[NA]Diagnose (and help fix) This!

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
Joined
Feb 23, 2005
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west Texas
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Dave Taylor
I was driving the riding mower and all of a sudden the engine goes into very high rpm, and the throttle is non-responsive. I shut it down and look things over. There's a lot of grass trapped around the engine compartment, so I blow it all off til it is nice and clean. Now what?
 
Linkage to the Governor? If the throttle linkage to the carb is working properly, then that is where I would look.
 
Check throttle cable at both ends. If it still attached and moves at both ends, could be a problem in the carb. Small engine carb rebuild kits are cheap and relatively easy to install.
 
You broke a PTO belt somewhere, the engine wasn't running under any load....
 
very good, all things I was looking at too.
The linkage to the throttle was fine. I worked the control back and forth and the cable moved the arm as it should, the butterfly shaft rotated normally.
The governor linkage was all under tension as it should be (spring loaded) and connected properly without interference.
The mower is all belts and it was moving well, the blade spinning fine, chewing through the west Texas grass like butter.
CJones tell me more.
 
The governor itself is usually a spring loaded vane of some sort positioned in the cooling air flow, somewhere. If that airflow is blocked, the spring loaded governor will default to high rpm. Check the cooling airflow from intake to outflow to make sure it is not blocked.

-Skip
 
governor is 100%, look elsewhere. I think this happened to a carbureted airplane engine once.
 
Could be an internal linkage between the throttle control and the actual butterfly valve. You should be able to remove the air cleaner and see inside to make sure the butterfly is actually moving correctly.

If the butterfly is actually moving correctly (try to put pressure on it to and move it to make sure it can move under a little resistance), it'll take some thinking to figure out where the extra fuel/air is coming from. Most small engine carbs are pretty simple to disassemble and reassemble with a simple fuel bowl and float and one needle valve to adjust the mixture with. Depending on the make/model of the mower and motor, you can get a carb rebuild kit at Lowe's/Home Depot/Wal-Mart/etc (look in the lawn & garden area instead of automotive). If all else fails, find the local John Deere dealer and they can order parts for a lot of small engines.
 
I could not see into the throat of the carb with this engine as the air intake is a curved duct. I pulled that off and looked in. Worked the throttle and choke, thought it was Ok but it is dark in there so I put some light on it....

and there was the butterfly shaft moving back and forth, with its two screw holes. Nothing attached to it, nada. Nothing floating around in the throat either. Butterfly and screws...swallowed!
I pulled the carb and looked into the intake manifold. It goes horizontally for a distance longer than my 3rd finger, then it goes down. I can feel nothing, so I am going to get some a long grabber tool I have to see if I can get the butterfly valve out. Probably not magnetic...I wonder if the screws are. Ah, they probably got blown through anyway. If I can get the butterfly at least....mo latuh.
 
If you had just filed a Flight Plan prior to departing on the MOA none of this would be happening...:fingerwag:


Chris
 
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Let'sgoflying! said:
I could not see into the throat of the carb with this engine as the air intake is a curved duct. I pulled that off and looked in. Worked the throttle and choke, thought it was Ok but it is dark in there so I put some light on it....

and there was the butterfly shaft moving back and forth, with its two screw holes. Nothing attached to it, nada. Nothing floating around in the throat either. Butterfly and screws...swallowed!
I pulled the carb and looked into the intake manifold. It goes horizontally for a distance longer than my 3rd finger, then it goes down. I can feel nothing, so I am going to get some a long grabber tool I have to see if I can get the butterfly valve out. Probably not magnetic...I wonder if the screws are. Ah, they probably got blown through anyway. If I can get the butterfly at least....mo latuh.
Click to expand...

Yuck.. Good luck with that. ;) At least you have found the problem. Now put a bullet in its block and trade it in on a local "Mower for Clunkers" deal. :D
 
Only mowers available where Dave lives:

goat-woman.jpg
 
Hiperbiper said:
If you had just filed a Flight Plan prior to departing on the MOA none of this would be happening...:fingerwag:
Click to expand...

yup faulty mx practices on my part, should have put a stethescope on the manifold every 50hrs of operation, listened for internal vibration.
I expect a suspended sentence of 2 years from the FLMA.
 
CJones said:
Now put a bullet in its block
Click to expand...

This could well happen depending on the damage the screws caused. I can move the butterfly around with the grabbers...but can't grab it. Will try sticky thing tonight.
If the screws did not just get sucked in and blown out with no damage, I have the 180 grain 40 cal pistol ready, is a shot through the case or the cylinder more humane?
 
Well, the head comes off of most small engines like that very easily, so open it up and see whether there's a screw or parts 'n' pieces thereof inside.

I bet it'll run fine for years to come...
 
SCCutler said:
Well, the head comes off of most small engines like that very easily, so open it up and see whether there's a screw or parts 'n' pieces thereof inside.
Click to expand...

I'd guess that anything that got ingested has been spit out by now. Might be some debris in the muffler...

I bet it'll run fine for years to come...
Click to expand...

I'd think so, too.


Trapper John
 
thanks for encouragement!
(except for Pete) :D ;) No it had nothing to do with %BAC, purely bad luck, ah tell yah.
was able to tease the butterfly out this pm with...baling wire, the farmer's Universal Tool (and help from a veterinary extraction instrument)
no sign of the screws, but I set the local shop to digging through their scrounge tray, they may find something tomorrow.
Or I might go to the airport and get some fillister head screws, drill the heads for safety wire!
 
Let'sgoflying! said:
This could well happen depending on the damage the screws caused. I can move the butterfly around with the grabbers...but can't grab it. Will try sticky thing tonight.
If the screws did not just get sucked in and blown out with no damage, I have the 180 grain 40 cal pistol ready, is a shot through the case or the cylinder more humane?
Click to expand...

I would vote for the cylinder. A shot through the case would cause prolonged bleeding (and a bigger mess to clean up).
 
tonycondon said:
there is grass in west texas?
Click to expand...
the way it is here Tony, is that much of the time through the year it is arid and no growth. And, for many years there can be terrible drought with no clouds, just blistering sun - dry, dry air and of course...no grass.
THEN....we will get our 5th season on a regular basis like the cycle we are in now. 5th se. being the time from July to Sept when it rains most afternoons. With this we might get 15" of rain, and adbundant grass. Great for gardeners, sightseers, and ranchers - they can feed cattle a lot cheaper. But grass means fires. Had one near us last week, I watched a nearby tcloud start it - thought it was going to blow through here, but they got it stopped. And its not that dry yet...waiting for a month for the extreme rating to be up. (/more than you wanted to know)
 
Those screws probably won't cause a problem... until they rattle down the intake manifold far enough to meet a rapidly opening and closing valve. All bets off then.

Glad you worked out the butterfly.
 
Let'sgoflying! said:
thanks for encouragement!
(except for Pete) :D ;) No it had nothing to do with %BAC, purely bad luck, ah tell yah.
was able to tease the butterfly out this pm with...baling wire, the farmer's Universal Tool (and help from a veterinary extraction instrument)
no sign of the screws, but I set the local shop to digging through their scrounge tray, they may find something tomorrow.
Or I might go to the airport and get some fillister head screws, drill the heads for safety wire!
Click to expand...

The original screws should have had the exposed threads "upset" a bit (mashed down) so they couldn't unscrew. To do that you need something long (like a screwdriver) in a vise to back up the head of the screw while you pound on the threaded end with a punch (after installation, of course). Just like driving rivets. Be careful not to pound on the screws if the head is not well supported - you will bend teh shaft. Or safety wire...

I would think about pulling the head to see if they went through (top of the piston should look like it had a real hard night) . You might be able to see through the plug hole.

Otherwise, I would consider pulling the engine to shake them out of the intake system.
 
Loctite will do the same. Just remember, uese blue if you need to undo the screw at some time in the future, red if it is a permanent install.
 
vontresc said:
Loctite will do the same. Just remember, uese blue if you need to undo the screw at some time in the future, red if it is a permanent install.
Click to expand...

You beat me to it. IIRC, there is a 'special' Loctite available for oily environment applications - might be worth investigating.

Also, a little JB Weld goes a long way. :D
 
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