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125 timing story

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Joe Cullison

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Hello, my wife and bought a 125 with a tiller on it around 6 years ago. It has always been really hard to start. It was a battle to get it to start before I ran a battery dead or jumped it with my pickup. Once it started it ran pretty well and tilled great.
Lately it has not wanted to start at all. Then the driveshaft broke. I got the driveshaft replaced and also picked up a very nice mower deck and front plow.
I put on a new set of points and a new plug. I had checked the spark and it looks good so I tried point gaps between .014 and .026. Still wont start, not even close. After laying the plug on the block and looking into the cylinder while bumping it over I saw that it was sparking at the bottom of the stroke. I'm thinking I have a very serious timing issue.
The tech at Kohler said I likely have a sheared flywheel key.
Today I removed the engine and pulled off the flywheel cover. I found the timing mark on the flywheel and the cylinder is indeed at the bottom of the stroke when the T line is on the mark.
The key is still solid and perfectly lined up with the shaft. The gears on the camshaft are perfect with no chips. The crankshaft is not broken, both ends turn together.
It's looking like I am going to have to check the camshaft to crankshaft timing. Now I just need to figure out how to do that.
I'll see if I can find instructions but from a quick look it seems as if I will need to remove the flywheel and the plate underneath it to get at the camshaft.
I can't believe it ever even started and ran at all with the timing that far off.
Be well. I just needed to try to talk my way through it.
Joe
 

gary noblit

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Joe, just recently had a 321 apart because of comp. release.There were dots on all gears for proper timing..also some very thin thrust washers to watch for....I once bought a used engine from a dealer that sat on shelf for 25 yrs.Same type issue..It was one tooth off from the factory.....Doesn't seem possible that it could run 180 off....I (opinion) would chase everything !! elec. first.
 

kmcconaughey

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Kraig McConaughey
Joe, WELCOME! Can you post a photo of the top of the engine? Typically the spark plug is above the exhaust valve not the piston, so I'm curious how you are able to tell that the spark occurs at the bottom of the stroke?
 

dschwandt

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Take the plug out and turn the engine by hand till you start to feel compression build up.
Put your test lamp on the negative terminal of the coil.
It should spark when the points break.
If not, the problem lies with the points.
If it does light, then you will have spark at the plug providing it is grounded and do nit have a break in the plug wire.
 

Joe Cullison

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Sweet Home, Oregon
I took a picture of the top of the engine.
20210223_194829[1].jpg

It does look to me like the piston is under where the plug is laying.
If I am looking at the top of the exhaust valve through the spark plug hole then the valve must be closing when it is at the bottom of it's stroke. That is when it sparks. I don't think I have ever seen an engine that didn't have the plug lined up with the piston. I suppose that is why the stroke seemed so short.
I realize I must seem totally ignorant here but I can live with that. I do know enough to ask for help from those who know.
I did notice that when the plug fires I can feel it through the plug wire. I have a new wire to put on there.
It does appear to have some compression as there is a very noticeable difference when the plug is in and removed.
Thank you for your help.
I'm certain we will get this running again and starting easier.
 

mgonitzke

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You are seeing the exhaust valve. Everything is probably normal. Here are some instructions for setting the ignition timing. Start with that and we will figure it out from there.
 

kmcconaughey

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Yep, the plug opening is above the exhaust valve, the piston is under where you have the plug laying. It appears that some one may have been in there previously, the hole in the engine tin is where the original head had the plug, see the red circle I added to your photo below. The earlier Kohler head had the plug between the valves, the later head had it more over the exhaust valve.

Kohler Head.jpg


In one of my 125s I have a similar engine with a replaced head. Note the modified engine tin and muffler heat shield.

Killer Kohler_01.jpg
 

Joe Cullison

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Sweet Home, Oregon
Ok, I have a small update.
I had a few minutes today so I drained the oil to get ready to remove the oil pan and have a look at the timing marks. After a long day I wasn't ready to try to roll the engine over to get the pan off. I can't believe how heavy this engine is.
Instead I put the plug back in and rolled the flywheel over to see where the compression happens in relation to the timing marks. I found and marked the S and T and marked where the center of the sight window is on the flywheel backer plate.
The compression begins to build somewhere around 90 degrees after the T passes the sight window.
Somehow I think that is not correct. I'll go ahead and pull the oil pan off and see where all the timing marks are.
Thank you guys for all of your help.
Joe
 

etopel

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Ed Topel
Before you pull the bottom off, pull the head so you can see exactly where the piston is in relation to the valve movement and the points opening. Are you turning the engine in the right direction? They are installed "backward" compared to most machines. It turns clockwise when looking at the flywheel end.
 

Joe Cullison

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Yes, that is the direction I am turning it. Clockwise it is.
Everything I read said the S passes the timing mark before the T. The compression begins at about 90 degrees past the S and T. So almost straight down.
Thank you
Joe
 

jstich

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Jerry Stich
Well, that is a pretty good indication that the ACR (Automatic Compression Release) is working properly, but it doesn't tell you anything about timing.
The s is for spark, t is for TDC. Spark should occur before TDC.
Removing the head will verify whether the timing is correct without taking the pan off.
 

dschwandt

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David Schwandt
Is your condenser any good?
Wire broken perhaps?

Exhaust valve will be closed at the bottom/start of the compression stroke.
Compression starts there and the ACR kicks in, opening the Ex valve part way about .035" just for a second after that. This happens part way through the compression stroke BEFORE TDC.

Eyeball the exhaust valve through the spark plug hole during the C stroke and you should be able to see it move by eye. To make it easier to observe, place a dowel or short bolt on top of the valve, That is IF the valve is below the plug hole.

Put the S in the center of the hole and time it from there.
The points should just start to break/open at that point.
Adjust the points until it does using a test lamp or a VOM.
The timing is now set.
.It's all on the PDF Mat linked to earlier.

Microsoft Word - static_timing (mgonitzke.net)
 

mfrade

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I'd pull the flywheel off and check the key and shaft ways. You don't hear of these motors breaking keys often, but there are stories of damaged shafts and keys.
 

mgonitzke

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I'd pull the flywheel off and check the key and shaft ways. You don't hear of these motors breaking keys often, but there are stories of damaged shafts and keys.
In his first post, he said he already checked this. Doesn't matter, because a sheared flywheel key on a K-series has no effect on the timing since the points are actuated by a cam lobe.

Not to mention I have never, ever heard of a K-series shearing a flywheel key in my nearly 20 years of working on these things.
 

gpapa

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No start; could it be weak spark from a failing coil, bad ground, bad condenser. Assuming that fuel system is all good, maybe do an ohm check on the coil, plug, plug wire, etc. Somewhere on this website there was a coil testing procedure that included the ohm values. Timing would need to be in the ballpark for the engine to run and then would need a final adjustment to run properly. The only other thing; new stands for never ever worked and even new parts, especially electrical items, need to be checked. Good luck.
 

etopel

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I'm wondering if it could have an AQS flywheel on it. The sight hole is on the carb side of those and would put the markings about 180 off. I'm not sure if they would fit under that shroud. Just guessing out loud.
 

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