2000 Scrambler 500 4x4
 

FNG here! I'm not mechanic, but I know the basics with this stuff. Just bought the Scrammy. The dude I bought it from told me it needed "carb work." I asked him what exactly it needed and he said he didn't know. Anyway, I got the thing home. It starts right up. Idles like crap * and at about 1200 rpm. Goes into gear fine and does fine at low speeds. When I get on it though, it acts like it's flooding out and bogs down and back fires. I've read some other threads and I tried removing the air filter and no changes. Any ideas? I bought the thing knowing I'd have to sink some money into it and I have a manual. Any help would be appreciated.

First thing I would check is the valve clearance(.006 intake and exhaust) and if there is noticeable wear on the center exhaust lobe. This was the the one major problem on all 1996-2000 model 500 engines.It may or may not be the problem,but I'd check it. Here's an example of one from another member that when they wear down this far they will idle good,but spit and back fire constantly when throttle is applied. 1.2766 is the service limit the cam lobe should measure.You can measure it if need be while still in the engine.When really worn,basically there is no lobe left as in the pics. http://forums.atvconnection.com/pola...d-cam-pic.html
If the cam and valves are eliminated as the problem,it may just need a carb rebuild kit. 1003-0083 - ATV Complete Carb Rebuild Kits Polaris 98-02 Scrambler 500 2x4/4x4 | ATV Parts | MFG Supply

Thanks, OPT. I'll give that a shot tomorrow

OPT, I took the cam out today and it was completely trashed. I'm picking a new one up tomorrow, but was wondering if you could give me some advice on installing the new one and the timing? I've done a lot of research and have a pretty general idea, but you seem to be the man in this forum and I think I can trust your guidance. Thanks in advance.

Since you've taken the cam out already,the easiest way on installing a new one is out the window. :) Now you have to be able to see the lower cam sprocket mark on the case which involves removing the recoil cover,flywheel and stator.Once it's lined up,the chain tensioner is out,then you can install the new cam. I would replace the chain along with the camshaft and exhaust rocker arm. Align the one plated link on the chain on the bottom sprocket at tdc,then you will see the two plated links at the top that line up with the sprocket marks. Then you can slip the upper sprocket on the new camshaft. Just look at the engine diagram and shows a cutaway of the timing chain,sprockets and cam timing on this pdf manual.Doesn't matter on the year of this manual as the engines are all the same on the 500. If you have a 2000 model Scrambler,not a 1999,then you should have had the 3085855 HO cam already?I didn't have any cam problems on these,but anythings possible?? Index of /ORV Manuals/Polaris/Scrambler/2009
OR if you can keep the tdc mark on the flywheel and recoil cover mark you can time the cam this way.

A little info
 

OPT, you know your stuff! I have been trolling for awhile, I have a question, I recently got a 2000 Scrambler 500 4x4. I did what I usually do and stripped it down, needs work. It would not idle when I got it, been sitting awhile, drained fuel, removed tank, carb.. Rebuilt the carb, cleaned the fuel pump, all new fuel lines. I know the throttle cable is stretched, on order. It will idle now, but, when revved it doesn't backfire but it pops through the exhaust when rpm's are coming back down. It seems louder than it should. Baffle removed? I am just hoping it isn't the cam I have read so much about...

Best way to tell is to pull the valve cover and check valve clearance and the exhaust lobe especially for any wear. Not all did this,but quite a few did. Popping back is one of the signs when they're beginning to wear, they will idle good,but pop back through the carb and exhaust when you give it throttle. Here's a pic from another member on his Scrambler that went to the max on the cam.http://forums.atvconnection.com/pola...d-cam-pic.html

Thanks, I was afraid of that. I will pull the cover and take a look. I have been putting it off...I will take a pic and let you know. If it is bad I would think I could position the old cam and put the new cam back in at the same location, correct?

If the cam is bad,just order another one and the exhaust rocker arm from Ebay or Cycle Parts Warehouse,which ever is cheaper. To change it out all you have to do is have it a tdc(index sprocket pin straight up center of the head) Remove the tensioner,thermostat cover to get access to cam cover on left of the engine ,unbolt the 3 sprocket bolts without moving the crank position,slide the old cam out,new one in move the sprocket and chain around as a unit(again with out moving the crank) align the sprocket to the new cam index pin,tighten the bolts,replace the tensioner and adjust the valves. Sort of a simplified version here,but I can go into better detail if needed..

Thanks, appreciate the info!