4 stroke break in???

JakeM250R
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JakeM250R
my bike just got a crank and complete top end in my 2015 crf250r. This is my first time having a re-built engine. (when I bought it, it had a new top end that lasted me roughly 2 years)

I've let the bike idle and get up to temperature about 5-6 times already so there's about 1hr on it. How much time should I put on the engine before I start riding more aggressively again?
Is there anything I should be looking for? (sounds, exhaust, etc)

sorry if this is a stupid question.

thanks,
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beamer
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beamer 4/5/2021 10:48am
4/5/2021 10:48am
Personally, I'll warm up the engine like you've done 3 or 4 times and ride it around the parking lot at the track 1/4 to 1/2 throttle. First time on the track I'll baby it some for 10 minutes and thats about it. Its worked for a few bikes now.......
Tracktor
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Tracktor 4/5/2021 2:28pm
4/5/2021 2:28pm
Warm it up, make sure everything sounds/looks good & rip it.....
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skypig
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skypig 4/5/2021 5:40pm
4/5/2021 5:40pm
Controversy

What’s a good technique for the crank, might be a bad technique for the rings.
What’s good for minimum warranty claims, might be bad for performance.

This makes a lot of sense to me.
I’ve used it to good effect of a few bikes.

Like “best oil”. Best “break in” is difficult to “back up” with facts.
Likely you could “break in” two identical bikes in opposite fashions and not have a problem with either.

I’d like to get 4 new identical bikes.
Idle 2 of them for an hour. Then ride them gently for an hour.
The other 2: start them, ride away immediately after one sighting lap, ride motocross (Staying off the limiter)

Then dyno the 4 of them and see if there is a power trend. (The 2 gently run in bikes should make a little less power, and use a little more oil.

http://www.mototuneusa.com/break_in_secrets.htm
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chump6784
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chump6784 4/6/2021 3:34am
4/6/2021 3:34am
The manual for my 21 yz450 was this

Warm the bike up then ride for 20 minutes at up to 50% throttle.
Let the bike cool down
Warm the bike up again then ride up to 80% throttle for 40 minutes.
Let the bike cool down. Change oil filter and oil. Ride normally.

I can't remember the website now but they got 2 brand new cb300 road bikes and ran them in using 2 different methods. Both were dyno'd and compression tested first. Ring end gap was also measured. One was run on as per manufacturers recommendations, taking it easy for the first 1500 miles, the other was flogged from the get go. They were both then dyno tested, compression tested and ring end gap measured. The results, no measurable difference between the two. Obviously these are not high performance engines but an interesting experiment none the less
Rickyisms
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Rickyisms 4/6/2021 8:30am
4/6/2021 8:30am
skypig wrote:
Controversy What’s a good technique for the crank, might be a bad technique for the rings. What’s good for minimum warranty claims, might be bad for...
Controversy

What’s a good technique for the crank, might be a bad technique for the rings.
What’s good for minimum warranty claims, might be bad for performance.

This makes a lot of sense to me.
I’ve used it to good effect of a few bikes.

Like “best oil”. Best “break in” is difficult to “back up” with facts.
Likely you could “break in” two identical bikes in opposite fashions and not have a problem with either.

I’d like to get 4 new identical bikes.
Idle 2 of them for an hour. Then ride them gently for an hour.
The other 2: start them, ride away immediately after one sighting lap, ride motocross (Staying off the limiter)

Then dyno the 4 of them and see if there is a power trend. (The 2 gently run in bikes should make a little less power, and use a little more oil.

http://www.mototuneusa.com/break_in_secrets.htm
This would be a great video idea for Project Farm on YouTube (Guy does some awesome tests and mechanical experiments, very thorough work). He would probably do it with some sort of small engine, but would be very cool to see with someone that has his attention to detail .
kb228
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kb228 4/6/2021 8:40am
4/6/2021 8:40am
Ride it easy for 30 mins and let it rip. Theres no concrete evidence on break in procedure. What a service manual tells you is different than what pro circuit says and is different than everyones method here.
kevinr
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kevinr 4/6/2021 8:53am
4/6/2021 8:53am
Agree there is no set formula. For new bike or engine rebuilds I am pretty cautious. Mixed throttle (roll on and off up to 50%) conditions for 30 minutes prior to "full send."

We were at Beans MX this last weekend and my buddy had his fresh rebuild (valves, piston, chain, etc) and just let her rip. If you're familiar with Beans it's tough on motors. Bike seems fine.
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Leeham
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Leeham 4/8/2021 1:06pm
4/8/2021 1:06pm
I just warmed the bike up a couple times, shifted through the gears, worked the clutch some, and banged off the limiter at least once (mainly to see if there was any slight defect that would show up at high revs). Changed the oil and filter. Rode normally after. Not a proven solution but works for me. Did it with my 19 Honda 250. After 50 hours I did a piston and it looked great. I bang off the limiter quite a bit and the valve train was perfectly in spec.
Yeti831
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Yeti831 4/8/2021 10:44pm
4/8/2021 10:44pm Edited Date/Time 4/8/2021 10:44pm
Not going off any expertise, just an opinion from a guy who hasn’t had any engine problems since they installed a piston backwards in a yz125 in ‘98:

Warm it up, nice and good, take a site lap to let it get to op temp, rip it for 30 minutes (not banging to limiter or lugging, use as much range as possible and load it up on decompression braking too), after 30 minutes change oil and filter, let cool, warm up again, shred for 2 hours in same fashion then change oil and filter.

That’s my opinion personally for four stroke break in. After that, should be set and ready for full synthetic.
1
captmoto
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captmoto 4/8/2021 11:27pm
4/8/2021 11:27pm
Yeti831 wrote:
Not going off any expertise, just an opinion from a guy who hasn’t had any engine problems since they installed a piston backwards in a yz125...
Not going off any expertise, just an opinion from a guy who hasn’t had any engine problems since they installed a piston backwards in a yz125 in ‘98:

Warm it up, nice and good, take a site lap to let it get to op temp, rip it for 30 minutes (not banging to limiter or lugging, use as much range as possible and load it up on decompression braking too), after 30 minutes change oil and filter, let cool, warm up again, shred for 2 hours in same fashion then change oil and filter.

That’s my opinion personally for four stroke break in. After that, should be set and ready for full synthetic.
Pretty much what I do. Just don't pin it. Rings need pressure to seat against the cylinder wall. You won't get that letting the bike idle in your garage in some goofy heat cycle scheme.
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mattyhamz2
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mattyhamz2 4/9/2021 7:53am
4/9/2021 7:53am
I've always been told that the motors are dyno'd before they ever leave the factory. So I'll warm the bike up once or twice at home, change the oil, go to the track, take 2-3 sight laps and start picking it up from there. My dad's done it this way for 35+ years and never had an issue. His dad told him, "if it won't hold together now, it won't hold together later."
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