just bought a komoto 150 with auto choke. took it out of box and assembled it. fueled it and checked all lines. starts up but dies after a few seconds. replaced fuel filter and still same. fuel shutoff is turned on. can keep running for a few more seconds by working throttle. could use some advice.

 

Since it is new and has never run there may be a lot of things that can cause this. Look at the easier things first:

1) Are you getting spark? Take out the plug, hook it up, and ground the threaded end while cranking. You should have a regular bright spark.

2) Does it start right up with starting fluid sprayed into the carburetor? If so then go through the carburetor. Check the float needle and seat. You may want to do some reading on carburetor troubleshooting. There are lots of places out there with good guides. Use google to find them.

If it is still hard to hard then I would look at engine compression next using a good compression checker. If it is low then spray a bit of oil in the spark plug hole and repeat. If it goes up substantually then the rings are leaking, if it doesn't check the valve adjustment.

Get yourself a service manual for your 150cc engine. I'm assuming it is a GY6 150cc (pretty standard). You can get a manual from here:

Service Manuals for 150cc GY6 (and some others)

 

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