Hello, I have a new to me 08 800 2 seat rzr. Its has 2,200miles & 240hours. Allegedly only has 20 hours & 200 miles on a new 09 S motor. After a 20min of riding on gravel roads at higher rpm I noticed I was 1/2qt low on oil. I found that there's a cut in the crankcase vent tube & its blowing oil down onto the throttle body. I did a compression check with both plugs out, both cylinders were similar at 120 dry & 170 with some oil. I found some dust in the wonderful intake tube. I plan on tearing it down today, inspecting the oil for shavings & inspecting the cylinder. Is it possible to get away with just replacing the pistons, rings & honing the cylinder or is replacing the cylinder a must? I plan on replacing the intake system when it goes back together. I put a link to a video of it running below. I have auto mechanic experience but haven't been into one of these engines yet so any advice would be appreciated. Thanks.

FYI... Your head and valve cover are from a 2011 & newer and your exhaust looks like it may be aftermarket. The slit in the breather vent tube is normal. If you are loosing too much oil from it, it is possible that the pressure relief valve is stuck (pictured at 56 seconds in your video). It is possible to just hone and replace pistons but you'd have to check all the gaps and clearance tolerances listed against what is listed in the service manual which also has the deglazing process recommendations (must use a diamond hone). If you send me your email address I can send you a copy.

 

Thanks for the info! I got busy yesterday & haven't got it apart yet, I may pull that oil pressure relief valve out & look at it. I can feel air blowing out of the breather hose slit at idle, is that normal? Also my compression numbers seemed low, I think I'll just replace the cylinder if I go ahead with the rebuild.

 

Yeah, any cylinder pressure less than 150 you will start to see performance problems. These have a nikasil coating so they do last longer. I wouldn't just replace it automatically. Once you get it apart you should be able to check the current ring gap, the cylinder bore size, and the cylinder to piston gap. If they check out as good then you can just get new pistons. Unless of coarse you wanted to go big bore.... That is good for extra horsepower. Also check to make sure the crank/rods are ok and don't have extra play in them. And also check your valve train for leaks.

 

I got it apart today. The pistons show wear, I put the second ring down from the top of the piston in the cylinder, which I believe is supposed to be about a business card gap and it appears to be much larger. The rod bearings checked out ok. I'm shying away from big bore, I think I'm going to go with this top end kit with the cylinder for $629 POLARIS RZR, RANGER 800 TOP END REBUILD WISECO PISTONS, CYLINDER, GASKET KIT | eBay

I plan on take the valves out, cleaning them up & replacing the seals.

Also I had the plastic piece pop off the end of one injector, will it just pop back on or do I need to replace the injector? Do the head bolts need replaced? Thanks

 

You can reuse the same head bolts, at least I did when I rebuilt. I've never had the injector tip come off. Maybe others can comment on that. If it's the plastic O ring sealer you can put that back on but if it compromised the tip I'd buy a new one or make sure it's cleaned extremely well before putting it back on. The last thing you want is a clogged injector. With the cylinder and piston you are looking at did you want the 10.2:1 compression? That was standard for the 2008 but from 2011 and on they all are 11:1 standard.

 

The Oring stuck in the head & pulled the piece off. It fell down around the intake valve, I haven't fished it out yet. Yeah, I'm not too excited about a clogged injector or the piece falling off and going into the cylinder. Good call on the compression ratio, I found the 11.2:1 setup, should be here next week.

 

Well I got it back together. It seems to run great. It has a ping or knock to it. I'm not sure if that's normal or if 87 gas is the issue with the 11:1 pistons. I might try to run 89 or 90 and see what happens.

 

Im not trying to scare you but I would definitely error on the side of caution and make sure you dont have a stuck lifter. I just did a top end on a 2014. We installed new lifters while we were in it. One of the bores must have had some trash in it even after we vatted the cases. It ran great for about 20 miles and start developing a tick. I pulled the head off with the motor in the machine. One lifter was stuck and chewed up. Bottom end is full of metal so back out it comes. This isnt the first time Ive seen it. My original motor in my 2012 ate 3 lifters after the pressure relief valve stuck. When I rebuilt it I seperated the original crank for curiosity sake and it was completely full of metal shavings from the lifters. A $4 small block lifter completely destroyed the bottom end. You live and you learn.

Yours definitely sounds like a lifter is hammering on the crank. If thats the case it will get louder, mine started knocking and wiped out a rod bearing. It takes about 20 minutes to pull the head off with it in the machine, I would definitly make sure the lifters are free. If you have a small enough magnet you dont even have to remove the head. You can pop the valve cover off, rockers and push rods and see if a magnet will move the lifters up and out. If any of them wont slide freely with the magnet applied they are mushroomed on bottom and chewed up. I had to remove the stuck on with a pair of pliers. There was significant scoring in the lifter bore after closer inspection.

 

Alright thanks, I'm not blowing oil out of the crankcase vent anymore so I don't think the pressure relief valve is/was stuck. The bed is still off so I'll pull the rockers, pushrods out & see if my magnet will go down there & move the lifters. I don't doubt it could happen but it would amaze me if its running as well as it is with a valve or two not working right. That knock seems louder from the intake side of the engine than it is on the exhaust/lifter side, fwiw.

 

Well, all 4 lifters moved up over an 1" freely. I didn't quite pull them all the way up, I was afraid I wouldn't be able to get them back in. I don't love that noise but I don't know what it could be. The rod bearings didn't have any play. I got the c clips back in the wrist pins. I torqued the rocker arms & they were all seated correctly. A stuck lifter made sense but they are all free.

 

If they all moved that far you are in the clear. When they mushroom you have to get ahold of them with some force to remove them. If you are concerned try removing the primary clutch, if you have no play on the rods I would suspect you are hearing the noisy primary clutch. Have you ever rebuilt it? With that kind of mileage Im betting the buttons are worn and you are hearing play in it.

There isnt much else that can cause that noise if you put new piston/rings and complete the top end. The lifters are usually the thing that kills a motor in a hurry. They take out the cam and then fill up the motor with metal shavings. Seen it too many times to count.


What are your compression numbers now after the rebuild?

 

I put a new comet clutch on before the rebuild. I did swap over the EPI clutch kit from the old clutch during the rebuild. The EPI weights didn't fit as well so that could be it but I don't think so. It's ran for about an hour since the rebuild. I just let it run for 1 min then did a compression check, back cylinder is 155 and 170 with the throttle open. The front cylinder is 150 with throttle open or closed. I ran the check twice, I thought I heard that knock on the front cylinder while it was cranking on the first test but didn't hear it on the second test. The valves looked fine, I did pull them out, clean them up & put new seals in while I had it apart. I'm wondering if I have a weak or collapsed lifter on the intake of that front cylinder? I am running regular 10-40 oil for the break in then plan to switch to synthetic 5-50.

 

Heres a vid of the compression test. it was pretty well cold. I'm going to take the valve cover back off & see if I can get any play out of that lifter/pushrod. This rzr is supposed to leave Sunday morning to go on a week long trail ride :surprise

 

So in an interesting turn of events, its the intake on the back cylinder? I spun the motor over by hand until I found the closed position for each valve. That's the only valve that has play, it has quite a bit of give to it. I did pull the lifter up again to make sure it wasn't stuck. No dealers around had lifters in stock so I've overnighted a set of a lifters and a gasket set. :crying Is it guaranteed failure to just replace the lifters without replacing the cam? Should I just replace the bad one?