Kawasaki FR691V cam lobes with ball bearing

[Rocket Surgeon]

Slomo:

Thanks for you last post. At least we can have some fun.

Per your last post, I've been through the rings, and they appear fine. I might just let the 10 acres of grass grow...how bad could that be?

I do sincerely appreciate your effort.

 

[Scrubcadet10]

it's simple, the flywheel key sits in a keyway on the crankshaft, and fits in a slot in the flywheel, if the engine was ever put under a heavy load quickly, or came to a sudden stop that key can break and cause improper ignition timing and running issues.
Probably have to remove the flywheel nut , and you should see that slot cut into the flywheel, the key should make a perfect square in the slot.

 

[slomo]

Everything you are checking "looks" to be legit.

8.2 compression sounds normal in a mower engine. You are reading 180psi which equates 12.25:1 static compression. You take atmospheric pressure at a normal rate of 14.7 times your static compression ratio. So 14.7 x 8.2 = 120psi. This is what you should be seeing. 14.7 x 12.25 = 180psi. I know Kawi's are strong but man. Try to borrow another compression gauge. Kinda pointless as you need to get the oil usage under control.

slomo

 

[cpurvis]

I can't say that I understand the Kawasaki compression release. At all. But like any engine with a functioning compression release, the numbers you obtain with a compression tester are suspect. They should be LOWER than expected, though, not higher. If there is a lot of oil in the cylinder, that might cause a high reading? Bottom line (for me) is that I would not worry about the unexplained high cylinder pressure. Compression gauges are mainly to answer the question "Do I need to dig into this thing?" and you're already there. Visual inspection of the internals will find what problems there may be.

There are only a few ways for oil to get in the combustion chamber--it has to get past the rings/piston, a faulty head gasket or through the valve guides, or through the crankcase ventilation system? That's all I can think of. Check the end gap on your rings, verify they are correctly installed on the piston. Replace the head gaskets. I can't speak to the Kawasaki CCV system; not familiar with it.

Most freshly rebuilt engines will smoke for a bit, burning up the oil used for assembly. Don't give up too quickly because it smokes on first start-up after rebuild.

Good luck. Let us know how it turns out.

 

[StarTech]

I don't see how the ACR would affect the compression test anyway, since I would think the cam balls would retract during the test, but as I said, the cam and ACR seem fine.

The ACR is active at cranking speeds then once the engine running it retracts. This why there is an ACR so the compression is less at cranking speeds as to not overload the starter. The service manual does states a minimum compression level with a working ACR.

440 kPa (64 psi) @ Engine Oil Temperature 50 ∼ 60°C (122 ∼ 144°F), Cranking Speed 450 rpm/5 Seconds

I threw my HFT compression tester and brought an Actron tester as I needed the 10mm adaptor and the fact the Schrader valve is at the cylinder end so it opens without having pressure the hose first.

 

[Rocket Surgeon]

Lawn Addict:
Righto, I had a brain-fart regarding the flywheel key. Upon disassembly I had already noticed that the flywheel key was in the key-way.

Also, you correctly quote the line from the service manual regarding compression, however it specifies the minimum compression. My previous comment referred to the fact that the manual addresses solutions for the compression being being too high but, as far as I could find, did not provide a specification for pressure that is considered too high.

My comment may not have been clear regarding the effect of the ACR on the compression. I understand the basic function, but I would expect that, at best, it would cause a lower compression reading if it is venting the cylinders during starting. Even if the ACR was not functioning, and the malfunction prevented the cylinders from venting, the compression would simply read the maximum compression. If it was malfunctioning and it prevented the valves from fully closing, the the compression would read lower than spec. Regardless, it seems to function properly on the bench. The control spring which governs the operation was found to be in place.

I hooked the compression tester directly to an air compressor and it accurately measured the line pressure, set at 125 psi. If there is a problem with my compression measurement, it seems likely it is with my process, though as near as I can tell I am doing it adequately.

Slomo:
I agree with all comments regarding the 180 psi. The service manual mentions crusting around the crown of the pistons as a possible cause for excessive compression, though it does not say what compression is considered excessive. I pulled both pistons and they, along with the cylinders and rings, are in great condition. I'll look at the crankcase breather today.

Thanks all.

 

[slomo]

So if your gauge is good and you see 180 psi, your ACR is definitely not working. As well as the stellar PSI number being over the top. I would agree at cranking only, you should see something like 64psi to less than 100'ish psi?? Running on a fully warmed up engine, around 120psi sounds good. At cranking your ACR will open a valve DUMPING compression to start the engine as you guys have discussed. Excess oil in the bore shouldn't cause 180psi. I would say 120-150 max psi. The oil would restore any poor ring sealing action. Clearly you have good rings rocking 180psi.

slomo

 

[Scrubcadet10]

Seems as though the few Kawasaki's I've done a compression test on, at cranking they were between 90 and 110 psi. Cold.

 

[slomo]

Seems as though the few Kawasaki's I've done a compression test on, at cranking they were between 90 and 110 psi. Cold.

Those numbers sound normal. Warming the engine, with excess oil in the bore, one shouldn't see 180psi. It's only an 8.2:1 motor.

To get 180psi, the cam timing MUST be advanced nicely away from stock.

slomo

 

[Rocket Surgeon]

I wish I was comforted by the high compression but I know from experience nothing comes for free. The service manual clearly states a compression ratio of 8.2:1...and that doesn't add up to 180 psi.

I checked the crankcase breather (valve?) and it is completely open both sucking and blowing on both the port that connects to the crankcase and the port that connects to the carburetor...does that seem right?