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Discussion Starter · #1 ·
Can someone tell me how to post a new thread.
I told my buddy I'd try to fix his mower. It's a Toro power drive walk behind approx 28-yrs old (model 20695) with a 4-cycle tecumseh engine. It starts right up and cuts grass fine for a few minutes, but when it gets warm the engine slows down and will keep running under no-load at fast idle, but when you start cutting grass again it immediately slows down until it stops and won't start up again until it cools off. I suspected that the choke needed to be turned off, but there isn't a manual choke. Does anybody have experience with this same problem who can offer advice?
Thanks
 

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Discussion Starter · #3 ·
Thanks for the reply 43128,
How would I verify that the valve stem is the problem?
To check the coil I guess I'd check for spark when the engine won't restart after warmup. This sounds like the easiest to do so that will be 1st. However, when the engine starts slowing down, I can keep it running when I take the load off and just let it idle. When I engage the blade again it starts slowing down again, and it regains speed when I again stop the blade - I did this cycle about 5 times before I let it slow down under load and continue to a complete stop, and then it wouldn't restart.
 

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Hello gordy, I agree with 43128 on the valves (usually the exhaust) as needing adjustment, especially after 28 years. Below are links to a not so well done video showing the adjustment procedure and also the engine service manual. The carb ( take pictures of the linkage configuration before removing) and muffler have to be removed in order to access the valve (breather) cover to expose the valve stems and lifters. There are many youtube videos showing the procedure on horizontal shaft engines and the procedure is the same for vertical shafts. I hope this helps.


Service manual-
http://www.barrettsmallengine.com/manual/tecumsehlheadmanual.pdf
 

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Discussion Starter · #5 ·
Thanks, Grunt,
I'll report back after trying to adjust the valves on this Toro. I adjusted the valves on my Honda HR214 a few months ago, so it shouldn't be too hard on the Toro.
 

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Hello gordy. Unfortunately, the Tecumseh is a flat head style motor and is considerably more difficult than the over head valves on your Honda. It is still very doable, just a little more involved if having to REMOVE the valves for adjustment. It is also recommended to lap the valves, check clearance, grind stems, check clearance and repeat. You DO NOT want to grind the valve stems more than necessary for proper clearance or you will have to buy a new valve(s) and start all over. Good luck.
 

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if engine always fires right up on cold start...you might be ok on valve setting...I would look closely at the flywheel key....slight sheering can cause it to run a tad retarded on ignition...and heat up...high temps on those engines cause big loss of HP...Also possible, after all those years it may have the wrong flywheel form some previous work...if all this checks out ok...then I would dig in for the valve re-gapping..IMO
 

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My guess is one of the moderators moved your post.
You asked how to start a new thread.
At the top of this page just above your name is a grey button that says "Post Reply". If you go back to "Toro" or any other sub forum heading you would see that same grey button say "New Thread". That is what you hit to start a thread.
 

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Discussion Starter · #9 ·
Kiss,
Thanks for the instruction for starting new threads.
I haven't yet gotten back to the toro for inspecting the valves because of other higher priority projects which popped up, but will get to it eventually.
Gordy
 

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Does anyone think this could be a fuel cap issue?:dunno:
 

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Discussion Starter · #11 ·
Smitty,
After it died when warmed up, I removed the fuel cap and tried starting the toro with several pulls with no luck.
Gordy
 

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Discussion Starter · #12 ·
Smitty,
I loosened the fuel cap after the engine died after warming up, and it still wouldn't restart.

Here's an update of my efforts:
I just started removing a few screws for getting to inspect the valves, and I noticed the engine cooling fins had some dirt on them (not a lot, but enough that I thought it should be cleaned off since I'm having this problem), so I thought that this may be contributing to overheating. I then checked the oil level and it was at the bottom of the full range. I remember checking the oil level before the 1st time I ran the engine (a week or 2 ago) and seeing that it was in the full range satisfied me, but now I thought this also could be contributing to engine overheating, so I added an ounce or 2 of fresh oil to get the dipstick to read at the top of the full range. I then cleaned the dirt off the cooling fins the best I could and blew them clean with compressed air. I'm now thinking that I improved the engine cooling system a bit, and now should run the mower again under load to see if it dies after warmup as it did before. Well, it wouldn't die after running it at least twice as long as it ran last time when it died, but since I last cut the grass friday, and it hasn't rained since, there wasn't enough grass growth to cut and give the mower a full load test. I'll have to wait at least until the end of this week since rain is forecast for the next few days to give this toro a full load test. I may still try to inspect the valve clearance before then. But, if I do this, and I find a problem, I should probably try to adjust the valves before putting everything back together again. My question then is this: If the valve clearance should be: int - .004" and exh - .008", how far off should the readings be for me to think that readjusting them is necessary? I'd appreciate any comments on this subject.
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Discussion Starter · #13 ·
Today I finally gave the toro another full load test after performing a few improvements. To summarize some of my comments above, the improvements were:
1) I Added approx. 1 1/2 oz. oil to bring the dipstick reading to the top of the full range.
2) I cleaned the cooling fins on the engine (which had some dirt & grime, but didn't look too bad to me).
3) Previously I added gas to the tank from the gas can my buddy (who owns this mower) gave me. I now noticed that this gas can didn't have a cap so I now suspected bad gas, so I drained the toro's tank and added fresh gas.

I cut my entire lawn today (which needed a mowing because it rained a few days this week) and the toro performed like a champ for the entire mowing with no sign of slowing or overheating. One other difference (other than what's mentioned above) between this successful mowing and the unsuccessful 1st mowing a few weeks ago, when the toro apparently overheated and slowed and then died, is that today's temperature was in the 60's, and the temperature during the 1st mowing was in the 80's - I don't know if a 20 degree ambient air temperature difference would explain the difference between overheating or not, but I thought this was worth mentioning.

I never checked the valve clearances, as was suggested above by some contributors on this thread - this was going to be my next step if the above mentioned improvements didn't work, but since the mower now apparently works fine, I'm returning it to my buddy, who only wants to use it this fall to pick-up leaves, and he intends to then buy a new mower before next mowing season. I'm trying to talk him into a Honda.

One last comment - someone commented that the flywheel might have been replaced sometime during the mower's life, which might be causing a timing issue. I did mention this to the mower's owner, and he did confirm that at some point in the past a mechanic replaced the flywheel.

Thanks very much to everyone showing interest and contributing to this thread.
Gordy
 

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i would try to buy it from in when he gets a new mower and throw a used briggs quantum on it. those cast aluminum toro decks are virtually indestructible and they cut really well. that deck was the same one used on the toro commercial models with the suzuki engines and it would be a shame to see it go to waste
 

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Discussion Starter · #15 ·
43128,
The rubber on the back wheels is worn off down to the plastic and it's expensive to replace, so I don't know about trying to repower it. If the wheels were good I might give it a try, but I've already got 2-mowers.
 

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Discussion Starter · #18 ·
I just read another thread about gasoline leaking thru the carburetor and getting into the crankcase of a mower, thus thinning the oil, resulting in poor performance. I'm now wondering if this could be the problem with this toro I'm working on? A few things I've noticed and haven't mentioned yet sort of point to gas possibly leaking into the crankcase. I'm gonna drain the oil and see if it looks ok. One thing I've noticed was that after I ran the mower for it's test under load, which was successful, that a few days later I wanted to start the mower again, but noticed that the gas tank was dry. I thought that it was a coincidence that the gas tank ran dry just as I shut the engine down the previous time that I ran it, but now I'm thinking that maybe the gas leaked out of the tank while it sat in my garage. I'll be reporting back again after I look into this.
 

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Believe many of us have experienced the slow leaking needle /seat on Walbro or Nikki carbs...One easy way I use to prove it...is to remove the airfilter housing, lay a thin strip of paper towel in the carb throat, tucked in a bit so as to be next to the metering tube.....walk away for awhile...[play a few holes of golf?]...come back and see it paper towel is soaked with gas...it should be dry...
 
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