Increased valve clearances?

[jsandidge]

I just finished a top end rebuild on my 850, but I haven't started the bike yet. A couple of my valve clearances are looser than they were. I will swap in the correct shims to bring them into spec. Should I be concerned that maybe something is wrong?

[Nessism]

How much looser? And what was done to the valves if anything?

Maybe the keepers are not sitting down exactly right compared to before? Did you turn over the engine several times to make sure everything is seated before checking the clearance? Any oil on the cams?

Kawasaki KZ bikes like the KZ1000/1100 use an almost identical shim over bucket valve system as the 850 and the KZ's spec the clearance up to .15mm compared to the GS bikes which spec .08mm. I'm of the belief that running more clearance is safe, particularly right after a rebuild. After a few hundred miles, when you go to retorque the head, check the valves again and then decide if you want to adjust then.

[jsandidge]

I lapped the valves in by hand. I have turned it over several times, and there is oil on the cams. I have 2 valves measuring .13. I was careful to label everything so I could put them back in the same place. I think I'll turn it over some more using the starter (I turned it over by hand before) and re-check.

[Steve]

What all was part of the "rebuild"?

Did you just clean things up and replace the seals on the valve stems or did you cut new seat and/or lap the valves?

Actually, cutting new seats would give you LESS clearance, unless you also trimmed the tips of the valves to match.

Lapping the valve seating area (head and valves) will roughen things up a bit, which might increase clearance slightly. Leave the valves loose. Treat it like a new bike and check them in 600 miles.

Also note that many of us do go a bit past the 0.08mm limit imposed by Suzuki. Using an upper limit of 0.10mm is common. I don't know how much the 0.02mm reduction in valve lift or the degree or two of valve timing change will affect air flow (and, therefore) power, but closing the intake valve earlier is one way to move the torque curve down a bit, bringing it closer to where most of us run the bike most of the time. That might reduce the claimed 78 hp to 76 or 77, but the additional torque at a lower engine speed might add some MPG as a trade-off. It also extends the time until the clearance gets small enough to need adjustment again.

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[Nessism]

I'd leave those .13 valves alone. Check them again after you put a few hundred miles on the engine.

[GregT]

I'd leave those .13 valves alone. Check them again after you put a few hundred miles on the engine.

Agreed - it's very easy to get false clearances after lapping if you haven't surgically cleaned the valves and seats.

FWIW, I use .005in clearance in the 8V engines as a matter of course. No extra noise and the checking intervals can be longer. Race cams frequently call for bigger clerarances again.