Just some off season fun. I wanted to run some diagnostics before I start my winter "up-fixen". I ran a compression test and both cylinders are 135psi +/- 4 so I'm ok there. However, after painstakingly finding TDC i run my leak down and it not only leaks but sounds like the exhaust valve is slightly open.

Some of you might remember, this is a Reno bike. I have what looks like an early A motor with Montjuich cams. Reno stroked it a bit. You can see the gap between the case and cylinder and the studs don't go all the way through. About two years ago Palmer helped me (basically I watched) time the cams to the Montjuich specs. So I have some overlap, right? The bike runs, it's not a rocket, but respectable. Thoughts? Comments?

Thanks,
Jeff

Maybe reading page 6 of my postings of the 1980 factory Pantah racer replica, in the Bike Build of the Year section, will help some. Maybe there are degrees of a part failure. From that experience, and some recent valve work I’ve done on some heads, I have learned that the sound cannot be ignored. But, as another thought, it would not hurt to check both shim measurements on that valve first. MikeV

Q: What lobe center did Palmer use? Do you remember?

Not sure but at the time we adjusted the valves while we were in there.

I fiddled with this some more today. I hooked up the compressor to the cylinder and just lightly cracked the air open. I could easily hear the hiss of air come through the carb as the intake valve opened, slow, stop, then come out of the exhaust, as I turned the motor over. I had it it gear so after experimenting with it a bunch of times, I decided to try again. When the hissing stopped I locked it up with the brake and dialed up the pressure. It didn't take much before the air started rushing out of the EXHAUST valve.

If the cylinder was pressurized I would think it would keep the valves closed unless the exhaust valve is open just enough to move when I turn up the pressure. Maybe the valves and seats are worn enough to let a lot of air through even at TDC.

I'm stumped.

Jeff