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Kohler K161 Rebuild :(


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  #1  
Old 07-21-2014, 08:48:09 PM
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Nevr-Enuf-Stuf Nevr-Enuf-Stuf is offline
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Default Kohler K161 Rebuild :(

The engine on my 1962 T707es loader Panzer, see my avatar, gave up this weekend. I was able to shut it down before the rod let loose but once I started hearing it knocking it quickly escalated. I havnt had the chance to pull the engine and start tearing it down, Im hopeful that a rebuild will get it back up and running and that it wont need an engine replacement. This was my Great Uncles Panzer and of course I want to keep it as absolutely original as possible. This will be my first small engine rebuild so Im probably going to be posting some questions for advice and guidance. First of which, Ive already read where there was an early and late version of the K161. Early version is a small bore without compression release and the later version being a large bore with compression release. So, I have to make sure of the parts Im getting for my engine which should definitely be the early version. Also Ive heard that no one offers a rebuild kit for the K161, K181 and others yes but not the K161. Anyone who has been through or rebuilt one of these I would be very grateful for any help. I'll also have to see if any of the machine shops around here can or will do the machine work.

Patrick
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Old 07-21-2014, 10:39:51 PM
K-Tron K-Tron is offline
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Default Re: Kohler K161 Rebuild :(

Hi Patrick,
I have rebuilt a couple Kohlers, it is pretty critical that the bore is trued nice and straight when boring oversize. The rods seem to be the weak point in these motors, and just about everyone that I have had apart had an egg shaped bore. I did get lucky once and saved a K241 from coming apart. It sounded like the rod was going, but ended up being a loose governor control nut. The nut backed out so far the governor was just dancing about! They are good little engines, but unlike B&S, its a little harder to get parts for some of the older Kohler engines. I try to use only genuine parts in my Kohlers, but most of the late model K series/Magnum series genuine parts are made in India and not USA. I do not think that there was ever an aftermarket anything for the K161, so perhaps you can score good/new parts on ebay made in the good ole USA.

Chris
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Old 07-21-2014, 11:44:07 PM
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Default Re: Kohler K161 Rebuild :(

Rapid knocking getting louder was probably the connecting rod bolts backing off. Not entirely unheard of in k-series engines.
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Old 07-22-2014, 02:45:49 AM
dkamp dkamp is offline
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Default Re: Kohler K161 Rebuild :(

I second both Lead and Froehlic's points-

I've rebuilt around a dozen of the K-series engines, the older models and the newer. I had two that performed the automatic rod-bolt-loosening routine, and one (a K241) had the BOLT sitting in the bottom of the pan, unscathed... and running fine otherwise. How it survived is beyond me, but it's problem was a stuck valve, not a conrod issue.

The VERY VERY EARLY K-series motors K241 and down, had no compression release... they had a centrifugal spark-retard system (and the engineers made it clear that it was not an 'advance'... it was a 'retard')... you'll see a diagram and description in the early K-series manuals. I've never worked on one with that feature, primarily because the idea was apparently abandoned in lieu of the 'valve delay' compression release concept which used a little metal tab on similar centrifugal weights to delay closing of the exhaust valve, and 'waste' some of the chamber volume to reduce compression for starting. The metal tab would sometimes break off and render the concept non-functional, and most of the time, that tab would fall to the bottom of the pan and drain out with next oil change. Sometimes it'd go someplace er... less desireable.

Back to typical issues... yep, they egg and taper the bores, like any air-cooled engine might. The crank throw and connecting rod wear most rapidly on the thrust axis, and the sides don't... because it's not a pressure-lube system. They also foul the valve stems with oil residue (like any flathead can), causing inconvenient power loss and strange temperament. They warp heads when mice make nests in the shrouds, and the oil breathers get plugged up with crud and cause excessive crankcase pressure, resulting in annoying leaks around the breather, crank seals, breaker point cover, fuel pump (where equipped) and large-scale mosquito-suppression out the exhaust. Sometimes, the points get oily enough to not fire well, and you get a whole lot of argument, and a blown-apart cannister or pepper-pot muffler.

Aftermarket support is good for all the K-motors. I'm pretty sure everything down to the K161 is carried by STENS... pistons, rods, rings, wrist pins. A 'full rebuild kit' however, isn't something I ever found... gasket sets yes, carb kits yes... but rebuild kits no, because you're deaing with crank bearings and seals and a pan gasket...everything else is reused unless bad. That meant boring the block, grinding/polishing the crank, and doctoring the rod to fit crank, then slapping it back together with new piston, rings, and a little blue loctite on the rod bolts.

On mine, I bored the blocks myself. Initially, I just drilled a flat plate to mount on the faceplate of my 22" Lodge... has holes that match up to the bottom of the block, and has X and Y slide space to center the block accordingly, and ran a boring bar down the middle to cut it true. I didn't have it at the time, but nowdays I'd run 'em on the Bullard VTL, just because it's easier having gravity turned 90 degrees.

More occasionally than we'd care to experience, a K-motor will break the rod loose, and swing around and slap the bottom of the cylinder wall area, and take a bite of iron out about the size of a half of a half-dollar. Most will dismiss the block as shot, but in reality, there's not much going on down that far, save for a little oil control... in high-zoot pulling tractor engines, guys will intentionally knock material out of there to make room for aftermarket high-strength forged rods (like Lakota). If you have a chunk in the cylinder, just get in there with a grinding stone and smooth out the chunked area, so that there's no rough edges to grant a good spot for a crack to start forming... then bore, hone, and clean it.

Grinding the crank throw requires using an offset chuck system. I've got a friend with a crank-grinding offset chuck system, he can set up and grind one round really quick, so I don't bother doing it myself.

Doctoring the rod isn't difficult, and I find it a fun task for some strange reason. Concept is simple- you have a hole that's egg or oval-shaped, and a crank that's ground say 0.010" undersized... so accomodate by milling off the rod at the rod-cap parting joint... and do same for cap, so that the rod hole is now short (and consequently, no longer 'round'). Now securely bolt them back together, and bore them to precise fit around the freshly ground crank. End result is proper fitment... no rattling, and no binding.

Don't be afraid to put in new valve guides, lap the valves in, and establish proper tappet clearance so they seat. Once it's back together, it'll run dandy for another 30 years.
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