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124 won't start.....again.

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John Garrison

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Discussion starter · #1 ·
I recently replaced the voltage regulator on my 124 with the one from my 125 just to see if that was the reason for it not starting and everything was fine. Since replacing the V/R I have plowed snow 4 times and it ran fine. I've been pushing some really deep, heavy snow with the only issue being an occasional sputter/exhaust backfire when I press the clutch while pushing heavy snow.
The issue now is that it won't fire up. It ran fine while plowing and when done I parked it in the garage and hooked it up to the trickle charger like I always do in sub-zero temps. The next time I went out to fire it up it wouldn't start. It was -15(-40 with windchill) that day so I got the garage heated up to about 40 degrees and let the tractor sit for 3 hours with an electric heater pointed at the oil pan. It is getting plenty of fuel and the spark is very strong but it will still just crank and crank without even the slightest sign of wanting to ignite in the cylinder. I have used it in cold weather like this all winter long and it has fired right up...well, except for when the voltage regulator quit working but that's beside the point.
When cranking it does not make any unusual noise indicating a broken connecting rod or any other internal issue. The engine is an original, unrebuilt K301 with who knows how many hours but it has always ran fine. It's just frustrating because it ran fine one day and not the next. It has fuel and spark, but no fire. Today it's about 30 degrees outside and it still will not start so the weather is not the issue.
What would you guys check first? I'm thinking maybe some carbon may have come loose and blocked a valve from closing all the way and making enough compression to start? I checked the cylinder compression and it's at 30PSI. That is extremely low and I'm thinking it's the result of an obstructed valve. I mean, I know the engine is old and probably doesn't have full compression anymore, I'm aware of that. However, it wouldn't just run one day with no indication of low compression like smoking and excessive oil consuption and then suddenly refuse to start because compression was so low from warn out rings or whatever. It would be using oil and smoking before that would happen.
Any thoughts?
 
#2 ·
Replace spark plug, plug may be bad and spark is getting blown out under compression


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Discussion starter · #3 ·
I could try replacing the spark plug but it's only about 6 months old and the plug appears to be putting out a very healthy spark. Bad plug or not, it would not be causing the engine to have only 30P.S.I. of compression.
 
Discussion starter · #5 ·
anixon said:
I would check valve clearances.
Click to expand...
My first item on my list is going to be checking tappet clearance at TDC but it's still kind of odd how one day it fires right up as it always does, with normal cranking effort, and then the next day it won't even attempt to start. I'm just going to check the tappet clearances and remove the head and inspect the valves. If all is well in those areas then it must just be it's not making enough compression to fire. Which as I said before, seems kind of weird since it doesn't smoke or hardly use any oil. Usually you can tell when an engine is getting long in the tooth and needs a rebuild.
Now that I think about it, I'm almost positive it's the valves that need adjusting because I recall back when I was putting in a new clutch and turning the engine over by hand, I did hear a hissing sound coming from the valve cover breather that sounded a quite excessive.
I'll let you guys know what I figure out when I tear into it in the next few days; hopefully!
 
Discussion starter · #7 ·
I opened the valve cover last night and in the process of rotating the engine to find TDC I saw the exhaust valve set screw was moving around. Everything was just loose and sloppy. I haven't had the time to make the proper adjustments yet but I'm pretty sure that's the culprit of my failure to start problem. I still ordered a new head gasket and I'm going to clean up the combustion chamber while I'm at it and look for carbon pieces that may be causing an obstruction.
When I bought the tractor I had noticed signs of a head gasket leak. When I was doing an initial tune up before my first time starting it I found a wasp nest on the cylinder cooling fins and I'm sure this was the culprit of the slight head gasket leak. The head gasket has leaked slightly for as long as I've owned it and this is as good a time as any to replace it.
 
Discussion starter · #8 ·
I removed the head and inspected the valves at TDC, it was quite a sight as you will see. Also notice all the old burnt gas sludge where it's been leaking out of the head. Yes that is gas and not oil. The headgasket definately needs to be replaced.
The piston doesn't hardly have any side to side motion when wiggled so the piston and rings appear fine just as I suspected. I did notice a few scratches down the length of the cylinder walls. My guess is that it's from carbon chunks falling down and scratching it up. Other than that it's smooth as can be in the cylinder; even at the top.
Take note of all the carbon on the exhaust valve and the fact that the picture is of the engine at TDC and both valves are slightly open still. It's no wonder the engine has hardly any compression; both valves set screws are so loose I can spin them with a flick of my fingertip. I also noticed someone else had been inside there not too long ago and scraped carbon off the piston. That would be my only explanation for the scratches on it.
Even though the cylinder has some scratches, still it has a tight seal(for now). Would you guys bother taking the whole engine apart to hone the cylinder or just clean the combustion chamber, adjust the valves, and run it like it is for now?

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Discussion starter · #9 ·
Really? All this time has passed and nobody has a comment? I thought for sure someone would take a look at that burnt up, warped exhaust valve and say, "Well there's your problem right there".
Since the engine is apart I'm going to install new rings and some new gaskets. The cylinders are true and only need a little freshening up but I did notice a potential problem with the camshaft.
I dropped the oil pan and noticed one of the teeth on the camshaft gear had a chip taken out of it. I checked the oil for metal debris and it was totally clean. This was the second time since owning it that I had emptied the oil and I've never seen metal chunks or even flakes in the oil. This chunk must have been chipped off long before I bought it.
That being said, the reason for it not running right was valve related and had nothing to do with this new issue. My question is, should I just leave it as is since it doesn't seem to affect anything or should I spend the extra money and replace it? All I'm using this tractor for is plowing snow and moving trailers. I really don't want to spend $130+ on a new camshaft when the whole tractor cost me only half of that.
 
#10 ·
John Garrison said:
Really? All this time has passed and nobody has a comment? I thought for sure someone would take a look at that burnt up, warped exhaust valve and say, "Well there's your problem right there".
Click to expand...
Funny, I read this thread for the first time when you posted the photos and thought to myself "John has got this nailed" so I didn't add to your already excellent review of what was happening in the combustion chamber. I was curious to if the valves were sitting proud due to carbon deposits or were the seats out of alignment.

Regarding the cam shaft, I would suggest having it filled and reground. Since you've gone through the trouble of getting so much correct in this old work horse, why not go all the way. If though you only use it for plowing...if it breaks you're stuck. Then you'll really be kicking yourself.
 
Discussion starter · #11 ·
Gary in NJ said:
...if it breaks you're stuck. Then you'll really be kicking yourself.
Click to expand...
If it does break I have a new walk-behind Cub Cadet snowblower, an L8 Gravely with a dozer blade, a Cub 125 with a 42" snowblower, and a 4wd Kubota tractor to finish the job. The 124 is just my favorite for snow removal.
The half-missing tooth on the camshaft has held up this long and it will probably outlast me. I could buy another used camshaft on Ebay with fully-intact teeth for like $35 but I don't really want to spend money on another used part with no warranty that may or may not even last as long as my slightly damaged camshaft. I'm sure the heck not paying well over a hundred dollars for a brand new one. That is crazy considering I've paid less for automotive camshafts. I'll probably just cannibalize one of my other K301 engines.
 
#12 ·
Since the 125 is from the same series, couldn't you take the whole motor and drop it in the 124?
 
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#13 ·
John Garrison said:
The half-missing tooth on the camshaft has held up this long and it will probably outlast me. I could buy another used camshaft on Ebay with fully-intact teeth for like $35 but I don't really want to spend money on another used part with no warranty that may or may not even last as long as my slightly damaged camshaft. I'm sure the heck not paying well over a hundred dollars for a brand new one. That is crazy considering I've paid less for automotive camshafts. I'll probably just cannibalize one of my other K301 engines.
Click to expand...
Well it sounds like you've answered your own question.
 
Discussion starter · #14 ·
Diesel332 said:
Since the 125 is from the same series, couldn't you take the whole motor and drop it in the 124?
Click to expand...
Great minds think alike. I already swapped the 125's engine into the 124 three days ago but I would like to fix the 124's engine and put it back in since I already promised my Cub Cadet 100 that it would get the 12 horse from the 125. I don't want any sibling rivalry going on.
 
#15 ·
:howdy: I may have missed it, but I see nothing in your post about doing some valve work. I would pull the valves, clean them and the seats up and lapp them. Depends on how big of a chip is on the cam gear wether to re-use or not. I would check the cam gear for cracks and if your going to re-use round the edges of the chip. :smilie_fl
 
Discussion starter · #16 · (Edited)
dbuck said:
:howdy: I may have missed it, but I see nothing in your post about doing some valve work. I would pull the valves, clean them and the seats up and lapp them. Depends on how big of a chip is on the cam gear wether to re-use or not. I would check the cam gear for cracks and if your going to re-use round the edges of the chip. :smilie_fl
Click to expand...
Sorry, I failed to mention that I was going to lap the valves before adjusting them. I just figured everyone knew that was essential to do on old cruddy valves before readjusting them.
After tearing further into the engine my plans have changed. The valves need to be replaced entirely, a good portion of the top rim of the piston is burned and eroded away, the top piston ring is in pieces, and the cylinder has numerous scratches. The scratches are clearly visible but they don't feel as bad as they look. The crank journal does not have any grooves but the connecting rod surface that mates to the crank journal is discolored. The rod cap is also fine. The valve guides are also in real good shape. The cylinder bore is at 3.3745". Those are about the only things this engine has going for it.
What would you guys do with this engine? I want exact build details please.
Here are some photos of it's insides:

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Third tooth down from top is the only damage.
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Nice scored up cylinder walls. Crank journal visible through bottom.
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Check out the ridiculous piston ring end gap! It measured out at .072, how is that even possible?
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Beautiful, isn't it?
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Well there's yer problem right there. With the valves all covered in carbon, exhaust valve warped and burnt, both valves out of adjustment so bad they wouldn't fully close during compression stroke, and the broken piston ring, I'm surprised the thing even ran as long as it did!
 
#18 · (Edited)
If it were mine....I'd bite the bullet and go through it. Be done with it and expect years of life from it. I just did a AQS321 and total bill for parts (stens) & machine work was $288 which was $60 more than one I did a year ago because they had to turn the crank on this one.

Why risk a catastrophic failure at a later date? If that tractor isn't worth that kind of an expenditure to Ya, I'll give Ya that sight unseen for it!!
 
Discussion starter · #19 ·
I'm going another route. Instead of paying $288 on machine work I was able to trade a little bit of my time to help someone fix something and in trade I got a real nice K301 block that doesn't need any machine work, only a refresh job. I've never paid more than $150 on a Cub Cadet in my neck of the woods and often times I find them TWO for that price. It's just not worth it to me to spend almost $300 on machine work and another $100 on a rebuild kit on an engine that's going into a beat up old tractor that I got for free. If I go that far I might as well restore the whole thing but that's not going to happen because it's just a fun little machine to me, not my livelyhood.
Then again, that is just where I stand now because I have a lot of other things going on but I think in the future I'll take your advice and do a full restoration of one of my old Cubs just so I can have one that's not always down for repairs every other year.
Even though I found an alternative route to go, thank you for your time and advice.
 
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John Garrison
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