[sentinal02]

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.

 

[Shryp]

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.

 

[BOSMECH]

Yes try lapping the valves and see if that helps.

 

[CarlB]

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

 

[sentinal02]

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

 

[Shryp]

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.

 

[HDNewf]

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.

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

 

[sentinal02]

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!

 

[sea salt]

did you try running with the gas cap off of the tank?

 

[sentinal02]

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?

 

[Colored Eggs]

Just to check you replaced the carb like you said you ordered last year correct? Is there any flame or does the exhaust get red at all? Also does it have an adjustable carb.

 

[HDNewf]

I am having a hard time understanding how a bad compression release mechanism could be causing this problem. Your engine would not idle well. The exhaust valve would quickly burn up without the benefit of valve seat cooling. In addition, if the engine was running so rich as to smell raw gas, you would notice the plumes of black smoke as it revved up. Usually a gas smell means a leak, not unburned engine exhaust.

For more information on the compression release mechanism, see this link:
Patent US5184586 - Mechanical compression release for an internal combustion engine - Google Patents

HDNewf.

.

 

[sentinal02]

Just to check you replaced the carb like you said you ordered last year correct? Is there any flame or does the exhaust get red at all? Also does it have an adjustable carb.

Replacing the carb was done last year without any real marked improvement to the issue. no flame or excessive heating (and I've blown several times in the dark away from the house lights) noted at the carb except right before it runs out of gas in the tank. at that point I sometimes get a quick shot of flame just as the engine dies. sadly it's not an adjustable carb or else I would have tried adjusting it before trying a replacement.

HD, trust me, there's no leak on this engine. if there was, it would be leaking all the time and not just when it was running. this thing is stored inside in my workshop. there's no way I wouldn't notice the gas smell at other times if there was. but when I came inside after using the machine, my clothes reeked of gas. Believe me, before this issue I would have agreed with your original diagnosis of it running lean under load and it was the first thing I tried to fix it. but it's not. I've been down that road every which way and sideways to the point of a full carb replacement. not a rebuild, but a brand new carb. it hasn't solved the problem. I even put the original on a friend's lawnmower over the summer and it ran fine on that engine all season.

at this point, I can only conclude that I'm lacking compression. I think my blower is running rich during the times when the engine bogs down because the governor does what it's supposed to (I confirmed this visually early on) and sends the throttle wide open. the engine simply doesn't or can't react to the increased fuel mixture and passed the unburnt fuel out the exhaust. I pulled the plug after that last time i used the machine and it's black. it's definitely running rich, not lean. I'm not really familiar with the unloader setup so you tell me if I'm barking up the wrong tree before I dump a couple hundred into having the cylinder rebuilt. my understanding is that the pin comes around to lessen the compression during starting but obviously it doesn't totally rob the cylinder of 100% of its compression which means the valve will still seat at some point and still cool to some degree. it's a bump in the cam, not a whole second lobe that will stop the valve from ever closing again. by "stuck" I mean that it still comes around even after the engine is running, not stuck as in froze to the bottom of the lifter. if the exhaust valve was sticking open somehow, then it could explain the unburnt fuel escaping since it would be coming out during the compression stroke prior to the power stroke. at this point it's the only other logical explanation I can come up with to explain the symptoms based on what I've changed. If you've got something else though I'm all ears.

 

[Colored Eggs]

The reason I was asking if it was red was because I would think if the Decompressor was hitting it some exhaust and heat would hit the muffler and make it run hotter. I'm wondering if it makes it run to rich when it hits some "work" and that makes it bog down even worse. I'm not the best at this yet but I think that would make some sort of logical sense.

 

[HDNewf]

Hey sentinal02.

At this point I think you are right. Black plugs = rich. Compression release is on the BOTTOM of the exhaust lobe, so I'm wrong about the valve cooling issue. The exhaust valve will close twice, at least at slow speeds. With the rich mixture it is well cooled anyway. The entire engine probably never heats up fully. The higher the engine speed, the more a stuck CRM will totally wreak havok with the valve dynamics.
If this is the case I am surprised your motor even runs at all...

So now the problem becomes splitting the case and getting a new cam.

HDNewf.

.

 

[sentinal02]

So now the problem becomes splitting the case and getting a new cam.

that's pretty much what I'm thinking as well. at this point there's just nothing left that I can feasibly think it could be and the more and more I think about the symptoms the more I'm starting to think the unloader could be the culprit. like you said it seems like the engine shouldn't really run too well at all but then it really doesn't compared to what it was when i first got the machine.

will idle ok, but no power under load
bogs to the point of stalling under load
running rich to the point of plug discoloring, likely contributing to the bogging issue
no issues in the auger system

short of a badly worn cylinder I'm not sure what else it could be. it's just not that complicated of a system! timing and fuel mix are non-adjustable and we've pretty much ruled both out. there's no restriction to the exhaust. If it were a lack of compression in the rings though I would think that as rich as it seems to run when bogging down, that I would see evidence of gas in the oil due to the blow by that it would be generating, at least a strong smell. but I don't see that. I also don't notice any oil consumption or blue smoke during operation. the oil gets changed every season (it's always been a golden color too, never brown or black) and it's never been run low on oil so i just don't see the cylinder wearing that much in the small amount of actual operating time. it sees action but 4 months out of the year and only a couple hours like every 2 weeks during those months so if it's got more than 200 hours on it in 7 years I'd be surprised.


I've got half a mind to see if i can just disassemble it and ditch the unloading mechanism all together if possible. it's not like I've ever had trouble starting a pull start motor (I can start my 350cc wolverine without trouble) and it's got an electric start on it if needed anyway. at least then I might get a definitive answer on whether or not that's the problem without dropping any more money into this thing.

Colored, it does make some kind of sense, but remember, if the unloader is opening while running the same as it was intended during startup, then it should happen right around TDC on the compression stroke and any escaping gases would be a "relatively" cooler mixture of unburnt gas and air instead of some 1500° spent combustion gases which the muffler will see at the end of the power stroke. since the valve to muffler exit distance is so short on a tiny engine, the unburnt fuel doesn't ignite in the muffler before exiting the way it might in a car's exhaust pipe. if anything I would think all of it would have a cooling effect rather than a heating effect. Like HD said, the engine probably never fully reaches optimum temperature with the rich condition.

 

[Colored Eggs]

That may be true. Would it be easier to just take the head off and see if its tapping when it shouldn't by just turning the engine over by hand. I know on my mower that I tried to get running I was able to see it crack open so maybe that would be an easier way to check it. But then again when its at speed things can change and act differently.

 

[td5771]

I have had plenty of engines that even with under par compression they pull hard.

have a briggs on a roto tiller that only registers 50 psi but its an animal.

anyway just a thought...what do you have the float set at? I used to do parallel to the carb body but it didnt perform right. I read somewhere to use an 11/64 drill bit with carb upside down with drill bit laying across the bowl flange and adjust the float so that the float just touches the bit.

The float will sit slightly higher than parallel. has worked well for me.

 

[Zerobf]

Lack of power

Did you ever check to see if the flywheel key is broken or sheered? If so it could cause the timing to become retarded causing lack of power under a load. The key has to be flush with the flywheel and cranksaft. The slightest bit off can cause power issues.

 

[HCBPH]

Other ideas

Another thought is whether the piston, head or valves are carboned up. I've seen carbon so bad a motor barely ran until it was cleaned up.
Another is whether this engine has electronic ignition or not. I've heard of some on larger engines on lawn tractors have had issues where when loaded or hot may cut in and out.
Last idea I had might be to switch out the carb with an adjustable one.
Just some random thoughts.