So, they say it's just breaking in at 50k miles?

[jay1622]

1988 BMW K75S, 38k mi.

To tell you the truth, I never actually believed this; the "just breaking in at 50k" stuff. I always thought it was just random nonsensical BS we threw around to make ourselves feel even better about our bikes. I mean, I know they're amazing rides, but the places the engineers got right ended up being really really right. Today, I understood, and thought I'd share with those of you who've never ventured this far into your bikes. I was simply amazed to see what great shape the Pistons and Cylinders are in. The cylinder walls? I kid you not; they look like they were honed yesterday. The piston rings and grooves? The top compression ring had only just started to fully seat and the secondary compression rings are about 1/3 of the way seated. Simply amazing.

I hope these pics will come across.

[MonkeyMcBean]

Thats almost unbelievable. Literally incredible!

[F14CRAZY]

Have to ask, what made you tear that engine down?

I was gonna say though that may not be uncommon in other engines. I replaced the head gasket in my now-wife's '95 Chevy Corsica (2.2L OHV) around 200k due to coolant leaking externally. I know these engines use head gaskets once in a while and figured I'd better do it before it got worse. That still had cylinder crosshatching too.

[Solly]

And that is why German steel is still the best steel on the planet, this quality of metallurgy in other manufacturers is reserved usually for diesels or aerospace or machine tools.

[jay1622]

Have to ask, what made you tear that engine down?

I was gonna say though that may not be uncommon in other engines. I replaced the head gasket in my now-wife's '95 Chevy Corsica (2.2L OHV) around 200k due to coolant leaking externally. I know these engines use head gaskets once in a while and figured I'd better do it before it got worse. That still had cylinder crosshatching too.

Some crosshatching, yes, absolutely. But the level at which it is pronounced is just unbelievable. As for the teardown, the whole idea behind me getting this bike was to teach my 13-year-old son about internal combustion engines, organizing a rebuild, ordering for parts and things along those lines. Granted, I probably would have done it anyway, but knowing he is doing a lot of the work next to me makes it that much more fun and motivates me to get right down to it. From here on out, it's going to be cleaning, repainting and putting stuff back together. Knowing the previous owner had it sitting for five years in storage, I removed the oil pan and cleaned it. I am glad I did to seeing that it was covered with the beginnings of what was sure to be sludge. Everything else in the engine is spotless however.

[Motorhobo]

That is one lucky 13 year old. I love my dad but he can't tell a screwdriver from a butterknife.

I have an extra K75 engine with 175K on it -- rebuild is one of my top bucket list items. Maybe in a couple of years I can hire your son to help me out :-)

[kris]

Great photos and an admirable goal to the project. Have fun! Quality father and son time....doesn't get much better.

[Chaos]

Quality father and son time....doesn't get much better.

+1 on that!  Been building a "gravity racer" with my 9 yr old.  He'd rather work on it than video games!