or exhaust cups.

Because the return tube orifices must be be submerged in return-oil in order to pull the negative pressure needed to empty the cup, they should work during the up-stroke even if the top covers are left off. I assume that this was the way the earlier 'baby food jar' assemblies worked, as there was no air-tight seal. Therefore, by this thinking the vent should be a good thing.

On the other hand, one might argue that by offering no vacuum in the valve cup assembly during the down (intake) stroke, the REDUCED resistance to oil flow past the valve guide offered by the venting might cause more oil to be sucked through the valver guide into the combustion chamber. I would think that the Factory must have worked this out by trial-and-error if the vent holes were added sometime after the closed cup assemblies were added.

This is what I'm vascellating over. Anyone care to offer comment on my over-analysis. Tom Cotton - any input?