recently bought the bike. was at the dealership just prior to me purchasing to replace all rocker box gaskets. less than 200 miles later they leak again.

very minor weeping leak that puts a mist of oil on the right bag, exhaust, etc....

checked the head breather and it's not clogged and does not blow any oil. all stock 98 motor is a 12k mile hd reman that runs fantastic. line runs to the filter.

have all reciepts and in 2000 rocker leak was repaired by extended warranty.

would adding a external breather help or is this just poorly designed evo issue? not sure how an external breather would be better than the factory setup that goes to the carb, but who knows.

looks like the top gasket is weeping on both cylinders so swap will be easy, may use a little right stuff sealant.

all ideas appreciated.

 

check the tourqe on the bolts. May have loosend

 

Before replacing the gaskets, check the rocker boxes to ensure they are flat and not warped. When you replace them put them on dry. Then a breather will help prevent future problems. You have to install it in the VENT LINE that goes from the engine to the oil tank. You have to let EVO's warm up before you start riding them hard, as the cylinders "grow" about .040" in length from cold to hot sealing everything up a little more. Hope this helps.

 

First, I'm assuming you are referring to the valve cover gasket(s) since you said; "looks like the top gasket is weeping on both cylinders" SO.... I've seen the spacers slide around even though bolts are tight. I have seen aftermarket covers warped and impossible to seal and I have seen the old cork gaskets leak, but I have yet to actually find a rubber gasket leak that was not cut or incorrectly installed. But in all fairness - first time for everything and everything does need to be DRY when it goes together. I've had mine off at least 20 times over the years and I am still using the same rubbers - no leaks. (replace fibers almost every time though)

99 times out of a hundred, it's one of the fiber washers under a valve cover bolt leaking. It's near impossible to see oil at them too - usually takes the glare of a bright light. Too often the chrome flat washers are re-used too many times and they tend to get concave and won't hold even pressure on the fiber washer. Also, the oil leaking from them goes everywhere like a mist due to the turbulent action of wind under the tank, up thru the center of the covers and all around and believe me - it'll fool you as to where it's actually leaking from.

So do yourself a favor by checking them very closely first. And they really don't have to be ham-fisted to seal, actually over tightening them will cause the spacers to shift around after being run at high speeds for some amount of time. If one or more of them turn out to the culprit, you can replace the 4 on the right with hex head bolts and use copper washers. Only 2 are visible when the tank is on anyway, but if you don't like that, get some stainless steel flat washers (they are hard and won't go funnel shaped under load so easily) or some thick 6mm flat washers and ream them with a Unibit to 1/4" and use only genuine HD fiber washers. The last 4-5 sets of James I had were so hard they won't seal well.

I agree with another poster of some time ago in that they could/should have put 2 locating dowels into the design, but otherwise, if it's actually leaking up there, all the "breather" in the world ain't gonna fix it - period.
　

 

i changed them tonight, we'll see what happens. looks like most of the leaking on both cylinders is where the oil is pumped in. factory gasket is substantially smaller than the pressured oil port that brings oil to the top in. i think that is part of the problem along with harley chroming where the gasket goes.

everybody mentions putting the gasket on dry, but i trimmed it and used black rtv around the oil port since both were leaking from the same spot.

i work on a lot of cars, but never the evo engine. the rocker box is a horrible design imo.

only rode about 10 miles as i got started late, not leaking yet. was able to install without lossening or removing any motor mounts. rear cylinder needed a shortened allen on the left side which i made ahead of time. few turns then used needle nosed pliers to get the rest of the way out.

 

The only place oil is "pumped up" to the rocker area is thru the pushrods, into the rocker arms and squirts out the other end at the valve springs. Maybe you mean the drains at the umbrella valves. Lower rocker gaskets (oem) are rubber-coated metal. Drain holes are smaller at the cylinder base gaskets and the pressure ports thru the gaskets under the tappet guides are "smaller."

Considering they were replaced by a dealer once, I can only assume the breather thru-bolts and associated plumbing is open and not restricted....

I'm totally confused by most of your last post.

 

Here's a few tricks we use on rocker boxes that keep leaking.First we remove them and ensure that they are flat and true with our granite plate (you can use a piece of plate glass). Then we drill out the small hole that is next to the umbrella valves on top breathers to 1/8", this allows a little more oil to drain back. We also take the rocker boxes while they are off and clean and use the smallest amount of Gasket-cinch on the corners of the bottom of the gaskets and assemble them. We let them set until the Gasket-cinch drys, take them apart and install them. Lastly we ensure that when we tighten them down we look all around the boxes with a small Mag lite to ensure that the gaskets are in place. This will stop 99.9% of the leaks. If it still leaks you have one of two problems: the first is the the owner is not letting warm up properly. The second is overpressure of the crankcase caused by bad ring seal or inadequate or blocked breathers. The breathing system on the V-twin engine was meant to inadequately vent an 80" engine at normal cruising RPM's. Enlarge the engine and/or rev it above 5200 and the system can and will fail. The next time you are at the drags take a look at the crankcase venting system that they use.The use of a Spyke Crank-vent or similar product on a secondary vent will also reduce the chances of leaks. Dont forget to us. a filter type vent on the end of any vent hose. Hope this helps explain some of the basic problems.

 

i assumed oil was coming, guess its a drain. i'll take for a decent 70 mph cruise and see what happens.

 

those rocker boxes are really designed bad. the center section just floats, no locating pin or nothing to line them up, and keep them in place. i put new oring gasket on mine and they lasted 800 miles before they started leaking. a harley mech. told me to clean everything and coat both side of orings and surfaces with permatix ultra gray, let sit for 20 minutes and install. well that was over 6,000 miles and still no leaks. but be sparing with the ultra grey, i know a lot of people are against using any type of gasket sealer but if your careful with it youll be ok. either that or buy a set of new rocker boxes, and my rocker boxes are the non breather type.