K301 Knock Under Load

[rustykan 140]

Now that I have started using the C-120 I restored, I've noticed a knock, only when under load. I did not do any work on the engine as it seemed to be running very well. The only thing I did engine related was remove the head and valves. Cleaned everything up, checked the gap on the valves, installed a new head gasket and put it back together. Am I looking at a connecting rod problem?

[Theroundhousernr 589]

Could check timing. If to advanced it will cause a pinging similar to a knock. Try retarding the timing first. I would also mention carbon build up but does not sound like the case since you cleaned the head. Also , unlikely , but could be the fuel. I am betting timing. Most of the kohlers I hear with a knock are through all rpms and under load actually get quieter .

[oldredrider 2,547]

As stated, try setting your points at .018 and see if that helps. Today's gas leaves a lot to be desired. Old Kohler engines were designed to run on the fuels at the time they were manufactured. Certain concessions and a little bit of tweaking seem to be the order of the day.

[WH nut 553]

If timing doesn't correct the problem I would say its piston slap