Are CCKs prone to sticky valves, or is it just me?

[Patrick]

I've picked up 2 3.5 CCKs that "weren't working properly" recently, in the last month, both only firing on one cylinder. Putting out about 150v instead of 240, under load. Both just needed the head taken off, a spray of WD40, then a light tap with a hammer to close the valve. Start up, and they run perfectly.
Burn no oil even under a far heavier load than they are rated for, and start on the button.
Just wondering if there is anything I can add to my gas/oil to stop this happening again, now that they are working?

[Birken Vogt]

We run an old woodsplitter with a 4 cylinder air cooled Wisconsin engine that gets stored outdoors with little protection. I suspect the valves rust. On the woodsplitter there is a tap with a little valve on the intake manifold (vacuum) where we fog it pretty heavy with marvel mystery oil before a prolonged shutdown. But I suspect if stored indoors and/or run more often, there would be no problem.

Birken

[BGunn]

Every CCK that I have ever worked with has had a sticky valve problem when run on gasoline. These were common in small Namco forklifts and Arctic Traveler refer units on semi trailers years ago. Both companies found the benefits of propane were numerous. Unfortunately if you run any carbureted engine a little rich with light load a lot of carbon builds up over time and coats the valve stem and the valve guide. The only way that I have found to deal with it on a generator is to add a cleaner to the gas every so often. Unfortunately with a generator and especially an air cooled one, trying to keep the temperature up no matter what the load is hard to do without a temperature sensitive air damper.

[Patrick]

Hmm, mine are used on gasoline only. They never get fogging oil because I fire them all up at once about every 8 weeks, to make sure the neighbours are awake at 7AM.
They've never got sticky valves in my ownership, maybe that's the reason? Stored indoors in a garage BTW, not out in the wet...

[Ben Cowan]

I acquired my 4.0 cck because no. 1 it was locked up. No.2 valve was stuck open, No. 3 because it is such a heavy SOB. No. 4. Previous owner has new motor home with new genset in it. I have a theory that these twin cylinder units need to be run under a good load to get the temp up. I believe that a run of 30 to 60 minutes once a month keeps the carbon from building up on the valves oppossed by units with very short run times that build up excess carbon and result in valve problems. Ben

[J.B. Castagnos]

I run me generators out of fuel, put a little 2 cycle mixed gas in and let it run out again. This leaves a light coat of oil on everything.

[VaughnSimon]

I am no CCK expert, just an owner of one unit. That said, I have been here on the SmokStak Onan board for several years and can tell you that stuck valves are not a terribly frequent complaint. At least, not frequent compared to certain other issues such as "bad points" or "stops running when stop switch released", or "flooding carb".

Vaughn

[Dave Edmonds]

I've got 3 opposed-twin Onan's (CCK, BF, NH) and have never had a sticking-valve problem with any of them. One is over 40 years old, the other two are not a lot newer.
I'm not sure if he has the "ultimate" answer, but I have a friend with a Harley V-twin who puts a small quantity of Marvel Mystery Oil in the gas tank every time he fills up. He has over 130,000 miles on his engine, and has never put a wrench to it, other than plugs, etc. Sounds like a bit of "top-end" lubrication might be a good thing, especially with what we get for gasoline these days.
Dave Edmonds

[Ben Cowan]

Hey Dave. Got any idea how much MMOil he's adding per gallon of fuel?

[Patrick]

Hmm, I might throw a bit of Redex into the fuel as well then, as a preventative measure!
Cheers all.

[Dave Edmonds]

I will ask him in order to find out for sure, but I think he's adding about 1/2 ounce per gallon. (Not a lot). I'll report back.
Dave Edmonds

[Ben Cowan]

Hey Dave, guess I'll save on of my stabil bottles, it has a small ounce measure built in on the side of the main spout. Should be mighty fine for measuring small amounts of MMoil or other desired additive. Ben