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Discussion Starter #1
A friend's son out oil in the gas tank and tried to start the thing. The gas system has been flushed and everything else done to correct the problem. Now the recoil starter is hard to pull but once I get past that spot it will move until it seems to hit that spot again and then will jerk the rope back sometimes. When I use the electric start it hits a spot where it strains to move but when it gets past that point it will turn the motor over fine and will start the motor which wil run fine. I am about to take the motor apart but does anyone have any idea what the problem could be? Bent crankshaft or something else?
 

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Just a guess but I'd say there is a little oil in the cylinder that is reducing the cylinder volume thus increasing compression. Remove the spark plug, spin the cylinder a few times to clear the oil, replace the plug and all should be fine. You ill probably need to replace the plug as the oil will most likely foul it. Just a guess.
 

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Just a guess but I'd say there is a little oil in the cylinder that is reducing the cylinder volume thus increasing compression. Remove the spark plug, spin the cylinder a few times to clear the oil, replace the plug and all should be fine. You ill probably need to replace the plug as the oil will most likely foul it. Just a guess.
What he saidΔΔΔ
 

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I'll add to put a little Sea foam into the cylinder through the spark plug hole to dilute the oil. You could pour a cap full of gas but be careful not to start a fire if the fumes are exposed to a spark like from the spark plug wire.

Just spinning the motor with the plug out will not get all of the oil out. Also once you get it to fire that oil in the cylinder is going to make carbon. Best to dilute it with sea foam and then spin the motor with no plug in.
 

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Discussion Starter #5
I can get the thing to fire up and run so there is no problem with oil in the cylinder. I just talked to the lady who owns the snowblower and she isn;t sure of her son put oil in the gas tank or just overfilled the oil reservoir. Anyways the motor has overhead valves so I checked the push rods and they are not bent.I adjusted the valve lash. With the spark plug out the motor turns over fine by hand. When I put the plug in it still jams like it has been doing. Still it seems that it must be a compression problem. What is the chance the camshaft could be bent? Any ideas?
 

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I just picked up a Craftsman Chipper, to flip and the guy put some diesel fuel in the gas. It needed the carb rebuilt. Needless to say,the combination of bad gas and the diesel, it stunk up the garage.
 

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Just a stab in the dark.
Do these have a flywheel key?
What engine is it?
A sheared flywheel key would do this?
This is most common on Briggs and Tecumseh engines.

The guy behind me had that problem on one his lawnmowers.
 

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Not sure if this will help, but this was exactly a prob that my friend was having with a lawnmower engine. He was describing it as a "bump" in the engine, would hit a spot in the recoil that you had to really pull hard to get past. He rebuilt the whole motor and said he still had the prob. Spark plug out, no bump, plug in and the bump was back. When I finally went to look at it, I realized he was trying to start it the whole time with the blade off. We put the blade on and wham, it was perfect. The resistance that the blade provided when pulling it was enough to take the "bump" out, maybe some physics inertia thing? Lol
So my point is are you trying to bench start it without it being hooked up to anything? Having the pulley/belts on may make some difference? Just a thought (sorry for being long winded)
 

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My old greyhound engine did that the first time I dumped oil down the plug hole for summer. Was hard to pull with the plug in but easy with it out. I pulled it over quickly with the plug out to try and get as much oil out as I could, but it still was a bit hard to pull over. I just put it back together and started it and let it run for a while. It smoked a lot, but eventually the smoking stopped and the hard to pull went away.
 

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I think a partially sheared flywheel key or reduced cylinder volume due to oil/carbon buildup is a distinct possibility. Maybe a stuck valve.

Is it possible that you have the wrong size spark plug? Could the carbon be on the head? Just throwing some things out there.

Can you do a compression check on the motor.

I had an outboard that did this but that was due to water being drawn into the cylinder from a bad gasket, you are not water cooled. I can tell you however that it doesn't take much of a reduction in volume to cause enough compression gain to lock up a motor.

I would definitely check compression just to confirm it's a volume, valve, or timing (flywheel key) issue. Actually a flywheel key will only affect the motor while it is running. It only changes the timing of the spark.
 
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