Carb help, older Tecumseh 10 hp - Snowblower Forum : Snow Blower Forums
 
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post #1 of 7 Old 11-17-2015, 06:33 PM Thread Starter
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Carb help, older Tecumseh 10 hp

Long story short, I picked up a free machine and flipped it for some cash and the dead (bypassed governor, blew the rod) machine 10 hp tecumseh. I've replaced the rod, and figured I'd muck out the carb while I had it off. Now with jets set at 1.5 turns (high idle, bottom of the bowl), 1 turn out for the 2ndary. I get a consistent pop-pop and blue flame from muffler (pretty beat up) when pull starting at full choke, but nothing more. I've checked the compression and found it to be around the 22 psi mark.

Am I looking at perhaps a bad seal in the carb? When primed a good few times it will drip, but I'm not sure if that's around the bowl gasket or just dripping from the carb throat. I guess I'll be rebuilding the carb, but I would think I'd be able to get it to run even if poorly, and the rebuild would only improve that.

Any advice appreciated, I've tinkered with this machine enough and need to make room for the next one.
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post #2 of 7 Old 11-17-2015, 08:17 PM
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Bones.
The carb will need to be cleaned in order for the engine to run with the choke off, but you also have all the symptoms of an exhaust valve that is not closing completely and will need to be adjusted. Since you are pulling the carb for cleaning anyway, pull the breather cover off and check the clearances on your valves. My bet is the exhaust valve has zero clearance and that is causing the low compression and popping through the muffler.
There are many youtube videos and knowledgeable people here to help you. As a start, here is a link to the Tecumseh service manual-

http://www.barrettsmallengine.com/ma...headmanual.pdf

The gas is dripping from the carb throat when primed and is a normal condition when over primed.

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post #3 of 7 Old 11-18-2015, 07:38 AM Thread Starter
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Good call. I'd been so focussed on the carb I hadn't even thought of the valves outside of a little voice nagging that maybe I'd maybe missed the timing by a tooth. I'll be sure to take a look at those clearances.
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post #4 of 7 Old 11-18-2015, 09:47 AM
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Originally Posted by Bones78 View Post
little voice nagging that maybe I'd missed the timing by a tooth.
I had over looked the fact that you changed the rod, that could also be a possibility, although slight. Since the motor had a hard life, I still lean toward the valves need lapping and adjustment. Let us know what you find, good luck.

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post #5 of 7 Old 11-18-2015, 05:41 PM Thread Starter
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You were spot on, there was zero clearance on intake and exhaust. One trip to the grinder and still zero clearance. On the second trip I botched the job so I'll be getting a new valve as well as a proper spring compressor, I should know better than to get impatient.

I still sorta marvel over how the valves can become longer over time. One would think that the cam would wear, the lifter would wear and maybe even the valve would wear, making them shorter over time, not longer. But I'm more of a GM small-block guy and still new to small engines. That said I'm learning quick.
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post #6 of 7 Old 11-18-2015, 08:42 PM
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It's not that the valve gets longer, but that the valve seat gets worn in allowing the valve stem to close the clearance gap.
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post #7 of 7 Old 11-18-2015, 11:17 PM
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On the second trip I botched the job so I'll be getting a new valve as well as a proper spring compressor, I should know better than to get impatient.
If you are only a few thousandths off, you may be able to lap the valves and gain back what you loss since they should be lapped anyway for a good seal.

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