Intake valve not moving on ST1032 / Tecumseh 10HP - Snowblower Forum : Snow Blower Forums
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post #1 of 34 Old 02-06-2016, 10:24 PM Thread Starter
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Intake valve not moving on ST1032 / Tecumseh 10HP

Hello all.
I heard a small pop, or snap then the engine stalled. It appears that the intake valve is not moving when I turn the engine by hand. Not sure where to start other than tearing into it and finding out what's broken. I get the feeling that I'm about to explore the bottom end... Any advice or prior experience is appreciated.

Snowblower: Ariens ST1032 924084 serial# 010536
Engine: Tecumseh HMSK100 159119V (H)
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post #2 of 34 Old 02-06-2016, 10:32 PM
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Camshaft may have snapped mid-shaft. Pull the side over off to check.

Any signs of crankcase damage (bulges, holes etc) in the path of the connecting rod? Wonder if it threw the rod and the rod itself acted as a battering ram and broke the camshaft. Just guessing...
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post #3 of 34 Old 02-06-2016, 10:54 PM
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it looks like the spring retainer busted. They're cheap. You'll have to pull the head and remove the valve. While you're in there, it would be a good time to check the valve clearance & reseat the valves.

was it overrevving when it happened? These valve springs will float above 3600RPM.


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post #4 of 34 Old 02-06-2016, 10:56 PM Thread Starter
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No signs of crankcase damage, but I haven't seen the bottom. No oil pouring out so that's a plus.

I just removed the belt cover and the crankshaft appears to still be in one piece. If the exhaust valve is moving then that would indicate that the teeth driving the camshaft are whole. Maybe a lifter?

I don't know small engines but I've dissected many auto motors.
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post #5 of 34 Old 02-06-2016, 11:02 PM Thread Starter
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Quote:
Originally Posted by classiccat View Post
it looks like the spring retainer busted. They're cheap. You'll have to pull the head and remove the valve. While you're in there, it would be a good time to check the valve clearance & reseat the valves.

was it overrevving when it happened? These valve springs will float above 3600RPM.
Yep. It was revving high, but then again I don't know the rev spec. I got the machine for free from a friend so I really don't know 'normal operation'. I replaced the carb and set the high idle revs by ear, but it appears I guessed wrong.

Power while throwing snow was a bit low and I noticed that the muffler was red hot after ~ 15 minutes of running. I understand that can be an exhaust valve problem or a carb tuning issue correct?
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post #6 of 34 Old 02-06-2016, 11:11 PM
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Quote:
Originally Posted by rpl3000 View Post
Yep. It was revving high, but then again I don't know the rev spec. I got the machine for free from a friend so I really don't know 'normal operation'. I replaced the carb and set the high idle revs by ear, but it appears I guessed wrong.

Power while throwing snow was a bit low and I noticed that the muffler was red hot after ~ 15 minutes of running. I understand that can be an exhaust valve problem or a carb tuning issue correct?
3600 is the max RPM measured on a warm engine.

you already have the breather cover off...go ahead and put a feeler gauge in between the lifter & valve stem to measure the clearance (with the piston at TDC)...there's a good chance that it's not closing completely and you're losing compression.


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post #7 of 34 Old 02-06-2016, 11:40 PM
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Quote:
Originally Posted by rpl3000 View Post
No signs of crankcase damage, but I haven't seen the bottom. No oil pouring out so that's a plus.

I just removed the belt cover and the crankshaft appears to still be in one piece. If the exhaust valve is moving then that would indicate that the teeth driving the camshaft are whole. Maybe a lifter?

I don't know small engines but I've dissected many auto motors.
Look at the bright side, this one only has one cylinder, and two valves, and you can lift it yourself. I can't tell from the picture if something is broken in the valve spring, but if a complete rotation of the crank only operates 1 valve, the it's either camshaft or lifter. Hopefully, any shrapnel from either landed safely in the bottom of the crank case, out of the way and didn't crack the casting where the lifter goes through.

If you have to open the engine, and you find that the problem is not overly expensive (depending on the age and history of the engine) you might as well check the other bits and pieces, such as governor gear, cylinder bore etc to see if there's any other things that need TLC before you bolt it all back together. Don't forget your gasket set.

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Last edited by skutflut; 02-06-2016 at 11:45 PM.
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post #8 of 34 Old 02-07-2016, 12:30 AM
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This is what you will be looking at after opening it up. Not to bad if it's just a valve. It could me bent chipped or even fell out after being damaged from over rev, stuck from high temp, valve bounce, etc. You got lucky you can still turn the engine over.
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post #9 of 34 Old 02-07-2016, 01:50 PM Thread Starter
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any tips to get the crankshaft pulley off? I got one set screw out, but the other one is stuck. Currently soaking with PB blaster.

Is the shaft tapered?
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post #10 of 34 Old 02-07-2016, 02:06 PM
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Heat it up using mapp gas and a puller. Just don't fry that crankcase seal.
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