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Discussion Starter #1
Hey,

First I have an old Davis trencher. In this trencher, I have an old Wisconsin Air Cooled engine, single cylinder (model AGND) I just put a brand new piston and rings in it a few weeks ago. It ran decent up to last week when my coil went bad. I bought brand new: Coil, Condensor, and Points and put ALL them in today. I set my points on 015" like it calls for. I also have a new spark plug and it's gapped correctly ( 030" ) So from my magneto, I'm getting good fire.
I know I'm getting good fire because, I took my spark plug out of the spark plug hole and cranked the engine over. It sparked so good that it was burning the gas off the end of the plug that we poured down the in "head" to "Prime" with.
Since we was getting good fire, we "primed" poured a little gas into the spark plug hole. we poured maybe 2 to 3 tablespoons into the hole.
After no response we manually checked the compression by putting our fingers/thumbs over the spark plug hole. The compression kept blowing my thumb off it.
As me and my neighbors think, with plenty of "fire" and priming it with gas, and with good compression, It should show a little sign of doing something, but it don't.
Is there anything else we should look for?? If the timing was off, Shouldn't it still do "Something". 'Cause it don't do nothing. We even dipped the end of a screwdriver into the gas we're using and lit it with a cigarette lighter to make sure it wasn't water :lol: Yep, it was gas. Like I said earlier, even the spark plug was burning the gas off the end of it outside the "head".

Thanks for any info..... We all walked away from it tonite looking like :freak:
 

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Discussion Starter #3 (Edited)
Thanks,
My neighbor has a compression gauge, but it doesn't thread into, (fit) by hole. I'm gonna ask around at work tonite and see if anyone there might have one. By the way, In case I find a gauge, what is bad compression /..lbs? The engine is a 12 1/2 HorsePower Single cylinder. I made a homemade "flapper" for my exaust pipe, like tractors and stuff has. when I turn the motor over, the flatter goes up and down like it did last week when the thing was running. And, I put my hand also, over the suction line (breather line) That was, to me, sucking pretty good, I thought.

My neighbors come back yesterday saying "so and so" told them a certain color of spark (blue, white, yellow, red) might have something to do with it. Is there any truth to that?

Oh yeah, The kill switch on my magneto is "Old Timey" to say the least. So I got inside the box and ran a small wire from my kill switch screw over to the screw on my points, where my coil hot wire and condensor wire goes. Looking at it very closely last night, it looked like the copper strands on the kill switch screw was allfull close to the inside of the box (metal) If it was not touching the box, but was allfull close, could it possibly "arc" over to the box, causing it not to fire once I thread the spark plug in??? I'm gonna put a "stake on" on it when I get back over there.

One more thing the ditch witch (engine) is setting a little "cockeyed" on a hill. I noticed yesterday that when we poured gas in the spark plug hole it was running right out of the carburator. So I jacked it up a little. Think it might need to be leveled out to where the gas can "run" towards the piston? OR would that make a difference?

And what's with the keyway? I checked the timing it's in Time.
Thanks for any info
 

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blue spark is good. orange/yellow is weak. compression can vary. ive had engines run on 60lbs.180 was the best ive seen.100lbs seems to be the rule with minimal leak down.
 

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Discussion Starter #6
O.K. I checked compression....

Checked compression on it today. It's holding at 45 lbs. Is that good or bad? Would 45 lbs. 'cause the engine not too "HIT"?? It's in time. I have a good spark, and we're pouring gas down the spark plug hole. Why won't it "hit"?? Again, It's a 12 and a half HorsePower motor, Single Cylinder, Wisconsin Air Cooled Engine, Model AGND.

Thanks again for any info....
 

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Discussion Starter #7
Welp, I found the problem...

As for the top ring on the piston, It broke half into. Don't know where it went but it broke. It breaking,......damaged my cylinder wall. That's why my compression was low. Gonna tear into it tomorrow or tuesday. Will probably have it bored, if possible.

Shoot I just put a new piston and a set of rings in it, not even 2 months ago!!!

Thanks for posts
 
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