about hard break-in question ...long term affect on BOTTOM END

[runester]

Hey all...

I just bought a new yz450f and am gonna' break it in tomorrow...I read the hard and heavy break in thread here and am wondering this...O.K>, as for the rings it seems like a sound philosophy but is it REALLY safe on the INITIAL break-in? Which involves MUCH MORE than just the rings...ALL meeting surfaces have to mate correctly and many other initial internal interactions take place during that initial break in..I can see doing it that way on the first cylinder rebuild but feel sketchy about the harsh and hard right off the showroom floor.

I would just like to hear opinions from experienced mechanics.

I spent a healthy chunk of hard earned dollars on that baby and I have always used the easy break in on my other bikes and they have all held up well.

My worry is that the hard break in might be GREAT on the cylinder performance but what will be the long term affect on the bottom end?

[gbalias]

id say youre fine breaking it in any way you like.

i have yet to come across an instance where the break-in was the culprit of engine failure. drive it in the way your normal riding style is and youll be fine... even in the long term for the bottom end.

if it matters....ive always done the hard break in in my bikes, even in our high perf cars (family owned auto shop).

mmm.mmmmmm.

[El Marko]

Sorry, but the hard break-in is more theory than I like to put up with. Most of the guys recommending it don't seem to have the credentials to back up their opinions.

There's no obvious or proven advantage to the hard breakin.

The factories have specific break-in descriptions in the owners manual and it's there for a reason. They know their motors better than anybody in these matters.

[elm327]

break it in like you are gonna ride it, i have done this tho counless new bikes without any issues.

[BergArabia]

whatever you do, change the oil at short intervals during / after the breakin period to get rid of all that metal being ground off as the surfaces mate...

[gbalias]

..... Most of the guys recommending it don't seem to have the credentials to back up their opinions.....

what would qualify as credentials for ya?

building X amount of motors, being a race mechanic, driver, engineer, etc?

i guess at the same time, you could say that poeple on either side of the fence have only the credentials of their own experience.

hence, you should break it in however you want and frequently change the oil during the process.

good luck.

[grayracer513]

What I alway tell people to do is to run their engines at about 80% of capacity for short bursts during the first two hours of operation, and to avoid 3 things:

> Lugging

> Extreme high RPM

> "Babying" the engine

Break in presents an interesting little problem, really; the piston rings should be put under considerable pressure to force them to seal to the cylinder, but nearly every other component would be as happy to run at a steady speed and a 10% load for the first 20 hours at a constant 160 degrees.

And in truth, modern piston rings use moly filling, and other similar technologies, and are made so precisely that they need only a few minutes run time to set up a good seal with the bore.

IMO, if you use just a little common sense, and are neither too hard nor too soft on the engine during its early life, it will break in and serve you well.

[runester]

G.R.

From what I gather you seem to have a solid knowledge base and no ego and a history in engines so I value your opinion...was hopin' you'd chime in and you make good sense...tis my usual method but am always open to a new and innovative approach to mechanical issues if there is science and or experience to back it up and as you point out and the point of my question...effect on the bottom end...I mean,heck, whats a top end rebuild...couple of hrs (give or take) and a hunert bucks or two but man...that bottom end takes time man...I will post a few photos of my "workshop" and the new bike later tonight...I am back off to the garage now for pre-track prep, so far the shop left about fifteen spokes VERY loose, no filter oil or filter seal grease, five LOOSE bolts so far and no front brake fluid...but honest to god at 62 out the door in L.A. it is worth it...

Will have photos up soon.

Thank you all for your help and Gray Racer I hope you dont mind if I ask you for advice now and then.

Kind regards,

Runester

[Wayward Son]

Sorry, but the hard break-in is more theory than I like to put up with. Most of the guys recommending it don't seem to have the credentials to back up their opinions.

There's no obvious or proven advantage to the hard breakin.

The factories have specific break-in descriptions in the owners manual and it's there for a reason. They know their motors better than anybody in these matters.

if you did some searches in other forums you find other wise.

[spud]

I remember seeing in a mag, that at the yamaha factory and on every engine they fill the gas line with fuel and run it up to full RPM and through the gears, on the assembly line.

It was commented on how strong the guys leg would have been after the starting all the earlier 400, and 426s'

[grayracer513]

if you did some searches in other forums you find other wise.

If he searched here he'd find out otherwise, too.

G.R.

From what I gather you seem to have ... no ego

That's pretty funny. You'll notice I never put an 'H' in "IMO". Why pretend?

I do try to keep it out of the way, though.

[Tattootodd]

If you think the factory didnt bouce that thing off the rev limiter and shift it numerous times before shipping it????YOUR NUTS And IMO i think most of the factory recs are for the learning curve and not the motor life curve....It is so IDIOTS dont hammer it till there used to it..ETC....etc....But theyll sell any joe schmoooo a 1000cc bike with 180 hp who has never been on a bike....SO who knows

[Racer24]

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

Hard Break in doesnt necessarily mean, run it and bounce or stay on the rev limiter...you need strong forces from hard Accel and Decel to force the rings against the walls...if they seat properly you won't have to worry about oil leaking through into the combustion chamber and getting burned...So you dont need to stay at high RPM's to break it in...

just let it warm up.. and then start with some heavy acceleration and deceleration...after that you can start going through the gears and climbing up the powerband...

the first 25-30 miles is key. "DON'T BABY IT." when the break in period is done, make sure to check and most likely re-adjust the clearances and replace oil and filter. Also dnt worry about shimming so early, after you shim after breaking it in, you won't have to check them for a while (depends on style of riding). Just make sure to stay on task when it comes to periodic maintenance and your bike should last for a long time

[grayracer513]

...you need strong forces from hard Accel and Decel to force the rings against the walls...if they seat properly you won't have to worry about oil leaking through into the combustion chamber and getting burned

Decel pressures are near non-existent, and contribute little, if anything to seating the rings. Combustion loads do force the compression rings against the cylinder, but have no effect on the oil rings, and are not a factor on seating them. The issue is only about forming a good compression seal, and limiting the loss of combustion force due to blow by.

Otherwise, you are correct. Running an engine under a heavy load does not have any correlation to high RPM.