Break in period

[askmrjesus]

Originally Posted by Sean

This is what my piston looked like after 2000 miles with a hard breakin:

Sorry, but you can't automatically chalk that up to a "hard" break in. Any number of things could have caused that damage.

My DR650 thumper was broken in to spec, and the fucker hand-grenaded the bottom end at 16K miles, (I'm pretty sure the shift fork was the culprit). So, what does that prove? Nothing. If shit's gonna break, then shit's gonna break.

I wouldn't rev the ever loving piss out of a brand new engine, but after the first oil change (100 miles), all bets are off.

JC

[Kerry_129]

I agree with the 'break it in with hard throttle, but gentle/repeated heat cycling' line of thought - and an oil change after the first few miles, not 600~1000.

http://www.mototuneusa.com/break_in_secrets.htm

[Homeslice]

The best method for this to occur is to run the engine right up to the manufacturers listed "red line", BUT with the LEAST LOAD POSSIBLE (remember load = heat and NEW pistons DO NOT like excessive heat!).
How do you do this? Well, with any vehicle that has a gearbox, it's real easy. When the bike/vehicle is brand new, you begin a series of "low load", HIGH RPM runs (right up to red line), but ONLY in FIRST GEAR. This gives the VERY necessary "high RPM wear-in" for the pistons and max "gas pressure" on the rings to press them into the cylinder wall so they can seat WITHOUT high load/heat.

Not understanding the logic here.....Why would a first-gear blast produce "less load" than, say, a second-gear blast? Just because it's shorter? But the accelerative forces are higher in 1st gear, so you would think that would produce more load.

[RedRider2k2]

Originally Posted by Homeslice

Not understanding the logic here.....Why would a first-gear blast produce "less load" than, say, a second-gear blast? Just because it's shorter? But the accelerative forces are higher in 1st gear, so you would think that would produce more load.

Where did you quote that from? I'm not sure I agree with it but anyway...

The reason there is less load on the engine in 1st is because the gear reduction in 1st gear makes it easier to drive the bike forward and reach redline. In higher gears the ratio is not so much in your favor and it takes more work. It's pretty much the same reason that if you have a worn clutch, it's most likely to slip in high gear.

[Homeslice]

Originally Posted by RedRider2k2

Where did you quote that from? I'm not sure I agree with it but anyway...
.

From Castor Troy's quote

Originally Posted by RedRider2k2

The reason there is less load on the engine in 1st is because the gear reduction in 1st gear makes it easier to drive the bike forward and reach redline. In higher gears the ratio is not so much in your favor and it takes more work. It's pretty much the same reason that if you have a worn clutch, it's most likely to slip in high gear

Eh....I think the reason most people experience clutch slip only in the higher gears is because those are the only gears they go WOT in......They're too pussy to go WOT in first

I was just assuming that 1st puts the most stress because it has to overcome momentum from a dead stop. You know how when someone needs a push start, and a bunch of guys start pusing on the car until it starts moving? Well, it's hard as hell to get it moving, but once it's moving, it's pretty damn easy.

[Dave]

Originally Posted by Homeslice

From Castor Troy's quote




Eh....I think the reason most people experience clutch slip only in the higher gears is because those are the only gears they go WOT in......They're too pussy to go WOT in first

I was just assuming that 1st puts the most stress because it has to overcome momentum from a dead stop. You know how when someone needs a push start, and a bunch of guys start pusing on the car until it starts moving? Well, it's hard as hell to get it moving, but once it's moving, it's pretty damn easy.

wot in 1st is asking for a 12o'clock on my bike

[CasterTroy]

Originally Posted by Dave

wot in 1st is asking for a 12o'clock on my bike

WOT and low load redline are complete opposites you can low load redline any bike in 1st without fear of a wheelie....takes what seems to be forever to get there, bcause you're cracking the throttle just above idle to GET there, but it's how I've seen a few engines "broke in" after rebuild...especially 2-strokes

[RedRider2k2]

Originally Posted by Homeslice

Eh....I think the reason most people experience clutch slip only in the higher gears is because those are the only gears they go WOT in......They're too pussy to go WOT in first

On a bike this is pretty much true but that's how you test a slipping clutch in anything.

[fasternyou929]

One question for everyone that likes to hit red-line before the first oil change: are you not worried about metal shavings cycling through the engine with the oil? Isn't that one of the main reasons for low RPM's at first, to cycle the oil at a slower rate, increasing the chances metal will stay at the bottom of the oil pan?

Originally Posted by Homeslice

Not understanding the logic here.....Why would a first-gear blast produce "less load" than, say, a second-gear blast? Just because it's shorter? But the accelerative forces are higher in 1st gear, so you would think that would produce more load.

Simplest way to understand this - assuming you've ridden a mountain bike or multi-speed bike. Put your pedal bike in 1st gear and sprint to your maximum speed. You should reach your maximum speed quickly and with little effort.

Now do it again in a middle gear... it'll take a lot more effort to get to that max speed (load to an engine), not just time.

If you're a glutton for punishment, put it in its top gear now (10th, 18th, 24th, whatever) and repeat. Have water handy and be ready for your quads to scream at you.

[Tmall]

I've been drinking, so bare with me slice.

The amount of power produced doesn't change. You can manipulate that with gearing, but the forces being applied to the gears should always be the same.

Power out equals power in. First law of thermo.