As you know from helping me so much i have had many engine issues. I just had the valve cover off and noticed that each cam lobe was worn on the clutch side of the motor. I would assume it is from a worn head and the camshaft no longer sits parrallet to the rockers. Or did i flip two parts on (one of) the assembly? are parts 26 and 27 the same? or are they different and one hold the rocker bar higher than the other?

Polaris ATV Parts 1999 A99CH50AA SPORTSMAN 500 CYLINDER Diagram

thanks OPT

 

I always installed them back to where they originally went. Even shows on the parts list the rocker shaft support block with the screw goes to the pto (clutch side)
Manual just says if the rocker arm support shaft screw(24) is ever remove or loosened,tighten it back down after the rocker supports,shaft and rocker arms are installed . This screw locks the rocker arm shaft to the support block. I just removed both rocker arms supports,shaft and rocker arms as an assembly. Never had to tear one down.If I had to replace rocker arms from ground down cams,I just slid the left (mag side) support block off the shaft and slid off the rocker arms. Possible that that the shaft od or support block id are worn causing the excessive wear. The manual gives you the measurement specs on this to check.

 

i swear i have it in there right but i had to check. The lock nut is on the correct side, i actually have a new one in there. since were probably dealing with a worn camshaft guide, what would happen if i would shim up the clutch side of the rocker shaft until its parallel to the camshaft? the rockers arn't pusing in a linear path on the valves so would a few thousands (or whatever i would need to shim it) do any harm?

 

Never shim any part to try to compensate for possible wear else where. This may or may not be a rocker arm support problem,but could be a head problem if excessive or uneven wear in the head journals where the cam itself rides.If one or both head journals are out of spec it can cause the cam to tilt at an angle causing uneven wear on the rocker arm pads.If this is the case,the head needs to be replaced...Same goes for an out of spec rocker support block or even a worn rocker arm shaft or rocker arm itself. You're talking thousandths of an inch here and measurements are critical. For accurately measuring the inside diameter of the support blocks and the head journals you need a set of snap gauges and a good micrometer,NOT calipers as most are not that accurate enough especially in smaller measurements such as the support block journals.Snap gauges are cheap at places such as Harbor Freight.Usually around 20 bucks or so. They may even have decent price on good quality micrometers? Doesn't have to be expensive ones like the NSK set I have.Here's a demo on how to use snap gauges.

 

oh my dad has a set of those and mitutoyo mics that i would need. Could even stop in at work and use a three point bore gauge if I wanted. I have worked in a machine shop for the past three summers running cnc lathes with tight tolerances. I have thought if it would be possible to bore out the journal and then weld on and re-cut the camshaft to a larger diameter.
The main problem is the earful i get from my old man every time the plastics come off.
If i were in the market for a head are there any suggestions besides a used one?

 

Just strip the head down,use his tools and mic the parts. Manual shows the tolerances. Easier to just get a used newer head like one recent member did on his Ranger if the head is the problem. My take on aluminum once it's machined,it's harder to try to weld/build up the surface and cut it back down than to just replace the head unless you like spending your time in a machine shop.http://www.ebay.com/itm/Polaris-sportsman-500-4x4-2006-06-cylinder-head-/360973122456?pt=Motorcycles_Parts_Accessories&hash=item540bacbb98&vxp=mtr

 

if i wouldve sold this thing years ago and bought a new 570 i probably would've been saving money by now.