What should idle be for a 2002 Sportsman 90? I've searched for Predator 90, Sportsman 90, Eton 90. I've found 800-1000 as well as 1700-1900. I picked up the ATV and kids rode it for a couple of weeks and then all of sudden it wouldn't stay running. I checked compression and found it to be low around 60. I bought a new cylinder, piston and rings from Polaris and installed. Checked compression again and it was the same. I'm thinking bad compression tester. Anyways, I've taken the carb off and cleaned it while waiting for parts. Reassembled and have it running again but trying to get idle speed set. Also during that time I deleted the oil injection and put a filter pod on. I have a 27.5 pilot (I think) and 90 main because of the filter pod. Air mixture screw is about 3/4 turn out. I have needle on middle groove. It will idle and rev up when given gas but bog when user load. I raised the back end up and it will rev up no problem. That's where I left it last night. Any recommendations? Oh, I also checked the stator resistance and white/red and black/red numbers were extremely low. The other numbers where within spec. I have a new stator on the way, could that be the reason for the bogging issue?

 

Mixture screw between 1 1/4-1 1/2 turns out from a lightly seated position.This setting all depends on the condition of the engine. Engine needs to be at operating temperature. Adjust this screw inward to richen the fuel mixture,out to lean it out. Just adjust to where you get the best idle and throttle response. Shows idle speed to be 600 rpms +/- 200 rpms according to the manual,but just adjust this screw to where you have an even idle. Stator could be the reason,or can be crank seals or condition of piston and rings. Compression again according to the manual needs to be at least 115 psi.Reading your post again I see that you show 60 psi.. Way too low! Top end kits are on ebay cheap for these machines now also.Polaris Sportsman 90 Cylinder Piston Gasket Top End Kit 2001 2006 | eBay

 

That's what confuses me. It was a new Polaris top end that I just installed. The compression was the same as before. If it's a crank seal can that be done with getting into the engine or will I have to do a tear down? I searched and could not find info on what the procedure is. When I pulled the oil injection pump I had oil behind the gasket. I plan on buying another compression tester to see how it reads to rule out the new rings. Then I have to wait for the stator to get here and depending on what happens I can rule that out. On the idle I put my tach on there and there and to keep it running the lowest I can go is about 1200 RPM's. I forgot to mention in the initial post my elevation is around 600. I appreciate the help and will make the changes you suggested on the air mixture screw and then recheck the compression with a different gauge.

 

If you have a new top end you still should have more than 60 psi!Think I'd check with another gauge. Leaking seals can drag top end compression down,but to drag one down that low a seal would basically have to be popped out. You have to pull the drive clutch and also the flywheel and stator to get to the seals. Hard part is to just get to them. Just pop the old ones out and install the new ones. If you have to keep a high idle to keep it running,it's either a seal problem or somethings wrong with the carb jetting,settings, or could even be a problem with the top end,rings,etc. Off hand can't remember what stock jetting is plus all the parts breakdowns just give the part numbers and not the sizes.

 

Ok. I purchased a new compression gauge and it reads 105. That's better but still not the 115. I also dug into the stator side crank seal. I have attached a picture. I'm guessing it shouldn't be leaking oil like that. Ha ha. To replace the seal is it as easy as prying out the old one and then seating the new one???

 

105 sounds better and would probably increase with a teaspoon of oil in the cylinder if the cylinder walls are dry. And yes the seals just pop out and you just seat a new one in. Don't do just one,replace the seal behind the drive clutch also.

 

Great! Thanks. I appreciate all your help! What are symptoms of just a leaking crank seal? Just so I can identify it if it happens on something else.

 

One of the symptoms is having to keep the machine at a higher than normal idle to keep machines from bogging down and dying. What you've been having to do already. Crank seals may or may not be the cause of this,but people over look the fact that they take as much beating as the piston,rings and cylinders do over the years.Once the seals are replaced and if you still have problems at least you've eliminated the seals and can move on to something else.

 

Hind sight is 20/20 but I wish I would have dig a little further because they are so cheap compared to other things I've done. I'm hoping this fixes the issue.

 

So do I..Hindsight is always 20/20 and we've all been there at one time or another. Live long enough and you'll experience it more than once..