breaking in yz 125

32:1 nothing less!!!!!!!!!!!!!!!!!! take it easy for the first few hours,then change case oil and let it rippppppppppppp.

Yes, 125's are hard working little motors........32:1 (4oz to 1gal). And I believe the "ride easy for 20 mins and let cool" is important. Do this for the first 60 mins on bike. Warming bike up before putting it under a load is equally important (always)

32:1 only for the first hour for break-in purposes only! Once you're out wickin' it wide open, run the thing at 40:1 MINNIMUM!!! A friend of mine runs his at 50:1 and has NEVER had a problem. Jet properly and you can even run it at 100:1 with a good synthetic like Rock Oil or H1R. He has done this as well. After break in I would never recommend any richer than 40:1. Nice bike too, by the way! Congratulations! The YZ 125 is super fun!

Most riders are very uncomfortable with the "super oil" manufacturers claims of going 50-60-.....or even 100:1. Especially on a 125! We need to remember we're providing lube to the lower-end of the motor too. I have always run a good synthetic oil and will NOT change from 32:1. On a 250.......maybe as lean as 50:1.........MAYBE. Why gamble? USE ENOUGH OIL........the factory manufacturers are not dummies. Jet accordingly.

I always ran 32:1 in my 125's. Any gains from running less oil (if any) wasn't worth the risk to me.

And for break in, I agree on the hot/cold cycles. And make sure to change the oil and clean the air filter frequently.

I know it sounds rich but run 20:1 for break in. Read your manual it will tell you exactly how to break the bike in. You do heat cycles, but to me it seems like you need more than a couple 5 minute rides to break it in so after the heat cycles i go out and ride and take it easy, but don't put around, for another half hour and let it cool. It always worked for me. I run 32:1 yamalube 2-R and my pistons come out looking like they couldve went for a much longer time, but it's all your preference and what works for you, that was just my experience.

You dont want to change your oil mixture at all during break in... But increaseing the amount of oil in the gas, you are acctually leaning out your air/fuel mixture... That will make your bike run hotter, and lots of other bad things can happen... You are better off leaving the oil mixture alone, use a good 32:1 mixture.

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Here is a good article about breaking in 2stroke engines...

1) Assemble the engine properly and torque all fasteners to specs.

2) Start the engine with the bike on a stand and allow the engine to come up to operating temperature (top of the raidator hot to the touch). Do not allow the engine to run at one RPM at all. Constantly vary the RPM and do not allow the engine to idle. When then engine reaches operating temperature (about 3 to 5 minutes of running time), shut it off.

3) Let the engine cool completely (at LEAST one hour). You want the engine to be dead-stone cold. Longer is better.

4) Start the engine with the bike on a stand and allow the engine to come up to operating temperature (top of the raidator hot to the touch). Do not allow the engine to run at one RPM at all. Constantly vary the RPM and do not allow the engine to idle. When then engine reaches operating temperature (about 3 to 5 minutes of running time), shut it off.

5) Let the engine cool completely (at LEAST one hour). You want the engine to be dead-stone cold. Longer is better.

6) Start the engine with the bike on a stand and allow the engine to come up to operating temperature (top of the raidator hot to the touch). Do not allow the engine to run at one RPM at all. Constantly vary the RPM and do not allow the engine to idle. When then engine reaches operating temperature (about 3 to 5 minutes of running time), take the bike off the stand and put it in gear. Take it for a ride. During this ride you want to keep the engine under a load at all times. Do not coast. Do not let the bike idle. Do not allow the engine to stay at one RPM. Riding on a mild slope is fine for this, as is slightly dragging the rear brake the entire time. Do this for about 15-20 minutes. Then shut the bike off.

7) Let the engine cool completely (at LEAST one hour). You want the engine to be dead-stone cold. Longer is better.

8 ) Re-torque the head and base nuts.

9) Go ride.

The cool-down steps are crucial to this operation. You must let the engine cool completely for the break in process to work properly.

Also, do the warm up procedure I outline here before EVERY ride. Your top ends will last much longer if you do.

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I do not 100% agree with the rear break thing, but if done correctly it can be good, to little load can be bad, but to much load can be alot worse