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Old 01-18-2011, 04:23 PM   #1
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Default Tec engine, no power under load

Hi guys,
I'm trying to figure out what's up with this snowblower (Husky Snowking) I just got from a friend of mine. I used it a few years back and it was a totally different machine back then. it's a 2 stage 5 hp Tecumseh LH195SA, spec 67419V. the thing has no power under load anymore. runs just fine without a load, starts on the second pull, no misses or backfires. i thought it was the governor, but after inspecting it and adjusting it to spec according to the engine manual the gov seems to be functioning just fine. as soon as the engine starts to slow down i can watch the gov arm push the throttle plate wide open. the engine just doesn't respond to the wide open throttle. instead it just continues to die out until you remove the load when it then throttles back up. put it under load again and you get the same thing. i checked the compression and it's reading about 90 psi, which sounds about right to me, though i haven't found a spec anywhere to confirm this. i've cleaned the carb multiple times but it still does it. I replaced the belts on both the auger and the drive wheels and adjusted the cables to make sure it's engaging both properly. it has no trouble driving the machine forward (or backward for that matter) but i can't really tell if the augers are turning as fast as they used to. when the machine is throwing it seems to throw the snow just fine. I'm wondering if the worm gear in the forward gear box is worn and it's just choking on snow because it can't clear the chute fast enough, but i tried to test that theory by putting the machine against a wall with the auger disengaged and put it in gear and really tried to bear down on the wheel to see if the load from the drive system could bog the motor down. even with me bearing down on the handles the wheels just kept spinning and i couldn't get the motor bog. if i spin the auger drive pulley by hand the tines move as expected. trying to spin the tines themselves by hand I can't do it so i don't think the worm gear is sheared.

this thing used to clear 20+ inches of packing snow (albeit in 1st gear but it cleared it without any problems) and now it struggles to throw 6 inches of fine power. I'm about ready to pull the trigger on a whole new carb in hopes that there's a passage in there that I just can't get clear but I'm hoping someone can point me in the right direction. any help would be appreciated.
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Old 01-19-2011, 03:57 AM   #2
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I was going to say clean the carb, but apparently you already did. I have heard that the valves wear often on those and need checked, but I have not done any.
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Old 01-19-2011, 09:25 AM   #3
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Yes try lapping the valves and see if that helps.
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Old 01-19-2011, 10:11 AM   #4
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I just fixed a tech hssk50 for my neighbor. It started fine but died under a load. The carb was fine and the engine was getting plenty of fuel and the governor was working properly just like your engine. What i found when i took the breather cover off was that there was no clearance on exhaust valve. I pulled the exhaust valve and ground the stem down a little at a time to get the required clearance about .009". Put on a new head gasket and put it back together. Last snow was only 8" but it ran like a new machine, no bogging at all went right through the snow.

What first lead me to believe there was a problem with the exhaust valve not closing completely was when you pulled the starting cord over slowly there was very little resistance when going over TDC.
Carl
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Old 01-19-2011, 03:30 PM   #5
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Quote:
Originally Posted by CarlB View Post
I just fixed a tech hssk50 for my neighbor. It started fine but died under a load. The carb was fine and the engine was getting plenty of fuel and the governor was working properly just like your engine. What i found when i took the breather cover off was that there was no clearance on exhaust valve. I pulled the exhaust valve and ground the stem down a little at a time to get the required clearance about .009". Put on a new head gasket and put it back together. Last snow was only 8" but it ran like a new machine, no bogging at all went right through the snow.

What first lead me to believe there was a problem with the exhaust valve not closing completely was when you pulled the starting cord over slowly there was very little resistance when going over TDC.
Carl
there definitely seems like there's resistance in the cord, but I'll check the clearances anyway and go from there. anybody have the spec for the compression? the 90 psi I'm reading seems like it might be a little low, but I'm used to working on car engines so 120+ is more the norm. i went ahead and ordered a new carb for it since a couple of the local shops around here agreed that it seems like it's a fuel delivery problem, hopefully it'll be here friday for the next storm. in the mean time I'll see if i can find a head gasket for it and have a look at the valve seats. thanks guys, keep the ideas coming!

Nick
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Old 01-19-2011, 03:33 PM   #6
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Compression is hard to measure because the engines have a compression release that opens the exhaust valve slightly during starting. I am actually surprised you managed to get to 90.
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Old 01-21-2011, 02:45 PM   #7
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Hey Sentinal02.
I find it hard to believe that this is anything but an engine going lean under load. Compression is good and no backfires or rough running means valves are working as they should. Before you install the new carb, check the float bowl bolt. It serves as the main jet and is easily clogged.
Bowl_nut.jpg
A varnish build-up or partial clog will allow full speed operation with no load, but not when the throttle plate opens up. I use a twist tie stripped of its paper to snake out the holes and spray carb cleaner through them.
I hope this helps,
HDNewf
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Old 01-21-2011, 03:31 PM   #8
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thanks HD, but I've had the jet out at least 6 or 7 times, soaked it in kerosene overnight, wire brushed it on the outside and ran a #71 drill bit down the main jet hole and cleaned it about as well as you could possibly imagine. it was the first thing i did since I've had trouble with carbs like it in the past. i did make some progress on this. I found that the fuel line off the tank had a soft spot in it that was kinking. replacing the line seems to have helped, though I don't think it's 100% yet. it does seem to me that it indicates that this is a fuel issue. I'm hoping that it's just a clogged idle passage somewhere that i can't reach with the wire and that it's just enough to cause the engine to starve for fuel at full load. I can't find any fuel filter in the tank and I seem to be getting good flow out the main line to the carb inlet so i think that's taken care of at this point. wish i had thought of that sooner. the new carb should be here today or tomorrow, so I'll keep you guys posted. thanks!
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Old 01-21-2011, 07:20 PM   #9
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did you try running with the gas cap off of the tank?
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Old 01-18-2013, 12:15 PM   #10
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well guys, it's a new year but it's the same old problem with this machine. it seems to get a little worse year after year. the last storm we had that dumped about 5 inches of wet heavy snow and I was out there for 5 hours clearing what should only take like 2. I couldn't get out of 1st gear and even then had to constantly stop the forward drive and let the augers clear the shute. this is the same machine that 3 years ago cut through 25" (deeper than the front of the intake chute!) without really bogging at all so it's definitely not running right.

I've gone through this thing with a fine tooth comb. at this point I'm leaning toward a loss of compression robbing me of power. what I've found is that the governor is working just fine, but the engine doesn't react to the full throttle condition. in that last storm I mentioned I came in smelling of gas like it was a two cycle engine so I know it's running rich when it bogs down. definitely not a lean fuel issue at this point so I've gotta look elsewhere. I relapped the valves and decarbonized the head last year, changed the head gasket and checked the valve clearances with no real change. the cylinder walls seemed ok, with no major scoring that I could notice, but I've only seen a few engines down to that level in the past so maybe I missed something.

this year I went through the entire auger system down to the final gear drive and everything checks out on that end so it's gotta be engine related.

the thing I'm wondering about now is the compression release system. I haven't been able to find out too much about how this thing works but from what I could find out it seems that it's a mechanical setup that works kinda like a starter overrunning gear in that it helps while the motor is starting and then centrifugal forces from the running motor push it back out of the way and allow the engine to operate at full compression. What I'm wondering is if it's possible for this mechanism to get stuck in the "on" position and cause the engine to constantly run on light compression. it would certainly explain the lack of power but the otherwise "normal" engine running conditions. any thoughts guys?
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