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Hi Everyone,

I have recently gotten into working on older Ariens (80s-00s) and currently have a ST1236 (924076) with an OHSK120 motor.

When i went to buy it i gave the cord a big pull and it ripped the handle right out of my hand and i thought it took my arm with it. Arm was sore for a week. Eventually got it started and it runs fine once its going. Clearly the previous owner also had issues as the electric starter gear is completed stripped and won't engage at all.

My first thought was the exhaust valve lash so when i got it home i brought it to TDC and checked the lash and sure enough it was .013" when spec is .004" so i thought that's definitely the issue and because it was so far out the compression release was not engaging on the compression stroke. Brought the lash to .004" and gave it another pull and this time it ripped the handle out of my hand and broke the handle and a part of the recoil starter on the kickback.

Scratching my head i double checked the lash and it was correct (.004). I've never heard of a snowblower having a sheared flywheel key, but know that can cause kickback on mowers so i took the flywheel off and checked the key and it was completely fine so the timing should be correct. I then gapped the coil with a business card and put it back together. I fixed the broken recoil starter and gave it another pull and it still kicked back.

I talked to a small engine shop owner and he suggested bringing the exhaust valve lash to .003 (spec is .004) so i did that and then pulled the recoil over with the valve cover off and i can see the exhaust valve every so slightly bumping during the compression stroke, not sure if its enough to lift it off its seat to reduce compression or not. Attempted to start it again and it still kicks back!!

Pretty stumped at this point and curious if anyone has any familiarity with this engine. There does not seem to be much info on it out there. I did see one forum post that someone said tecumseh had advanced timing issues with this engine from the factory and the fix was to retard the timing one tooth and that actually resolves the issue without reducing power as they had over advanced the timing in the original design. Has anyone else heard of this? Any other thoughts on what could be causing the kickback?

I did read a few people said leaky carbs can cause hydrolock. Is this possible?

Thanks in advance!!!


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Welcome to SBF JB1212
177329


IF it was hydrolock you'd yank the cord and it would stop abruptly. The raw fuel wouldn't be able to ignite as it would foul out and ground the spark plug. If it did pull over there would be gas coming out the exhaust.
Hopefully one of the guys more experienced with that OHV might have a solution.


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Welcome to SBF! Lot of smart and knowledgeable people on here. Hope someone has your answer. Your making the right steps except .003 & .004, Come on Man, Really, .001, doesn't matter, he gave you bad advice.

I had that problem with the fresh gas I bought, same kickback, cord handle hit my knuckles, pain. I put that gas in 5 mowers and did the same thing, I wish I was ambidextrous. I went to a Top Tier gas station with an empty gas can, drained the gas from 5 mowers, and all of them started fine.
 

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Discussion Starter · #4 ·
Thank you both for the responses, i appreciate it! Definitely a lot of good knowledge here.

The gas tank did have some debris in it when i got it so i took the tank off, cleaned it, replaced the fuel line and put new fuel in it and still have the issue unfortunately :/. I have run the same fuel in another blower without issue.
 

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Discussion Starter · #6 ·
Makes me think of advanced ignition timing.
Hi Chris, any ideas of what else could cause advanced timing other than a sheared flywheel key, which i already ruled out? I wouldn't think a bad coil could cause advanced timing, but could it?
 

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Hi Chris, any ideas of what else could cause advanced timing other than a sheared flywheel key, which i already ruled out? I wouldn't think a bad coil could cause advanced timing, but could it?
On a car, yes.
On these engines I have no idea, but I have very little experience with them so it doesn't mean it's something bizarre.

Are you sure it kicked back, as in literally fired and pushed the piston back down. Or is there a chance the compression release simply isn't working?

Its hard to know what you experienced via text. I have an 8hp briggs that doesn't have a compression release and I have no idea how I don't break the string pull starting it. But I know what to expect and make sure I pull hard.
 

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The breaker point gap can change the ignition timing to cause that, even faulty points and condenser will cause the 'Kick-Back' problem on an engine that uses points.
An older 'Electronic' ignition coil can also do that when the 'Pick-up' sensor in the ignition coil goes bad and throws the timing out of spec.
By replacing the coil with a new one, it usually stops the 'Kick-Back' problem at start up.
The air gap between the ignition coil/armature and flywheel can change the ignition timing a little bit, but usually not enough to cause the kick-back that severe unless it is way out.
Some electronic ignition coils use a 'Pick-up' or 'Signal coil' to tell it when to fire, others use a 'Zenor' type diode to sense change of direction of the magnetic field when the magnets of the flywheel pass the legs of the coil and as soon as it changes direction, the 'Zenor Diode' signals the main ignition coil to 'Fire' because the 'Charge' is at its 'Peak'.
If the 'Zenor' diode goes bad, that will throw it out of 'Time' and cause a 'Kick-back.
 

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The breaker point gap can change the ignition timing to cause that, even faulty points and condenser will cause the 'Kick-Back' problem on an engine that uses points.
An older 'Electronic' ignition coil can also do that when the 'Pick-up' sensor in the ignition coil goes bad and throws the timing out of spec.
By replacing the coil with a new one, it usually stops the 'Kick-Back' problem at start up.
The air gap between the ignition coil/armature and flywheel can change the ignition timing a little bit, but usually not enough to cause the kick-back that severe unless it is way out.
Some electronic ignition coils use a 'Pick-up' or 'Signal coil' to tell it when to fire, others use a 'Zenor' type diode to sense change of direction of the magnetic field when the magnets of the flywheel pass the legs of the coil and as soon as it changes direction, the 'Zenor Diode' signals the main ignition coil to 'Fire' because the 'Charge' is at its 'Peak'.
If the 'Zenor' diode goes bad, that will throw it out of 'Time' and cause a 'Kick-back.


I'm curious how a bad condenser could cause it?
 

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How do you tell if you have a Zenon diode? Is there a physical difference? What engines use a Zenon diode? More specific to certain equipment?
 

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Discussion Starter · #12 ·
The breaker point gap can change the ignition timing to cause that, even faulty points and condenser will cause the 'Kick-Back' problem on an engine that uses points.
An older 'Electronic' ignition coil can also do that when the 'Pick-up' sensor in the ignition coil goes bad and throws the timing out of spec.
By replacing the coil with a new one, it usually stops the 'Kick-Back' problem at start up.
The air gap between the ignition coil/armature and flywheel can change the ignition timing a little bit, but usually not enough to cause the kick-back that severe unless it is way out.
Some electronic ignition coils use a 'Pick-up' or 'Signal coil' to tell it when to fire, others use a 'Zenor' type diode to sense change of direction of the magnetic field when the magnets of the flywheel pass the legs of the coil and as soon as it changes direction, the 'Zenor Diode' signals the main ignition coil to 'Fire' because the 'Charge' is at its 'Peak'.
If the 'Zenor' diode goes bad, that will throw it out of 'Time' and cause a 'Kick-back.
ST1100A, thank you. I really appreciate the feedback. I did not realize that could happen. My thought was if the coil started to go bad it would retard the timing if anything and not advance it.

My machine does have a solid state ignition (PN 35135B). I am going to order an aftermarket coil on amazon and give it a try! I will report back with results. Thanks again.

Amazon Coil Link

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A bad condenser could discharge at the wrong time by 'Leaking',causing an 'Arc' at the breaker points, making the engine miss fire or fire before it is supposed to.
A Zenor Diode is built in to the coil as part of its 'CDI' or 'Electronic' discharge system. The Diode is one part of what makes it work, there is a condensor, a capacitor, and a 'Thyristor' or another word for it is a 'Signal Switch' to make it discharge or spark.
Most small engines have all of that built into the ignition coil, some use a little box mounted separately as on some Kawasaki engines.
Motorcycle engines have a separate box, usually called the 'Black Box' that houses all the parts in an epoxy so they are not visible, and isolates them from vibration and helps insulate them from heat.
There are a lot of videos explaining how electronic ignitions work. Some are called 'CDI' some 'TPI', DTPI' and other names. The 'CDI' is the most common name.
 
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