Snowblower Lack of Power

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  #1  
Old 12-28-03, 02:02 PM
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Snowblower Lack of Power

I have a 6 year old MTD Snowblower with a Tecumseh HSSK50 engine.

It starts very reluctantly, and is suffering from a real lack of power. It stalls in situations it used to laugh at. There is also a high gasoline consumption, and I think the exhaust might smell different. I changed the spark plug which made very little difference. I confess the machine has had no maintenance other than checking oil, and adding gas. I found a screw-in compression tester and it has about 30 lbs of comp. The spark plug is a nice dry brown color. The engine runs fairly smoothly until it bogs down.

25 years ago, I raced Karts and still have enough tools to do anything, but my troubleshooting memory is not what it could be.

It took way too many hours to clear our driveway here in Salt Lake.

Any ideas on where to start?

Thanks in advance.
Peter
 
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  #2  
Old 12-28-03, 03:25 PM
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peterb
How does the engine sound at full rpm with no load? Your carb may be getting varnished from old gas that has been sitting in the float bowl and plugging up some of the tiny orifices. From your experience with karts before you will probably feel comfortable with doing some carb adjustments. When it gets under load and it stalls, it may be from lack of fuel or it's getting too much fuel so you can either richen or lean out the high speed screw maybe 1/8 of a turn (ccw to richen or cw to lean)) and see what difference that makes. It is located right under and in the center of the float bowl.
The way Tecumseh states to set a carbs' high speed screw is after the motor has been running about 3 minutes and is up to operating temp. put the throttle to full and turn the high speed needle in (cw-lean) until it starts to sputter then turn it out (ccw-richen) until it starts to sputter and count the number of turns and put the screw halfway between the two. That will give you a very good starting point. After that you may have to adjust it under load. The normal starting point to get your motor started on the high speed screw is 1 1/4 turns out.and do your settings from there. I would suggest also using some type of fuel stabilizer to keep your fuel fresher a little longer. Briggs or Tecumseh has very good products for this.
I'm not sure about the compression though because of the compression release system in those motors it's hard to get a proper reading but since you stated it's only 6 years old I doubt that is the problem.
Let me know how it works for you.

snoman
 
  #3  
Old 12-28-03, 05:06 PM
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I am not telling you that this is the problom, but, you might have a problem with the coil. I had a weedeater one time and after 20 years of use the coil became faulty. Which means it was enough to keep the engine running but was not enough to keep it going when you throttle the engine up. Eventually the problem had gotten worse and the engine would no longer start ever again. After that I replaced the coil and it started running again. I suggesting testing the coil some way so you can rull out that. Don't foget to check the carb as well for trash build up...
 
  #4  
Old 12-28-03, 07:50 PM
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It sounds OK under full load... as long as I run the throttle up slowly. Otherwise it will stall. (is this a fuel starvation issue.

I'm not sure how to check a coil, so I guess I go the Carb Cleaning route.

I looked in the bottom center of the bowl where I expected to see a HS needle, and there was only a screw which held on the bowl - and a little drain button. The only exterior adjustments are the idle screw. (have I lost my mind or have they made a non-adjustable carb?

There did seem to be some varnishy deposits on the exterior bottom of the bowl.

I presume the next step is to get a carb gasket or rebuild kit, take it off, soak it in carb cleaner, blow out the passages, and try to get all the parts back into place.

Is there anything else I should try? or is this a reasonable place to start on round one?
 
  #5  
Old 12-28-03, 10:42 PM
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Hello Peterb!

The screw that holds the bowl on needs to be cleaned out. Remove it and look carefully at it. There should be 2 small holes opposing each other near the head of the screw. Then, closer to the end, is a tiny hole that can easily be overlooked if it is clogged. Then there is a hole down the center of the screw. Make sure all these holes are clear, open, and completely cleaned out. Yes...it is a non-adjustable carb.
 
  #6  
Old 12-29-03, 06:40 AM
jlm
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You stated you had 30 lbs of compression in your first message!
I would check the vale clearence, my guess is that the exhaust valve in not fully seating. I believe the gaps are .008 and .010 for this engine not sure though. 008 on intake and .010 on exhaust.
 
  #7  
Old 12-29-03, 10:00 AM
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I may not know much about snow equipment because we dont see any where I am in Texas, but sounds to me like a clogged carb. if nothing else works spray some carb cleaner in. Even if that is not the major problem i doesn't hurt to give it some anyway.
 
  #8  
Old 12-29-03, 08:24 PM
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Thank you all for your input so far.

Cheese/Snoman
I removed the screw/jet at the bottom of the bowl It did not look as bad as I thought it would, The third tiny hole was a stinker to find. I found a strand of copper wire and cleaned it out.

It may have been a little better - but I'm not convinced yet. More snow in the forecast for tonight. When I test ran it (after dark).. there seemed to be a very little bit of blue coming out the muffler when I engaged the auger and put it under a bit of load.

JLM - Called a shop and asked about replacing a valve - they tried to sell me a new machine. Only strenghtend my DIY tendancies. How do I measure the Valve Clearance? and how do I adjust it if it is off? I do have a set of feeler gauges. After seeing what an old Briggs could put up with - It seems odd that the limited # of hours this has been used could cause problems. But you never know.

Mancoowner
This is an engine issue. It would be the same on your kart. All input is helpful - the fact that it blows snow (sometimes) don't matter. (My last Kart had a pair of Yamaha KT100S engines - Great ride when it all worked)

There also is an audible knocking - It almost sounds like a rod, but with as long as it's been there, it would have blown up long ago if it were. It does not seem to increase with RPM so I'm confused as to what it might be. (Drive Train?) Could this be related to the Valve.

I went looking at Amazon for books and found one for Tecumseh "L" engines. Is this they type that I have?

The other strange problem is the the reverse 1 speed goes forward and I need to use Reverse 2 to back up ???

Thank you all again.

Peter
 
  #9  
Old 12-29-03, 10:30 PM
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If you have low hours on the machine, (and it only being 6 yrs old), I doubt it is the valve clearances, but you never know. You do have an L head engine. The blue flame could be indicative of a lean condition. I still think you have carb problems if it doesn't run well next time you get to try it.

Look at the pulley or whatever drive mechanism is on the engine output shaft for a possible source of the knocking. It could be loose.
 
  #10  
Old 12-30-03, 05:51 AM
jlm
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As far as the valve issue I only say this because you stated you had 30 lbs of compression. This is way to low it should be 90 to 110 lbs.
You would have to remove the carb. and get to the breather cover , remove it and then bring engine to top dead center and check clearence as bottom of valve and lifter.
Purchasing an engine manual may be your best bet to get a step by step procedure I believe there around $8.00.
Good luck.
 
  #11  
Old 12-30-03, 03:02 PM
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peterb
With the reverse problem, if you look at the transmission assembly does it run on a rubber coated friction wheel against a metal driver wheel? If so then I believe that your rubber friction wheel doesn't go far enough past the center of the metal driver wheel to enable the machine to go in reverse 1 but reverse 2 goes past center enough to move you in reverse.
How those transmissions work is the metal driver wheel spins in only 1 direction and wherever the rubber friction wheel is on there will determine the speed and direction. So when it goes past the center of the metal driver wheel, the direction and speed of the machine will change.

Also I just checked my book on the HSSK50 and the specs for the valves (cold) are .004-.008 for both.

snoman
 
  #12  
Old 12-30-03, 04:56 PM
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My guess that you have an obstruction in the air intake of the engine. I say this for two reasons. First, you've stated that you have only 30 lbs of compression. This could be from a lack of air in the cylinder to compress. Second, you say the engine bogs down on loads that it used to just tear through. Again, another indication of possible poor air flow causing a drastic reduction of HP generated. I would, of course, check the air filter, and then the choke to make sure that it's actually working. I always forget to block all air intakes to the carb to a full open position before checking compression and sometimes I get what I think may be an unsatisfactory reading because of that. Your 30lb compression reading is also suspect. I can't imagine an engine starting with such a low compression. Things get dicey below 80lbs.
 
  #13  
Old 12-30-03, 07:09 PM
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Thank you all again for your input. I have learned much more here than in the books from the Library.

Carb Rebuild
I got a rebuild kit today. It was an Oregon Products 49-019 (replaces Tec 632760) It looks like it may have some extra parts. I plan to take the carb apart and soak it this evening. I'm not sure how to remove the two caps on the side of the carb..(on the left side above the bowl) but we'll be creative.

I guess that being a snowblower, they figure their is no dust in the air and an air filter is not included in the design. So there is a clear path for air to the carb. - I'll check the intake manifold for spider nests or ???

Compression Test
The way I did the test may not have been right. All I did was screw a tester into the plug hole, and pull the rope a few times. (I read somewhere that I need to spin the engine in reverse to compensate for the compression release) - perhaps I did not get an accurate reading.

Exhaust Valve Clearance
After I took off the carb, I tried to measure the exhaust valve clearance between the bottom of the valve and the top of the lifter. There was no clearance no matter where the piston was! The intake did have some, but not the exhaust. This worries me.

Drive Train Noise/Reverse
Uncovered the drive train top and bottom. I can see some dust from the traction drive belt, and the reverse issue is just as Snoman describes. I just need to figure out how to adjust it to the other side of center. The noise sounds like it might be the play in the gears. The large one on the drive axle, and the small one that drives it. I can see several places to grease. The idler wheel bracket also has more side to side play than I would expect.
 
  #14  
Old 12-30-03, 11:17 PM
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30 lbs is low indeed, but testing compression on small engines can be affected by many variables, like how fast was the engine pulled, compression release, etc... I agree that it may be that the valves need adjusting, but with low hours I would be suspect of other problems.

Peterb, did the problem exist last year when you put the machine up for the summer? Did the problem get gradually worse, or just appear one day? A valve clearance issue will normally cause hard starts, low power, very poor acceleration, and these problems will begin unnoticeably small and gradually develop into noticeable problems over time. A carb can do the same thing, but it doesn't have to be a gradual thing.
 
  #15  
Old 12-31-03, 11:12 AM
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peterb
The plug you're describing , is it the size of a dime and look like it is made of aluminum. If so that is one of the two welsh plugs. There is one inside the carb that you can see after you take the bowl off and the other is on the side of the carb near the mounting flange. The one on the side you have to be very careful how you take it off due to the fact that there are small orifices directly below that plug. By directly below I mean maybe 1/32 inch. so what ever you decide to use to pot that plug off, don't allow it to go too far through the plug. Once it is off, clean out the orifices with some tag wire.

snoman
 
  #16  
Old 12-31-03, 04:22 PM
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I suspect that it was gradual onset over the course of the summer and it showed up with our first snow of the season.

If I have NO clearance between the valve and the lifter, is this something to worry about?, and if so, how do I improve the situation (an ignition file)

Welsh Plugs
The one inside the bowl was easy, and I figured the other would have the same amount of clearance behind it... I think the gods were watching over me when I used a 3/16" drill bit, and did not cause any damage. I then used a snap on dent puller. I think I had a very generic kit as there were extra parts.

I got everything back together and it still runs, maybe a bit better, hard to tell.

Where do I go from here?

Happy new year to all.
Peter
 
  #17  
Old 12-31-03, 08:35 PM
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There has to be a certain amount of clearance between the lifter and the valve on both the exhaust and intake valve. If there isn't then the valve will not seal completely and the engine won't put out the rated hp due to lose of compression. Then once the engine heats up and the metal starts expanding, the problem just gets worse. Sometimes, engines won't even start due to the lose of compression from tight valve cleanances.
 
  #18  
Old 01-01-04, 09:29 AM
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peterb
Use a good and fine file to increase the gap to the desired specs.
I use a file for filing the rakers on a chain saw chain to do this. When you're dealing with only a few thousandths of an inch, it won't take to many swipes of a good file to get you there. Care must be taken in keeping the filed surface even.
Once the gap is achieved, you should lap the valve, this will (depending how aggresively you lap) bring the clearance you just made even closer. You will have to take this into consideration and file accordingly.
Hope this helps.

snomanl
 
  #19  
Old 01-01-04, 10:27 PM
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Agreed...If you have no clearance then your valve(s) is the problem. You can remove the head, valve spring and retainer, and pull the valve out and remove material from the stem until you get the proper clearance. Be careful not to remove too much...we're only talking about thousandths of an inch.
 
  #20  
Old 01-02-04, 03:00 PM
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While I feel bad, I want to thank you all for your help. I took the ego hit and brought it into a shop. They will do a full valve job for about $80 which when I consider the number of dollars I would spend on spring compressors, seat grinders, and the miles around town to find these.. it seems like a fair deal.

I did learn something about the troubleshooting procedures and that was a lesson in itself. All of you clearly know your stuff.

This is a great forum.
Peter
 
  #21  
Old 01-02-04, 11:12 PM
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I hope it goes well! Let us know!
 
  #22  
Old 02-05-04, 07:13 PM
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Lack of Power - The Resolution

Thank you all again. They did a full valve job on the engine, charged a bit more than they quoted, but it really runs better than I can ever remember.

Signing off until something else breaks around the house.

Peter
 
  #23  
Old 02-06-04, 12:58 AM
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Glad to hear you got it fixed! Thanks for keeping us posted!
 
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