20 hp tecumseh, won't run unless choke all the way out and gas lever all the way up, also backfires. spark plugs good and seems to be getting plenty of fuel. Any ideas?

Sounds like your fuel jet is plugged. if you have a fuel cup on the bottom of your carb remove it and clean it out real good.The fuel jet should be the little screw tat holds the cup on Take it out and blow it outwith an air compressor or put a real fine wire through it if you do not have air pressure. You should be able to feel air if before you put it together you blow through it.
Might be a good plan to dump your old gas out and make sure your fuel tank is clean and put fresh gas into it.
A large percentage of when the engines have to be choked all the time the jet is plugged or partly plugged. Do not mess with the float when you take the bowel off or you could have other issues to get it put back together properly.

If the plug is wet, it is likely fouled and the cylinder flooded. Dry off the plug and reinstall it. Open the choke and throttle so the carb throat is wide open and crank the engine over. This will evacuate excess fuel out of the cylinder faster then anything. It should fire at least once.

hi
remove the bowl again and get the centre jet out and lok very closely use a jewlers eye piece you wll find a passage that is plugged on the side of the jet look around it you ll see some sign of a hole that is not clear through its pretty small use a welders torch cleanng tool with various size rods use very thin one dont make the hole bigger

Joe

Your problem could be one of several things.. A bad spark plug, bad gas, failure to lower the idle and let it run a few seconds prior to shutting it off, unadjusted valves, etc.

I'd start with the plug and some fresh gas, then go from there. Always idle the engine down for a few seconds before shutting it off. This allows all the gas in the combustion chamber to be burned up preventing backfire.

Did you check for spark of assume that since the spark plug was not dirty that it is not firing. I am leaning toward water in the gas since you have to keep the choke on and it is blowing white smoke. You may want to drain the fuel tank and carburator and put in fresh gas. Good luck!

try changing the plug may not be getting enough spark to start

I would take a close look at the valves, if you are sure the carb is entirely clean. (Accelerator pump and everything)
A closed up exhaust can harm an exhaust valve.
Start with a compression test.
Good spark?
Is the plug wet?

your automatic choke is defalting

Several things can cause the problem. First, spring for a new spark plug. The stock plug is NGK CR8E. Now the plug is eliminated as a problem. Next, pull the slide out of the throat of the carb. Now remove the jet needle. Put the needle clip on the 4th notch, (this is the stock setting). Use only premium gas. Next, follow the starting instructions below.

There is a proper way to start the engine. Four controls are on your bike to assist in starting.

• The choke, used when the engine is cold. Pull the red knob for choke.
• The " Hot Start " Lever, used when the engine is hot. Pull the lever to lean the fuel mix when the engine has been running.
• The de-compression lever, always used.
• The throttle, used to prime the cylinder.

Don't kick, instead, push the kick lever downward. You will feel the back pressure as the piston is going upward on the compression stroke to the point the pressure is great enough that the kick lever "locks up". You are very close to TDC. NOW, pull in the de-compression lever. Push the kick lever a little bit more to get the piston past TDC. Give the throttle a 1/4 turn then let it snap closed. A diaphragm in the carb gives a shot of gas when this is done. DO NOT do this multiple times because you will flood the engine. Leave the throttle closed when kicking. Release the de-compression lever and give a strong kick through the full sweep of the kick start lever. Quickly get your foot off the kick lever at the end of the kick to avoid any chance of "kickback" from a backfire. It can be very painful, and can even break a leg. I am serious about that. Repeat the process (but without the throttle priming), until the bike starts. A good battery and clean air filter will also aid in starting.

This will likely tame the beast for you. Please rate this answer. Thanks!

To run, the engine needs fuel/air mix, compression, and a spark. See if you can narrow your problem down to one of these. Remove the plug, then connect the plug wire and set (or carefully hold) the base of the plug against the cylinder head. Crank the engine and see if there is a spark. If not, the problem is in the ignition system.
If you see a spark, replace the spark plug. Remove the air filter and pour about a tablespoon of gasoline down the carburetor throat. Crank the engine, being careful to stay away from the carburetor in case it backfires. If the engine fires and runs, then it probably is not getting gas (fuel system problem), or not getting enough gas (carburetor or choke problem).
Compression problems are less common, unless the engine has been abused somehow. You can check for compression with a compression gage. Remove the spark plug, install the compression gage in the spark plug hole, then crank the engine with the throttle open and the choke off. If you get at least 60 or 70 psi when you do this test, the compression is probably not the problem.
.