My scrambler was starting up and running fine, but would not idle. I first took the carb off and tried spray cleaner. I reinstalled the carb and now it won't start. I pulled the carb again,tore it apart, soaked it in cleaner and reassembled. all the jets,seats etc. looked good to me but I'm no expert. Reinstalled the carb again but it still won't start, no firing ...nothing. I pulled the plug and it seems almost dry. I'm not sure any gas is getting to that plug. The carb bowl is full of gas. Please help

 

First things first. Replace the plug if you haven't already and ground it against the cylinder to check for spark. If you have spark and it was at least running before you tore into the carb,retrace your steps.Not a bad idea also to do a compression check to see where you stand on the top end.

 

First of all..thanks for your help. Ok, I changed the plug, new gas again and it started up. Now I'm back to my first problem which is it won't idle. I'm sure I messed up the fuel and air screws. I backed off the air screw about 1 1/2 turns, same with the fuel Which I keep adjusting in and out with no success. the throttle cable is screwed all the way down. Even though the engine is running fine, and warmed up, I always have to choke to restart.

 

Sounds like it's time for a carb kit. Won't idle is usually a stopped up pilot jet,but once you're in there,might as well install a new carb kit.Air/fuel screw normally sets between 1 1/2 to 2 turns out. http://www.ebay.com/itm/Polaris-Scrambler-400-1997-2001-Carb-Carburetor-Kit-/380717280350?pt=Motors_ATV_Parts_Accessories&hash=item58a484ac5e&vxp=mtr

 

OK
I ordered the carb rebuild kit. I got a kit for 1997-2001. I couldn't find a kit for 1995 which is the year of my scrambler(I think). I compared the blowup pictures on the polaris website and they seemed the same. when I got the kit, most items had the same numbers.I'm not sure on the main jet, and the needle for that jet was definitely thinner. Replaced the parts and now it doesn't start. I put all the old parts back in and it still won't start. Actually when I put the old parts back in , it did start once. I checked again for spark and that was fine. I really don't understand why the spark plug seems so dry. I would think that with all the choking and throttle cranking that the plug would be wet. Thanks again for your help...

 

A different size jet needle wouldn't stop it from starting.I've installed several different kits that were different. If you have fuel in the bowl,spark,air filter is clean,retrace your steps,plus if you haven't done a compression test I'd do that also. Plus you can't over look the common problem with crank seals either. If the engine doesn't have enough suction from either low compression or leaking seals,doesn't matter if it's getting fuel or not,it wont crank.

 

Maybe this. Click on top bar of link.
http://www.ehow.com/video_4468404_polaris-atv-thumb-throttle-maintenance.html

 

Despite the posts not to use starter fluid I gave it a try. Scrambler started right up and as long as I manually kept the throttle high, it would keep running. I would slowly lower the rpm until it would finally die, and of course, it would not start. This whole issue started when it would start OK as long as the choke was used, but it would not idle.Now it won't start without starter fluid and it still won't idle. I'm totally frustrated. Do Carbs just die at some point? It would seem that if all the internal jets etc are replaced and the body is soaked and cleaned..it should keep working

 

The reason it will run with starter fluid is because it's lighter than gas and will crank in an engine even if the carb is stopped up or even if compression is too low for vacuum to pull in a load of fuel and air. Do a simple compression check before you do anything else. You can "borrow" compression testers from most auto stores if you don't have one.

 

Thanks again... two things...when I run the compression test, what should it read? and second, the fact that it keeps running after it starts( as long as I hold the throttle )Doesn't that indicate that gas is getting to the cylinder and the high rpm part of the process is working?