Boxerworks.com

Hello everyone!
I'm new to these airheads. I bought mine for $100 as a project that I really want to complete. The previous owner started but ran out of time and energy to complete. So as of right now I have a 1977 R100s that is in pieces and I have to put it all together like a puzzle. I've been trying to formulate a good question that hasn't been asked over and over again so please excuse me if I do. I ran a search but I didn't find what I was looking for.

So, I believe a lot of the engine needs replacing; new cylinders, pistons, rings, and few other bits. One of the original cylinders are over the +.25mm over bore recommendation in the Haynes manual. My first question is what is the maximum bore you can have? If I can avoid buying the whole new cylinder kit from seibenrock I will so I can have enough money for other parts I need.

My original vision for this project was to make it into a cafe racer but for now I just want it to run and see if I like the bike enough to put more money into it to make it into a cafe racer. Once running what do these bikes go for? All I can find are prices for the RS and newer models in the 80s. The reason I ask is because I want to be sure if I put $5,000 into this bike I want be sure I could get the $5000 back or more if possible.

Sorry for the long post and if this has been covered a million times. Can't wait to get this thing running so I can ride it!

Welcome! I've read where boring the 1000cc jugs may or may not work. There is a limited amount of liner to begin with and if the boring isn't done right, the result will be a wavy wall which won't seal well. Even if you bore, you'll still have to guy matching pistons and rings, which can expensive on their own.

I'd price both approaches. If boring is the far cheaper option, give it a shot...you might like the results.

Kurt in S.A.

Depending on your skill level, you could have bought a bargain, or a cash suck. Really nice, completely working '77 R100Ses can be had for $5-6K. If you'll need professional help putting yours back together, plus a bunch of new parts, you could burn that much up pretty quickly producing a well-working bike.

A full restoration of most airheads (except maybe the R90S, and, perhaps, the R80G/S, which have fairly irrational cult followings) is a labor/expenditure of love, or an investment in a pretty narrow educational niche---few owners who bother to do a reasonably accurate accounting break even or make money flipping airheads. But, if you just plain like'em, it's your labor/expenditure of love, and that's OK.

Thanks for the reply! Didn't think I'd get one so quick. Are there any other go to airhead websites to buy parts? So far bmw2valve.com is the only one I can find that has almost everything I need.

khittner1 wrote:Depending on your skill level, you could have bought a bargain, or a cash suck. Really nice, completely working '77 R100Ses can be had for $5-6K. If you'll need professional help putting yours back together, plus a bunch of new parts, you could burn that much up pretty quickly producing a well-working bike.

A full restoration of most airheads (except maybe the R90S, and, perhaps, the R80G/S, which have fairly irrational cult followings) is a labor/expenditure of love, or an investment in a pretty narrow educational niche---few owners who bother to do a reasonably accurate accounting break even or make money flipping airheads. But, if you just plain like'em, it's your labor/expenditure of love, and that's OK.

I am quite knowledgable when it comes to engines and putting stuff back together won't be a huge problem. It's the stuff that requires years of professional work and special equipment that I will pay someone to do. Things like gas tank repair, paint, boreing of the cylinders and valve work that I will leave to the professionals. I could have bought a running r100 but this one seemed special for some reason. Plus the ones that I found in my area were way to overpriced and needed just as much work and money to get running properly and looking decent again. I'm on the fence on what to do really. Either spend whatever necessary to get it to look and run the way I want or just get it to run and ride it for a bit and see if I like it enough to keep.

Welcome. It might not be a bad idea to spend just enough to make it ride safe, then see if you like it. The R100S is not for everyone. I had an 84 and decided it was not really for me. It was beautiful though!

BMW does a good job of maintaining parts availability for a long time, so a dealer can get most OEM parts fairly promptly. The number of dealers who have staff who are truly knowledgeable about the airheads are fewer---the bikes are getting to be older than the available mechanics and parts staffers. The IBMWR website is a useful resource for stateside used parts and assemblies, as well as "airhead friendly" dealers, aftermarket parts purveyors, and specialized repair providers.

For used parts e-bay is a good source, I am attaching a link to a seller that sells BMW parts, low starting price, accurate descriptions. http://www.ebay.com/usr/lamontsanfurd. It may be a good idea to list him as a favorite as he breaks bikes down all the time. He is prompt in shipping, I have bought many items from him, they have always been very good parts.

I've done the same thing--starting from a $0 bike. What I ended up with is nicer (to my taste) than an unmolested original and I have about the same $$$$ in it.

Mine did take a bore, but did not need head work beyond lapping the valves. It's an R75, so what Kurt said was not a factor in my case. Note that new pistons are $250 plus PER EACH. With a 1977 R100, you may do better looking for a later set of good used Nikasil pistons and cylinders. They should bolt right up.

Good luck!