Vacuum gauge to diagnose rockerbox leak

[aben]

I am sure that someone has hooked up a temporary vacuum gauge to help in diagnosing oil leaks in the rocker box system, if so, where did they tap in for the gauge and how much vacuum would be sufficient ? I have thought about brazing a fitting onto a spare push rod cover. Are the pin holes in the spring cups necessary ?
Thanks,
Ben

[knuckleheadtim]

That's not a bad idea. You can also connect to the fittings on the rocker boxes where the cup drain lines connect. I don't know how much vacuum you'll get, but I think 5 - 10" HG would be plenty.

The pinholes in the cups are necessary on the intakes so vacuum leaking by the guides doesn't fight the crankcase vacuum trying to pull the oil through the drain tubes.

[Steve Little]

Hi Ben.
Just a quick thought...how long have you had this bike? Is it new to you.

When I had this problem, I thought about making a tester on a pushrods tube.
But after a little more thought, I realised that I was only making more work for myself.
It was evident that I had a loss of vacuum to the rocker box's, because the oil was staying up there.
The gauge won't diagnose where the problem is, although I t would be nifty to make the tool after you fix the problem and let us know the reading.

Do the easy job first.
Use some "Three bond" crank case sealer to smear over the pointy peak area of the cam cover, which is between the lifter blocks. Let it cure until a skin forms and then run or ride the bike like you have been doing, to see if the oil fills the rocker boxes.
This test would eliminate the leaking cam cover gasket issue that has caught a few knuckle owners and will save you disturbing the timing chest unnecessarily.

Next I would check to see if you have the Eastern lifters as I described in earlier post.
At the same time you can inspect the cork gaskets and the sealing faces of the pushrod tube assemblies.
Regards Steve

[aben]

Thanks Tim.
Ben

[harleytoprock]

Has anyone mentioned that the drain lines going to the rocker boxes could be clogged with carbon?

[aben]

Thanks Steve. I have had this bike for over 30 years, it came from Mexico and was not running when I got it. After overhauling the engine, (back then) it leaked some but it is leaking much worse now. It has not run much in 30 years. When I got it, the cylinders showed evidence of long time leakage, (oil caked up between the fins in the area below the tins and around the exhausts).
You have a good point about the fact that I would not gain much for a diagnosis, I hadn't thought that far ahead. Loss of vacuum wouldn't really tell me where the problem is.
Is THREE BOND sealer available locally ? I assume that you mean smearing it over without removing the gear cover.
I really appreciate you and Tim sharing your knowledge.
Ben

[aben]

Thanks for the reply Harley, yes I cleaned them out with piano wire and a syringe then irrigated with lacquer thinner. It still leaked.
Ben

[Steve Little]

Hi Ben. I don't think we will get very far in trying to help you, until you identify where the oil is escaping.
You may have full vacuum and the oil may be getting sucked down the return lines but it may also be dribbling from a crack in the base of the lifter cup, or past the seal between the head and cup.

I would take the gas tanks off your bike, go down behind the garden shed and rip the little gas tank off that old turf mower, and rig it up so that you can ride your bike and look all around the rocker boxes.
Your locality isn't listed in your details on the right of the screen, but I'm guessing that depending on where you live, it will either be cold or very cold outside.
It is 40 degrees C here (105F)
Regards Steve

[MJW]

Aben, have you read thru this thread? http://www.caimag.com/forum/showthre...blem-on-the-41

[MJW]

cut to the chase. http://s567.photobucket.com/user/pro...c2f5f.jpg.html If the gasket doesn't seal the top hole completely vacuum is lost...

[Steve Swan]

Three bond should be available at any good motorcycle shop. aka yamabond, hondabond, kawabond,

or http://www.ebay.com/itm/Three-Bond-L..._Tools&vxp=mtr

[aben]

Thanks for the tip MJW, I am learning.
Ben

[aben]

Thanks Steve.
Ben