Polaris ATV Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter #1
Looks like I need to do a top end on my 2008 sportsman 800. Been looking at kits, one of them being Wiseco pistons/jug, as well as a few others. My question is the pdf manual I have for the 08 sportsman 800 lists it as an 11:1 engine (will attach screen shot) however all the factory spec rebuilds I'm finding are for 10:1. I emailed the one company that was selling the Wiseco rebuild kit and he said he had never seen a factory one with 11:1 but he did have the pistons to make it that. So is the manual wrong or if I buy one of these kits that are listed as factory specs 10:1 am I going to lose compression? I don't mind factory rebuild, (would like a little more, but who wouldn't?) But definitely don't want to end up losing power.

139103
 

·
Premium Member
Joined
·
9,409 Posts
Bud chk out some of the rzr 800 rebuild kits!!

also my 2011 comp ratio is also 11:1.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #3
I found a forum post earlier that was on a RZR forum. According to them the 07-10 rzr was 9.78:1, and 2011+ was 11:1.

Wonder if I did swap to the 11:1 wiseco pistons if the computer would be fine. I was also talking to a buddy of mine who has a 2013 rzr 800 and he mentioned running a rzr cam, not sure how different they are?
 

·
Moderator
Joined
·
10,367 Posts
Only the head is different and raised the compression ratio on the 2008 to 13 I think. Pistons, rings, cylinders are the same.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #5
That makes sense. I'll do some more digging, can't really find any discussion on it in the sportsman groups. Only info I've stumbled across has been in the rzr forums, I assume the engines are the same across models for the same years?
 

·
Moderator
Joined
·
10,367 Posts
Just get the standard bore piston/cylinder combo and you will be fine. With the newer style head yours will still be 11:1 same as original.
You won't get any noticeable performance increase with any higher compression piston kit but would probably need to use higher octane fuel, will likely run hotter which is already a problem with the 800's and may experience harder starting and need more battery/starter muscle to crank it.
 

·
Registered
Joined
·
13 Posts
Discussion Starter #8
Finally got the 800 out/pulled down. Looks like rings are definitely shot, and pistons have some carbon build up on them. The cylinder walls aren't scratched and still have visible cross hatches. Any reason I shouldn't just do a set of Wiseco pistons/rings and put back together with factory jug?
 
1 - 8 of 8 Posts
Top