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Discussion Starter · #1 ·
I'm currently rebuilding my RMK because last year it somehow got a hole in the crankcase and some foreign object made its way into one of the cylinders and tore it to absolute pieces.
I couldn't find a head to replace it with so I went ahead and bought one from a 2003 because on visual inspection it was identical and I'd seen the part listed with 2002-2005 compatibility (same with the pistons). It turns out that the 2003 head I got is ever so slightly less dished than the 2002. Not enough to see, but enough that once it's torqued down, the pistons bind against it at the top of their stroke and the crank wont turn all the way over.
My first thought was that I had just assembled something wrong but everything seemed to be where it belongs. I confirmed that the heads are different by bridging the dishes of both heads with a straight edge and measuring the depths with a caliper. Sure enough, at the deepest point of the outer dish, the 2003 is .070" shallower (2002 = .190" | 2003 = .120").

Long story short, I still can't find the correct 2002 head anywhere. Anyone have any suggestions on how to proceed?
These are the options I can think of and I'm sure some of them will be shot down quickly
1. I'm doing something completely wrong somewhere and these parts are in fact interchangeable. Maybe theres supposed to be significantly more clearance between piston and head. (is 70 thou a silly amount to worry about?)
2. Clean up my original cylinder head and slap it back on (pictures attached)
3. Take the new '03 head to a machine shop (expensive as frig)
4. Get different pistons and re-rebuild the top end
5. Keep looking for a head of an '02
6. Buy this one
7. Give up


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Discussion Starter · #3 ·
There's no way you can use that head. You'll have to find another one. It's shot.
Thats what I had figured. I messaged the seller on that ebay one to see if he'll take the critical measurement, he says its off an '02 so I'm hopeful.
Since this is my first rebuild I'm just hoping for some confirmation that I'm not crazy and that the 70 thou difference in piston clearance makes sense as the culprit before shelling out 80 bucks on another head.
Silly me though, I hadn't thought of just torquing on my old head to confirm that it works. I'll try that when I get back in the shop.
 

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Discussion Starter · #4 ·
Update:
I wire wheeled my old head just in case, popped it on and torqued to spec. No piston binding. The ebay seller got back to me and his part meets my spec so thats the route I'm going.

BUYER BEWARE!
People will list RMK cylinder heads with 2002-2005 compatibility. This is not necessarily true. If you have a 2002 rmk you need a 2002 head.
Someone in another one of these forums (do we acknowledge that they are all identical forums? clearly owned and operated by the same company?) mentioned that the OEM part numbers differ. Checking this ahead of time instead of trusting and Ebay seller would have been wise.
 
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