kingmoochr
Husqvarna
B Class
Yes, a leakdown test says explicitly what is leaking. You charge the cylinder with compressed air hooked to a dual gauge, one reads the input pressure, and the other reads the actual cylinder pressure. From there you get a leakdown %. Depending on what you are doing, there are acceptable pressures (racing, street, etc.). The leaking air then escapes from wherever the seal is bad - crankcase for rings, intake for intake valves, exhaust for exhaust valves.Let me preface by saying I am not a professional motor builder. My experience comes from owning and working on dozens of motorcycles over more than 40 years. If you have a different recommendation from a professional builder then I would certainly have to concede to that.
The initial ring gap is the factory spec. In my experience rings wear at a much greater degree than cylinder wall. But yes, you certainly would want to measure the bore for wear as well, taper, out of round, etc. When rings wear the gap opens up, and they can get thin at a point around the circumference creating a greater risk of breakage. And you'll get oil blow by thru the gap. It's a great time to check for carbon build up in the grooves as well.
Yes, a leak-down test will certainly tell you if it's holding. If it's not, can you tell if it's valve wear or rings? One could also wait 'till they find oil consumption. Hard to tell if it comes from valve guides or seals, or rings though.
I have no experience or knowledge of awesome little cameras.I'm old school! If you can tell motor condition from a camera then that would make a lot of sense.
I don't put that many miles on a bike per year, so ten to fifteen thousand miles is probably likely five or six years for me. At some point in there I would probably just pull the cylinder off to check everything. If the rings are worn and everything else looks good, putting in a new set of rings is an easy way to extend the life of the top end. If there are lots of other issues then they can be addressed.
In a production motor, there is the gap the factory aims for, then there is the gap that the machine actually produces. Without matching a ring to a cylinder and gapping by hand, there is really no way to make an accurate determination of what has happened. WITHOUT a leakdown tester, I suppose measuring for excess gap would really be the only way to check the seal (but at that point, there is no reason to check - install new ring). I'd just rather pay a shop the 50 dollars it would probably cost to do a leakdown

