My Tractor Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
So I acquired a Toro GROUNDSMASTER 120 for free as the owner said it was “under powered” but still cut grass when he chose to buy a new one. Once I got it home I initially thought a cylinder valve was stuck, pulled the valve covers off and this was not the case. I replaced the forward bow spark plug as it is the only one you can replace without removing the gas tank and still seems to spit a miss from time to time. I bought a harbor freight spark tester to verify the coil is working properly, it is a constant glow on the front cylinder. As soon as I give the mower PTO power for the front deck the mower dies. I have lubricated the bearings on the deck and the Electronic PTO shaft. Still no go… Looking for direction on this to move forward as mowing season is upon us. I can freely move the deck by hand from the belts so I this rule out the following:
• Deck Bearings
• Electronic PTO (maybe not need feed back)
• Hydro system
My caveat with this is I know nothing about GROUNDSMASTER Toro mowers, I have a John Deere 130 Hydro, Dixon 4422, and a Dixon 429. I like the fact the Toro has a front deck so I can get under my trees ( 4 acres with over 100 trees ) I have no problem putting money in this mower for this purpose but need a baseline starting point for troubleshooting. That being said and unfamiliar with these mowers, is it possible the aft plug may be the problem, or…. Is it a bearing I am missing? **** thing is loud as **** when it misfires as well.

Thanks in advance,
Michael

my email is [email protected]
 

Attachments

·
Professional Homeowner
Joined
·
7,013 Posts
I don't think I'd give up on the valve theory just yet. I had a single cylinder tecumseh do the EXACT same thing you're describing. I later found out the engine had a partially stuck valve. I don't recall if it was intake or exhaust. If I just started the tractor and drove it around it was fine. But as soon as I engaged the deck, it did exactly as you describe - stop nearly dead like a bearing on the dck was seized.

Plugs wouldn't be a bad idea, though. A comparison may lead you to to narrow down which cylinder you're intermittently dropping.

Other possible causes are a shorted out PTO (disconnect mower deck drive mechanism be it belt or shaft) and engage the PTO. This would also eliminate something wrong with the deck itself (bearing or something wrapped around a shaft).

You might also be able to check the exhaust pipe temps right off the heads with an IR thermometer. If one is cooler than the other, you've found your weak cylinder. Believe it or not, I've had two twin cylinder engines that ran VERY smooth with a partially fouled cylinder or a broken rod. The bad plug one would idle incredibly low, and wouldn't run full RPM with wide open throttle with the deck engaged. The one with the broken rod still had the block intact, so it ran on one cylinder - until the deck was engaged, then it would pretty much fall flat on its face, often with a loud BANG. Sometimes when running with no load, it would still go BANG and die.

Nice score on the mower, though! Shouldn't take much to get it right.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #3
So an update on this, I have the spark tester kit on the Bow plug, it glows constantly but when I pull the plug wire off it runs the same so now I am thinking a fuel issue on the front cylinder. Suggestions?
Thanks,
Michael
 

·
Professional Homeowner
Joined
·
7,013 Posts
It's strange if it were a fuel problem. Normally if both cylinders share a carburetor and intake system, in theory both would have the same fuel/air mixture. I'm still thinking one of your valves doesn't close quite all the way. Can you do a compression test in both cylinders?

Some guys might say to put your finger over the spark plug hole for kind of a poor man's test, but I'm always paranoid the the piston could come up and smack/amputate my fingertip. Maybe I'm just a coward.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #5
I have a compression tester, 60lbs and remains constant.... Uggg, I got compression, spark and the front cylinder isn't working...
Michael
 

·
Registered
Joined
·
4 Posts
Discussion Starter #7
Not sure about the ACR, I am not familiar with the Kohler engine nor the Toro mower, I have Dixons with a single cylinder and a dual John Deere....
Sorry, not sure,
Michael
 

·
Registered
Joined
·
6,899 Posts
Hopefully you fixed it by now. I had an older 117 Groundsmaster with a KT17 lose compression in one cylinder after I mowed a steep incline.
 
1 - 8 of 8 Posts
Top