Can of worms......

[Yee-Haw_400EX]

Which way is the best way to break in a new motor? And why?

[alberto]

I would think slow and steady. Bring the bike to regular operating temp, run the bike through all the gears slowly dont over rev. Let it cool the change the oil and oil filter. Then repeat. That is how I broke in my 05 450R. Thats my VOTE!!!!

[krt400ex]

i would not completely baby it. with my 400ex. i didnt go above half throttle for about the first five hours. there were a couple of times where i jumped on it, but it was not much and not long and i never held it wide open. after that i changed my oil. and rode it. you cann feel when eveerything in the engine starts to settle and loosen up a little. that is when i started to ride it like i stole it.

[SET THE STAGE]

i just wrote a whole thing up on what i've read and then i remembered the site that i learned it all from lol so here:
http://www.mototuneusa.com/break_in_secrets.htm

[Honda#4]

I did the heat cycle break in, seemed to work great.

[400exrider707]

I run mine pretty hard, AFTER they get to temp. Just got to put a good load on the motor. Dont be bouncing off the rev limiter, but dont baby it either.

[BlaineKaiser450]

i let mine idle for 10 minutes then cool for 15 minutes 3 times, the took it to the track and rode at about 60% for an hour. Then i rode it like normal

i always did break-in's with a more slow and steady approach. i would still get on it but i wouldnt be revving all the way or going full throttle for the 1st 5 hours. i would do the varying throttle more like regular riding going only about 3/4 throttle maximum on the 1st tank then after that i would ride it full throttle but not going up near the rev limiter just hard rompin but not revving it all the way out for another tank. then I would just do whatever go all out ride how i want to ride and have fun. pretty sure 2 tanks and its completely broekn in, i think most of the breakin occurs in the 1st few hours but i wanted to make sure my new motor would be ready for whats ahead

[sc400ex_rider]

hotcams says to run the engine at about 3000 rpms under light load SO THE CAM GETS LOTS OF OIL. i would use the short heat cycle method also. (run it 5-10 mins let it cool) also get up some speed (not WFO) and let off the gas in gear so you get max engine braking. this cause's high vacuum and is suppose to seat the rings.

[Toadz400]

I broke it in exactly how I was going to ride it. So far my YFZ has been my most reliable quad. Going on 4 years: everything inside the engine is original, valves have never gone out of spec, starts up instantly, doesn't burn a drop of oil, etc. It's also got plenty of power for being a stocker even after 4 years. When this engine goes out (if it ever does) I'm going to break it in the exact same way.

[ohsobad_chevy]

I heat cycled mine a few times and then rode the heck out of it. I and my fellow riding buddies have always had better luck with seating the rings hard rather than babying it. :)