Kawasaki FR691V cam lobes with ball bearing

[Rocket Surgeon]

Greetings to all, new member here.
I am working on a Kawasaki FR691V 23 hp 2 cylinder engine, and after dismantling it and removing the cam shaft, have found that the two lobes nearest the PTO each have a single ball-bearing on the bearing surface of the lobe.

I repaired a bent pushrod, adjusted the valve clearance, and reassembled the engine. When I started it, it ran roughly and smoked. I removed the valve covers, checked the valve clearance, and all looked good. As I cycled the motor by hand, and watched the valve train operate, I noticed a little "jiggle" in one of the cylinder's valve operation...instead of a clean opening and closing of the valves. Since I didn't understand this behavior, and it was smoking, I thought perhaps I'd broken a ring or skipped a tooth on the timing gear on the cam, or perhaps a damaged cam lobe...so I removed the motor and opened the case.

The good news...and the bad news, is....I see no damage inside, no metal flakes, cam and crank are aligned, motor looks brand new, and all is good.

At this point I'm not sure what is going on, but I discovered that the "bump" in the valve train is undoubtedly being caused by these ball-bearings on the two cam lobes. Perhaps used to pop the valves open prior to the normal valve cycle.

I'll post later on the underlying engine problem if necessary, but for now, can anyone tell me what these cam lobe ball-bearings are all about? I searched Google extensively and found nothing.

I can post a photo of the cam lobes with ball-bearings if helpful.

Thanks for any input.

 

[StarTech]

The camshaft has an ACR (Automatic Compression Release) system. The design that Kawasaki design operates on both valves (off the top of my head I don't remember if it the exhaust or intake valves; though it seems to be the exhaust valves). If you look closer you see the ACR parts which contains six more steel balls besides the two you noted along a spring and retaining system. Here is a exploded view of the camshaft. IF you only see movement in only one the two valves at near TDC of the related cylinder's compression stroke then there is a problem is the camshaft.

 

[Rocket Surgeon]

Ahhh, I understand. The cam you have pictured appears to be what I am dealing with, and I have noticed the additional six ball bearings that you mentioned. Thank you for that input.

One thing I noticed is that the intake and exhaust valves cycle normally on one cycle, and then return to the closed position. In this closed position they reflect the .004 valve clearance that I set. However, during the next cycle, they become loose, with a clearance well beyond the .004 value. Is this normal behavior? Fyi, the push rods and valves are new.

A separate issue is that the compression tests unusually high (IMO) at 180 psi, in both cylinders. The local Husqvarna shop says this is ok. I'd be interested in additional opinions.

The motor originally started sounding funny, so I opened it up to have a look see. I found a loose rocker bracket and bent push rod. It appeared as though the rocker bracket retaining bolt had come loose, and allowed the rod to bend as it jumped from the pocket on the end of the rocker. There is a nub in the head casting designed to restrict the rocker bracket from rotating, and this nub was sheared off of the casting, allowing the bracket to rotate out of position, and to bend the push rod.

I reassembled the head, and used red locktite on the rocker bolt. It ran like a top for one season. (750 hours total time).

Recently, the mower exhibited a sudden loss of power and began smoking out of the exhaust (I would call the color of the smoke light blue, smells like oil). On the assumption that it might be a oil ring issue, I began disassembly.

When I removed the valve covers, I found that the same cylinder as before had bent the same push rod, and that the rocker bracket was again out of position. I guessed that the locktite didn't hold. I replaced the head with a new one, with the retaining nub intact, and reassembled with a new push rod. I did notice that the loose push rod had apparently knocked a hole in the floor of the block pocket containing the push rod, but the loose rod somehow didn't fall into the block. After reassembly, the motor ran roughly and still smoked. I found the valves to be heavily fouled and the plugs to be wet.

At that point, because of the valve behavior, apparently related to the compression release mechanism, I suspected that the loose aluminum from the bottom of the pocket, or perhaps a damaged tappet, had messed with the cam. I've now put the engine on the bench, and removed the case cover, cam and tappets. Everything looks normal, and I'll check the cam specifications to be sure.

I'll now pull the pistons and check the rings, though I seems unlikely to me (limited experience) that they are the problem with the engine having such strong compression.

Thanks in advance for any input.

 

[StarTech]

I wish I could be of further help but my experience on Kawasaki engine is limited too. I do know however the the lower 6 ball assembly is the governor for the engine as I had one on a customer engine last year.

It does sound something is flakey with the ACR on the camshaft as the normal cranking compression should be much lower with a working ACR. Maybe it spring is missing.

 

[slomo]

180PSI at cranking, you better have a hoss battery and starter. Pull starting, good luck.

slomo

 

[slomo]

Look up that parts schematic for YOUR engine like show above. Read the parts names. Should give you a clue on what they do. Isn't 92145 the ACR release spring?

slomo

 

[Rocket Surgeon]

Thanks all for the information.

Yes the battery does have a tough time turning it over.

For reference: When I said I was inexperienced; I should have said that I have no experience in small engine repair. I do not work in the industry.

I will focus on the ACR mechanism.

Does the smoke and fouled valves and plugs sound like rings? It seems a little odd that both cylinders would develop ring issues at the same time.

Thanks.

 

[Scrubcadet10]

what color was the smoke? Blue-ish white?

 

[cpurvis]

Your bent pushrod problem may be caused by the valve guide working its way out of the head. When it moves far enough out, the rocker arm collides with it and the pushrod keeps on pushing, and...the pushrod is the weak link and bends.

The valve guide migration problem is assumed to be caused by high cylinder head temperature, caused by inadequate airflow, caused by not keeping the cylinder fins clean.

If you can, measure the distance that each valve guide is above the valve spring surface on the head. See if the one that keeps bending pushrods is higher than the rest.

edit: added the word "guide" to the first sentence.

 

[slomo]

Your bent pushrod problem may be caused by the valve working its way out of the head. When it moves far enough out, the rocker arm collides with it and the pushrod keeps on pushing, and...the pushrod is the weak link and bends.

The valve guide migration problem is assumed to be caused by high cylinder head temperature, caused by inadequate airflow, caused by not keeping the cylinder fins clean.

If you can, measure the distance that each valve guide is above the valve spring surface on the head. See if the one that keeps bending pushrods is higher than the rest.

What was the part cpurvis about keeping the cylinder block cooling fins clean??

slomo