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Austin Estes

500 Top end rebuild to 520

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I have a 2012 Honda foreman 500. It needs a top end rebuild as it is smoking. I would like to bump it up to a 520, but I need to know what the best way would be. Will an OEM Honda 520 Cylinder bolt right on like a 500 cylinder? Or would there be enough room in the cylinder walls to bore it out to a 520? And if I did put a 520 top end on it, would the bike run and function correctly since it is supposed to be a 500 fourwheeler? I haven’t heard of anyone trying to do it before, so I can’t find any knowledge on it. 
 

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Hi Austin, welcome to ATVHonda!

 

@jeepwm69 knows all about the 520 swap, I'm sure he will be along shortly to fill you in on what is required to do it.

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Welcome Austin, glad you found us, pics are always good....

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Welcome aboard. 

 

I have done a 500 swap onto a 420 Rancher, and for that one, it bolts right on.

 

The 520 swap I have not yet done, but I did look into it.   The bore in the crankcases isn't quite bit enough to allow the larger cylinder to slide down into the bottom end.  There are two ways to address this.  The first, and easiest, is to contact Reduction Boss

 

https://reductionboss.com/

 

They were offering a bolt on kit that was accomplished by slightly machining down the outside of the cylinder where it would slide into the bore and bolt right on. 

 

The other option is to remove your top end, grind out the crankcase bore yourself, but then you'd need to tear the engine all the way down and clean it clean it clean it to get that dust/ debris out of everything.  The benefit of doing it this way is, if you plan to keep the machine long term, you'd be able to swap another stock 520 cylinder straight on at some point in the future.

 

If your engine already needs a rebuild from being sunk, or if your connecting rod is bad requiring a crank rebuild, then option 2 is, in my opinion, the way to go.  If you think you'll be fine just slapping on a new top end, then option 1 is much, much less involved.

 

The 520 cyilnder and piston bolt right on to the 420 and 500 motors once that clearnacing is addressed.  You'll need a fuel programmer to be able to tweak the amount of fuel going to the engine. 

 

Other than that, it should be plug and play.

 

 

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Austin Estes , Welcome to ATVHonda --- I know two families with that last name that are not related to one and another , you have any kin down here in south east Louisiana ?? 

 

 

 

 

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