I bought a ofna hyper .21 8 port for my hyper 7 and I have been having trouble breaking in the engine. What is the best way to break in the engine?

Read this Thread and go threw FUELMANS Posts you will learn alot and have a great running motor when done.
[link=http://www.rcuniverse.com/forum/m_2786285/tm.htm]http://www.rcuniverse.com/forum/m_2786285/tm.htm[/link]

What 'trouble' are you having? Ofna gives out good instructions and the needles are usually set right or are easy to set to get running. Plus Ofna explains the heat cycle method that is proper the tried and true way to break it in.

If it is hard to start, the Hyper .21 needs to be heated with a hair dryer thoroughly before you pull the cord. The piston will always lodge itself in the sleeve until the engine is broken in. If you don't heat the engine thoroughly, you will most certainly snap the pull cord.

You will need some spare glow plugs to survive as well.

Once running, and you shut it down, you must move the piston to the bottom of the stroke (BDC).

Also, though the books may say the engine is broken in after 4 or 5 tanks, I say the engine is not fully broken in until 8 to 10 tanks. Once you've brken in the engine according to the books, keep the engine on the rich side but slowly lean it for a little more performance each time. If the engine blubbers at full trigger, then richen it; it is blubbering from loss of lubrication and is about to stall from friction.

You got that 100% backward. IF its blubbering, then it has excess fuel in there and it is too rich which is just as bad for the engine as too little fuel where it fades away and sags at full throttle due to being lean.

If too lean, they do not stall due to friction, they fade, sag or stall out due to loss of compresson because the sleeve expanded past the point where the piston expanded to.

Please try to refrain from spreading misinformation.

This is a case of misunderstanding of semantics.

When I say blubbering, I am referring to the stuttering the engine makes from being too lean.
I refer to the engine noises from being too rich as stumbling.

When the engine is not fully broken in, the piston and sleeve DO cause friction since the sleeve and piston have not worn to the proper operating diameters yet. Even at operating temps, an engine not fully broken in will still not have the correct expandeded diameters. That's why we break in our nitro engines.
What you are saying is true if the engine has already been fully broken in and is running at temps that are too hot.