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Discussion Starter #1
I get alot of heat off the motor on my 94 520 more than my 89 520 H . I Measured it with a infrared heat gun an its a hundred or so degrees hotter .
We were useing both macines that day an just pulled them up side by side an left both running full throttle an shot the mufflers at the same spot . I also
checked other places on the motor an it varried . The only differece other than age of the two is the older one has Amsoil it . But I was wondering has anyone ever rapped there muffler with that heat tape like you see on some cars with headers ? Because with that hot air comeing off the cly's an picking up the muffler heat its like a furnace it this hot weather .
 

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I get alot of heat off the motor on my 94 520 more than my 89 520 H . I Measured it with a infrared heat gun an its a hundred or so degrees hotter .
We were useing both macines that day an just pulled them up side by side an left both running full throttle an shot the mufflers at the same spot . I also
checked other places on the motor an it varried . The only differece other than age of the two is the older one has Amsoil it . But I was wondering has anyone ever rapped there muffler with that heat tape like you see on some cars with headers ? Because with that hot air comeing off the cly's an picking up the muffler heat its like a furnace it this hot weather .
so the cooler running one uses amsoil?? 100 deg is a very big difference are both engines the same size and type??
 

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Discussion Starter #3
Yep both 20 HP Onans but I just changed the hotter running one the 94 modle to
Amsoil but haven't mowed with it yet since the change so I'll let you know if it cooled it down . But the 89 also has it in the Trans as well so we'll see . Both run good an don't seem to have any issues except for the heat difference . I'm just wondering if that heat wrap would make a difference an not cause any i'll effects ?
 

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A couple of things can cause exessive heat. I would remove the engine tins to make sure there is no debris clogging them, moreso the rear cylinder as this is the one that allways has the valve seat come loose. Another would be valve lash.
I would not use heat wrap. These are aluminum blocks with the only steel being the piston sleeves and valve seats. This would only cause the engine to build more heat and could cause major issues.
 

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you can use the heat wrap if you want but i weouldnt use it and heres why if you wrap it weres the heat going no were thats what the muffler is for not only to quite it down but dispate the heat unless you put your leg up there leave it alone and do what refracman said
 

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Discussion Starter #6
Thanks guys for the feed back makes since to me . When I replaced the Air Filter
I blew compressed air all around an down through the blower houseing an then back
through the fins . But I guess to do a good job I need to remove the fan houseing, an I did cover the carb when I did that . I had thought about valve lash because at 600 hrs is when they say it should be done they may be to tight . I haven't had a chance to look at the shop manual yet is adjusting the valves much of a task on these are the TDC
marks easy to locate ? An since they are flat heads I suppose there is a cover to remove to get too the adjustment nuts ? Also is there any differnce in the later modle motors the manual I got was for my 89 .
Thanks
George
 

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If I remember correctly( only adj 1 onan) there is a lash adj bolt? To get to them you'll have to remove most of the stuff on the top and remove 2 covers for access to them. Make sure when you take the tins off that the block is clean also, some times gunk will plug up the passageway between the intake and head.
 
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