Bubbles in coolant with cap off at idle/blipping throttle

[JZ05220r]

It is in the sound and it runs badly, it runs extremely bad like it starving for fuel or running out of gas. If I wait like 5-10 seconds it will run fine again until next time. When the power valve gets stuck open will the bike run very lean off the bottom? I know I could probably tell if I go full throttle in these situations and if it runs good then I would know but if not I worry I could cause damage. I know from experience when it’s stuck closed it runs very rich off the bottom. Also this is something that I noticed when I first got the engine rebuilt by FRP the power valves returned very slowly compared to a video I had before the rebuild. So it was perfectly clean yet still hanging up. I don’t think it being gummed up is the answer: I’m think maybe debris from the plating process has effected it. I have to get a video with the go pro to share with you guys.

[Chuck78]

Ahhhh... I've heard of this happening before with replated cylinders....
I'd call Jeff Fredette and ask him, as I don't think it's worth your time pull the engine and ship it back to him. The same amount of labor could be used to take the top end apart and and deal with the issue yourself.
As you likely have already learned, the top ends are pretty easy and simple to tear down and reinstall. Just make sure to use an adjustable spanner/crescent wrench to hold the power valve external linkage toothed fork when installing or removing the left hand thread nut off the top of the external actuator rod.

And yes, I would agree, if you get the bike to act up in a wide open safe area when closing the throttle, then give it full throttle again, if it runs fine at full throttle, then that's definitely seeming to be your issue.
Thanks for reporting your findings, and mental note has been made to check power valve smoothness with fresh cylinders from now on.

[JZ05220r]

Ahhhh... I've heard of this happening before with replated cylinders....
I'd call Jeff Fredette and ask him, as I don't think it's worth your time pull the engine and ship it back to him. The same amount of labor could be used to take the top end apart and and deal with the issue yourself.
As you likely have already learned, the top ends are pretty easy and simple to tear down and reinstall. Just make sure to use an adjustable spanner/crescent wrench to hold the power valve external linkage toothed fork when installing or removing the left hand thread nut off the top of the external actuator rod.

And yes, I would agree, if you get the bike to act up in a wide open safe area when closing the throttle, then give it full throttle again, if it runs fine at full throttle, then that's definitely seeming to be your issue.
Thanks for reporting your findings, and mental note has been made to check power valve smoothness with fresh cylinders from now on.

For sure I’ll check it out. I may just have the spare cylinder replated and have all the riding surfaces for the kips smoothed. I have plenty of gaskets for the top end. Also I like to slide the boot down on the actuator shaft when tightening the left hand but and you can see a cut out kinda like on a tie rod where you can use a wrench to actually hold the shaft itself. This ensures that the power valves are as closed as possible with minimal play while governor isn’t engaged. Thanks