How worried should I be?

Was mowing the grass with Miss Cubby II (Cub Cadet model 70 with a K301 12HP engine). It started acting funny, engine speed was erratic, then all of a sudden it was like the throttle wasn't doing much. I moved it back and forth and it didn't do much, eventually it came off an idle and was running a bit faster than I was comfortable but the throttle lever wasn't doing anything. I shut it off before I let the noise out of the connecting rod. Opened the hood to see what I could see. Noticed I can't move the governor arm back and forth with the engine off. I play with it a little bit and the governor arm pops off the carburetor arm. H'mm maybe that's the problem, I look some more and the arm on the carburetor looks like it's bent down, I grab it and try to bend it and the whole darn throttle shaft comes out the top of the carburetor. At this point I've identified the problem- the throttle plate has fallen off the throttle shaft explaining why the throttle/governor wasn't doing much. I rolled it back to the shed and finished the grass with the walk behind mower. I took the carburetor off the cub and the throttle disc fell out (no surprise) I look up the back side of the carburetor and one of the screws is MIA, the other most of the head is broken off. I get the screw shaft out with a pair of needle nose vice grips. I've gotten replacement screws for the butterfly and a new bushing to go into the top of the carburetor and some lock-tite to keep them where they belong.

Here is the question -I can't find the missing screw, how worried about that should I be? Should I remove the fuel tank and the shrouding, pull the head and see if it's in the cylinder? Or do I figure it's really small, made of brass and probably some where south of the exhaust valve, re-install the carburetor and call it good?

My mother bought a "cottage" and this was in the garage of the place when she moved in. The spark plug threads in the head were stripped out and the PTO clutch had been "improved" to the point it didn't work anymore. I installed a used head, PTO clutch and clutch lever and it has been working pretty good. With the quality of some of the work on this unit and the fact it was someone's "up north mower" it wouldn't surprise me if the screw's disappearance pre-dated my ownership.

As long as it isn't hammering away in the engine I wouldn't worry. My dad had a rider eat a screw but it sounded like Thor was banging around in there. I had to open it up to get it out.

I've had cars eat things like that. One of my VWs ate the accelerator pump jet (brass) and it nailed me in the shin when I was standing back there revving the engine to figure out what was wrong. It didn't dawn on me until later when I found it missing that this was what had flown out of the exhaust.

Do you know of any body that might have one of those cameras that you can put in spark plug hole and take a look around in cylinder?

That is why they use brass screws. The brass is softer that the piston, head, valves,etc so it will take the beating without doing any major damage and be spit out the exhaust. Or so goes the theory. Hopefully.

I'd pull the head. Good time to check out the gasket and carbon situation too.

If someone you know has a bore scope light you can< look >into each cylinder for the screw. Still have to pull the head if you find it. Hal

Pull the head . It only takes a few minutes

I have seen screws go through an engine without a trace, and I have seen them imbedded in the piston, (accompanied by a lot of noise). Since you are already experienced at removing and replacing the head, it would be best to pull the head and just make sure the screw isn't lurking around somewhere.

I had a '77 Dodge Omni, 4 cyl. engine that ate a throttle plate screw. Acted just like your Cub when the plate shifted out of position in the carb. Never effected the engine, no increase in oil usage, or anything that I could see. Not a good car overall but did last us 9 yrs for short drives to work, this was the second to last Chrysler product I ever owned, the last was an early ( 1988 ) Dakota that had a major tranny failure along with a number of engine issues. Wife forbids any Chrysler product on the property.

UPDATE Finally found the right screws, ended up buying a throttle shaft kit with a bushing and the screws. I would of pulled the head if it hadn't been off 25-30 hours ago and I had or knew where to get a head gasket for it (I live in a really small town). Judging from the way it acts now compared to what it was before it quit the screw has been missing a while, maybe since last fall or at least all spring. Of course I had to back the idle screw off quite a bit to be able to get the throttle plate screws started and tightened. I eyeballed the plate position to reset the idle screw before I put the carb back on and was surprised that it idles about where I want it, started a lot quicker too! I used purple Lock-tite because that's what Lock-tite recommended for screws that small. Now if it would only stop raining long enough for the grass to dry I could mow. It's been so wet here some of the farmers are wishing they went for rice in their crop rotation plan and I hear a rumor the motor home plant up the road is thinking about switching over to Arks.

Well gotta go- the week is going buy fast and I have Honda heater hoses and wheel bearings to do and if I can find my stupid refrigeration gauges I might be able to get the air fixed on the truck this week. Still waiting for Honda lawnmower parts, those Honda mowers are good but every 25 years or so you have to put wheels on them and fix the drive ratchets but hey it still starts on the first pull most of the time.

Thanks for your input. I would of tried the boroscope but it won't clear between the block and head. The head I'm using has the spark plug over by the valves.

I used one of those bore scope lights on a Ford Mustang. Never seen so much carbon in an engine.
Had to rebuild the engine. Hal