Another valve adjust story - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 16 Old 01-28-2016, 06:06 PM Thread Starter
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Another valve adjust story

So we just did the valves on my wife's (ttractorgirl) 07 KLR. Yes, she helped and all went very well. Everything was close to spec, but still out. Set them on the loose side so should be good for awhile. Seemed to start much better. Mine is next!
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post #2 of 16 Old 01-28-2016, 06:43 PM
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mtmedic,
Do you have access to a proper compression gauge to do a before and after cold cranking compression test on your bike? Just to see how much it might gain with the valve adjust.

I write the Mileage and CCC and tappet clearances and shim sizes on the frame spine with a 'Sharpie'. Erase with Carb Cleaner. Repeat every 10,000 miles or so.

pdwestman
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post #3 of 16 Old 01-28-2016, 10:44 PM Thread Starter
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No compression gauge, but I did keep a record of the clearances before changing the shims and what was in there and what I put in. I did learn something here, glad I did. Wasn't as bad of a job as I thought it was going to be, I had a good helper.
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post #4 of 16 Old 01-29-2016, 10:34 AM
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Quote:
Do you have access to a proper compression gauge to do a before and after cold cranking compression test on your bike? Just to see how much it might gain with the valve adjust.

Would a compression test be compromised by the KACR?
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post #5 of 16 Old 01-29-2016, 07:05 PM
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Quote:
Originally Posted by Damocles View Post
Would a compression test be compromised by the KACR?
Not if you put a small piece of rubber tube between the weight wings on the KACR (Kawasaki Automatic Compression Release) to hold them out in the non-released position.
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post #6 of 16 Old 01-29-2016, 09:09 PM
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Originally Posted by Damocles View Post
Would a compression test be compromised by the KACR?
NO Damocles, it would Not!
The engine has got to start with currently available compression!
The KACR is in there to allow for a smaller, lighter, starter motor and battery.

There is NOTHING in the OEM service manuals about active vs in-active "Kawasaki Automatic Compression Release's", Cold Cranking Compression numbers. We have to start from Cold. I couldn't care less about Hot compression numbers (or DE-Activated KACR numbers)! Whoever even wrote that in a book 100 years ago didn't Work on them for a living!!!

This is what a "Cylinder Leak-Down Tester" is for.
If initial CCC is found to be low, we measure and adjust tappet clearances to the wide end of specifications. Then re-check CCC again. If still found to be at or below minimum (77psi) CCC, we use the Cylinder leak-down tester to decide WHY the CCC is too low and What needs to be Done About IT.

To the best of my knowledge and experience, all years of KLR650's start very well at 'rideable' temperatures with CCC #'s of 90-125 PSI! And reasonably well at 75-80 psi CCC.

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Last edited by pdwestman; 01-29-2016 at 09:12 PM. Reason: or De-Activated KACR numbers
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post #7 of 16 Old 01-29-2016, 11:34 PM
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Thanks, Paul!

I thought the KACR cracked an exhaust valve at cranking rpm, facilitating development of rotational inertia to start the beast. Then, after the first-ignited power stroke, increased rpm de-activated the KACR's valve-cracking action.

I appreciate the fact service manuals list a wide compression psi specification with the KACR active, as you point out. Further, that the cylinder psi with active KACR provides valid diagnostic data.

I've read of KLR650 owners removing their KACRs; to each his/her own; I'd think the practice unnecessarily increases stress on the mechanical starter system components, not to mention increased initial peak starter motor electrical load.
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post #8 of 16 Old 01-30-2016, 12:29 PM
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Quote:
Originally Posted by pdwestman View Post
mtmedic,
Do you have access to a proper compression gauge to do a before and after cold cranking compression test on your bike? Just to see how much it might gain with the valve adjust...............
I am curious about the "how much it might gain" part of this comment. Since most valve adjustments increase a tight adjustment to a looser one, I would think that there would be a slight decrease rather than a gain in compression.
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post #9 of 16 Old 01-30-2016, 01:23 PM
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Originally Posted by GoMotor View Post
I am curious about the "how much it might gain" part of this comment. Since most valve adjustments increase a tight adjustment to a looser one, I would think that there would be a slight decrease rather than a gain in compression.
GoMotor,
Closing points are the critical issue here for CCC. Not lift, nor opening point.
When we loosen the valve tappet clearance to Max spec the RH exhaust valve is allowed to close earlier coming Off of the KACR, trapping more compression. When we perform the MC Mod (exhaust cam advancement), we also close the KACR even earlier.
Normal running compression is not so much effected, provided that all valves were not excessively below Min spec.

In a normal non de-compressor type engine the earlier closing of the Max spec Intake valves trap more volume which gives Higher measurable compression.

pdwestman
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post #10 of 16 Old 01-30-2016, 01:24 PM
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A valve which doesn't close will allow leakage. Leakage will lower compression pressure, so I assume the reference is to notice compression change due to less than no clearance before the adjustment?

Otherwise, I'm with you in not understanding why there could be any change. If one is to do a compression test for reference, it would seem better to do following the adjustment in case something has gone amiss. I don't bother unless there is some other reason.

If looking for problems, Paul has explained the difference in use of a compression test versus leak down when an ACR is involved. I've never thought to mention this because it seems obvious.

Dunning-Kruger again....



Quote:
Originally Posted by GoMotor View Post
I am curious about the "how much it might gain" part of this comment. Since most valve adjustments increase a tight adjustment to a looser one, I would think that there would be a slight decrease rather than a gain in compression.
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