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Exhaust valves deliberately set looser than spec? 23 Nov 2021 17:02 #858265

  • Flatblackobsession
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KZ Riders,
I've got a mystery I am hoping you all might help me solve.

I got a hold of a 1988 KZ1000P. It has needed a little work to bring it back to life (carb clean, leaking intake boots replaced, fork seals, etc...), but nothing too major. Seems to run pretty good. Nice compression.

The constant issue that has vexed me, and made me feel less than confident about the bike, though, has been top end noise. At first when you fire it up, it sounds good. But, after it warms up a bit, the top end noise emerges. Sounds like valves ticking around, or an exhaust leak.

I have replaced the copper exhaust crush gaskets, and it did help a bit, but the noise persists.

Having tangled with timing chain issues before, with other bikes, I checked that out. Everything looks good, both in terms of visual inspection and chain measurements. No weird bits of guide debris in the oil or anything like that. But, I replaced the automatic chain tensioner with a manual APE tensioner, just to be safe.

Still, the top end noise persists.

Given that it sounds like it could be valves, I checked the valve clearance. I found that all four of the exhaust valves are loose, each by about the same amount. According to my manual, the clearance should be 0.05 - 0.15 mm. All of the intake valves are well within spec. However, all of the exhaust valves have clearances of 0.18 to 0.20.

There are obvious signs that the previous owner had adjusted the valves, and I inherited his shop manual, and found some of his notes in it from when he adjusted the valves.

Given the obvious attention paid to the valves by the previous owner, and the fact that all of the exhaust valves are all loose by just about the same amount, while the intake valves are all within spec, it kind of seems to me that the previous owner set the exhaust valves a little looser than spec deliberately (the bike was otherwise completely stock, from what I can tell).

So, do any of you have any idea why this guy might have deliberately set the exhaust valves looser than spec, while keeping the intake valves right within specifications?

And, other than the clattering noise caused by the loose valves, is this a threat to my engine's health?

Thanks. I'm interested to hear your thoughts.

 

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Exhaust valves deliberately set looser than spec? 23 Nov 2021 18:52 #858269

  • hardrockminer
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The noise may be coming from the valves.  They generally quiet down as the clearance decreases.  I don't think valves being a bit outside spec is a serious issue, but I would re-shim if it was my bike.
I have several restored bikes along with a 2006 Goldwing with a sidecar. My wife has a 2019 Suzuki DR 650 for on and off road.
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Exhaust valves deliberately set looser than spec? 23 Nov 2021 19:05 #858270

  • daveo
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The noise may be coming from the valves.  They generally quiet down as the clearance decreases.  I don't think valves being a bit outside spec is a serious issue, but I would re-shim if it was my bike.

 

+1

The FSM spec may be incorrect, but I don't think so.

Also, taking lash measurements with the cam lobes pointed directly away from the valve is not correct according to the KZ1100 FSM instructions.  If it was that simple, then why would Kawasaki engineers describe using a seemingly more complicated method?

1982 KZ1100-A2

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Exhaust valves deliberately set looser than spec? 24 Nov 2021 00:02 #858277

  • zed1015
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Stock spec with stock cams on all Z/GPZ - 903cc to 1089cc is 0.10mm to 0.15mm except the GPZ1100A UNITRACK which is 0.18mm on the high end.
With performance cams you can go as wide as 0.20mm so make sure that's not what you have installed before closing the gaps.
With stock cams going wider than stock won't do any harm if that's where the shim size takes you but you may get a bit louder ticking.
I tend to go to 0.17mm and if you have some at 0.20mm stock cams i would drop a shim size on those to get them at 0.15mm.


 
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Exhaust valves deliberately set looser than spec? 24 Nov 2021 01:13 #858280

  • Flatblackobsession
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Thanks. I may well do that. Even though it seems like it won't do the engine harm, I like to be able to listen for engine health and that ticking sort of has my internal alarm going off all the time, since the engine isn't supposed to sound that way.

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Exhaust valves deliberately set looser than spec? 24 Nov 2021 10:07 #858292

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Also, taking lash measurements with the cam lobes pointed directly away from the valve is not correct according to the KZ1100 FSM instructions.  If it was that simple, then why would Kawasaki engineers describe using a seemingly more complicated method?



 

The method detailed in the manual is to ensure measurements are made at exactly the same 'spot' every time otherwise you might be changing shims to account for slight camshaft deviation rather than cam/valve/seat wear.
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Exhaust valves deliberately set looser than spec? 25 Nov 2021 08:41 #858323

  • slmjim+Z1BEBE
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The method detailed in the manual is to ensure measurements are made at exactly the same 'spot' every time otherwise you might be changing shims to account for slight camshaft deviation rather than cam/valve/seat wear.

The FSM method has always been a little vexing.  Seems the cam base circle would be consistent from ramp to ramp.  Maybe it was specified that way in the FSM as a timesaving measure for the shop Tech.  We've done it both ways; pointing away vs FSM method.  Can't tell any difference.

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Exhaust valves deliberately set looser than spec? 25 Nov 2021 10:27 #858326

  • Nessism
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There are many older threads on this, and several different cam positioning methods.

One thing I know: if the adjacent valve to the one you are measuring is depressed by the lobe, that will result in the cam being pushed upwards, thus skewing the cam in the journal clearance.  Kawasaki adjusted their adjustment method in the later years of the 1000/1100 engines to compensate for this.  Bottom line: the best method is to position the cam so that both the valve you are measuring and the adjacent valve are both on the base circle at the same time.  This incidently isn't just the later year KZ method, it's also the Suzuki GS method.  

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Exhaust valves deliberately set looser than spec? 25 Nov 2021 12:08 #858327

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  We've done it both ways; pointing away vs FSM method.  Can't tell any difference.

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slmjim & Z1BEBE
 

I've only ever checked this difference in clearance measurements on one motor (900F - which are known to have slight 'wobbles' in the cams and associated loose cam journal clearance spec so I don't know what it's like on other motors) -  some cylinders have no difference in measured clearance between 'lobes up' and lobes parallel to cam cover split, while others cylinders show a difference. Since the spec is given with cams parallel to the cover split, it makes sense to measure clearance only at that position.

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