ReBuilding a K301S

[IronPony]

I want to rebuild or have rebuilt my K301S but I am not sure what all this takes - OK - I have to have the cylinder bored and what else? What happens to the valve seats before putting in new valves? After that what is left to do other than change out the piston, new valves and ?? I think I am convinced that I should rebuild this myself. Dan www.family-fishing.com

[MikeES]

Typically the K series Kohlers will require: Most likely to least likely. The cylinder bored, new piston, new rings to fit new bore size. Grind the valves and valve seats, this may require a new exhaust valve if it is badly burnt. Carb rebuild. It may require the crankshaft journal to be ground down and new oversized bearings. It may need a new camshaft. Of course all new seals and gaskets. Check an engine rebuilder instead of a small engine shop. I have experience with a complete rebuild (without camshaft) for $400. Most small engine shops send the engine out to an automotive rebuilder for the boring, grinding, and "boiling out" work anyway. Good Luck! Mike S.

[Dutch]

I think Mike offered an excellent suggestion. Suppose you spend $200 or more on parts, another $100 with a machine shop, and the rebuild turns out bad, who do you think will be blamed? If you don't already have one, get the Kohler manual and read what a rebuild entails.

[HubbardRA]

I agree with Dutch. I rebuild my own engines, but to do this a person must know exactly what to look for inside the engine to determine the extent of the work to be done. I did one this spring in which all I installed was new rings of standard size. I had another that had to be bored and a new oversize piston installed. It also had one valve stem that was worn out of spec. It takes a lot of time checking and measuring if you are trying to save money on parts. Usually a rebuilder will just do it all to prevent overlooking a critical item. If you do it yourself, you are taking a chance and betting on your abilities. Rod H.

[arjr111]

Hi Dan, I agree with the above comments, especially if you are in dire need of the machine and can not afford to mess up an engine. If not, there is a "fun factor," and "learning experience," that can make a rebuild worthwhile, even/especially, if you have never done one. I learned more from my rebuild, than I could ever get from reading posts. But, like I said back when you first posted there will be an additional outlay for the tools you need to do the job. And like Rod says, you will be doing a lot of measuring, to determine what is, or is not, within specs. Take Dutch's advice and buy a manual, it will give you a walk through, and, an idea as to whether you feel confident enough to undertake the challenge......good luck.....Art BTW, is yours knocking or just blowing smoke?

[IronPony]

Art, Thanks for the reply (thanks to ALL that sent a reply). The engine seems to have plenty of power but puts up a good smoke screen when started and when put under load. Goes through about half quart of oil (30w HD) per tank of gas. I think I can manage a rebuild but do not want to have the tractor down while I do it. Thanks again, Dan www.family-fishing.com

[arjr111]

Dan, if the motor is not knocking, pinging and is producing sufficient power, chances are it may require nothing more than new standard rings. Of course you would need to remove the rod, and piston to replace the rings, (which would require engine removal), and IMO, you may as well replace the piston and rod, too, but if they are within specs. and not damaged/burned/scored it would not be necessary. It is really quite easy to pull the 301, head, and measure the bore with a telescoping measuring tool. This will let you know if your cylinder is within specs. (whether or not it will need to be bored oversize) and give you a look at the piston, and valve conditions. You would need the Kohler single cylinder engine, service manual, a new head gasket, a 3"-3.5" telescoping measuring tool, a measuring caliper, and a torque wrench to replace the head after inspection......Art

[HubbardRA]

My philosophy is that if the cylinder is smooth, no lumps or bumps, and no scratches, then I will put in new standard rings. I know they will not last as long as original because of the cylinder wear. I usually take the chance because making a 20 year old engine last another 8 - 10 years is good enough for me. If I find any flaws, then I bore and put in oversize piston and new rod to put it back like original. It doesn't have to be totally like new to run good. Rod H.

[powerking_one]

Even if a cylinder looks totally smooth, scratch/score free, and appears to have no defects, it can be REALLY screwed up dimensionally. That's why the bore must be mic'd. Preferably measurements are taken 120 degress apart at 4 different depths. Kohler CI singles are very prone to out of round an taper wear problems. If the bore isn't true, you'll have a smoker and blowby "special" after the rebuild. On STD bore cylinders with some wear, but still in spec and good overall condition, I get .010" OS rings and file the gaps down till MINIMUM gap spec is reached at the tightest area/depth of the ring travel. This usually takes a very slight amount of filing. Typically, if STD rings are used, the gap(s) end up near or over the maximum. My $0.02 worth

[acjohn]

Powerking makes a good point. Always...ALWAYS check ring end gap. Even if everything is supposed to be to spec. If the ring end gap is too tight, the ring can bind in the cylinder bore and wreak havoc on new rebuild. Use a piston to ensure that ring is square in bore and use a feeler gauge to check end gap. File if it isn't at least the minimum spec. Takes 5 minutes and you know everything will work.