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Breakin in fresh top end

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Ok well im in process of putting in a new top end (both piston and valves) and a new crank because the rod bearing shatterd and screwed up everything but o well :thumbsup: My question is break in time on a 4 stroke. With the way things are lookin im not goning to have time to break in the motor befor my race sunday. I race novice so the motor is going to be run hard so will riding around on there trails just to run the motor and maybe slow laps during practice be enough or should I just hold off and not race.

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Let 'er rip dude. Ride it like you stole it in practice a couple laps then pull off and check your fluid levels and check for leaks. If everything is tight you're good to go.

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What I would do is let it warm up, then take it out and go easy for about a lap,go back to the pits and make sure everything is tight with no leaks, then go out and do some throttle rolls from like 25%-50% then like 25%-75% then start to crack it from 25-100% do this for about 10 mins and go easy between the throttle rolls and cracks. Dont just shread it apart like a lot of guys say, give it a little resting but not to light. I personally think that new engine parts need to seat and find there spot.

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kelstr gave me this advice:

after assembling the rings and cylinder DRY, turn engine over 100-150 times with no oil in it, after that, put some oil in it, and do the same thing, then start the machine up, and ride it.. come back from practice and change the oil and filter, and your good for your race!

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kelstr gave me this advice:

after assembling the rings and cylinder DRY, turn engine over 100-150 times with no oil in it, QUOTE]

Just to clarify in case he's a newbie, turn it over dry by hand. I used this method and it worked great for me. Sounds weird but it works :ride: I thought maybe he was beyond that point, but good thought Dan :thumbsup:

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here is how I broke in my first rebuild

dry rebuild

kick 50 times no spark plug

started 3 kick

felt cyclinder warm to the touch

started riding

1/4 to 3/4 throttle for the first couple minutes shifting

then let her rip

hit the rev limiter a couple of times

runs like a raped ape now and uses no oil :thumbsup:

Love this crf250f

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alright thanks guys and ya I am gettin the cylinder honed and im not a newbie just a newbie to 4 strokes did plentttyyy of rebuilding on my 125 and did you say turn it over by hand 100-150 times!! cuz thats alot lol

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run it through like 5 heat cycles. Start the bike, dont ride it, make sure its good and warm, then let it cool down completly, repeat.

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