1972 Combat timing chest excessive pressure???

So I made a goof when I installed my cam bearing holder. I drilled the 2 holes a little too deep and broke thru to the outside. Not a big deal except I had oil weeping out using the threads for the retaining screws as a path. I pulled it apart and cleaned and sealed the screws. Re assembled, reset the timing and took it for a jaunt around the block.

During the jaunt I pissed off some neighbors. The guy was being an ass, he steeped right out in front of me and told me to stop it. Apparently the exhaust is too loud, I passed their house too many times and I was going too fast. Stock exhaust, it was 7pm on a public road, and I was doing 25 - 30 MPH in a 25mph area. Screw them. I digress.

When I got back home I checked my repair and observed oil being pushed out the threads. Now the best Idea would be to weld up the case, but I would need to disassemble to do that, not happening.

I thought of JB weld, might be a temp fix.

But my concern is that there is enough pressure to push the oil out the threads.

So what are my options for controlling the pressure.

Blanking off the timing chest? Different breather valve? I need some expert opinions so fire away. Thanks much, Brent

What are you using for a breather now?

Stock combat bit.

Try a Mike's XS reed valve. If you do, I'll bet your problem disappears.

Inline with the stock valve?

There are differing opinions where valve placement works best. I used it inline with the stock breather still installed. Mounted the reed valve on the back of the stock filter back. No more oil leaks, anywhere. Some blank off the stock breather hole in the crankcase and plumb to the old magneto blanking plate. CNW sells one that bolts directly to the crankcase. Jim Comstock did some extensive testing of reed valve efficacy and placement. Try a search.

I have one of GP's valves on my alloy bike. Ill steal it and give it a try.

What's a GP valve? Is it a reed valve?

I've repaired holes and cracks in busted up cases and can tell ya that JBW is literally like cold welding in this application so its a permanent bodge. Just has to set up for days and maybe a good heating to really harden it up against case thermal swelling contracting. JBW is magnetic so can be held in place and drawn into cracks via a strong magnetic on other side. Blow by sucks and a number of reasons and solutions to learn up on.

Some sort of reed valve sounds like a good idea.

Your neighbor reminds me of a trip I made to Laramie, Wyoming to look at a couple of Commandos a guy had for sale. The peashooters had lost all their packing years ago and were a little on the loud side. The seller, his buddy, and me were taking turns riding the two bikes around the neighborhood. One of the neighbors called the cops! No worries though, the seller knew the officer who responded. Small town. :lol:

Debby

I like the plain reed valve behind the timing chest for the typical Commando.

They're simple, clean, and they work, period.

JimC said:

What's a GP valve? Is it a reed valve?

Click to expand...

The reed valve that GrandPaul sells. I made a slight change to it and welded on a tube so it is easier to install.

I would like to see a picture of your issue.

Here is my setup.

For us lazy guys there is the inline $100 Krank PCV Kenny Dreer, the mis-informed un-educated Commando slackard, sold me or the cheap ass inline Mini-Mite brake valve that both have worked on my two Combats and a whole bunch of others prior w/o the reed valve, gooder as it may be. I got Comstock to admit his extra reed draw down ability is just extra icing on cake of case pressure lowered below ambient a bit. On the other hand its fun to adapt new stuff to old Commandos, if ya don't care about jumping the Norton fence. If still some oil escape, might consider the silk, cotton or dental floss back up, next time around. I think the engines become elastic seam openers after about 6000 rpm as blow by is reduced compared to idle rpm.

Here is the lower one with the sealant oozing out

and the upper location followed by a close up, hard to get a good picture. Its down in the pocked behind the tach drive.



Like I said these were self inflicted issues, but watching the oil being pushed out the threads makes me wonder about the pressure in there.

Oopsa daisy!