I have a fairly fresh hyper 21 that burns out glow plugs in about 2 min run time. Seems to run good otherwise, any suggestions?

Mine did that at the start, but when tuned it stopped. try leaning it out a bit, if it's still at factory settings, mine used to eat them when it was rich.

When you say eats glow plugs do they just go dead or is the coil burn out and broken?

try adding a head shim, I had a small block that did that after a bunch of different suggestions the only that did work was the head shim. I think it was something with the compression.

what type of plug and what fuel are you using? If the plug is too hot you will burn them out very quickly and will also depend on the % nitro you are using too.

I am using 20% blue thunder and #8 os plug also tried A5 plug, The coil is always broken.

If the coil is burning out I say you are running to lean. Most engines other then OS run a long plug not a short OS plug. Not sure what yours is suppose to run but I recommend checking.

Another reason could be a worn conrod (too much slop) or a bearing that's on its way out.

Just went to Ofna web site and that engine takes a long plug not a short OS. He all so said all most fresh engine and with a OS short plug do not think a rod or bearing is the problem.

OK, A short plug sounds likely. Tuning with a short plug to make it run OK is a pain and he's most likely running lean.

I agree!