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Need Help with Run Away Motor

3K views 48 replies 6 participants last post by  JustMowin' 
#1 ·
First of all I'm new here so please forgive me if I'm posting in the wrong area. I have a Snapper NXT 2346 I just put a new carburetor on and when I press start it immediately revs to what seems like beyond redline. I can idle it down by using my finger to close the carburetor butterfly to idle. I have another one that's identical and I cant see any difference. I even pulled the carburetor and verified the butterfly plates aren't sticking. What could it be? They both sat for almost 6 yrs so the fuel was gelled and that's why I replaced the carbs on both of them. One works fine.
 
#3 ·
I never disconnected it. Just unbolted the manifold and removed the linkage to the front and rear butterfly's. As mentioned, I have two identical models. Did exactly the same thing on both. One works just great but this one just seems to want to blow up as soon as I fire it. I've triple checked the linkages, they're the same.
 
#5 ·
First time running in almost 6yrs. Ran great when I parked it. Never thought it would be for that long in storage. So, new battery and cleaned the fuel system but the carb was a mess. Found a couple pretty inexpensive ones online. I disconnected the smaller spring at the bottom of the linkage but now there's nothing to return the throttle to idle. LOL! I had the brilliant idea of switching the carb from the one that runs good to this one. Not sure what I'll accomplish since I can control the throttle with my finger once my wife starts it. It makes zero sense to me.
 
#7 ·
I have a Kawasaki twin that was running fine, but with an oil leak, replaced the governor seal and reassembled the engine, and then it would also over-rev when started, and I couldn't adjust the carb or governor to make it run properly. Turned out the governor happened to have failed at that particular time (plastic piece that the camshaft drives had both small pins that engage with the cam break off), replaced that piece and it was back to running fine.
 
#9 ·
it's not a JD, so the engine should have the OEM markings for who made it and it's specific configuration for parts, and from that info, you should be able to get a service manual for it. Some manufacturers will make that manual freely available for download as a pdf, others will charge money for it. That's where I would start...
 
#11 ·
If it has the same setup as mine, it could just be plastic aging. For mine, the first pin had failed sometime in the past, and the second pin was on it's way out, and perhaps just my jostling of the motor by removing/cleaning/fixing/installing it, was enough to finish off the job.

It could be something similar, six years of sitting, the metal balls rust/glue to the adjacent parts, and the force of starting it up with them stuck might be enough to finish them off.

But, before digging in, definitely do more diagnosis. I finally knew it was something inside the engine w.r.t. the governor when I noticed that it wasn't providing any resistance to my hand when the engine was running, regardless of rpm.

As for diagnosing the problem, I would suggest the O.P. puts a tachometer on the engine during testing, and physically prevents the engine from overrevving by working the throttle plate manually. While it might not immediately kill the engine, overrevving is likely to at least shorten the life of the engine.
 
#12 ·
I ventilated my first block blowing a governor apart... this was when I was about 13 or 14 and I had a couple of old engines the shop gave me, back in PNG. Of course I thoroughly 'tested' them, turns out one had a plastic gear gov. with metal weights on. ZoooOOOOOOOOMMMMM BANG. 🤓 Learned a lot that day.

Postmortem and salvage, built up the other engine and made a lawnmower out of it. Briefly.

Fun times.
 
#13 ·
Don't know how anyone can actually help you without knowing what engine you have. Snapper model number no help as who knows if it is original engine even. IF it is B&S, oil slinger is part of governor and if governor not be functioning, may not be getting lubrication either.
Walt Conner
 
#14 ·
Okay guys, thanks for putting up with my ignorance. I took some time to do some Googling and found out where to get the engine ID. Doh! It's right on a valve cover! So this is an Intek Engine I believe? 44L777. I'll include some pics I took this am. It's raining and I've already made myself sick so I'll wait for it to stop before working outside again. Maybe tomorrow. In the 3rd pic is what I believe is the governor shaft. Am I right? No matter what I do to that makes no difference. And it only turns from like the 10 to 2 position. I can hold the rpms down by holding the throttle plate with my finger so I'm pretty sure it's not the carburetor. It runs fine and I can rev it up and back down by my finger. I'm a pretty fair wrench, but this engine is new to me. I greatly appreciate your help!
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#33 ·
ALL mechanical governed engines have ways to determine your problem. First do not run it till you find the problem as overspeed failure is evident in a matter of seconds. A manual is available from briggs and will help. First feel the throttle on the carb - rotate it by hand and feel the spring tension at idle throttle setting and at high speed setting. You should feel a higher tension at high speed and you have also verified the throttle moves freely without binding. Next look inside the carb and actually see the butterfly is intact not missing or loose. Next if all that seems normal, with the manual do a static governor lever adjustment. If any change in this adjustment is found, then correcting it may solve the issue. It is a simple adjustment but must be done correctly or more issues will be introduced. Once all that is done, prepare to start and test by 1) throttle at minimum, 2) know how to shut down quickly before starting it, 3) Start and shut down if it revs up, if not, see it all reacts to normal throttle control. If the internal governor has failed at this point, all external effort has been performed to insure it will function under centrifugal forces when running and if it does not function it has failed to drive the throttle back. If you do not find a manual, contact me.
 
#16 ·
Yes the the clamp on the shaft is tight. I just watched a YouTube video showing how to properly adjust it by holding the throttle linkage in wide open position and turning the shaft clockwise and then locking the nut down. Should I be able to see this shaft move if it's operating properly? I could use my finger to control the throttle.
 
#17 ·
First, with the engine running at a controlled speed, check that that governor lever is being pushed one way (as in, you can push it the other way, but it takes some effort with your finger).

Second, that third pic in post #14 shows a spring hanging down. It looks like it connects to the end of that governor lever, the other end of that spring should connect somewhere to control the throttle.
 
#20 ·
Hah, yeah that was obvious. In post #5 I mentioned I disconnected that spring just to see what happened. I wish it was that simple too! I'm old but I'm also OCD. I do my own work on all the family's vehicles and our two Harleys. I've just never dealt with a governor before. I suppose I could use a zip tie or a length of wire around the Idle Screw and throttle bracket to hold the rpms down. How much movement am I looking for on that Governor shaft? I noticed when I loosened the locknut the shaft only moves counterclockwise/ clockwise maybe 80 degrees total. Or like from 10 to 2 on a clock face.
 
#22 ·
Sooo, I reset it according to a video I watched. Hold the throttle linkage at full open with the engine off, push the bracket on the governor shaft clockwise as far as it will go, turn the shaft also clockwise, and tighten the locknut. Didn't help. Does that sound right?
 
#23 ·
Wish I were closer... however. A cut and dry procedure is one thing, but you have to see.

Have you verified that it's the governor holding the throttle open? I guess so.

Cause and effect... watch the governor shaft as it operates (not blowing up your engine), which way does it 'pull' (or push).

Take the tension off by adjusting the governor arm until it no longer does that. With the engine running (and under control) have the arm bolt loose and play with it. You may need three or four hands, or somehow limit the throttle plate travel temporarily with wire or a ziptie or whatever.
 
#25 ·
Given that the governor lever pulls down on the spring (so, looking at the governor shaft head on, it would rotate CW), adjust and secure the lever to the shaft, then with the engine running (and manually adjusting the throttle with one hand), push up on the end of the governor lever where the spring is connected. You should feel resistance doing this, and it should increase in resistance (as in, you need to push harder with your finger) if you speed up the motor.

If, instead, it just goes up all the way, as if the motor wasn't running at all, then some part of the governor mechanism inside the motor is broken.
 
#26 ·
And.... since I have two of these I just did a little comparison. I started the good one and at idle watched the governor. When I forced the rpms up with my finger the governor pushed back. The other one doesn't do that. Now I'm really depressed. But I also noticed the good running one doesn't rev up as high at 1/8" off the stop. What does it all mean? I'm thinking the governor is bad on the one.
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