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Rebuilds are bad?

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Chokey Help me out. 

 

So I was reading here and elsewhere that the best way to break-in the newly rebuilt engine (new rings and whatnot) is the Ridiculous Hot Laps, then change the oil and ride normally.  These articles and posts stressed that you need to find hills and traction and put positive and negative (engine breaking) pressure on the engine.  They were emphatic that you shouldn't even idle the motor or ride it "nicely" during this break-in. 

 

That's what I tried to do for the last two top ends (different bikes -- 450F and 85)  I rebuilt.  I've got 40 hours on the 450 and it seems to be running fine.  The 85 has probably 20 hours and is OK as well.  I guess I'll have to tear then down this winter and look at things to know if I did it right?

 

On the 450, I rebuilt it over the winter, and had to wait for the thaw to ride it.  I couldn't wait, so I did start it very briefly in the garage when I finished the re-build.  When I finally got it out to ride, the ground was full of mud and ice, so there was very little traction, so the "Hard" break-in was actually probably soft. 

 

But with the 85, my son definitely ripped it as hard as he could at my instruction.

 

Did I screw this up?  Did I fall for the snake oil?  Will my bike blow up like the OP's did?  Should I immediately stop the bike and step back?  Or should I just NEVER do that again?

 

Here's an article that I found Here related to this:  http://www.mototuneu..._in_secrets.htm          

 

Here's one of 50 from TT:  http://www.thumpertalk.com/topic/636213-2009-yz250f-break-in/

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BTW:  I think it was William1 that recommended the Hard break In Method.  And he's recommended it many times.  This isn't "So 2013" is it?

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Chokey Help me out. 

 

So I was reading here and elsewhere that the best way to break-in the newly rebuilt engine (new rings and whatnot) is the Ridiculous Hot Laps, then change the oil and ride normally.  These articles and posts stressed that you need to find hills and traction and put positive and negative (engine breaking) pressure on the engine.  They were emphatic that you shouldn't even idle the motor or ride it "nicely" during this break-in. 

 

That's what I tried to do for the last two top ends (different bikes -- 450F and 85)  I rebuilt.  I've got 40 hours on the 450 and it seems to be running fine.  The 85 has probably 20 hours and is OK as well.  I guess I'll have to tear then down this winter and look at things to know if I did it right?

 

On the 450, I rebuilt it over the winter, and had to wait for the thaw to ride it.  I couldn't wait, so I did start it very briefly in the garage when I finished the re-build.  When I finally got it out to ride, the ground was full of mud and ice, so there was very little traction, so the "Hard" break-in was actually probably soft. 

 

But with the 85, my son definitely ripped it as hard as he could at my instruction.

 

Did I screw this up?  Did I fall for the snake oil?  Will my bike blow up like the OP's did?  Should I immediately stop the bike and step back?  Or should I just NEVER do that again?

 

Here's an article that I found Here related to this:  http://www.mototuneu..._in_secrets.htm          

 

Here's one of 50 from TT:  http://www.thumpertalk.com/topic/636213-2009-yz250f-break-in/

 

 

To properly seat the rings, you need high cylinder pressures, and the best way to accomplish that is to use large throttle openings at the engine's torque peak, not at maximum revs. The rpm range where torque is highest is the range where cylinder pressures will be highest because that's where the engine is breathing at it's most efficient. Once you rev beyond that range the cylinder pressures begin to drop, both because the engine is no longer breathing effectively, and because the higher piston speeds reduce the amount of time that combustion pressure can build before the piston's downward movement reduces the combustion chamber volume significantly.

 

High revs are also not particularly good for new bearings. When brand new, even the best bearings and races will not be perfectly smooth or round, and the high spots must wear down. If you're subjecting brand new bearings to high revs before they've finished bedding in, hot spots occur at those high spots, resulting in localized micro-melting and galling that will shorten the life of the bearing.

 

The best way to break an engine in is by using varying loads at moderate rpms, up to the torque peak. 

 

And I have always, and will always, give a fresh engine a couple of heat-cool cycles before I really start reaming it for everything it's worth. There are plenty of people that will say this is no longer necessary with modern manufacturing techniques, and as sandlvr says lots of people get away with beating on brand new engines, but I've never had an engine failure so I'll continue with my ways.

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After a rebuild i run my bike on the bench at a slightly high idle for 15 minutes ten let it have full cooldown then repeat 3 more times and its ready to go.

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To properly seat the rings, you need high cylinder pressures, and the best way to accomplish that is to use large throttle openings at the engine's torque peak, not at maximum revs. The rpm range where torque is highest is the range where cylinder pressures will be highest because that's where the engine is breathing at it's most efficient. Once you rev beyond that range the cylinder pressures begin to drop, both because the engine is no longer breathing effectively, and because the higher piston speeds reduce the amount of time that combustion pressure can build before the piston's downward movement reduces the combustion chamber volume significantly.

 

High revs are also not particularly good for new bearings. When brand new, even the best bearings and races will not be perfectly smooth or round, and the high spots must wear down. If you're subjecting brand new bearings to high revs before they've finished bedding in, hot spots occur at those high spots, resulting in localized micro-melting and galling that will shorten the life of the bearing.

 

The best way to break an engine in is by using varying loads at moderate rpms, up to the torque peak. 

 

And I have always, and will always, give a fresh engine a couple of heat-cool cycles before I really start reaming it for everything it's worth. There are plenty of people that will say this is no longer necessary with modern manufacturing techniques, and as sandlvr says lots of people get away with beating on brand new engines, but I've never had an engine failure so I'll continue with my ways.

Very well stated. I think a lot of people see "hard break-in" and stop reading. The process is actually pretty specific and more gentle than normal riding but "harder" than most manuals recommend thus the name.

 

My beloved father has always scoffed at the method, stating that the manual is always right and that a new motor should be run very easily and gently for many hours. This despite the fact that he's a banker and I'm a mechanic, ha.

A couple of weeks ago he asked if it was normal for his fairly new Subaru to consume a quart every 1000 miles and I said certainly not. Of course he broke in the engine per the manual, 1/4 to 1/2 throttle everywhere, putting around for many miles. The kicker to the story is that the manufacturer doesn't see this level of consumption a problem and won't give warranty. After explaining for the umpteenth time how cylinder pressure forces piston rings into crosshatch teeth promoting ring seal, he may be a convert.

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The one (and only) ring set I did in my old 200 (after 150 hours :eek:) was broken in using the Hard break-in, only because we put it in saturday night and I raced Sunday. As long as the bike runs for 30 minutes with the new parts at a speed slightly above idle, I tihnk it's fine. The bike ran great.

Edited by BoxcarWilly

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I add no idling at all! Cam receives the most pressure at low rpms. For cam brake in, you want it cycling from about 2k to 3k for 15 or 20 minutes.

Service manual prob tells you what is best.

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I add no idling at all! Cam receives the most pressure at low rpms. For cam brake in, you want it cycling from about 2k to 3k for 15 or 20 minutes.

Service manual prob tells you what is best.

 

true but the valve spring tension is so low on these 4v little motors that your not going to wipe a cam not following that procedure.

 

also with a new car your not only breaking in the rings, you have brakes, transmission, whee bearing, drive train etc to consider.

 

if the rings don't seat in on a dirtbike just going out and riding normally there is problem beyond the procedure used IMO.  1000cc sportsbikes are a different story, where you can lose your license without even really loading the motor.

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