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loosening belt


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Forgive me for not having a manual. I suspect there are words of wisdom contained therein... The engagement arm from the PTO driving the 42" deck on my 725 loosens after the tractor begins moving, to the extent that after about 15 feet, there isn't enough tenson on the belt to drive the blades. Holding the engagement lever down while driving with one hand is getting old... I have the spring adjusted so there is approximately 1" of space towards the engaging arm when fully pressed down. That is typically enough tension to engage the blades. The idler pulley can be pushed further "into" the belt to add additional pressure, but not so easily using the engaging arm and spring mechanism...at least as I can tell. The belt is the correct length and appears to be the correct design. The pulleys all rotate freely and do not appear worn. The belt does not jump off. The mechanism justs naturally loosens up. So the question is, what is the correct method for tensioning the belt, and/or what might be wrong. Sorry the tractor isn't clean enough to eat off,...I still love it... Thanks again for all the great ideas and comments! Galen http://chainsaw.rutgers.edu/~gwork/misc/mowerbelt.jpg
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It sounds to me like your PTO handle isn't going " over center". When I engage mine there is a definate snap into position while going "over center". OR... mabey your spring isn't strong enough to hold it "over center". When mine is engaged on my 3112, my spring coils are almost totaly colapsed, as in no space between coils. There is more like 1 3/8" space towards the engaging arm when engaged.
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Jordan, Good question. I, unfortunately, don't have a good answer. Perhaps I'm misinterpreting how this mechanism works, but the only "tensioning" system around the left axle is directly connected to the brake housing and manipulates the clutch system on the other side of the tractor. The rear connection on the large tension spring appears connected to a stationary small plate bolted to the frame. The opposite end of the same plate connects to a long spring positioned to oppose the tensioner for the clutch. The clutch works fine. Is there something else I should look for, as the tension on the spring would definitely affect how the idler puller works? Thanks, Galen
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palmrose2, I thought there should be a center to the arm travel as well, but there doesn't appear to be in this design. The arm is bent and merely travels around a pivot until it can actually rest on the connecting arm of the engaging mechanism. There just isn't anything in the length of its travel that would suggest a point of engagement. I believe there is a problem in tightening the pressure spring on the arm indefinitely, as when the mechanism is disengaged, the spring housing actually travels off the end of the arm (next to the idler pulley) as the spring is adjusted to increase tension when engaged.
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Do you have the lever pulled upe that puts spring tension on the center PTO? See the big spring back behind the pulleys in your pictures... that spring is connected to a lever that preloads tension on the center PTO. If that lever is not pulled up, and that big spring pretty tight, the drag of the mower deck will swing the whole PTO mechanism toward the front of the tractor. This will loosen the PTO drive belt, as you're describing, in addition to loosening the drive belt from the PTO to the mower deck. This is what Jordan was suggesting above.... If that lever is up, and there is considerable tension on that big spring, then it has to be either the adjustment of the collar on the engagement rod, the belt length, or the size of the idler pulley... One off the wall question -- check the position of the offset bracket where the engagement lever mounts. This bracket will move forward and back, by loosening the large bolt that's holding it. You may need to loosen that bolt, and adjust this offset bracket as far toward the rear of the tractor as possible while still allowing the engagement lever to go over center and rest down on itself.... This will add addition length and leverage on the travel of the engagement rod....
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Kent, Thanks much for the clarification. I will more closely examine both the rear spring connection and the offset bracket you mention. I know that the large spring appears much less tight than I would expect it to be, presumably allowing the behavior you describe. Thanks for all your efforts on this site, and to those who so willingly contribute! Galen
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