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WillB

420 mods.

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Hi,

Curious whether a 520 top end will bolt up to my 2021 Rancher 420? If not, will a 500 bolt up? Should I get the cylinder head too?

Would I need a tuner?

Thanks,

Will

Edited by WillB

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Wow Will I'm sure you know your warranty is going to be void with a mod like this?

 

Prolly a few guys here might have your answer but haven't heard of any attempting this yet.... 

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8 minutes ago, bcsman said:

Wow Will I'm sure you know your warranty is going to be void with a mod like this?

 

Prolly a few guys here might have your answer but haven't heard of any attempting this yet.... 

Thanks.  Im going to plan the build, buy the parts and do it Summer 2022.   My warranty year is up October 2021, no need to extend it, being a footshift.

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3 minutes ago, WillB said:

Thanks.  Im going to plan the build, buy the parts and do it Summer 2022.   My warranty year is up October 2021, no need to extend it, being a footshift.

Sounds like you have the plan, you may be able to inform us how it fits and works.....

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Welcome to the forum   .....  I don't know about 420s    ------   my 450 has  a 500 sleeved 450 jug ,  J+E custom made piston , basically a clone of the old  Highlifter Big Bore Kit , running a 400 head which  has a smaller compression dome   ---  only problem with a set up like that is , it is a one time deal , mess up the bore or piston and there is no over size , you have to re-sleeve and have another piston made ---- I wouldn't do it again 

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well, at least it's a foot shift, so plus there.... but I'm curious as to this planned build. 

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15 minutes ago, _Wilson_™ said:

well, at least it's a foot shift, so plus there.... but I'm curious as to this planned build. 

As am I, wondering if a 500 kit will bolt on.

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14 minutes ago, WillB said:

As am I, wondering if a 500 kit will bolt on.

 

Welcome to the forum. My guess is you'll be plowing this field as the first one. 

 

Look forward to reading about it.

 

Good Luck!

Edited by 87Iroc

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2021 part breakdown has not hit Partzilla yet , looks like 2009-2020 420 heads were the same part number , the 520 head and head gasket carry a different part number , but the finche looks identical , many times Honda numbers are different but the parts are interchangeable   ------ the crankshaft and wrist pin for the 2020  420 and 2020 520 are the same part numbers , the stroke of both engines are the same at 71.5mm , so I would assume the lower ends are the same , the bore of the 2020 520 is 96mm @ 9.5-1 compression and the 2020 420 is 86.5mm  @9.9-1 compression 

 

The heads look pretty much the same to me , even though the part numbers are different 

520 head image.png

420 head 

 

image.png

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Then you might run into tuning problems , being the 520 and 420s are fuel injected , more displacement seems like it would require more fuel .... I am just a Neanderthal with a carburetor  , LOL  ------ 

 

 

On a different note I have wondered whilts  sipping suds on the porch , what would happen if a carb was replaced with fuel injection  or vice versa fpr that matter 

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I am sure there's a fuel programmer out there somewhere that would be adequate for adjusting the FI system.

! I custom made a turbo kit for my 2010 Yamaha Apex snowmobile and all it took was a $200 programer to pour the fuel to her. Worked good. The programmer i had measured boost pressure too and adjusted fuel based on that as well as standard set points.

The problem with these types of programmers though is knowing your setpoints. I had other people that had done this already to bounce numbers off from for mine. You might not be so lucking being such a new model. But what do I know now? Those programmers probably sense engine performance and adjust automatically.?

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OK, here's what you're looking at.

 

500 cylinder and piston will work on your 420.  Bolts right on.  Some say you need a programmer, others say you can do without. 

 

When I did it, I did a Weisco programmer with the 500 (actually 475) cylinder and piston.  HUGE waste of money.  Practically no perceivable power gain, and doing it wasn't cheap.  The ONLY way I would recommend doing this is if you have a ruined 420 cylinder that must be replaced completely.  If you're going to have to buy a cylinder, might as well go bigger, but on a machine with no issues, or even one needing a top end, as long as the 420 cylinder could be bored that would be the way to go.

 

I did the 500 top end on the wife's Rancher about 4-5 years ago.  Just isn't worth the effort or the money.  Hundreds of bucks spent and you just can't tell any real difference. 

 

The 520 might be worth it, might not be.  I haven't done it yet.  People report that it really wakes up the low end grunt.  You can go to Reduction Boss and get one that will bolt right on.  I think he turns down the outside of the cylinder to allow it to fit.  If you want to do it otherwise you have to grind the opening in your crankcase to allow the larger cylinder to slide down into the engine.

 

If I ever try that, I would go with the bolt on from Reduction Boss unless I was doing a full engine rebuild where the crankcase would be completely apart anyway. 

 

The 520 sounds interesting, but not enough for me to drop $500 on it and be disappointed again.  You would definitely need a programmer using the 520 top end on a 420.

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3 hours ago, jeepwm69 said:

The ONLY way I would recommend doing this is if you have a ruined 420 cylinder that must be replaced completely.

 

being the OP has a 2021 mint condition rancher ?? 

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52 minutes ago, _Wilson_™ said:

 

being the OP has a 2021 mint condition rancher ?? 

 

I would leave it alone until it's trashed and has to be rebuilt.  No way I would do either the 500 or the 520 on a machine that was running and didn't have major issues.

 

Best bet is to buy a 520 out of the gate if you want a 520.

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38 minutes ago, jeepwm69 said:

 

I would leave it alone until it's trashed and has to be rebuilt.  No way I would do either the 500 or the 520 on a machine that was running and didn't have major issues.

 

Best bet is to buy a 520 out of the gate if you want a 520.

There was not one footshift 520 Foreman/Rubicon to be had anywhere.  My dealer had 5 Ranchers left when I bought mine, im super happy with it.

 

when It needs a new top end, I will look more in to this.

 

Maybe add a turbo too.

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Thanks for all the replies.  My Rancher has 250km/157 miles on it, bought it late October 2020.

 

will leave the engine be until it needs a new top end.   May look at swapping the clutch springs out.  Which means buying more tools.

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omg...why the heck don't you folks just buy a dang dragster ?..sigh.

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15 minutes ago, shadetree said:

omg...why the heck don't you folks just buy a dang dragster ?..sigh.

I'm still trying to figure out how to put a 6th gear in mine....

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1 hour ago, TBRider said:

I'm still trying to figure out how to put a 6th gear in mine....

Let me know if you do.

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On 2/12/2021 at 4:21 PM, WillB said:

Thanks for all the replies.  My Rancher has 250km/157 miles on it, bought it late October 2020.

 

will leave the engine be until it needs a new top end.   May look at swapping the clutch springs out.  Which means buying more tools.

 

I tried that too, on a different machine.  HATED it.  If you ride in hills at all it won't end well for you. 

 

Only thing those spring kits are good for is a dedicated pit bike.

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1 hour ago, jeepwm69 said:

 

I tried that too, on a different machine.  HATED it.  If you ride in hills at all it won't end well for you. 

 

Only thing those spring kits are good for is a dedicated pit bike.

Thanks.  I will leave it be.  Im so used to owning a Polaris, things had to be upgraded...lol

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you can't compare a Honda to a Polaris  , i think you might have meant fix things more then upgrade ?? at least you moved over to the good side, and away from the dark side. :-) 

Edited by _Wilson_™
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