Rusting cylinders before assembly???

[10drum]

Greetings,

I took the cylinders from my ‘71 r75/5 to a bmw guy to check whether they need to be bored or just honing and rings. He thought they only needed to be honed and install new rings. He also told me that after he hones the cylinder, he rinses them in scalding hot water, blows the outside dry, let’s the cylinder wall develop a thin coating of of rust, then install the piston dry??? He said it’s the best way to get the rings to seat???

Has anyone ever heard of this method?

I was told by british bike guy to assemble the pistons dry with no oil, but never heard of rusting?

 

[20774]

Has anyone ever heard of this method?

Yes. That small amount of grit will help to begin the process of abrading the piston rings. Typically, the break-in process is heavily influenced by the first 30-60 seconds after engine start. If the cylinder walls get too glazed too early, there's nothing there to work on the rings. What I've done is keep everything dry, but before installing the rings, I drop them on a paper towel saturated in engine oil. Then I put a small patch of smeared oil on the piston skirts. Everything else is kept dry.

Snowbum discusses the "rust" technique here, about mid-way down the page:

http://bmwmotorcycletech.info/break-in.htm

 

[toooldtocare]

Agree. Sounds stupid, but that is what my BMW guru also recommends. He has many years experience rebuilding Airheads.

 

[lmo1131]

A friend of mine was an old school Butler & Smith mechanic. He did my top end like this; don't know about the rust, but it was assembled dry.

 

[RPGR90s]

Rust

Yes, that's the agreed upon process.

Years ago, I rebuilt my R75/5, with a 1st over bore, new pistons, rings. The literature from the dealer that did the bore work recommended washing the cylinders with soap and water and letting a thin film of rust to form with no oil applied.

For the piston, apply one drop of oil and spread across the entire piston, and liberally oil the wrist pin.

Upon starting, hold RPM to 2500 -3500 for 90 seconds with fans blowing on the cylinders.

I did that, and I have to say, that motor nary used a drop of oil in the next 15 years.

RickR90s

 

[10drum]

Thanks for all of the replies, I pretty much have done everything except for the rust. On a rebuild I install the pistons dry, run for 30 minutes at 3000 rpm, with a fan on the cylinders, using 30w non detergent oil. I let the engine cool over night, retorque the heads, change the oil, then ride it. Ill try the rust, an old dog can learn new tricks.

 

[lkchris]

This of course applies to early iron cylinders and not to later nikasil cylinders.

 

[20774]

On a rebuild I install the pistons dry, run for 30 minutes at 3000 rpm, with a fan on the cylinders, using 30w non detergent oil.

Really? 30 minutes? That seems a bit extreme.

Full break-in needs to be done over a wide variety of speeds and RPMs. Each RPM band has a certain dynamic nature thus putting the engine parts in different conditions. If you spend too much time at one RPM, then the parts wear in for just that RPM, forsaking how things fit at other operating RPMs.

 

[10drum]

Really? 30 minutes? That seems a bit extreme.

Full break-in needs to be done over a wide variety of speeds and RPMs. Each RPM band has a certain dynamic nature thus putting the engine parts in different conditions. If you spend too much time at one RPM, then the parts wear in for just that RPM, forsaking how things fit at other operating RPMs.

Just like Imo referenced an old school mechanic, the procedure Ive used on the British twins I've built, was recommended by an old school British bike mechanic. I'm cutting the time by 30 minutes, he told me to run it for an hour. This is the initial run in, what I do next, is torque the head, switch to 40w non detergent for about 800 to 1000 miles of break-in riding, re-torque the heads, switch to straight 50w non detergent oil, then I usually sell the bike, and start looking for another project.

 

[SCBuckeye]

Really? 30 minutes? That seems a bit extreme.

Full break-in needs to be done over a wide variety of speeds and RPMs. Each RPM band has a certain dynamic nature thus putting the engine parts in different conditions. If you spend too much time at one RPM, then the parts wear in for just that RPM, forsaking how things fit at other operating RPMs.

This is what I was taught. Due to different harmonic vibes at differing RPS's and loads.

 

[10drum]

This is what I was taught. Due to different harmonic vibes at differing RPS's and loads.

You all need to understand the 30 to 60 minute run in, is not the break-in. It is to get the head, cylinders, cams, crankshaft, and crankcase settled/temped in. The break-in takes places in the first 1000 miles, with the 40w oil.

 

[20774]

I've never heard of this kind of "run in" before. Personally, I think holding the engine at some constant RPM wouldn't be good. How do you know that 3000 is the right RPM? What about 2300 or 3400? Why not choose something else? You are still breaking the engine in during this "run in" period. Breaking in is the wearing of parts in a minute way so they work well down the road. The engine should be broken in the way you're going to ride it...varied speeds and RPMs.

But, it's your bike and if it works for you, have at it!

 

[nrpetersen]

This is what I was taught. Due to different harmonic vibes at differing RPS's and loads.

There's nothing harmonic about break-in. The reason supposedly is the splash lube system delivers oil only to certain places when operated at a fixed rpm. Varying the rpm is recommended to hopefully deliver oil to a more widespread areas just due to the randomness of the whole process. I'm not real sure I buy that. but for certain I wouldn't operate with fan/ground cooling for 30 minutes either.

Think about it - a four cylinder engine probably has a lot of huffing and puffing within the crankcase due to the pistons going in and out at different times. This probably moves the oil fog around more randomly.

A two cylinder opposed like our oilheads probably not so much.

What's critical is the rapid establishment of an oil fog to get everywhere. Thick and or cold oil tends to inhibit this until things get really hot. I suspect that's why break-in oils are so comparatively thin.

FWIW - Strictly my BS.

 

[WooDmEn]

Dry Start Break In

My learning is that a dry cylinder initial start up (dab of oil on piston skirts and well lubed wrist pin) is for race engines only or mostly. Racers have no opportunities to speak of to break in a new motor, which might be at every event.

I’ve used the technique on a street motor successfully, but would not do so again; too risky for me personally. Effective piston ring break in seems to occur best by changing speeds and most importantly, engine loading. Powering through the power band, from low revs to high revs increases combustion pressure especially at the lower rpms, thus loading side force to the rings and pressing them more tightly against the cylinder wall. 30 seconds, then ride lightly for ten minutes to cool thing down, then repeat. With German iron bores, it seems to take about 2000m to approach normal seating. With Nikasal, twice that or more. My $0.02.

 

[stevenrankin]

Break in

My old BMW dealer/mechanic told me to break in a bike by riding the hell out of it and not lugging it for the first few thousand miles. I guess it worked, I never had an oil consumption problem with my two bikes. St.

 

[ccolwell]

This reminds me of the old saw that engines generally last longer if they have some oil in them and longer yet if it gets changed every once in a while.

 

[10drum]

I've never heard of this kind of "run in" before. Personally, I think holding the engine at some constant RPM wouldn't be good. How do you know that 3000 is the right RPM? What about 2300 or 3400? Why not choose something else? You are still breaking the engine in during this "run in" period. Breaking in is the wearing of parts in a minute way so they work well down the road. The engine should be broken in the way you're going to ride it...varied speeds and RPMs.

But, it's your bike and if it works for you, have at it!

20774, I had never heard of rusting the cylinders till now. “Personally”, I wonder what damage does the rust, that is rinsed off the cylinder walls, below the rings, do to the bearings? Hopefully, the oil filter will keep the rust particles from reaching the bearings. The British bikes don’t have an oil filter.

The 3000 rpm point, is to run it with the ignition fully advanced.

I am not the hammerhead here, I am going to try the rusted cylinder method, the 30 minute run in has worked well on the 6 bikes I’ve built to date, but perhaps a rusted cylinder will accomplish the same results as 30 minutes at 3000rpms.

Thanks for all the replies, I appreciate being forced to “think about it”.

 

[20774]

Probably time to drag out the "beating a dead horse" smilie!! I think if you ask 5 mechanics on how to break-in a motorcycle engine (or any engine), you'll get 8 different answers. Just see how people have responded to this thread.

I've looked at three documents I have...and there will be dozens more out there. One is a restoration manual for /2 BMWs by the Betjemann's in New Hampshire. I also have rider's manuals for my R25/2 and my /7. The common theme in them for "running in" is the idea of riding the bike in varying speeds, RPMs, increasing load, decreasing load, no lugging, and staying away from maximum speeds/RPMs. The length of time varies, but after some amount of time, the oil is changed, heads retorqued...all those good things.

I've heard the extremes for running-in or break-in. Break it in like you're going to ride it. Run it hard. And everything in between. Here's a link to a break-in procedure:

www.mototuneusa.com/break_in_secrets.htm

One of things mentioned here is that the engine break-in happens mostly in the first 20 minutes after engine start. Certainly, there are things happening out to the 300-500 mile mark. Anyway, there are all kinds of suggestions.

Bottom line is if you understand what you're doing, have reasons for doing it, and it works for you, then nothing wrong with doing that again and again. People like to pile on with what they've done based upon suggestions they had. Not sure how many engines the average person truly gets a chance to break in...probably a pretty small number. Best advice would be from someone who does this sort of stuff for a living and has many satisfied customers based on those recommendations.

Have fun!!

 

[brittrunyon]

Thanks for starting this thread.
Today I will be installing pistons, cylinders and heads on a 76 R90/6.
I now get to use the advice in this thread that I like and toss the rest.
Opinions are like........oh never mind.

BR

 

[10drum]

I’m an electrician, I have worked with mechanics and machinist. I connected and disconnected industrial rotating equipment, so the mechanic(s) can remove the pump, valve, or what ever, so we could take them to the machinist for rebuilding. Both mechanics and machinist are inevitably hammerheads. When I started building motorcycles as a hobby, I realized that I don’t have the years of experience, so I rely on other people who do have the experience. The man that recommended the 60 minutes at 3000rpm run in procedure, has made his living building and repairing british motorcycles for over 50 years. People send him engines to build. He runs them in on a stand in his shop, for 60 minutes at 3000rpms with 30w non detergent oil. I know there are many ways to skin a cat, and the man who recommended this method is just one man, but he was willing to help me.