Z1 cam caps
Jesus fucking Christ. Just when I think the z1 is solid and done, something else breaks.
The first gen KZ motor has a weak spot. The caps which hold the camshafts down and in place, have shitty bolt holes. They’re m6 threaded holes in the soft aluminum head. The sequence for removing the cams and installing the cams almost guarantees you’ll potentially strip out a couple bolts. As you tighten the cam caps down, it’s essentially pushing a valve open, so you can’t always guarantee it’s going in smoothly. Combine that with the fact that the service manual has the wrong (overly tight) spec for how much to torque them down.
Everyone on kzrider says to go super light or hand tighten them only. It’s the number one fuk up on the KZ motors that everyone fuks ups. Especially if you have high lift cams, which I have, it extra aggrivates the risk.
Anyway, long story short: I heli coiled a couple holes about 4 years ago, and had Larry C fix a couple holes when he ported my cylinder head. (Shoulda had him do all 16 holes).
It’s been exactly a year since my last engine rebuild. Bike rips and has been super solid. The other week while on a Thursday ride I instantly heard a super loud valve noise from left side of my motor.
I limped the bike home, and pulled the valve cover the next morning. Turns out, that out of no where, for no reason, 4 bolt holes on the exhaust cam stripped completely out. Fuk.
So, with Nates help, pulled motor out of frame and gonna heli coil them myself without taking the head apart. If I can’t fix myself without taking head off, I’ll break engine completely down and take it to Mar auto to have them fix the holes.
While the motor is out I’m gonna clean a bunch of shit up and paint my frame gold.
I’ll update once I try and fix the holes myself… See how it goes. When I put heli coils in 4 years ago, I didn’t loctite them in… but I’m thinking about using blue loctite on the heli-coil itself so it never moves in the fresh cut head threads. Thoughts anyone?
4 responses to “Z1 cam caps”
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Published - Jan 1, 2011
Auckland, NZ – overview
I’ve made some observations of Auckland: It’s way nicer than I envisioned it would be. From what I’ve seen and heard, vintage cycles are slim to none. There is no trash on the streets of NZ. Cleanest place I’ve ever seen. People are in no hurry… everyone drives way under the speed limit. Everyone is […]
I put red loctite on the bolts i couldn’t heli-coil for the very reason you experienced. I didn’t think they could come loose or on their own but I wasn’t take any chances… Fuck that! Turns out it can happen. Sorry it happened to you.
Red loctite may be a smart move or bad move next time I get in there. As long as you apply heat you can remove them safely so I hear.
Re-read your post. I would also avoid blue loctite on the helicoils. Heli-Coils are way stronger and won’t ever strip from the re-tapped hole.
Def not knocking whatever method you choose for your cam-caps, do whatever you want, but I would be a little cautious of red loctite.
Red loctite is pretty gnarly shit. It’s basically for bolts you never want to remove. When removing your cam-cap bolts in the future, it may possibly strip out the aluminum threads because as you’re loosening the bolts, the red loctite is prob gonna take the head-threads with it, then you’re potentially fucked.
I put a small drop of blue loctite on the outside of heli-coil when I threaded it into the head, to help ensure the heli-coil never pulls out, but the bolt will still go in and out of the heli-coil smoothly.
The only thing I’ve ever used red-loctite on is my camshaft adjustable cam gears which are slotted. I never want those bolts to move and never plan on removing them.
I’m making a post about heli-coil stuff so if you want to comment, go over to that post >
[…] seen in previous post, the z1 blew out 4 (non-heli’d) cam cap bolt holes randomly, out of no where after a year of […]