Hi,
I just bought a new Hpi T-15 Engine, and everyting i pull it to start its very hard to pull, seems like is getting stuck but it can still be pulled, and it makes something like a pinging sound. but It still starts and runs. can anyone help me with this?

It could be you're just feeling the "pinch" of the tapered bore sleeve. The piston gets to a tight spot as it gets toward the TDC (Top Dead Center ) position.
If you take the glow plug out and pull the engine over slowly, how does it feel?

when i take the plug out and pull it, its very easy to pull. so what i am experiencing is normal? or just for a new engine?

Hi!
It's normal!
Just let it rew! But remember to always let it run a little rich.

From your description, it sounds like the engine is o.k.(?)

The factory recommended needle valve settings are quite rich (usually ) and there could be excess fuel building up in the crankcase as well...you could be experiencing a partial "liquid lock" so if that happens, just tip the vehicle on it's side w/ the exh. stack pointing down and slowly pull it over (carefully, because you can break the recoil if you pull too hard ) to drain the excess fuel out.
If you see a bunch of liquid fuel dripping out of the pipe, then that's what's happening (more than likely )
If you get a lot of raw fuel down inside the engine, it will be easier to un-flood it by taking the plug out and then pull it over several times as above.
As you get a little run time on the engine, and get it adjusted properly, it will get easier to start.

It also helps if you have a really good glow plug battery...one that makes the plug glow bright orange.