Breaking in Rebuilt Enging

[DJACKSON141302]

Howdy, I just had the top end of my '78 R100 rebuilt completely and am looking for advice on breaking in the engine. My mechanic said to get away from stop 'n go traffic to break in the engine, and not to go over 100mph. At this time of year, I'm not even tempted to go that fast, so I think I'm okay there.

He also said to come back around 1,000 miles post-rebuild to have the oil changed. I've been looking through the forum, and it sounds like some people are saying to do this, as well as have the valves adjusted, at 500 miles...

Any input?

[DennisDarrow]

Am sure you will get several replies about break-in techniques. A bit of searching will find you several threads that discuss this in depth. You mention that you had your "top end" rebuilt so really do not understand if this involved piston/rings or just valve work.
If it was just the valves, YES, you do need to adjust them at 5 or 6 hundred miles and change the oil and filter. This valve adjust would also include a retorque of the heads using the proper procedure. (do a search)
If inclined, you can easily do the valve adjustment yourself. The first time may take a couple of hours; but you do need to learn to do this normal procedure that usually takes maybe a half hour.
Let us know if there was piston/cylinder work done and I am sure you will get more information about that break-in procedure.

God bless the USA.........Dennis

[26667]

see snowbum and the airheads list, as well as just doing a search here. Tho' many say things like "drive it hard and fast right away", my impression, having been thru it recently, is that most people advise the "gradual" break-in procedure recommended in "the book". That is, no more than 1/3 throttle for the first 500 mi. Change the oil, torque the heads and adj the valves. No more than 2/3 throttle for the next 500. Increase to full throttle over the next 500. Oil and valve adjust again, and you should be good to go. You'll get several opinions here I bet, but that's what I was most often told. The thing I believe an even greater number will agree on is that it's critical to vary the engine speed. In other words, don't just sit at 3500 rpm for "long periods." I suppose that definition is subjective, but if you're riding around town, or anywhere exept the freeway, it's hard to maintain any speed for very long.
good luck

[PGlaves]

Assuming you used a competent mechanic you trust, then I would follow his break-in recommendations to the letter and hold him responsible for the results.

[20774]

Assuming you used a competent mechanic you trust, then I would follow his break-in recommendations to the letter and hold him responsible for the results.

However, the mechanic has no control over how you ACTUALLY perform the break-in, so he might have an "out". But certainly, getting his input is a good place to start.

Now, maybe the mechanic wouldn't mind borrowing your bike for 500 miles and doing the break-in himself...:laugh

[DJACKSON141302]

Am sure you will get several replies about break-in techniques. Let us know if there was piston/cylinder work done and I am sure you will get more information about that break-in procedure.

God bless the USA.........Dennis

Yes, the cylinders were rebored, the pistons were replaced, the heads were resurfaced, and the valves and valve guides are new.

I went for a 25 mile ride after picking the bike up - combo of city driving and a brief jaunt on the freeway, varying the rpms from low to about 5K. Then a few days later went for a longer, 100-mile ride down the coast (I live in San Francisco), where I did basically the same thing, gradually increasing rpms.

I try to accelerate immediately upon shifting into the next higher gear, as that's what my bmw (car - a '74 2002) mechanic told me was important to do when breaking in an engine, in addition to varying the rpms...

Sound about right?

[20774]

The reason for varying the RPMs is to get both acceleration and deceleration forces to the rings. So just varying the RPMs is not enough, but when you are going to downshift, let the engine compression do some of the braking rather than the brakes. This also helps seat the rings. IMO, a good portion of the ring seating happens when the bike is first started. When the cylinder walls are not glazed or oiled up, you're going to get the most abrasion. After a while, the hot oil glazes things up and the abrading process slows down. So if rings don't seat within a couple of hundred miles, maybe out to 500 miles, likely you'll have oil consumption problems or blow-by problems to contend with.

[DennisDarrow]

Excellent advise from Paul to get recommendations from your mechanic as to what to do.

Perhaps, it might be a bit late for this discussion as in my knowledge of doing this, the first few miles/minutes are what really matter. It sounds though that you are doing pretty much the right thing.

My ol auto shop teacher, Mr. Peterson, drilled and this into us over the several years we got exposed to his wisdom.

For me, I would fire that puppy up and immediately head out for deserted roads. There I would spend miles and time:

In 4th or 5th get down to maybe 2500 RPM and full throttle to 4K or so, then back off and let it coast back down to the low RPM. Repeat again and again........and again.....Hills are great for doing this as it causes the engine to work even more.

As Kurt pointed out, what this does is push the rings against the cylinders. Full throttle acceleration floods the cylinder walls with gas and allows the rings, through friction, to get properly "fitted" to the cylinder............

God Bless.......Dennis

[108625]

Whichever technique you decide to use; all I can add is be sure to get the engine up to operating temperature each time you fire it up, and before you start any RPM "exercises".

[DJACKSON141302]

One last question - how much oil should the engine consume during break-in?

[PGlaves]

One last question - how much oil should the engine consume during break-in?

For sure - not all of it.

Don't be surprised at a quart per 500 miles.

[DJACKSON141302]

So just keep adding to make sure it's topped off, right?

[PGlaves]

So just keep adding to make sure it's topped off, right?

Check frequently. Top off. Don't overfill.

[RandyB]

One last question - how much oil should the engine consume during break-in?


General consensus is don't use synthetic and change frequently.

[Na Cl K9]

A shop in Colorado Springs (Doc's) put a 0 miles BMW airhead out front each year when the new models came out so potential customers could ride one. I spoke to one of the mechanics there who told me that the demonstrator bikes consistently performed better than most of those sold to individuals "out of the crate".

The theory was that people who “test” rode these bikes took them out and ran them hard. Much harder that any factory recommended break-in. They varied the throttle position, accelerated hard, jammed on the brakes, bounced the tachometer needle off the red zone and generally flogged the poor beasts for 20 minutes or so...and then, the bike sat out front and cooled off till the next test rider came along a few hours or days later.

What prompted me to ask was I was in the process of purchasing a new R75/7 from them and I noticed that the demo of the month had headers that were blue all the way back to the mufflers and only had 1200 miles on it. I was curious. The mechanics comment was that after they were sold, and in the years that followed, the "demos" used less oil, spun up faster, were smoother at high RPM, and shifted better than their counterparts which were broken in "properly".

[DJACKSON141302]

Thanks for this. I admit, I've been trying not to overdo it on the break-in, but I'm sure I've already ridden it harder than recommended in the 125 miles since the rebuild. This is a hilly area with a lot of twisty roads that are conducive to higher rpm riding. As soon as it stops pouring, I'll be out again.

[jdmetzger]

I sent off my heads for new valves almost two years ago, and ended upgrading to nikasil cylinders and new rings. The break-in procedure I was told was a bit different then the ones I've read:

Put everything together - don't oil the pistons or anything (though I replaced my lifters and was told to put a smear of assembly lube on those)

Start the engine and run it up to 3000rpm for two minutes.

Shut down the bike and change the oil and filter, check and/or adjust valves.

Ride bike trying not to get over 5000-5500rpm for the first 600 miles. No highway, no long idles (don't want a consistent RPM).

At 600 miles change the oil and filter again, adjust valves, ride as normal after that.

This worked VERY well for me. Some won't believe me, but my R80 consumes NO OIL that I can detect over 3000 miles. Nothing AT ALL (mind you, I've also replaced the rear main and oil pump seals, as well as the breather valve). Still runs great with a lot of power and no oil consumption all this time later (and it gets ridden). I was apprehensive about the instant 3000rpm thing, but was told the factory used to fire them up and take them near to redline right off the assembly line.