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!

One last question, should I get the gasket kit as well?

Most of the time I didn't replace the valve cover or cam cover plate gasket as they just came off with the covers. A little film of Three bond 1104 or Yamabond usually does well enough when you replace em back on the engine...

here is the cam...
http://forums.atvconnection.com/pict...ictureid=44777

http://forums.atvconnection.com/pict...ictureid=44778

If I am not mistaken, to me it looks like the intake valves are worn pretty good too correct?

Measure the intake and exhaust lobe with a micrometer or caliper,borrow one if you can or rent one from any auto store.You can do this by having the lobes at an angle to allow measurement. The std lobe height on all 3 lobes is 1.2884 to 1.2924. The minimum allowed is 1.2766. If the exhaust lobe is at this reading or less,then replace the cam before it does go out and destroys the exhaust rocker arm with it.If the measurements are within tolerance,just adjust the valves. Valve stems can wear over time,but it's usually not a problem. Most "normal" reasons for valves to tighten,especially intake valves is that they are softer and "mushroom" out at the valve face in the seat over time and doing so close the gap between the adjuster and valve stem. The exhaust lobe itself was the problem on many cams.

so to me, it looks like the exhaust lobe is pretty bad, is that correct? I am ready to replace it if you think it needs it. This is my first Polaris, I am a newb with these. I fully restored my Banshee, which is way easier to get parts and my wife's 97 Fourtrax is indestructible :)

http://forums.atvconnection.com/pict...ictureid=44780

Just measure the clearance on the lobe to the std lobe height. If worn,then yes replace it. Hard to tell from the pics. Here's where I ordered cams before and got it in about 3 days and fairly cheap compared to a dealer. Plus there are now aftermarket cams showing up on Ebay,but I haven't heard good a or bad on them.The 2000 Scrambler has the stronger updated HO cam already,but anythings possible,if wrong oil used,not taken care of etc. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse Does look like the lobes have gotten hot (blue color)

It definitely was NOT taken care of. I will measure and see.
Thanks again for the help

1997 Polaris Scrambler 500
 

My bike starts up just fine, idles perfect. When I give it throttle it spits and then bogs down and dies. It will go into gear just fine, but it will not move.
Your help would be much appreciated. Cleaned the carb thoroughly through and through no build up or anything. I still ordered a rebuild kit though. What is the issue with this thing? I'm not that mechanically inclined, I just know a little. HELP PLEASE!!!

Sounds like the same issue we've been talking about. Pull the cam cover and check out the exhaust lobe on the cam for wear. Popping back,spitting back through the carb, no power,but runs good at idle is usually a few of the symptoms of a ground down cam exhaust lobe. If it looks like this,then replace the cam shaft and exhaust rocker arm. http://forums.atvconnection.com/pola...d-cam-pic.html If the cam is ok,could be a carb problem as you mentioned

Are these bad cams ATVs been using Synthetic 0w-40?

I know on my Honda Foreman and Yamaha 350s I world just use any oil or weight car dinosaur lying around in the garage, but one these Fuji dry sumps they want synthetic and the correct weight.

I couldn't tell you what mine had before, I just bought it a couple of weeks ago. I changed the oil and used the polaris oil change kit. From the looks of the old oil that came out it looked pretty bad. I have only rode it far enough to load it on my trailer and start it up in my garage. Reving it sounds like a hot mess when you let off of the throttle.

Old Polaris tech.

How do I get to the cam?

Have to remove the cam cover :) Second thing is to down load this free pdf manual to help you out..Will show you quicker on what to do than I can type. Index of /ORV Manuals/Polaris/1996-1998 - All Models

Ok so I got to the cam, yes it is pretty rough in there, do you have a link to a cam replacement?

1997 polaris scrambler 500

Be sure to order the exhaust rocker arm as well as the cam. The rocker arm pad usually is scored up also. Here's about the cheapest Oem parts online I've foind,But I've seen cheaper after market cams on Ebay. Don't know how they'd hold up. You can either go with this updated cam for your 97 model(3086212) OR install a later model HO cam(3085855) as some have done. Only difference is the duration,the lobe height is the same on both cams.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehousehttp://www.cyclepartswarehouse.com/f...2000&fveh=5498 Just my :twocents: on this.If you don't go to the larger HO carb,the HO cam wont make that much difference on the 97 model. I'd stay with the recommended 3086212 cam.

The cam lobes were within spec. They were far out out adjustment. At TDC I couldn't get the feeler gauge in between the adjuster and the valve. I adjusted them. Haven't started it yet, will let you know. Thanks OPT

Sounds like you may have gotten lucky! If you cant' fit a .006 gauge under the adjuster,then it's too tight. Let us know if this solves your problem.

I think that is why the cams were blue, from the heat generated from them being too tight. I started it. Feels like it has more power on rev. Still pops a little on deceleration of the throttle, but as loud as it is I think someone took the baffle material out of the muffler. Have a replacement on order.

Also got new throttle cable, what a difference!

OPT, do you know what the specs are as far as the Valve clearance, torque on the 3 bolts on the cam sprocket are supposed to be, and torque on the 4 bolts that hold down the rocker arms are supposed to be?

Thank you

.006 clearance on the intake and exhaust valves,8-10 pounds torque on the rocker support blocks,6 pounds torque on the cam sprocket bolts(use blue lock tite)

OPT!!! you are the man!

opt, my wheeler is still spitting when I give it throttle. changed cam and rocker arms, and valve adjustment is pretty close to perfect. no clue what I need to do next?

Retrace your steps on the carb rebuild you did along with making sure fuel flow is good from the pump,if you're sure the cam is timed ok,valve clearance ok,cam detent spring hasn't slipped from the lever . If it was spitting before the cam install and still doing it,then there's something somewhere you've over looked.

What is my valve clearance supposed to be for both the intake and exhaust side?

.006 intake and exhaust clearance.

You'll probably be upset with me, I ordered the cam and no rocker, my buddy said "you don't need that, your old one will work"

So my question is, how will I know if my exhaust rocker is bad? My exhaust lobe on the cam was completely gone, it was almost perfectly round.
Once again thanks for all of your expertise advice.

Look at the rocker pad where it rubs the cam lobe and you'll probably see why I said to order a new one! Everyone I got a hold of was scored badly..

Well, I got the valves adjusted perfect, started up, ran good, no popping. However, carb was leaking, took it off for the third time, had already rebuilt it, floats adjusted where they should be, still leaking. I also cleaned it, took the main jet out etc. The tab that holds the needle on the float, is that supposed to be bent up and clip on the float to hold the needle? One pic I saw it looked like it. Now it seems the starter is going bad. Every time I fix something another issue comes up. I already have some good money in it but I am about ready to part it out...