Rear Rocker box leaking after top end rebuild : V-Twin Forum: Harley Davidson Forums

jandjkemp · 09-15-2009, 09:27 PM

I have 1998 Ultra that has 75000 miles on it. After the motor started burning oil and the tappets went bad, I rebuilt the top end. Honed cylinders .10 over, decked the heads, new pistons, new SE4 cam, new tappets/blocks and pushrods. Used Cometic top end gasket kit to put it all back together. Almost made it through a break in period of 500 miles, when the rear rocker box started leaking quite a bit of oil from the rear left. I've been noticing much higher oil pressure than before I rebuilt the top end, sometimes I'm seeing psi as high as 35-40 upon cold idle start-up. Generally at highway speeds, it is pushing around 20 psi. Could the oil pressure or crankcase pressure blow out the rocker box gaskets?? Could high RPM's raise the pressure enough to blow the gaskets. Just wanted a few ideas as to why this happened before I tear into it and put new gaskets on it.

strokerjlk · 09-15-2009, 09:39 PM

Quote:

Originally Posted by jandjkemp

I have 1998 Ultra that has 75000 miles on it. After the motor started burning oil and the tappets went bad, I rebuilt the top end. Honed cylinders .10 over, decked the heads, new pistons, new SE4 cam, new tappets/blocks and pushrods. Used Cometic top end gasket kit to put it all back together. Almost made it through a break in period of 500 miles, when the rear rocker box started leaking quite a bit of oil from the rear left. I've been noticing much higher oil pressure than before I rebuilt the top end, sometimes I'm seeing psi as high as 35-40 upon cold idle start-up. Generally at highway speeds, it is pushing around 20 psi. Could the oil pressure or crankcase pressure blow out the rocker box gaskets?? Could high RPM's raise the pressure enough to blow the gaskets. Just wanted a few ideas as to why this happened before I tear into it and put new gaskets on it.

I wouldn't worry about the oil pressure at those readings.
some would kill for that kind of pressure on a evo.
it will contribute to a leak if it wasent a good seal in the first place. I have had my share of problems on the rear rockers myself on evos for some reason.
make sure it is clean free of any gasket material and final prep with a little acetone. I started using a little permatex gasket sealer on evo and sportster rockers.
maybe just me ....but it keeps ME from having to re-due them

rcsoftail · 09-15-2009, 11:40 PM

I have had problems with cometic rocker box gaskets leaking on several builds. I stopped using them and now stick with the orignal harley gaskets. Others on this forum have had similar problems with after market rocker box gaskets.

As previously mentioned, don't worry about the oil pressure. I am running higher pressures with my s&s high volume pump with no problems.

jandjkemp · 09-16-2009, 04:50 PM

When I tear it apart again, is it unheard of to reuse the gasket I just built the top end with, just using a bit of gasket sealer with it. Or do I tear the rocker boxes off of both cylinders and replace them both with Harley gaskets??

1949shoebox · 09-16-2009, 05:20 PM

dont use harley gaskets ... when you up compression you need to upgrade gaskets est mls gaskets are best spend the extra dollars or so . dont use silicone or gasket maker . can heat or get brittle and fail causing leaks

rcsoftail · 09-16-2009, 07:11 PM

I am assuming it is just leaking through the rubber gaskets. If so, I would just remove the top and center portion of the rocker covers and replace the rubber gaskets with Harley ruber gaskets. Sometimes you need to stretch them just a bit so that they will stay in the channells as you re-assemble. If it leaking out the bottem between the head and rocker box, you could try spaying some copper coat on your cometic mls gaskets and re-assemble.

jandjkemp · 09-16-2009, 09:24 PM

There's so much oil that leaked out because I limped the bike home about 70 miles. It's hard to tell if it is coming out the mls gasket or the rubber ones, I probably should take the lower section of the rocker box off and redo it. Is it possible that the mls went bad or is it that it just didn't seal quite right?

rcsoftail · 09-16-2009, 10:59 PM

My bet would be on the rubber ones. Part of one may have come out of the channel or got twisted when you tightened the bolts down. If this is the case, you will probably see a deformation in the rubber. Hopefully that is it and you won't have to remove the lower rocker section. I have had good luck with the cometic mls metal gaskets, just not their rubber ones.

jandjkemp · 09-16-2009, 11:30 PM

Thanks all for your info. I plan on wrenching on it tomorrow night.

rcsoftail · 09-17-2009, 01:45 PM

If the rubber rocker box gaskets don't look like the culprit, also check the o-rings on the push rod covers to make sure they are sealed. If they leak, the wind can sometimes blow the oil around, making it hard to tell the source.

jandjkemp · 10-19-2009, 09:43 PM

Well after redoing the rubber gaskets on the top of the rear cylinder, I still had a leak. Tore it apart again last week and used some copper spray on the metal gasket for the rocker box. Put it back together and put on about 300 miles this weekend without leaking a drop. Thanks for all of your advice, looks like that worked.

ironheadbuck · 10-19-2009, 10:06 PM

could of had a little warp on mating surfaces