K301 Bizarre Starting Problem

[Hephy]

A few months ago I acquired a Cub Cadet (109, I think) with a K301 motor. When I first got it, it had some starting issues that I temporarily remedied by replacing the spark plug (which was black with carbon and wet with fuel). However, now that I’ve done some what should have been pretty basic maintenance on it -- including pulling, de-carboning and planing the head, and adjusting the valves -- it won’t start at all, and exhibits some very strange symptoms.

First of all, despite the battery having a full charge (12.65v), the motor cranks very slowly, and seems to pause between successive revolutions of the starter/generator. And when it does actually turn over, it spits a mixture of brown smoke and atomized fuel out the mouth of the carburetor on every other revolution.

This behavior seemed so strange to me that at first I thought I must have switched the battery leads, and that I was somehow running the motor backwards! Although the battery is in fact hooked up correctly, I wanted to be sure that I really was getting suction on the intake stroke anyway. So I closed the fuel valve and switched off the ignition circuit so that I could safely put my hand over the mouth of the carb.

To my utter surprise, with my hand blocking the air intake, the S/G cranks at normal speed, with no hesitation — and I do get suction on the intake stroke. (BTW, for the record, I haven’t had the guts to try this same experiment with fuel flowing and the ignition enabled. )

I asked the previous owner of the tractor (who is much more mechanically savvy than I am -- I'm really quite a noob) to come over and have a look, and he is also stumped. We’d be leaning toward an explanation involving failure of the automatic compression release if the slow cranking symptom was consistent -- and wasn’t eliminated by covering up the air intake.

Any ideas what might be happening here? Or what we might try next, to figure out what’s happening?

To the best of my recollection, here’s the complete list of maintenance items I did between the time it was starting OK and now:

• Pulled head, cleaned carbon; planed head, reinstalled w/ new head gasket & torqued to spec;
• Cleaned carburetor, tested carburetor float, examined needle valve (looked good), renewed rubber gaskets at bowl & fiber gasket at attachment to block;
• Did valve adjustment (.010 intake, .018 exhaust); renewed fiber gaskets behind breather plate.
• Checked coil: 9500 Ω (+ to tower), 2.6 Ω (+ to -) [that second number seems a bit low]
• Replaced condenser;
• Removed, checked & reinstalled points (looked clean, no pitting).

Next post, I’ll try to attach a video of the difference between cranking with the carb mouth uncovered vs. covered up.

[REDDHOGG]

Recheck timing and valve adj.

[Hephy]

We verified the valve adjustment as part of trying to get to the bottom of this. The clearances are dead nuts on .010 (i) and .018 (e), and the valves move freely throughout the full 2 revolutions. Likewise the point gap is dead nuts on .020.

Neither of us had any clue where to find the timing marks, but a search just now turned up J-Mech's Static Timing article, so will check that ASAP.

[Hephy]

Okay, video is posted at https://www.youtube.com/watch?v=YF-P2Mxpy8A

On the first cranking attempt, the ignition switch is on, and you can clearly hear the pauses, followed by the whoosh of the smoke/vapor out of the carb. If you look closely, you can even see the smoke/vapor come out on the final rev.

On the second cranking attempt, the ignition is off (so I don't get my hand blasted), and the cranking proceeds without any pauses at about the cadence I came to expect when everything was working normally.

Not shown (due to my oversight) is what happens when the ignition switch is off and intake is open. In that case, the cranking pauses as (in the first instance above), but of course there are no expulsions of smoke/vapor from the carb mouth.

[ol'George]

Your battery appears weak, and the timing is a bit too much advanced.
Check your ground strap @ the engine to frame and battery to ground.
Also your starter might have a broken magnet inside.

[Dart1917]

When you cover the intake you prevent the cylinder from filling on the intake stroke so there is nothing to compress and the motor turns over easily. Check the compression release.

[Hephy]

Originally Posted by Dart1917

When you cover the intake you prevent the cylinder from filling on the intake stroke so there is nothing to compress and the motor turns over easily.

A-ha! Now that makes sense to me, finally!

Check the compression release.

Yes. Can you point me to one or more posts on this site that discuss in detail how to check the ACR? My (perhaps faulty) understanding is that it's completely internal to the motor, and that there's nothing to see without taking the motor apart.

Is that not true? Or is the check not visual in nature?

[Dart1917]

One way to check would require pulling the head and watching the exhaust valve on the compression stroke. At some point it should lift off the seat a little bit when turning the engine over slow. You should be able to see the ACR spring on the cam by removing the cam gear cover on the side of the engine. I have heard of people changing the spring from there but I've never tried it.
http://www.kohlerengines.com/onlinec...df/tp_2379.pdf

[Yosemite Sam]

You can also remove the breather cover and watch the exhaust valve move when you turn the engine over by hand.

If you remove the cam cover you can also actually see the acr mechanism.

[Alvy]

All good advice. Use the static timing method and not points gap as stated. Make sure as viewed from the front, that you're engine is turning over counterclockwise. Also you're off on the model, if it came stock with k301 you have a 122 if it's gear drive or 123 if it's hydro.