GroundLooper wrote:

I'm pretty certain it's a stuck valve, probably two. Nothing that a few bales of cash won't resolve. I just need to find out where they're harvesting some. Aggrevating as it is, I'm still really happy that it didn't die at Minam.

Craig,

I had to do the rope trick to our old 172 before we rebuilt the engine the next year. It is not hard to do if that is what is wrong. The O-300's are good at sticking exhaust valves, the rope is stuffed down spark plug hole. Then the piston is gently brought up to put pressure on the bottom of valves; this allows you to remove valve springs without valve falling out until you want to drop it into the cylinder; if necessary. Sometimes you can smack the valve stem with a soft hammer and break it loose, or lash up to a rubber hose and a small hand drill to lap in; if needed. Sometimes, before undoing the spring, you can put air pressure in the cylinder and smack the top of the valve with a soft hammer to move the valve under pressure, may break the valve loose.

Another thing to check is the OHMS resistance of each spark plug. Plugs should be less 5,000 ohms, if it pegs the meter, 20-30,000 ohms, no matter how good the spark plug looks, it will not work properly. It needs replaced. They are easy to check.

These are simple things and easy to do. Did you find a local mechanic to help or bring your mechanic to Joseph? Keep us posted.

We had a lot of fun in our 172! But I am now addicted to the 235 hp in our Maule. Good luck!


John

Little John wrote:GroundLooper wrote:

I'm pretty certain it's a stuck valve, probably two. Nothing that a few bales of cash won't resolve. I just need to find out where they're harvesting some. Aggrevating as it is, I'm still really happy that it didn't die at Minam.

Craig,

I had to do the rope trick to our old 172 before we rebuilt the engine the next year. It is not hard to do if that is what is wrong. The O-300's are good at sticking exhaust valves, the rope is stuffed down spark plug hole. Then the piston is gently brought up to put pressure on the bottom of valves; this allows you to remove valve springs without valve falling out until you want to drop it into the cylinder; if necessary. Sometimes you can smack the valve stem with a soft hammer and break it loose, or lash up to a rubber hose and a small hand drill to lap in; if needed. Sometimes, before undoing the spring, you can put air pressure in the cylinder and smack the top of the valve with a soft hammer to move the valve under pressure, may break the valve loose.

Another thing to check is the OHMS resistance of each spark plug. Plugs should be less 5,000 ohms, if it pegs the meter, 20-30,000 ohms, no matter how good the spark plug looks, it will not work properly. It needs replaced. They are easy to check.

These are simple things and easy to do. Did you find a local mechanic to help or bring your mechanic to Joseph? Keep us posted.

We had a lot of fun in our 172! But I am now addicted to the 235 hp in our Maule. Good luck!


John

Thanks for the info. My mechanic is out there looking at it today. While I don't want to become an A&P, I do need to learn more skills to field fix these sorts of problems, particularly since stuck valves are not uncommon on the O-300. I need to pack a few more tools, including a rubber mallet in my box of supplies. I should pick up an old cylinder and practice some of these techniques on it as well and find that grizzled old mechanic to show me first hand.

If the airplane was at home, I'd take more time to play with it.

The Bushwheel folks have generously offered hangar space and I don't want to dilly dally around getting it back out of their hangar.

One stuck valve. This is the same one that stuck on me shortly after I bought it and, from what I've gleaned, wasn't the first time. It had been reamed out which made it even more prone to sticking in the future.

The jug is off and is being overhauled. That should reduce the likelyhood of this one sticking again from what I understand.

Stuck a valve twice on my C85. First time unstuck with a screw drive. Second time had it reamed. It had a Auto stc and when auto fuel ran fine. Only stuck after having to use ll100 all the time. My 0300 in a 1962 172 flew lots with no valve problems. Again. Lots of autofuel and great luck.
My first stuck valve was on take off. Got it stopped before the runway ended. Second was on run up three weeks later. I did put new rings in just because when the jug got back.
Good luck and carry some rope and the tools to us it.
ML

GroundLooper wrote: One stuck valve. This is the same one that stuck on me shortly after I bought it and, from what I've gleaned, wasn't the first time. It had been reamed out which made it even more prone to sticking in the future. ...........

Why should (properly) reaming out the guide make it more likely to stick in the future? Should prevent it. However, it may lead to the valve wobbling around & allowing the valve seat to erode-- eventually to the point that it won't make compression at inspection time. Kind of a screwed if you do, screwed if you don't situation.
About 800 hours after overhauling (with new ECI cylinders) the C145 in my old C170, I had an exhaust valve stick, hard. Did the rope trick, valve was tight in the guide so I reamed the guide with a .437" reamer, no further problem with that one. Had another one stick, hard, at about 1000 hours SMOH, so I did the rope trick on all of the rest & had to ream 2 more (the other 3 were fine). That took care of sticking valves.
FWIW I've had 3 incidents of hard-sticking valves & every time it was with that Continental and happened on startup.

The way I understand it, with the larger gap around the valve, more hot gasses enter, vaporize the oil which builds up carbon.

I find that part to make some sense in how it forms in the first place. There are recommendations that running cooler reduces carbon buildup. What I find confusing is that lead also contributes but doesn't burning hotter reduce lead buildup? It sure works on the plugs.

Heading over to Joseph, I leaned more than I normally do but was running at less than 65% power and up around 7500' where it was cooler.


After reading more it seems the general rule of thumb is: Don't run it too hot but lean it out so it doesn't run too rich or cold either. Shaking a dead chicken over the cowl before every flight can't hurt.

Sounds like you will be back in the air soon. Good deal!