I am new to RC and have been flying a Nexstar with an instructor for 5 weeks. Yesterday while flying, the engine (OS .46AX) surged several times in mid air, and when we brought it down we noticed that there were some air bubbles in the fule line. The instructor asked me to check the fuel tank and fuel lines when I get home. So I did. I removed the engine and checked everything and all was fine. I reinstalled the engine, all bolts tight. I tried starting the engine at home to check that it runs alright but the whole plane vibrated and shaked. Any idea why? I did not change anything in the setting of the engine. And I made sure all bolts (engine mount,...) are really tight. I am cluless. Please help.[]

Check the prop. Has it hit the ground on some landings? Do you have a prop balancer?

No, it did not hit the ground. All landings were ok. I do not have a prop balancer but will get a new prop to try it.

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