I recently bought a new yz 125 and i didnt really break it in, well not the traditional way anyway.
I warmed the bike up PROPERLY then really hit it on the track, could this have a bad effect on my motor and damage it in the long run???
I also did that for my yz 250 when it was new...so yeah

Depends on whose theory you go by you either did it just perfect or you screwed it up big time. Just be sure to change your oil and filter which is the most important part.

Swede73, on 10 April 2012 - 07:54 AM, said:

What are the 2 theories?

One is to use multiple low load heat cycles and the other is to warm up the bike all the way and do 1 very high load cycle.  Your route would obviously be the later.

Remember they are theories, not facts. I prefer the multiple heat cycles with low/increasing load but that's me. On a 125 by the time your done with that your half way to a new piston anyways by the time your done cycling.

I like the chain saw method.... fill with gas, warm up and run like hell!

Don't you think you should have asked this a little earlier?

If you run it like hell it will blow up easier. when you rebuild the top end you want to start it up and let it worm up then let it cool down them start it up let it worm up and then ride it for ten min no more than half throttle then let it cool down then worm it up and then ride it for 20 min no more than half throttle the cool down then worm up and ride for 30 min no more than half throttle then let it cool down the the break in is done.. if you just start it up and give it hell the piston ring will expand more than it should and it will wear more off than it should then it will have low compression. that's why you do those worm up and cool down cycles because when you break it in the ring is wearing into the cylender and it causes alot of heat and will cause the ring to expand more. so just slow and easy will break it in. every experienced mechanic will tell you that. I'm 15 and I do all my engines and I even know that.

P.S. If you get a service manual it will tell you everythying!

its a 2 stoke. Whats it gonna do burn oil lol. As long as its still running and has good compression I wouldn't worry about it. Like previously stated every bodies got their own opinion or method

Yamaha15DK, on 10 April 2012 - 05:51 PM, said:

Apparently 15 year olds don't understand what an opinion is and have absolutely horrible grammar.

every 125 i ever had i would start it, warm it up take one slow lap then hammer it.

never had any problems

I'm not trying to say my way of doing it (The right way) is always the best way butt if you get and owners manual it will tell you the same thing. And dude you don't half to be a dick I guarantee I could have a 2 stroke motor apart and putt back together  and running before you and I mean tearing the transmission apart too.

what the hell is worming up your bike?

but yeah it's a 2 stroke, what you did was probably good for it. there's a lot of discussion on how to properly run in a fresh top end. apart from cold seizing it, not alot else you can do wrong, few minutes steady riding then ride normally.

and i don't think that 15 year old would know an experienced mechanic if one hit him in the nose with a wrench

I normaly just run a little richer oil mix for the first half filled tank, (32:1 for a 250 and 26:1 for a 125), run one size larger main jet, an extra half turn in on the airscrew and a high idle. The first few min I run it easy, go thru the gears and just listen for any odd noises, bring it back to the pits and look for any leaks, get the idle set and get the air screw set. Then I take it out and run it harder, but short shift it and make sure not to hold it wide open and constant in the top of the rev range (like big power sapping sandy uphills or panic revs).

After that tank is gone (20-30min) I let it cool down, check for leaks again, re-torque the head and cylinder bolts, I fill it up with my regular mix (40:1 for a 250 and 32:1 for a 125), throw in the next size down on the main, set airscrew, and give it hell.

Thats just me though, I am not going to go through all the steps in the manual, nor am I going to run it hard right out of the hole...I figure I am taking proper cautions and it has always worked well for me.

Yamaha15DK, on 10 April 2012 - 06:19 PM, said:

Care to share your experience at 15 years old? I understand your hormones must be going crazy at that age and trying to be the alpha male is the thing to do, but I wouldn't make comments like that without knowing someone. For example I can assure you I have rebuilt many more motors of all different kinds.

ikis86, on 10 April 2012 - 06:22 PM, said:

He is 15, life is already all figured out for him

He is the exact reason why I wish TT still had the users age posted next to their name like it was on the old board that way you know who's advise to heade and who's advise to just ignore.

And to Yam15DK. Just because you can follow directions and "putt" together an erector set doesn't make you a mechanic. My 10yo son can tear down an engine and "putt" it back together it's how it runs, if it runs afterwards. Any monkey can tear something apart but takes skill to make it work.

Edited by Swede73, 10 April 2012 - 07:05 PM.

Just because he's 15 does'nt mean he does'nt know anything. I'm turning 16 in a month and i've been wrenching on all different engines with my dad (mechanic) since i was about 4. Just last month i did a top and bottom end rebuild on a yz250f (completely by myself), and before that i did a full rebuild on a 1984 cr80r (completely by myself). Age doesnt mean anything other than maturity and how deep your voice is lol, ive seen 10 year olds hold more knowledge and have more skill than a full grown man.

sweet! you and that other kid should have an engine building race!

all you get from rushing is smashed hands and bastard kids

why be a smartass about it? you must be jealous that two 15 year olds have more knowledge than you. i dont rush either.