Rebuilt K301 Knocking

[mattd860 161]

I finished rebuilding the K301 about two weeks ago but had to finish some minor wiring before firing it up. Today I finished the wiring and started the motor. It started right up and idled nicely however when I revved it up even slightly, it knocked very loudly I can't tell if it's coming from the piston or the valves. The engine doesn't smoke at all.

Here's a bit of history of what I did:

-Replaced piston, rings, wrist-pin, rod, & seals with STENS rebuild kit from ebay.

-Removed balancing gears since bearings were worn.

-Had a shop verify the crank and cylinder were within spec (they were).

-Adjust the new valves after lapping them.

-Lubricated rod to crank shaft with assembly lube and poured some 30wt oil on the rings prior to new piston installation.

-Filled crank case with 30wt oil and marvel mystery oil in gas to make sure everything remained lubricated.

The only complication I ran into during the process was when I bolted the rod to the crank shaft. The directions stated to torque the bolts to 22 ft lbs (260in lbs)and not to remove and re-torque. So I set my torque wrench to 22ft lbs and began to tighten the bolts however as I was turning them, I didn't hear the distinct 'click' from the torque wrench and I know 22ft lbs isn't a lot. So I stopped and got a new torque wrench the next day. The new torque wrench had a dial on it instead of the twist handle. When I checked the torque on both bolts they were above the 22 ft lb spec so I backed them off and re-torqued to 22 ft lbs. However, after I did that, I could not turn the crank shaft because somehow 22 ft lbs was no too tight.

So I backed the bolts off again and had to determine the necessary torque in order for the crank shaft to turn with little force. Any torque past 8ft lbs made the crank impossible to turn so I ultimately torqued the bolts to 5ft lbs and used thread locker to prevent them from coming free.

If you can understand my rambling - is this where I may have screwed up? Should I just go get a new rod? Will the engine possibly stop knocking after I run it for a while. I only ran it for about 5 minutes before shutting it off.

[rueger-99 0]

Somethings not right with the rod/crank clearances. I wouldn't run it again until you pull it apart and see what's going on.

:thumbs:

[clintonnut 126]

Somebody might have confused a .010 rod with a standard. You'll be lucky if you don't need to regrind your crank now and actually NEED a .010 rod.

Charlie

[daemon2525 5]

I agree with the others. It sounds like that rod is a bad fit.

You should be able to tighten the rod bolts down better than that and it still turn.

[mattd860 161]

Got the engine apart today. The rod and crank are scored but not badly. The oil is black and has a ton of very fine metal bits in it. The metal bits are the same aluminum color as the rod. The new piston and rings looked good. I bolted the rod back to the crank shaft after removing it from the engine and there didn't seem to be any play but I'm sure they must be when the engine is firing and turning at +1500rpms.

I'm bringing the rod to a local machine shop on Monday and I'll let you know.

One question on the rings. They both have the inner chamfer indicating up or down. However, one ring is all black and the other ring is black with a chrome 'lip' on the outside. Which one is the top ring?

[IDriveWheelHorse 0]

Theres really only a couple things that will make these engine "knock".

Number one and for most reason is the crank pin (or journal as some call it). It seems as though that if the rod had a loose fit it would knock and thats what happens 95% of the time with these engines.

Now you said that you could only tighten it down to 5 lbs???

Probably either the wrong size rod or your journal is out of round. Take a dial and measure it in two spots and see what you get.

[gzx3sc 0]

I've rebuilt several of these Kohlers, 8-12HP and I always end up with a knock at light load mid throttle. What I've found is my machine show (performance minded) bore based on piston size. They claim the piston sizes are all over the map on these re-build kits so they bore based on the actual size of the piston. That said I end up with more compression than these engines were intended to have. I back off on the point gap to retard the timing and it has helped considerably. They run great at wide open throttle with tons of power, no noise at all.

[Polaris2007 4]

My newly rebuilt K301 has a very slight noise that is evident in the mid range RPM with no load, AND my machine shop also bores according to the actual piston diameter. They made me give them the piston before they would finish the bore. They are definitely a performance oriented shop too. Could you explain how slightly higher than normal compression could produce this knocking, and how retarding the timing a little helps this? It is so slight in my engine that I can easily ignore it, or I might order a new rod from Kohler and see if that helps. It has a STENS Rod and piston in it now.

[gzx3sc 0]

Spark knock is what we're hearing. Higher combustion pressures will ignite the charge earlier so setting the timing "by the book" doesn't work anymore. Changing the point gap from 0.020" to 0.015" retards the timing which cuts back on spark knock. In other words it opens the points later. When it sparks before top dead center, it hammers the crank on the wrong side of its power stroke which isn't good. If pre-ignition gets bad enough you can break a crank or a rod.

[Polaris2007 4]

BLINK! The light just went on! That makes perfect sense. I have been planning to get a timing light to do a good accurate timing on it anyway. I think the points are set on the high side of .020" right now. I think I'll try .015" tomorrow and see if it helps. Thanks a bunch! Would the points being set slightly over .020" explain this K301 being a real bear to start. It runs perfect once you get it started, but it's a bear to start.

[gzx3sc 0]

If the timing is advanced too far it will generally crank harder. Don't mess with the timing light. Like I said the factory settings are not valid anymore anyway. Backing off the point gap to 0.015" helped mine considerably but it didn't go away completely.

[mattd860 161]

Wow I will try this too but I'm not going right to .015 since my K301 is bored .010 over, not .020. I will try .017 & .016 first since I am still experiencing somewhat of a knock but it's so slight I was prepared to live with it before reading these posts.

[rmaynard 14,932]

Wow I will try this too but I'm not going right to .015 since my K301 is bored .010 over, not .020. I will try .017 & .016 first since I am still experiencing somewhat of a knock but it's so slight I was prepared to live with it before reading these posts.

The size of the bore has nothing to do with where you set the points.

[mattd860 161]

Oops. I thought I read gzx3sc say that compression was increased if the cylinder was bored. Definitely a bad case of reading too quickly.