Sears intek 20 hp, fresh gas, filters air and gas, oil, and plug still won't start where should small valve and screw adjustment be set to, may be the problem don't know. won't stay running will run a bit withstarter fluid but soon quits

If its been a while since you used it, most likely bad gas. Ethanol can pull water out of air, so there may be a little in the tank, also. Siphon it out & dispose of it properly. Get as much as you can out. There should be a little drain valve at the bottom of the carb. Drain it into a container. Put in fresh gas, make multiple attempts to start. This pulls fresh gas into carburetor. Also buy a new spark plug. Check for mouse nests around air intake (happened to me with a garden tractor). Check air filter, replace if it looks dirty. Buy a can of carburetor cleaner, follow directions. That covers all the possibilities, I think. BTW, to prevent future bad gas problems, don't just turn off the engine unless you plan to use the machine again soon. Turn off the fuel valve and let engine run out of gas. That keeps old gas from leaving gum in the carb over a long period. I do this with my snow blower every time I use it. Any snow can be the last snow of the season. This applies to every small engine, of course, not just chippers.

Answer to your question is this,if this keeps up smoking,i would check the carburetor fuel filter,for signs of gas collected up in the filter. If there gas you need to adjust the carburetor,by adjusting the fuel mixture. The carburetor uses both fuel and air mixture. To much fuel(Rich) floods the carburetor,too little fuel(Lean),there is more air than fuel. You will have adjust the carburetor's needle valve to receive the correct balance between the two. To do this check the carburetor for a slotted screw,take a screwdriver. Turn the screw in to get a lean mixture,turn screw out to get a rich mixture. After making your adjustment,start the tractor,if not already running. Watch to see if it is still smoking,if it is, adjust the needle valve screw in more until the smoking stops,also keep watch on the filter for gas,in the filter assembly. This is not where your gas needs to be. I need to inform you to also,to be sure that the air filter is cleaned up(No Gas Accumulation in the filter) -This is a must do to possibly,keep from having a (FIRE). When making fuel adjustments,i would check the spark plug(s) for carbon deposit building up,that would cause the motor not to start,or run smoothly. Anyway,be SAFE,your dealing with GAS. Sincerely, Brad Locke 12/03/15

Valve may be stuck, this happens with overheating a lot. Remove the small oil air baffle cover, remove plug, pull starter rope and see if both valve stems are moving.

No adjustment for carb on newer mowers. All mowers now have a low oil cutoff. Ensure oil is full. 30w oil. If any grey is observed vin oil drain all oil. Moisture in oil. Dump old oil out every 2 yrs and refill. Ensure spark pluf is clean and gapped correctly. Ensure air filter is clean. Replace spark plug and air filter each year. Always use Stabile in gas. Spray outside of carb with carb cleaner to ensure proper choke movement.

You can get one anywhere that sell small engine parts

Gas in the spark plug chamber should mean it is flooded.trying to start it for too much time with the choke on will do this.when starting cold,engage choke.turn engine over till it tries to start.if you can't disengage the choke before it stalls,do not re-engage the choke.just keep turning the engine over,or pull starting,whichever you have,until the unit starts.it will.for now,if the sp.plg.hole has fuel in it,blast compressed air to clear it somewhat,re-install sp.plug,never overtightening,just snug,and try starting without the choke.hope this is useful.bart.i am a certified small engine mech.and remember when finished,let unit idle for 2 min. Or so and cool before shutting off.change oil religously every 50hrs.for units over 10hp.,every 25 hours for engines below that.they will last a long time.clean air filter after every two or three uses.never empty fuel when storing,use STA-BIL.

Did you drain fuel tank before refilling with fresh fuel? Drained carburator bowl good, drained crankcase and refilled with fresh oil good,removed air cleaner and dried out good. One question for you , did you remove spark plug and drain any water that may have gotten into your cylinder through an open valve? There could be water sloshing around in the cylinder, gas and water will not fire, and water on spark plug wont allow plug to spark. If you need any more help please get back to me , I believe this is the first under water problem I've encountered. GOOD LUCK.

i would say it is the head gasket , there is only a little space between the valve train and the piston, and this is where the gasket lets go, when the piston goes down on intake or power it sucks the oil past the gasket then out the exaust valve

This sounds like a compression release issue, which is directly related to the OH valves needing adjustment. Remove the valve cover and adjust the valves per B & S exact instructions and your starting issue will likely be solved. The valves are needed to be adjusted periodically on these machines. The compression release feature works off of the camshaft and is controlled by the action to the intake valve. It works at low speeds and then cancels as the engine starts running.
Many, many users have this problem and are unaware of the compression release mechanism and the fact that the valves periodically require adjusting, They tend to blame their starting problems on a weak or bad battery, which this problem mimics quite well.

Here are a few things to consider :
- fresh fuel ratio 40:1
-new spark plug
-choke not sticking
-air fuel mixture correct
-bar and chain oil tank full, oil getting on chain
-bar sprocket in good shape getting lubed.
Please let me know what you find.