Kohler Command Pro 25HP CH730S cylinder heads

[myedsore]

Hi Guys

After some advice. I have just stripped down my cylinder heads after a bent pushrod and corroded exhaust valve was discovered. I took ownership of the mower with this damage so am trying to get it back up and running as cheap as possible so I can check out the rest of the components.
Both cylinder head gaskets were leaking and the barrels were caked with dried oil / carbon. The side with the bent pushrod on the exhaust the valve seat had dropped out slightly. The valve is corroded and will need replacing.

Unfortunately the valve seat has a tiny hairline crack down the side nearest were the corroded edge of the valve was. I have tapped the valve seat back and plan to peen the edge to stop it dropping back out. In theory I know a new head is in order but until I can access the running engine I don't want to spend lots of money on something that may work out cheaper getting a new engine completely.

I have cleaned up both heads and the valve seats and existing three valves seem good condition so I plan to buy a new exhaust valve, lifter, four pushrods, four springs, stem seals & head gaskets to get her back up and running. Also I will lap in the valves prior.

My only concern is the cracked valve seat but I plan on stripping the mower over winter (Australian) so will fit new cylinder heads etc then.

Attached is the two cylinder heads one showing a crack.




Can the exhaust valve seat be reseated as I don't see any part numbers for valve seats anywhere?

Thanks for any input.

 

[ILENGINE]

I didn't find parts numbers for the seats either, but did find that the part number for the head has superceded twice.

 

[motoman]

Since you do your own work the repair attempt to the loose seat may be worthwhile. I do remember guidelines from Corvair repair where peening was used. But I think that method will not hold up. Try tradeoff of weld fill and remachine vs new head. However , again, I do believe the degradation of the aluminum alloy (softening) during weld could ruin the whole effort. Berts...?

 

[Rivets]

The Command Pro engine do not have replaceable valve seat inserts. You are down to two choices, find a used head or purchase new. Sorry for the bad news.

 

[bertsmobile1]

And it will leak like a sieve through the crack which will pressureise the crankcase cause more blow by and all your good work will be a waste of time.
Buy a new head.
Now that Prime Line has exited Australia I get all my Kohler parts from Jacks Small Engines in the USA.
Including postage ( use USPS ) they are 1/2 to 1/4 of the local price due to Kohler's wholesale pricing policy and 100% retail mark ups.
Eg your flywheel $ 770 in OZ / $ 125 in US , your stator $ 475 in OZ / $ 122 in USA.

Those Kohlers are very robust so check the rods for play and the cam shafts for wear in the bushes, buy the new bits & button it up.

 

[myedsore]

Yeah I agree I probably should buy a new head. My main concern is if I get it all back together it may need new oversize pistons and reboring and I read somewhere that some of these engines can't be rebore but then again they sell the oversize pistons & rings for that model so go figure. Maybe someone can enlighten me.

If i was going down the path of a new head, I really should be using new valves, etc etc but then the price was creeping up again.

Bertsmobile don't I know about the price difference! That is why I am buying from US, we get raped here on prices. A new cylinder head locally is A$470, A$180 from US. Yes I am pricing all my stuff from Jacks Small engines although OPEngines also ship to Australia as do Shankslawn, all three have similar prices.

 

[ILENGINE]

Some of the Kohler 25 hp engines used a nicosil plated cylinder which cannot be oversized. If the oversized parts are available for your spec number then you are probably OK.

 

[myedsore]

I managed to get a secondhand head complete with valves in good condition. Same part number as well however how now discovered it came of a vertical shaft engine so the oil drain back is not drilled from the rocker side however I assume I can just drill it through.
Anyone done this looks pretty straightforward and can't see any other issues.

Guy I bought it off had a yard full of bits just lying around but was cheap.

 

[bertsmobile1]

Get out the Black & Decker and make a hole