Topic: Piston clearance

[88BuckMeister]

Just got done doing the clay trick with the 650 cam in my 550 motor. There's plenty of space. Or so it appears. Valves not coming close. Obviously the exhaust valves come down farther, the intake valves don't come closer than like .145. Let me know what yall think from the pics.

But I wanted to measure the distance between the piston dome and the cylinder tops. Is it normal for the top of the piston to protrude above the cylinder decks?

[Mark1976]

  Depends, who made the pistons, check with the mfgr. Those pistons do sit a bit down in the cylinders. Did you do a full head torque or another method. That's a generous clearance and that's fine, but there's numerous ways of doing it, just curious. The exhaust would be the one to give primary concern .080 a good place to be with the exhaust. Appears your a ways from there. With those numbers, just about anything's going to drop in.
   

[88BuckMeister]

  Depends, who made the pistons, check with the mfgr. Those pistons do sit a bit down in the cylinders. Did you do a full head torque or another method. That's a generous clearance and that's fine, but there's numerous ways of doing it, just curious. The exhaust would be the one to give primary concern .080 a good place to be with the exhaust. Appears your a ways from there. With those numbers, just about anything's going to drop in.
 

I did torque with the gasket on, in proper sequence. I've seen people do it without the gasket, but then you're inserting numbers into the equation that are presupposed. I wanted to see what the cold clearance is in real time under real conditions. I'd be lying if I said it wasn't bothering me lol. I'd hate to assemble this and have it go boom. The pistons are Dynoman 61mm 10:1 set.

Im also not playing any games with the springs. There was a thread on here from 2019 I think about a guy who did the EXACT same build I did. His engine went boom. There was a lot of discussion about the possible cause. A keeper giving out was adamantly denied by members, who said they're very beefy in this bike. Cam chain jumping was also an option, but these cam chains are tight. I can't even get it on the gear barely. I suspected valve surge. So I ordered the racing spring kit. Just waiting on a new head gasket and the spring kit and I think I'm ready to assemble.

[Mark1976]

   Ok, sounds good. The more ya know the better you'll feel about what you're doing. New springs definitely will give ya more piece of mind. Can't stress enough, keep it clean and keep it covered....