Recommended way to break in fresh top end (351) and new bottom end rebuild?

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Old 09-25-2011, 01:53 PM
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Default Recommended way to break in fresh top end (351) and new bottom end rebuild?

I see a lot of differing opinions looking through some of the older threads when I searched. What's the general consensus right now?
 
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Old 09-25-2011, 02:14 PM
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I doubt you'll find a true consensus. I tend to be easy on any new run-in (I don't like the term "break-in", since I'm not trying to break anything) for a few miles, then, I gradually let the rpms increase for several miles. I turn it off and let it cool down. Start it back up, ride gently, then ride increasingly hard, so by the time the bike has 20-25 miles, it's seen WOT a few times. THEN I find the longest downhill around, and head down in a fairly low gear...rev it up to high rpms and get off the throttle and let the engine slow the bike down. Re-accelerate and back of the throttle for engine braking effect. Do this a few times.

At this point, I consider the bike 90% "run-in", and I ride it as I normally would. Sometimes I change the oil early, but, I do NOT change the filter early. Filters get more efficient as they get loaded with debris, but, it takes a LONG time for them to get loaded. I'll wait until the first filter change is specified by the manufacturer, and I'll change it then. I always cut it open to observe what the filter caught. Always some shavings in there. Never have these shavings been a shockingly large amount.

Never had a bike or other vehicle that burned oil later. That doesn't mean what I tend to do is correct, either...it's just one general technique that one person has done. I hope yours goes well!
 

Last edited by Blackheart58; 09-25-2011 at 02:14 PM. Reason: removed a stupidly-placed apostrophe.
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Old 09-25-2011, 02:18 PM
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I broke mine in doing a 65 mile single trail loop filled with hill climbs and rock fields.

Motor is perfect 5k later.
 
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Old 09-25-2011, 04:51 PM
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There seems to be a consensus also that you should not let the engine "float" at high rpm: either it must be under load or braking hard. I would be curious to kow why...
 
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Old 09-25-2011, 06:06 PM
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Heat; would be my guess. No sustained hi loads[long up hill?]. I do four or five heat cycles, warm up ez ten minute ride then a complete cool down.
 
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Old 09-25-2011, 06:55 PM
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I still think this guy has the best take on the issue. I've used it with great success and no issues.

Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power
 
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Old 09-26-2011, 02:42 AM
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Originally Posted by TNC
I still think this guy has the best take on the issue. I've used it with great success and no issues.

Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power
Followed this method. Thanks everyone.
 
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