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Bush Hog Hd-12 Hydro Or Engine Doesn't Seem Right

bush hog hd-12 hydro transmission

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#16 NUTNDUN OFFLINE  

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Posted April 14, 2013 - 09:12 PM

So, it bogs down, when you put demand on it, and then doesn't want to

recover?

 

Yep, only way it recovers is if you take the load off or ease up on it. Even though I have wheel weights and the tires filled I would think it should still spin the tires before killing the engine.


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#17 Texas Deere and Horse OFFLINE  

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Posted April 14, 2013 - 09:56 PM

I don't think you can fix it, so just put it out with my other stuff and I'll bring it home with me and see what I can figure out !! :smilewink: :poke:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Seriously, I agree with the guys that you have a fuel/Carb.  issue, but had to pull your chain !! :thumbs:


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#18 olcowhand ONLINE  

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Posted April 15, 2013 - 08:58 AM

If you test with the trail mower, be sure to abruptly drive it into the tall grass to mimick dropping the instant heavy load as when dropping the hydro pedal.  If you drive it in slow, the governor will have time to react in a more normal manner.


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#19 HowardsMF155 OFFLINE  

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Posted April 15, 2013 - 09:47 AM

I went through some of this when I was having the wrong timing issue with my Tecumseh HH120.  I'd suggest you stake out an area where you get the grass cut and the adjacent area left uncut.  Pick a slow enough speed that your engine seems to be running ok, then drive from the cut area into the uncut area without changing speed.  That should rule out the hydro and leave the engine as the culprit. 

 

 

PS Swipe one of TD&H's carbs if it will fit.  Carb mis-match is just going to make it worse to diagnose your issues..


Edited by HowardsMF155, April 15, 2013 - 09:50 AM.

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#20 NUTNDUN OFFLINE  

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Posted April 15, 2013 - 10:14 AM

One thing I can do is take the video camera out and chain the tractor to a tree and stand off to the side and use the handle lever to control the hydro. Get some video of different throttle levels and let you guys get a better idea of what it is doing and what it sounds like.

 

The governor does kick it up in rpm when it is in the lower throttle positions to keep the engine running. Doesn't seem to do as much at the higher throttle but could be because the carb isn't sensitive enough due to not being the right one.



#21 NUTNDUN OFFLINE  

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Posted April 15, 2013 - 10:15 AM

Worse case scenario is I have a 12hp Kohler I could put in it.



#22 sacsr OFFLINE  

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Posted April 15, 2013 - 05:31 PM

George,

 

When I get time this weekend, I will put the new carb on my HD12 and if it works, I can send you my old carb to use till you find a replacement. That way you can find out if it is a carb issue or something else. I prefer to get it back eventually since I need to keep one as a spare. As you have found they are not easy to find and certain parts are no longer made. I will also keep looking for one you can keep. If I remember correctly there were a couple of models that work on the S-12D


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#23 NUTNDUN OFFLINE  

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Posted April 16, 2013 - 07:44 PM

As promised I got some video of what the engine / hydro is doing. 

 

We hooked the hog to a tree stump and I had the throttle around 1/4 throttle the first try and then I increased it to around 1/2 throttle for the second pull. I had dad shoot the video at the carb so you could see the governor movement. Thought that might help with the diagnosis. At the end of the video I drove up the small hill I mentioned earlier in the thread. Started up the hill at about 1/4 pedal and then floored it and the first try it bogged down a little and the second attempt it really bogged down.

 

Here is the video:



#24 DH1 OFFLINE  

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Posted April 16, 2013 - 07:54 PM

Does that motor have spark advance?

If so is it working?


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#25 olcowhand ONLINE  

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Posted April 16, 2013 - 08:04 PM

I don't know exactly what it could be, but I feel that the engine is at fault and not the hydro.  I could be wrong, and have been many times.


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#26 NUTNDUN OFFLINE  

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Posted April 16, 2013 - 08:08 PM

Does that motor have spark advance?

If so is it working?

 

I think it might have some sort of spark advance as I recall something being mentioned in the manual but I don't know how to check it. It has points on it.



#27 NUTNDUN OFFLINE  

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Posted April 16, 2013 - 08:09 PM

I think it is the motor too. You can see in the video where the governor is kicking the throttle open but you can't hear the motor change in sound other than to bog down.

 

The motor does respond well to the governor when there isn't as much load on it though. If I am on flat ground and hammer the hydro it picks right up.



#28 MH81 ONLINE  

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Posted April 16, 2013 - 08:10 PM

Is there any flow diagrams for the tranny?
Also, can you advance the timing any further without keeping it from working correctly?
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#29 DH1 OFFLINE  

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Posted April 16, 2013 - 08:14 PM

Not sure what engine you have but it has points and I found 3 different ways to set the timing in a manual
1 - point gap
2 - test light, more accurate, static.
3 - timing light, lining up the marks dynamically.

It also appears that the points are camshaft driven, if the cam/crank is off 1 tooth the engine would probably run but would not run right and the ignition timing would be off for sure.

???

I think the motor is not making the power it should from what I see in the video.

Edited by DH1, April 16, 2013 - 08:17 PM.

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#30 NUTNDUN OFFLINE  

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Posted April 16, 2013 - 08:15 PM

Is there any flow diagrams for the tranny?
Also, can you advance the timing any further without keeping it from working correctly?

 

This is the only thing I have so far which is the parts diagram for the hydro.

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