Problems with an old nitro engine

[stebedford]

Hi all, ive got an old nitro car with a .21 engine. the engine was seized up when until a few weeks ago, i managed to get it free again but now when its in the car it takes a while to start (using the pull start) and when it does start it runs for about 5-10 seconds and then stalls. the carb is clean, ive took the air filter off to make sure fuel gets in there. ive tried putting fuel directly into the carb too but its the same effect.

ive tried adjusting the fuel mixture but nothing else seems to work.

anyone got any ideas?

I was wondering if there might be a problem with the clutch?