# tecumseh hs50 starting problem



## spanishtrain (Feb 27, 2008)

Hi there;

I am new to this forum and I will just say hello. I joined this forum because I was looking for information on a problem I am having with my snowblower and this forum seemed to have a lot of info. My name is Al.
My problem is I inherited an old snow blower. A blower with a tecumseh hs50 motor. The unit has been out of commission for a long time and everything seems to be rusted out and seized. I did a carb job on it, changed the plug and a general overall maintenenace to make everything run smooth again. Except the blower will crank and the vales go up and down, the spark plug has fire but the darn thing will not start. I checked the magnito and flywheel. It was rusted out and I cleaned the magnet of rust and regaped the thing. I am new to small engines and really don't have a clue where the problem could be. Any help would be greatly appreciated. thks.


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## pyro_maniac69 (Aug 12, 2007)

first thing I would do is a compression test, thats if you have access to a compression tester

if not, put some gas in the spark plug hole and give it a pull, if it does not start, than I would say you have a compression problem which could be bad valve guides and/or seats, and the slight possibility the rings are bad

also, and HS50 is a 4-stroke motor, not a 2-stroke


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## spanishtrain (Feb 27, 2008)

thanks pyro maniac69. I did that test of trying to start it with some gas directly in cylinder and nothing. I do not have a compression tester so I am a little lost as to what else I can try to figure out the problem. Is an engine re-build the next step?? As I said before this machine has been sitting a long time without use and never stored properly. Any other guesses would be appreciated. thks


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## pyro_maniac69 (Aug 12, 2007)

if it would not start with gas in the cylinder, and you have spark, I would guess that either your valve guides and seats are wore and are not sealing correctly

quick way to find out is to roll the motor over while watching the valves move through the breather, and watch for them to both close, then, take some compressed air (from an air compressor) and push the air through the spark plug hole. If you feel any air coming from either the exhaust port, intake port, or both, than the Valve seats will need to be recut. If you don't fee anu air coming from either of the ports, take out the oil fill cap (or dipstick if your motor has that) and put air to the motor again, if air is leaking out of the bottom of the motor, good chance the rings need to be replaced


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## spanishtrain (Feb 27, 2008)

Thanks pyro maniac69;
I will attempt an air leak test on the valves. The other item, putting air into the oil chamber, will this not force oil through the oil ring and out the exhaust? Just want to knnow what the results should be and what am I looking for. In car engines I believe there are three rings and one is for the oil. Is it the same with small engines? How many rings are on the piston?


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## spanishtrain (Feb 27, 2008)

Hi Pyro;
I did the air leak test today and I am not sure if I did it correctly. I tried to visually look to see when the valves where closed but I don't think they closed properly. I tried to turn the engine with the crank to see if it leaked. I was able to pull the crank enough to close but as I pulled more the air escaped from the carb or the exhaust. So there is a position I think that it does close, however does it close enough and for how long should it be closed. As the engine turns the valves go up and down respectfully. I think my question is, is there a position on the cycle where the valves are completely closed for a period of time? 

Thks


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## pyro_maniac69 (Aug 12, 2007)

normally its BDC (bottom dead center) when the piston is at its lowest, and both valves are closed.

Make sure you have the carb and muffler off, and then take the breather off if you haven't already. Behind the breather you are able to see the valve stems and also the lifters.

Another thing that it could be is there isn't enough valve lash between the lifters and the valves


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## spanishtrain (Feb 27, 2008)

Hi Pyro;

I took off the head and checked the valves. The valves were dirty with carbon but nothing else I could see. I cleaned the head and saw hairline cracks in the casting. I am not sure if these went through but cleaned everything out and reassembled everything. Before I closed the head, I made sure that the piston was at top dead center and the valves were closed. I checked the valve closure by trying to turn the valves when they were closed. I could not. Then I did the air test. The test showed leaks around the head gasket. So now I think that there is not enough compression. Now I am not sure if the gasket is bad or the bolts are not torqued enough. I don't have a torque wrench. I tested for leaks with soapy water and got bubbles forming where the air escaped. Is there a specific torque required on these gasket and if so how much? I can always purchase a torque wrench.
Thks


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## 30yearTech (Sep 14, 2006)

Yes, there is a specific torque value for the head bolts as well as a pattern in which to tighten them. Below is a link to a service manual that covers your engine, you will find the torque specs on page 91 and the pattern on page 82 I believe.





http://www.cpdonline.com/692509.pdf


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## spanishtrain (Feb 27, 2008)

Hi 30yearTech;
Thanks for the link. I will try it and see if this helps to seal the gasket.

thks


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## spanishtrain (Feb 27, 2008)

Hi guys;

i torqued the bolts to specs. and I cleaned very well the heads and the gasket. But the air test still leaked. Is there some sort of gasket goop to put on the head gasket or is it just the metal gasket?
Thks


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## 30yearTech (Sep 14, 2006)

Did you replace the head gasket with a new one?

Once these gaskets have been compressed, you may not get it to seal again. Generally head gaskets are replaced every time you remove the head.


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## spanishtrain (Feb 27, 2008)

Hi 30yearTech;
No, I did change the gasket. I was told that I could reuse the gasket as long as it is not broken. I will replace the gasket tomorrow and see if it will start. Does anyone know how to tell if the engine has an electronic ignition or a standard ignition with points. I don't see any wires for the points if they would be there behind the flywheel.
I will try all these things tomorrow and update tomorrow.
Thks to all for your help to try to resolve my problem.


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## spanishtrain (Feb 27, 2008)

Hi guys;
Does anyone know how to tell if he flywheel key is sheared as this is one of the things that prevents the motor from starting. I assume that the position of the flywheel affects the timing. Is this assumption correct?
Thks


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## pyro_maniac69 (Aug 12, 2007)

spanishtrain said:


> Hi guys;
> Does anyone know how to tell if he flywheel key is sheared as this is one of the things that prevents the motor from starting. I assume that the position of the flywheel affects the timing. Is this assumption correct?
> Thks


correct, easiest way to tell if you have electronic ignition is when you have the blower housing off, follow the spark plug wire, if it goes behind the flywheel, than you have points and condensor, if it goes into a coil above the flywheel, than you have electronic ignition.

and the only way to check a sheard flywheel key is to take the flywheel off


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## 30yearTech (Sep 14, 2006)

pyro_maniac69 said:


> correct, easiest way to tell if you have electronic ignition is when you have the blower housing off, follow the spark plug wire, if it goes behind the flywheel, than you have points and condensor, if it goes into a coil above the flywheel, than you have electronic ignition.
> 
> and the only way to check a sheard flywheel key is to take the flywheel off


Pyro,
That is not necessarily correct, as Tecumseh has models with points that have the coil outside of the flywheel as well as under, and solid state units with the module underneath the flywheel. The most common ones are as you described but you can't be 100% sure just by following the plug wire. If the engine is equipped with an external coil/module and no wiring leading underneath the flywheel then it's probably solid state.

Spanishtrain,
If you post your model and spec number or use it to look up your engine you should be able to tell which ignition you have on your specific engine.


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## spanishtrain (Feb 27, 2008)

Thanks Pyro;
The reason I am asking is it possible that the lack of compression will prevent the motor from starting? And will a sheared key offset the timing enough to prevent the motor from starting. I looking for all the possible reasons that a motor won't start and eliminat them one at a time. So far I have eliminated the carb, the plug, the ignition coil maybe since it does spark when cranking. So up to now I am looking at the possibility that it is the loss of compression and the timing. So I want to rule these two items out first before looking at other items.
Thks


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## spanishtrain (Feb 27, 2008)

Thanks to pyromanic69 for pointing out that I am posting in the wrong forum. My engine is a 4 stroke and not 2. I hope that this will not make a difference for my questions.
Sorry!!!


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## spanishtrain (Feb 27, 2008)

Thks 30yeartech;
I think that since my ignition system only has one lead wire and a spark plug wire that it is an electronic ignition. Because if it had points, other wires would be connecting the points to the winding for the timing I think. Anyway the coil will be the next thing to check out after I get the head gasket changed. I think that since I am not getting any firing, it must be the timing. Would you not still get a start if the compression was low?
And would you not start if the timing was a little off?
Thks


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## spanishtrain (Feb 27, 2008)

Hi guys, 
Looking back at the posts of earlier today, I asked is it possible to tell if a flywheel key is sheared? Is there not an alignment mark on the flywheel to do a visual inspection of the position it should be in? This would be easier than pulling off the flywheel. I am told that it is no picnic to remove the nut holding the flywheel without the proper tools. Which I do not have. (no strap wrench to hold the flywheel)
Thks


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## 30yearTech (Sep 14, 2006)

On some engines you can see if the key is sheared just by removing the flywheel retaining nut and starter cup. If you can see the key way on the shaft and the key way in the flywheel you usually can tell if the key is sheared, but as pyro said sometimes the flywheel must come off to tell. If you had a points ignition system and the key was sheared you would not get any spark to the plug, or it would be very weak at best. If you have a solid state system, you will have spark regardless of the condition of the key, however with this type of ignition if the key is sheared the ignition timing will be off and your engine will not start. If this was the case you may have the starter rope jerk out of your hand when attempting to start the engine.

Taking the flywheel nut loose is not that hard, you could use the "rope trick" that has been described in many threads or a pipe wrench on the pto side of the crankshaft to hold while the flywheel nut is loosened.


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## spanishtrain (Feb 27, 2008)

Thanks 30yearTec;
I don't mean to sound stupid, but what is th rope trick and where is it described.
Thks


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## 30yearTech (Sep 14, 2006)

Even though I have never used this procedure before, it sounds like it should work just fine.

Remove your spark plug, then drop a few inches of small rope down into the cylinder, leaving out enough so that the rope can be removed when you are finished. Then rotate the engine around so as to trap the rope between the piston and cylinder head and causing the engine to "lock" and allow you to remove the flywheel retaining nut. To remove the rope, just reverse the direction and rotate the piston back down a little to remove the tension on the rope and then pull it out. you can also use this to tighten the flywheel back in place.

Good Luck.... :thumbsup:


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## pyro_maniac69 (Aug 12, 2007)

30yearTech said:


> Pyro,
> That is not necessarily correct, as Tecumseh has models with points that have the coil outside of the flywheel as well as under, and solid state units with the module underneath the flywheel. The most common ones are as you described but you can't be 100% sure just by following the plug wire. If the engine is equipped with an external coil/module and no wiring leading underneath the flywheel then it's probably solid state.
> 
> Spanishtrain,
> If you post your model and spec number or use it to look up your engine you should be able to tell which ignition you have on your specific engine.


really?, all the Tecumseh with points I ever see the coil is behind the flywheel

I know that every briggs that I've seen has the points underneath the flywheel and the coil outside

and spanish

the rope trick is taking a thick, and about 1 1/2 foot long piece of rope (little thinker than recoil rope) and putting it down the spark plug hole (with the head on of course) and rolling the motor over by hand so that the piston will get caught on the piece of rope, and stop the motor from rolling over as easy

but I cannot say how well this will work on a 4-stroke engine especially since most (if not all) 4-stroke L-head engines the spark plug hole is normally located closer to the valves than it is the piston. I have used the rope trick on 2-stroke, but never have on a 4-stroke


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## spanishtrain (Feb 27, 2008)

Thanks Pyro;

As you said the piston on the four stroke is offset to the spark plug hole so I am not sure how easy it will be to insert the rope into the hole and to the side to be on top of the piston. Anyway I will give it a try and get back to you on the results. Something new everyday!!!
Thks


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## 30yearTech (Sep 14, 2006)

Spanish,
I don't think it would be very hard to angle a piece of rope into the cylinder area of a 4 stroke the plug hole is not very far away, but I have never tried this myself.

Pyro,

Don't you know about the difference in the "Silver" flywheel key vs the "Gold" flywheel key for many early Tecumseh TVS series engines. The "Silver" key is for points ignitions and the "Gold" is for Solid State ignitions, both have external coil / modules (Ref 5). The point engines are getting to be pretty rare sights these days.

http://www.hobbytalk.com/bbs1/attachment.php?attachmentid=54950&stc=1&d=1204260858
Page82.pdf


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## spanishtrain (Feb 27, 2008)

Hi Guys;

I want to thank all for your help in trying to fix my problem. Today I replaced the head gasket, and the flywheel key. The flywheel key was sheared,( not a very good way to make them) white metal! Anyway I basically put everything back together and tried it and it started. So now all that is left is to grease and loosen everything up. I guess that the problem was the low compression and the timing. 

On another note: I was afraid that I would have problem getting off the flywheel. I used an impact wrench for the nut and did not need to use the strap wrench or the rope trick. The impact wrench is a great tool not only for tires and other things but for all type of situations that need to be held to be removed.
Thks again


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## 30yearTech (Sep 14, 2006)

Thats Great!

I would have suggested an impact wrench as that is what I use, but I mistakingly thought you only had hand tools and did not want you to think you had to purchase an expensive tool to get the job done.

Glad you got it going again.


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