Valve problem?

The last couple times I tried to use the tractor, it had trouble starting. The last time it didn't start at all, but I didn't have the time or tools to mess with it. So today, when we were heading out to the cabin with lots of time, I brought the tools...

I started by putting a charger on the battery. Then, I pulled all the plugs and cleaned them with a propane torch. And since the plugs were out, a compression test seemed like a good idea. 90-30-90-90. Bad valve?

To make things interesting, though, I put the plugs back in and tried starting. Surprisingly, it started very easily (when I pulled the choke for a fraction of a second). Seemed to run smoothly, too.

When I finished mowing, I let the engine cool off, and retested the #2 cylinder. 90 psi. Do sticky valves become unstuck in a running engine? Or is something else going on?

On the bright side, the replacement radiator (that I installed back in the spring) seemed to be doing its job nicely on its first real test on a warm day. Previously the engine would overheat within 20 minutes, and the oil pressure would drop under 5 psi. Today, I mowed at full throttle for close to an hour--no overheating at all, and for much of the time the oil pressure (at full throttle) was around 20 psi, although by the end it had dropped to 10.

-Paul

An old tired ring (or two) can stay temporarily stuck in its ring groove, when that piston is sitting at the bottom of its bore for a lengthy time.

Cylinder walls taper from wear over time so that they are smaller at the bottom. When they are too tapered (funnel shaped) is when and why one rebores the block.

Just a thought.

sure
rings and valves can stick when sitting even a short time,
especially with rust or carbon muck present.
When lucky and things don't break, a good hot workout will loosen em up....sometimes...

run your favorite snake oil in the gas for a few tanks to help clean things up a bit.
(ATF, MMO, Seafoam)

You can run it-them with the oil too, but I personally don't like anything in the oilpan except good oil, so if I do use them for a flush in the oil, short hot run, then change the oil.

Glad it is working out for you.... nice to have a tractor you can use.

I have never understood, though, why folks think that running at full throttle is the proper way to use machinery... on rare occasion and for a short time... measured in SECONDS, yes. I have never seen anybody work their own BODY at full throttle unless in a foot race, either.

Doesn't work in horse farming, either. Just sayin'...
duey

Duey,
My teacher in ag class in HS told us that a tractor engine was built to run WOT all day every day and not hurt it.
I'm not afraid to open mine up once in a while.
Not working it hard, but like yesterday running it from one property to the other, it's starting to sprinkle and I didn't want to get wet.
So I hammered it - all the way - about 4 miles and made it before the deluge.
I got there and let it idle for about 5 minutes before I shut it off

Thunder Road!
Did you have your Ultradog Tee shirt on?

There's your "good hot workout" as previously mentioned in this thread -- probably cleaned up your piston tops and valves to a degree.

It's like they say when buying a car . . . "It's only got highway miles on it and that's when Grandma drove it to church."

Yes, valves can stick when setting and unstick when running.
I have one engine out here that does it fairly regularly.

Personally, I think its a sign of other problems though.
Too much crud in the engine or inadequate oil flow, etc.
I have no technical data to back that statement, just my opinion.

Thanks all!

An oil change is probably in order anyway, so perhaps I'll pour in some snake oil and let it run a bit before I drain it.

As you can tell from the compression and oil pressure numbers, a rebuild is probably not too far in the future. Not desperate, though--there is some oil pressure and the compression is at the low end of acceptable (at least after that valve or ring worked free). It will wait until I finish rebuilding my '49 Jeep.

As for throttle--I wanted the PTO speed high for the mower. While the engine speed was high, it wasn't actually working very hard. (Except when I got to the 7 foot high grass--that needed two passes, the first with the mower raised high.) How much difference is there between full throttle and the "second screw" recommendation for 540 PTO rpm? (I'll try to remember second screw next time, though.)

-Paul