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Discussion Starter · #1 ·
I am working on a craftsman mod# 917.270722 it is hydrostatic and in the back there is a pull lever to push the mower you put it in 1 position to drive it in another, well the thing broke part# 156970 and i learned that it has been discontinued . Anyone have any experience with this or know how to fix it, the spring is what broke.
 

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Discussion Starter · #3 ·
Thanks Mark! That is interesting i went to this same site right before i posted to the forum that is where i got the part # from, i even chatted with a specialist who told me the part was discontinued, maybe i brought it to there attention because it definately has a different part # from when i looked before. Thanks for your help!
 

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Discussion Starter · #4 ·
I got part# 167696 it is identical to my part except the 2 holes for the pin are missing. The way mine works is you pull the lever to one hole put the pin in that holds the transmission in the right position to push the mower. I take the pin out move the lever to the next hole insert the pin and now you are ready to mow. Other than the holes for the pin being missing it is identical. I am going to drill the holes in the right position and it will work fine.
 

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Good to hear that it's going to work out and thanks for the update! :)
 

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Ditto! Thanks for the feedback on what you found out and glad to hear it will work for you. :cool
 

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Discussion Starter · #7 ·
New update ! I did not have to drill holes in the new part. It has a flange on it that was not on the original so it would lock in place for pushing the mower without having a pin to hold it in place. So when you are mowing you just pull it from the unlock position. I did mow with it yesterday and it did work.

My only concerns are the mower is a craftsman model #917.270722 it says it is automatic i dont know if that is the same as hydrostatic. I have never used this mower before so i have nothing to compare it to, but it seems slow.I normally use a 7 speed MTD and i put the engine to about half throttle in 7 and mow the speed is perfect and it mows good. I cant even get this to go as fast at full throttle and i dont like to run the engine at full throttle even though thats what the book tells you to do. If the previous owner did this that is more than likely why the engine had a slight knock in it.

I guess my question is how can i run my engine at half throttle and get the mower to go faster or is this just something i have to get used to on an automatic transmission mower.
 

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...My only concerns are the mower is a craftsman model #917.270722 it says it is automatic i dont know if that is the same as hydrostatic.
Yes, it's a hydro.

...I guess my question is how can i run my engine at half throttle and get the mower to go faster or is this just something i have to get used to on an automatic transmission mower.
It will be something you'll have to get used to. The hydros only give full power at full throttle and that is part of the reason the book recommends full throttle. It is different from a gear drive in that with the gear drive you have a direct connection to the engine so whatever the engine is putting out power wise goes straight to the tires. With the hydro the internal hydraulic pressure on the hydraulic motor is lower at lower rpms thus less power to the wheels. As a result at lower rpms the hydro has to work harder and can actually as a result run hotter then at higher rpms. Also keep in mind the hydro has a fan on it and the lower the rpm the less air the fan will move over the transmission to cool it.

As for engine speed you don't have to search these type of forums too far to find a debate about that. The argument generally boils down to more heat with less movement of air through the fan and lower oil flow increasing wear at low speeds versus more engine wear (more rpms turned per hour) and fuel usage at high rpm. To each his own. I personally run mine (which has the hydro transmission) at full throttle mowing and about half to 3/4 when towing. I mulch so I really need the extra rpm mowing to re-cut the grass and avoid leaving clumps and uncut grass behind. Depending on the towing load half to 3/4 rpm seems to be enough to keep it from lugging the transmission too bad most of the time. If it does sound/feel like the transmission is struggling some with the load I run it at full throttle.

The engine does have a governor on it that is set from the factory to hold it to a spec of 3200-3600 rpm at full throttle depending what the manufacture specified when they ordered the engines for the tractor. Then depending on load it opens and closes the throttle plate to hold it at that. So even at full throttle on the control lever the engine is not running wild with the throttle plate wide open all the time. Only under heavy load would the governor actually open the throttle plate in the carburetor wide open to try and maintain the set rpm spec by the manufacture at full throttle.

I went from a 3 speed gear on my old Jacobsen to the hydro. They do take a little getting used to. It's great for me mowing around all the obstacles I have in the yard not to have to be riding the clutch and shifting gears all the time which is 95% of my usage of the tractor. On the other hand when towing a heavy load I would leave have the old gear drive back.
 

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Nice explanation, Mark!
 

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Discussion Starter · #10 ·
I appreciate the information Mark! I will try to get used to that, i never have run an engine at full throttle for very long always figured i was hurting the engine. I did notice it surging a little at lower speeds and when i wouuld speed it up that would go away.
 

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.... i never have run an engine at full throttle for very long always figured i was hurting the engine. ....
I know, I was the same way for a long time and still to some extent with my older engines. But I've read about commercial guys out there with 100's to 1000's of hours on these engines and it's a pretty safe bet most of them are running full throttle being time is money for them. I guess it is kind of like cars. What we used to worry about as far as engine overhauls at 100K plus highway miles we now are fairly safe until 200K plus for such problems. Tolerances between engine parts are better and the oil is of a higher grade then in the past.

But your actual mileage may vary. ;)
 

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There seems to be a little misunderstanding here on the meaning of "full throttle". Full throttle means the butterfly in the carb is fully open. Mowing, as per instructions, with the engine speed lever in the max position, does not necessarily mean you're operating at full throttle. It just means you're running the engine at the correct design RPM for cutting. The speed lever controls the engine speed, not the throttle opening. Under light load the throttle will only be partly open to maintain the engine speed. If you encounter heavy, tall grass, the governor will increase throttle opening and engine power to maintain engine speed. At that point the throttle can move to wide open and beyond that, the engine will slow or stall because it's wide open but has no more power. The speed lever controls RPM, but the governor controls throttle opening to maintain that RPM. There's no harm in running at a lower RPM when towing, but the blades won't cut too well if you reduce RPM when mowing.
 
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