Hey I was trying to run my nitro buggy today (im on tank 3 of the break in) and I got it started but shortly after every time i got it started it would stall. I think im starving the engine and my hsn is to lean. I have not touched the lsn yet so it cant be that. But I was also thinking maybe its the weather since its so cold here! Any help appreciated

How cold is cold?? If its any colder than say 45-50F you may very well need to wrap the cooling head in tinfoil or a sock to keep the heat in. If you are down around freezing, maybe wait until the weather warms up before you break it in. In cold weather you'll run way more lean because the air is so dense, but an inexperienced user will then 'want to get the temps up, based on his temp gun..' and proceed to lean the needles out even further. Wrong move. Instead, in cold weather you'll need to richen up more, (which will in turn cool the engine off), so to combat that you need to keep the heat in via the tinfoil or whatever.

During break-in you want tons of lube going through the engine(ie. running very rich), but you want temps to be up to at least 200F+. With a new engine the mechanical pinch is so tight that you need those warm temps to help the sleeve expand so that the engine doesn't beat the tar out of itself during break-in(excessive wear on piston/sleeve, rod, bushings etc), which will dramatic reduce performance and engine life.

Also, be sure to pre-heat the engine as much as possible before starting it. Get it going, then take it easy on it during break-in and run it continuously for as many tanks as you can. See if you can run it without shutting the engine off for the entire RX pack. Once most of the pinch is gone(glow plug removed), you are broken in and ready to tune. Don't pay attention to this garbage about '8-10 tanks and its broken in'. It's simply ridiculous, every engine is different.

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in the cold weather here, i had to richen my needles. and for break in i highly recommend you do so. afterwards, lean it out. but it still needs to be slightly richer for the cold air. make sure there is always some exhaust smoke too

Its in the 20`s here. And during my first two tanks I was keeping it in the 210-230 range, measuring with my temperature gun. I did put tin foil around the cooling head. The highest temperature I got to was 248, but ofna says its okay as long as it doesnt hit 260. To reach those temperatures I did lean out the hsn as recommended by some. So its not good to be a little lean in the winter when its pretty cold?

No! Especially not during the critical break-in period. Leaning out means less lube = bad news. I know you want to run that new rig, but 20F is no weather to be breaking in an engine. You need to have a bit of patience and wait for warmer weather.

oh great so dont tell me i may have caused damage to the engine?

another question: If I put the hsn back to factory default and I can still maintain 210-230 range with tin foil on it will it still be okay?

Well...hopefully not. The key is that you were leaning it out to get temps up. It's not as easy as looking into the engine and 'if you don't see any damage, then you're good to go'. These tolerances are so minute that you can't 'see' damage with the naked eye, unless there are scratches etc.

The Also I forgot to mention that as soon as you turn the engine off each time, you need to put the piston at BDC when it's still warm, and store it that way. That way when the sleeve contracts(cools off) the piston is at the bottom of the taper.

Again - it's not 'impossible' to break-in during cold weather, it's just not advisible unless you know what you're doing, and take all the proper precautions.

Yes, that would be great.