Honda gx120 starts runs for 45 secs, cut out then will restart 45

These low tank profile engines necessitate a fuel pump. Anytime you have problems starting, fill the fuel tank to full or to a level higher than top of fuel pump.

If fuel level not the problem then fuel flow, or carb fouling.

Gs is not properly getting into the motor. Check and clean the carburetor. Also make sure that the float in the carb is not getting stuck. If so it will stop fuel flow into carb and the motor will cut out after the fuel from the float is exhausted.

the problem is with the carb. not able to keep enough fuel going into the float bowl to support engine staying running. could be hose off gas tank clogged or petcock, coud be main jet sticking closed or float level out of adjsutment.

If this has the thick silver gas cap, I have had similar problems on a number of these engines because it is a vented fuel cap and it will slow or even stop the fuel flow if they stop venting Try loosening or better yet replacing it. If that doesnt solve it then you may want to drain the fuel and put in fresh fuel Pressure washers will get water in the tank. Also make sure you drain the carb bowl. There is a bolt on the side of the carb bowl for that purpose.

Try draining all the fuel from the tank and carburetor. Replenish with fresh fuel. Try using an additive that keeps the fuel fresh longer and will displace some moisture. Good luck.

Recurring issues with honda engine no start. Engine was thought to be out of gas however engine was actually shut down by oil alert. Check/change oil to reset, or unplug wire from oil alert and check engine. Vacuum in fuel system due to faulty fuel cap. Loosen cap to allow air in tank. Water in fuel. Water will condense out of the fuel in fuel container and will be introduced into tank. Water is heavier than fuel and will enter carb bowl. Check engine fuel tank with flashlight for signs of water, remove fuel bowl (shut off fuel) and clean. Spark plug is rarely issue, however could be wet from too much choke. Good luck

Disconnect fuel supply line from carb and verify that you have "Full Line Flow" from the fuel tank to the carb. If not, check line, filter and in-tank screen for restrictions.
Sounds as if the fuel supply is trickling in the carb very slowly and the engine burns it faster than the line can supply.
Hope this helps.

Most Honda engines have an oil pressure switch that prevents engine damage due to low/no oil pressure. Make sure there is sufficient oil in the engine and that the wire is connected to the pressure switch.

check oil level. it has a low level shut off switch ?? May be it

Pressure washers work under very dirty conditions, no wonder they encounter engine problems. Here are a few pointers from a former pressure pump tech. The unloader is a source of engine overloading however this can easily be checked with a pressure guage attached to the gun with a tee fitting having the guage and the normal tip used for the unit. The pressure should never rise over rated pressure. The pressure should drop considrably when trigger is released. The life of the pump and engine can be increased by setting max pressure to 75% of rating. Most engine problems are from following conditions:
Leaking or misadjusted valves; clogged muffer /spark arrester; weak spark coil that is about to fail completely; kill switch/oil sensor wiring and or sensor mal function; gas cap not venting properly causing vacuum in tank and wet or dirty air filter.
All these problems easy to check, fastest repair is to disconnect oil sensor wire to check oil safety system. Then temp replace coil with known good coil. Loosen muffer bolts to check for clogged muffler. Temp run engine without gas cap to check for vacuum. Finally if everything fails, run the engine with carb cleaner spraying directly into the intake. If the engine continues to run with carb cleaner then the problem is fuel delivey and faulty carb. enjoy