1996 720K PROBLEM......

CMN

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I have a 1996 720k with 1074 hrs. and the problem is when I go from Half throttle to full there is a strong vibration happening right under the seat area. When it kicks in to full throttle it goes away. Same if I go from full to half throttle. I noticed that the left side pump fan is a little wobbly but not loose or anything. I got this mower from a family member for free and they bought it new in 1996 and always serviced it properly. It has sat up for over a year though. I have already changed oil and filter, cleaned carb, and have a little list of things to order for it . Like new steering dampers, fuel pump, pump fan, a couple of pto switches..lol..and some new belts. other than the loud hummmm with the vibration it runs pretty good. So if someone could chime in and help me figure this out I can add to my parts list and get this thing going...

Thanks, Chris
 

HarryHarley

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Could it be the pto universal joint on the shaft? Do you have the mower on it? Or, it it just coming from the engine itself?
 

CMN

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Thanks for the quick response. Before I joined this forum today I filled out a ask a tech form on the grasshopper website it said we will respond within 3 to 6 days. so I came here hoping to get a quicker answer to my problem cause I have a guy wanting to trade me for a Harley this weekend. Then I got a phone call from customer service at grasshopper an hour later. I was like WOW. The guy was very helpful and helped me narrow it down. He told me to check fro the front vertical plate the pumps bolt to for cracks cause they are prone to cracking due to pump bolt being loose and causing stress there. I looked and no cracks. Then he said check the fiber disc between the shaft for cracks I looked and no cracks. He sent me a email on how to fix each problem if they happen to be the reason for the vibration and they were step by step and very detailed. While I was reading the steps in replacing the shaft fiber disks and how to align it correctly with to specified run out he quoted that disc shouldn't be warped after the procedure. Well I go out and take a look at mine again and both disc are warped but not cracked.... So I think I need to re align the shaft. Should I buy new disks or when I get it to the specs he told me will they straighten back up? But he also said that there is some vibration and it is normal and need to run full throttle anyway. So I was amazed at the customer service today and also the quick response here and to top it off the first reply came from Harry Harley. Is this a sign that the trade is gonna work out for me.....lol....I hope so been wanting one for a long time...Ill try and copy what he sent me cause It may help out someone on here. He was very specific and explained it to me like he has done it 1000 times.....Anyway thanks
 

HarryHarley

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Enjoy hearing stories like this. Glad to hear how Grasshopper was so helpful to you. Let us know how you make out.
Good luck
 
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