Well, here's what happened today, and how I modified this thing to work and run on Christmas Day until I can get the parts to fix it right:

Never got a good compression reading. I found my old cheesy tester, that just has a tapered rubber end that you jam in the spark plug hole and crank it. But it won't go in straight enough to really get it in the plug hole, so you can't get an accurate reading. Best it did was 75psi before it started leaking around the rubber. Can't find my nice MAC gauge. I'm thinking it might have grown legs.

But I can't hold my finger in the hole...the pressure blows it off. So that's good, I guess.

So, I went through the carb again. I set the float level, and I had a box of O-rings and replaced the one on the seat and the mixture screw. Made sure air flowed in all passages. Put it back on. Used my hand to block it to get it running. No leaking. It would idle for a pretty good while after I removed my hand, but didn't want to take the gas unless you gradually worked the RPM's up, or put my hand back partially over the opening.

SO....here's my workaround: The little snorkel tube that runs up towards the gas tank....I took a piece of radiator hose that has a good bit smaller inside diameter, and basically used it as a restrictor for the air intake tube. And it runs like a champ. I drove it up the driveway and back, never even hesitated. Awesome. And I didn't get busted, either. The kids were watching a movie and didn't see or hear me.

That'll get me through Christmas, which is what I needed. I'll order the crank seals and I guess a new carb. A complete Mikuni carb is only like 25 bucks, and a rebuild kit is 17 or so. But it runs, and runs pretty well.

Couple of things: One, what's the best way to adjust the carb? I have the main screw at about 1 turn out. Two, how can you tell if the oil is being pumped to the carb? I don't want to smoke the rings.

 

Restricting the air tube down in size is a good idea if it works,but take the air box apart and you might find a rotten air filter causing the too much air/not enough fuel problem. That is one thing I did find on some older machines. Some would crumble in my hands. Kinda of hard to adjust the carb while it's running like all the other atv's. Just try at 1 1/4 turn out,1 3/8 out and see where it accelerates and runs the best. Usually I had em between these two points,but since you've modified the air inlet,you may have to set differently. As far as the oil pump,just pull the line at the carb and see if it's moist with oil. I never had one of the little ones oil pumps fail. OPT

 

I had already changed the air filter, but it was exactly as you described. All to pieces.

One thing I noticed, the new filter seems to have a lot bigger 'cells' in it.....the old one seemed to be a much 'less holey' type. Denser cell structure.

I wonder if the new one simply flows too much, or if the old one was just that way because of age and exposure to oil/gas?

With regards to the adjustment: Am I adjusting air or gas flow with the big screw on the side?

And the small screw right next to the air horn, what does it adjust?

Thanks, and Merry Christmas to everyone!

Edit: and I feel like a moron. I just noticed I have been calling this thing a Sportsman. It's not. It's a Scrambler. Hopefully they are the same other than the bodies.

And which way do you push the starter lever to activate the electric choke? It'll crank if you push it left or right, but I assume one way is for cold start and the other for warm?

 

The old filters simply get caked up and shrink a little. The big screw on the side of the carb is just the idle screw. The small screw is the air/fuel mixture screw that you can adjust normally from 1 - 1 3/8 turns out from a lightly seated position. Doesn't matter on the electric choke,most don't work worth a flip and after market manual kits aren't wort the price! The choke is supposed to open when cold no matter what the throttle position is and shut when warm,but usually doesn't! You can get complete carbs on Ebay cheap! 2001 2002 Carburetor for Polaris 50 Scrambler ATV Quad Four Wheeler Carb New | eBay OR you can get the manual choke models,BUT when cold almost all the little ones need to have the air tube blocked to crank when cold!! OPT

 

Put a new carb on it. Still cold-natured, but starts fine if the temp is mid 50's or higher.

Runs pretty well overall. I do wonder just how much this thing should smoke, though. It seems to puff a pretty fair amount. More than the Predator 90 2 stroke we have. But we're pleased with it so far. I have probably 350 in it so far, total. Not too bad.

 

After a period of time I've noticed these little ones do smoke more than when new. Can be an accumulation of oil in the exhaust pipe,plus exhaust ports can become caked with oil/carbon build up restricting flow and cause harder starts. I've removed pipes,soaked in kerosene to clean oily residue build up and cleaned exhaust ports up also. If it starts getting harder to crank, top end kits along with complete cylinder/piston kits are cheap. Replacement Cylinder Kit Aeon Dinli Polaris Kasea 50cc ATV | eBay
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