Boxerworks.com

Hey Y'all,

Nicholas here down in Charleston, SC. This is my first day and first post on the forum. Although I cut my teeth on early 70's honda twins, I have spent the last few years digging, wrenching on, fabricating, modifying, etc Harley "choppers". However last year i went on a vintage motorcycle ride "the vintage 500" with "Speed Deluxe" (look them up, they are an awesome team that coordinate a variety of vintage motorcycle adventure rides) and it really reinvigorated my love for getting out and riding on longer trips, camping, nature, and the vintage motorcycle tinkerers community. Last year my buddy let me borrow his '73 CL350 in trade for getting it road worthy for him. The bike did great but as soon as I got back I started hunting for another vintage metric bike of my own since it had been a few years since I had one. I had always wanted a BMW as I thought they were just a little bit more neat and classier. I didn't set out to find a BMW specifically I just new I wanted something with a little bit more motor than the 350 for the longer road stretch parts of the ride which i'd say is 70% off road (gravel, jeep trails, etc in the mountains of TN,GA,NC) and 30% on street (mostly backroads). The bikes for these events are supposed to be '81 and earlier. Folks ride all kinds of stuff from BMW, hondas, triumphs, kawasaki, suzuki, etc including a variety of engine sizes, 2 and 4 stroke. Anyhow to get to the point I was working on one of my Harleys one saturday and I sat down for lunch and a beer and started scrolling craigslist and saw this 1975 BMW R90/6 posted up in Augusta, GA. It had been posted only like 19 minutes ago. It said it had a title, 84K miles on it, and hadn't run in a while. $500 I called the guy up immediately and told him I would hit the road immediately to come grab it. He was on board to hold it for me for just a few hours. I cleaned up, brewed a pot of coffee and made the 5+ hour round trip to go get it. That was a few months ago and I recently pulled it out of the shed and started tearing into it to get it ready to ride!

So...here are some of the questions I've got:

I am looking at website EuroMotoElectrics where I have already ordered some other stuff (450w alternator and electronic ignition) and I need to get a gasket kit since I pulled apart the top end and I am replacing the rings. The site offers 2 different kits. One kit is for 1970-1975 (I have a 1975) and Includes among other things a set of metal base gaskets which I did find on my motor and also includes 8 cylinder stud/rocker support O-rings, which after reading some other forum threads it appears that I do not need the 8 spacers and O-rings for the rocker box towers, although they are already installed on my heads.

The 2nd kit does not include metal base gaskets, but rather O-rings for the cylinder base. I did not find my cylinders to have these o-rings on them and doesn't look like they have a groove for them. This kit also includes 4 cylinder base O-rings (2 for each cylinder on the top 2 studs in the recess cut out for them. My motor did not have these when I tore it down and I don't see a place for them either.

In summary Kit 1 (1970-1975) Includes 8 rocker support O-rings that I don't need

Kit 2 (1973 -1995) does not include metal base gaskets which I think I need. Also includes O-rings for the top 2 studs on each cylinder and this makes me wonder if I need these!


Here are some pics of the cylinders and heads. Obviously they all need cleaning, etc. This is just where they are now.

Kit 1




Kit 2





Description of O-rings in kit 2

The bike and some of the ugly stuff I found inside. Found lots more corn and seed in the exhaust pipe!

Good score. Welcommen. That food isn't an uncommon sight on stored bikes.

I expect you'll find this site helpful...plug in your vin and it should tell you what your bike uses.

https://shop.maxbmw.com/fiche/PartsFiche.aspx

Nice score!

Mine is also a 1975 and I don't recall the rocker support o-ring. You definitely don't need the large cylinder base o-ring.

Max BMW is a great resource here in the U.S Still very knowledgeable in all things airhead and willing to help. Also has a great online fiche.

Thanks y'all. After more online searching and such it seems as though I will just use the metal base gaskets (with sealant) as my model/year doesn't use either the large cylinder jug o-ring nor the small o-rings on the top 2 studs. Im enjoying learning about all of the many changes and variations between models/years.

Next I'll be pulling the trans and drive shaft stuff off to have a look.

Boudreau said: "After more online searching and such it seems as though I will just use the metal base gaskets (with sealant)"

Be careful with the sealant! Use it VERY sparingly (if at all).
There is a small hole (at 6 o'clock) right where each the top stud enters the block.
These holes provides oil (very low pressure pulses) to the rockers.
I've seen many blocked by sloppy sealant use.

If all the mating surfaces are perfect, all you need on the base gaskets is a very thin film of grease and they won't leak.
It also makes future disassembly a breeze.
Many people will disagree with this, but it always worked for me.

I had an R90/6 for over a decade. Best thing I ever bought. If you end up doing the bottom end, I would suggest you not lighten the flywheel to keep the vintage feel, and low end tractability. There is always the desire to get better performance, but some things are not measurable. Just my 2 cents.

On the other hand, if you can come up with a dual front disc set up IMO that would be most excellent!

Thanks for those insights.

I will definitely be careful with the sealant. I have learned some methods over the years in regard to that. I did see those 2 oil passages. I was kinda surprised to see that the stock configuration did not use any type of seal other than the parts being mated and torqued.

As far as performance, I've never been a big performance buff. Im more of a rebuild/repair to stock kinda guy on that end and I lean way more towards the fabrication side of stuff when it comes to modifying anything. Kudos to those who have the patience and the brain for all that math, physics, engineering when it comes to performance upgrades.

The plan is to just go thru everything and make sure there are no big gremlins hiding. The previous owner said nothing catastrophic happened, rather he just stopped riding it and let it sit. I just want it to be mechanically sound and lubed up to put down some good miles. I don't go nuts over a little leaking oil, etc as long as its not on any pressurized supply side of things. Since I saved so much on the initial cost of the bike I am fine spending a good amount on parts and upgrades. Considering the price these bikes go for, i could have ended up buying one for much more money and still needing to replace/upgrade stuff.

I did buy the upgrades charging system as well as the electronic ignition because some of the guys that I rode the 500 last year said they had problems with the points getting wet during water crossings. Now that I own one, and see that the points chamber is somewhat sealed i'm kind of surprised they had that issue but maybe it was something else. Anyhow, i'm interested in trying it out. I've never put one on a bike that originally came with points. I will likely keep the points in place as a backup anyhow like other folks have done in threads I have read.

Thank you all for the replies. I will continue to post throughout this process and hopefully will be involved in other topics on the forum as I learn and encounter more stuff. Couldn't be more stoked to finally be the owner of an old BMW!!!