tecumseh 5hp loses power

river2 · 11-23-2008, 01:01 PM

Hi there, I am new to this site and exited to see the amount of information in here. I always love forums.
My problem is whit my antique snowblower. It's an Eaton Viking with a hs50-67075 tecumseh motor(5hp). It's got points and a condensor that were changed 2 years ago.
The model of the snowblower is 324-450.
The problem is that after about 30 or 40 minutes of use, it loses power. The engine seems almost as if it's running on idle, even with full throttle. At first, when it's cold, it's got lots of power considering the size of motor. It starts easily, a couple of manual cranks with choke. Whitin a second, I can completely shut off the choke and it runs good. It's got no primer bulb.
I've also seen it stall, tried replacing the spark plug and didn't do any good. If I let it stand for a while (1 hour or so), it's good to go. The spark plug is a bit black but doesn't seem that bad.
Any ideas where I should start. I've been suggested to replace the coil but they are about 50$ but I havent had the one that's on there tested yet. I wanted to wait to see if something else would help before putting that much money in something 35 years old.

MrChooks · 11-23-2008, 01:32 PM

Hi & welcome to TSF.

OK so your engine starts, develops power OK but once it gets warm - it loses its power - so it has to be something associated with the engine and its components warming up or as fuel is burnt - and my 1st suspicions would be to agree with the advise you were given - that it is something to do with the ignition - BUT that usually causes the engine to stop altogether.

As you say that then engine doesn't stop - but just loses power - I am leaning towards fuel delivery / mixture issues. Just as a quick test - once your engine starts losing power - does putting choke on make any difference + or - ?? Pls let us know.

If putting the choke on improves the situation once the engine starts to act up - it might be a piece of "rouge muck" in the carb or something similar - so you should be able to fix that with a carb clean.

BUT before you do anything - have a look at the fuel cap - make sure the breather hole (there is a tiny hole in the fuel cap to prevent a vacuum forming in the tank as fuel is burnt) is clean & clear.

If it gets blocked - then the engine will start and run perfectly - but as you burn fuel, a vacuum forms in the tank and the fuel flow drops off - so you don't get enough to deliver engine power. Take the fuel cap apart, clean it out thoroughly and make sure you can poke a thin piece of wire through the breather hole. Then see if the problem is solved

Pls let us know how you get on

river2 · 11-24-2008, 09:35 PM

Thanks for the reply.
Could a coil cause such a problem where it stalls and then I start it with choke and then it stalls about 30 seconds after. This is of course after it ran for 30 minutes with no trouble. Any other suggestions? Someone also mentioned the valve lash... Is this a big job to check the adjustment?
Thanks again.

MrChooks · 11-24-2008, 09:59 PM

river2 - With "Lill engines" anything is possible - BUT if your engine starts - works OK and then starts giving trouble - my initial response would be "carb / fuel delivery / mixture problems - ignitions problems generally manifest themselves with a "no-go at all" outcome.

Frankly - if it runs OK at all then I would discount valve and clearance issues - they would be there all the time - so if that were the issue - your engine would not work at all.

Did you check the fuel tank cap - - if not try this - when you run the engine once it plays up - try 1/2 un-screwing the fuel cap so that it is no longer sealed - does that solve the problem????

I am pretty confident that your problem is fuel delivery related - our problem is to locate WHERE THE PROBLEM IS within the fuel delivery system

river2 · 12-26-2008, 10:47 AM

Hi there,
Thanks for all your help. I think I have found the problem, it seems to be running alot better now. I used it on the last snow storm and it worked really well.
What I did was drill a small hole in the gas cap to make sure the tank wasn't creating a vaccum and then I reset the carburator valves. Didn't even need to clean it. Hope it keeps on going like this for a while.
Thanks again.

MrChooks · 12-26-2008, 12:05 PM

Well done river2,

Doesn't it feel good when you get something fixed

Tks for the feed back - The feed back helps lots of other people who read TSF threads.

11-23-2008, 01:01 PM	#1 (permalink)
river2 Registered User Join Date: Nov 2008 Posts: 6 OS: win98 sp2	tecumseh 5hp loses power Hi there, I am new to this site and exited to see the amount of information in here. I always love forums. My problem is whit my antique snowblower. It's an Eaton Viking with a hs50-67075 tecumseh motor(5hp). It's got points and a condensor that were changed 2 years ago. The model of the snowblower is 324-450. The problem is that after about 30 or 40 minutes of use, it loses power. The engine seems almost as if it's running on idle, even with full throttle. At first, when it's cold, it's got lots of power considering the size of motor. It starts easily, a couple of manual cranks with choke. Whitin a second, I can completely shut off the choke and it runs good. It's got no primer bulb. I've also seen it stall, tried replacing the spark plug and didn't do any good. If I let it stand for a while (1 hour or so), it's good to go. The spark plug is a bit black but doesn't seem that bad. Any ideas where I should start. I've been suggested to replace the coil but they are about 50$ but I havent had the one that's on there tested yet. I wanted to wait to see if something else would help before putting that much money in something 35 years old.

11-23-2008, 01:32 PM	#2 (permalink)
MrChooks Gearhead Join Date: Apr 2008 Location: Sydney, Australia Posts: 613 OS: Windows XP Home SP 3 My System	Re: tecumseh 5hp loses power Hi & welcome to TSF. OK so your engine starts, develops power OK but once it gets warm - it loses its power - so it has to be something associated with the engine and its components warming up or as fuel is burnt - and my 1st suspicions would be to agree with the advise you were given - that it is something to do with the ignition - BUT that usually causes the engine to stop altogether. As you say that then engine doesn't stop - but just loses power - I am leaning towards fuel delivery / mixture issues. Just as a quick test - once your engine starts losing power - does putting choke on make any difference + or - ?? Pls let us know. If putting the choke on improves the situation once the engine starts to act up - it might be a piece of "rouge muck" in the carb or something similar - so you should be able to fix that with a carb clean. BUT before you do anything - have a look at the fuel cap - make sure the breather hole (there is a tiny hole in the fuel cap to prevent a vacuum forming in the tank as fuel is burnt) is clean & clear. If it gets blocked - then the engine will start and run perfectly - but as you burn fuel, a vacuum forms in the tank and the fuel flow drops off - so you don't get enough to deliver engine power. Take the fuel cap apart, clean it out thoroughly and make sure you can poke a thin piece of wire through the breather hole. Then see if the problem is solved Pls let us know how you get on Last edited by MrChooks; 11-23-2008 at 01:35 PM.

11-24-2008, 09:35 PM	#3 (permalink)
river2 Registered User Join Date: Nov 2008 Posts: 6 OS: win98 sp2	Re: tecumseh 5hp loses power Thanks for the reply. Could a coil cause such a problem where it stalls and then I start it with choke and then it stalls about 30 seconds after. This is of course after it ran for 30 minutes with no trouble. Any other suggestions? Someone also mentioned the valve lash... Is this a big job to check the adjustment? Thanks again.

11-24-2008, 09:59 PM	#4 (permalink)
MrChooks Gearhead Join Date: Apr 2008 Location: Sydney, Australia Posts: 613 OS: Windows XP Home SP 3 My System	Re: Tecumseh HP loses power river2 - With "Lill engines" anything is possible - BUT if your engine starts - works OK and then starts giving trouble - my initial response would be "carb / fuel delivery / mixture problems - ignitions problems generally manifest themselves with a "no-go at all" outcome. Frankly - if it runs OK at all then I would discount valve and clearance issues - they would be there all the time - so if that were the issue - your engine would not work at all. Did you check the fuel tank cap - - if not try this - when you run the engine once it plays up - try 1/2 un-screwing the fuel cap so that it is no longer sealed - does that solve the problem???? I am pretty confident that your problem is fuel delivery related - our problem is to locate WHERE THE PROBLEM IS within the fuel delivery system

12-26-2008, 10:47 AM	#5 (permalink)
river2 Registered User Join Date: Nov 2008 Posts: 6 OS: win98 sp2	Re: tecumseh 5hp loses power Hi there, Thanks for all your help. I think I have found the problem, it seems to be running alot better now. I used it on the last snow storm and it worked really well. What I did was drill a small hole in the gas cap to make sure the tank wasn't creating a vaccum and then I reset the carburator valves. Didn't even need to clean it. Hope it keeps on going like this for a while. Thanks again.

12-26-2008, 12:05 PM	#6 (permalink)
MrChooks Gearhead Join Date: Apr 2008 Location: Sydney, Australia Posts: 613 OS: Windows XP Home SP 3 My System	Re: tecumseh 5hp loses power Well done river2, Doesn't it feel good when you get something fixed Tks for the feed back - The feed back helps lots of other people who read TSF threads.