Hello Jacob,
I'm sure we can get through this with little to no trouble. Your video helps tremendously with troubleshooting this problem.
In the video, the model is not spooling past the low end due to a rich condition. Make sure your low end needle is set parallel with the carb. Your clutch is finally grabbing at 50% throttle because your air to fuel mixture is too rich. Increasing the throttle opens the barrel of the carb but doesn't really affect the RPM because there is too much fuel. Your assessment of drowning the motor in fuel is correct, the sudden RPM change is because the motor finally became hot enough to begin to handle the amount of fuel. This is also very apparent by the amount of smoke you are putting out in the video.
The mid range needle should be set around 1/2
The high end needle to start should be around 1 3/4
Check your exhaust pressure line.
Check all of your fuel lines and fittings.
The clutch liner gap is correct, no need to worry about that anymore. One thing that will cause a clutch to slip is grease and oil. However, once your helicopter spooled up to a normal head speed and you were applying pitch, I did not hear the clutch slip at all.
If you are new to nitro, tuning is one of the most difficult aspects of owning a nitro powered helicopter. The next is knowing the warning signs of when your engine needs to be rebuilt. With an OS55HZ, with regular flying, the engine should be rebuilt at least once a year. If the engine has been sitting for a long period of time without some sort of engine treatment applied, the rear bearing will rust and cause all sorts of problems.
If you can not get it tuned properly before IRCHA, I would be more than happy to help you tune the engine at IRCHA.
Thanks!
Matt Botos
