hi im sorta a noob but really hoping i dont need a new engine

i built a little rc car with my uncle bout 5 years back and just pulled it out from the back of the garage 5ish days ago. its a simple car that he bought and im not sure the engine size but all it says on it is "15 FE nitro star"

anyway i clean up the engine best i could and today i actually got it to fire up and run. need less to say it ran like crap but would go to full power. will i worked on getting the battary back to stay in its little holder with zip ties and took her back out. she works

however it will not go up to full power. i can rev it up and it will act like its going to go to full power but dies and doesnt come close and just goes down to if i were barely hold the accelerator.

i tried playing with the carb a bit but still wont go to full power.

so basically i dont know if just 4 years of sitting around screwed the engine and she's cooked and wont ever get up to full speed or if their is something i can look at and fix/adjust.