blocking rocker oil feed

My bud Wes brought over a spark plug he'd JBW'd air fitting on so we used that to listen in but also learned how dam hard to keep it exactly at TDC in our vertical twins. Here's some window shopping and protocols to wonder through before doing the deed, or not. I encourage you to and double so to video to document your education for our entertainment. It will be a memorable event in your Nortoneering lore.
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A leak down test is typically conducted with 80psi in on input gauge (adjusted to maintain this figure 'in' depending on how much is leaking out of eng.) while holding piston at TDC. Output gauge indicating 60 psi (25% loss with 80 psi in) is pretty much as low as you would want to go , that is if the loss is only past the rings. Listen to any opening to sump or crankcase to determine ring blow-by, such as breather hose, oil fill port if wet sump, dip stick tube etc. Listen at end of exhaust pipe for leaking ex. valve, none should be allowed, same with intake valve by listening at carb inlet. Leaking valves don't usually get better unless maybe you have dislodged some carbon or other swarf that's trapped between seat and valve. You can rock the engine either side of TDC and watch the compression change as rings seat unseat or move off highest wear point of cylinder. A high mileage engine at 25% ring loss can still give decent performance but usually burns oil and won't be long before one or another cylinder drops below minimum.. a good leak down tester will have an easy on/off valve that you should be holding so that you can immediately dump pressure if things start to get away from you. This test will not tell you how warn your valve stems/guides or guide seals are but will tell a lot in the right hands...if all cylinders are within a few pounds of each other tells you one thing but if one cyl. is significantly lower, then it's time to investigate further. Combined with mileage or hours, known oil consumption, fouled plugs etc., the leak down test will give you a quick and easy measure of an engines general health and where you might start your investigating, more so than just a normal comp. check...doing a leak test with a hot engine gives as close to a real world running scenario as you're going to get, before things cool down and dimensions change and oil thickens up...Mark

from the wisdom in article Dances from damages left us. I"m still waiting to hear the method to allow rocking a Norton just off TDC and not have it get away faster than a human can press a release in time. I did mine with only 80 PSI. Hope the leak gets discovered and solved one way or another with all digits intact and skin too around a hot engine.

On motorcycle engines locking the engine can be fun. If the engine is in the frame you can put it in gear and apply the rear brake. If the engine is on the bench, things are a bit harder. Now you have to lock that engine. If you use a wrench on the crankshaft bolt be sure to use a long one with lots of leverage. If you used a regular sized wrench you will find that the 100 psi of air pressure will apply a tremendous amount of twisting pressure to that wrench. You must be ready for that!

Even if you are ready, with a tight grip on the wrench, the crank might turn. Yes indeed, it might turn and cut your hand on the crank case like a scissor and you might get mad, say some bad words and throw that wrench across the room and stick it in the wall! Of course, a master mechanic of my stature would never do that and besides it did not stick in the wall. It bounced off. If I had thrown it which I did not! Anyway, you get the idea!

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