BMW R90/6 Cylinder Options

This was the reason I was able to give Marco my rear wheel to get him home over the weekend…

After getting the BMW running great for the first time in 2 years and having too much fun zipping around town I decided I’d better focus on fixing other long time issues to continue with making the R90 into a solid and reliable side car platform. The pushrod seals and rear main seal had been done by the previous owner shortly before I got it which helped push me over the edge on pulling the trigger on this bike.  Unfortunately now 7 or 8 years later the pushrod seals were now starting to weep and were in need of being replaced again.   I had already gotten a full set of top end gaskets and oil pan gasket with the carb rebuild parts.  I figured it would only take a weekend tops.


What I found when I pulled her apart was shocking and unexpected to say the least. The left cylinder had quite a bit of pitting on the top side of the cylinder and a lot of discoloration on the bottom. The biggest rust spot on the bottom did have a bit of a slight raised swede feel to it and the other spots were smooth with the barrel. The pitting did not feel very deep but could feel it with a finger nail.

Listen to the video, there was no indication that one cylinder was this damaged.

Top of left cylinder

What a way to kill a guys spirit. From the high of finally getting the thing running great and seeing it starting to come together to your dreams dashed on the rocks. Ouch.

I knew one thing, fixing this was not going to be cheap.

Bottom of left cylinder

The other cylinder looked perfect by the way.  Pretty damn good for around 90 to 95,000 miles on it.    The right side had always had a bit of oil weeping from the base of the cylinder and I was expecting to find a pulled stud but instead I found it was leaking because this side did not have the O ring at the bottom of the cylinder!  Some good news.

Right Cylinder

At least now I know why I had a ring set in the box of spare parts from the previous owner that was missing the oil ring…

This also finally explains why this thing smoked like crazy if you happened to leave it on the side stand.  I know everyone says that they all do that but this was on a whole other level, we are talking Uncle Buck car type smokeage. After I smoked out a tech day and sent people running for air even fellow airheads said mine was particularly bad. If left on the center stand, however, it never smoked, again check out the video up top. Unfortunately you cant always park on the center stand.

I had always assumed that it needed valve guides done, probably still needs those too, and I’d been trying to avoid that expense as long as I could by never parking on the side stand when possible.

I sent a few emails out to several vendors to price out my options and compare services offered and received an outstanding response from Ted Porter of BeemerShop with some great info on the R100 cylinder differences that I was not aware of and had to share for others and I’ve included a few snippets from him below in the list.
This is a common problem, I can’t tell you how many times I have seen this over the years. It’s moisture and this is what happens when a bike sits.
Considering the mileage, the bores are probably both tapered out of spec. This is not something you can see with your eye, a bore gauge is required. In a steel bore with this many miles, it’s very likely that the bore gauge needle would swing pretty significantly indicating that it’s time for a bore restoration.
In the old days we would simply purchase first oversize pistons and bore to the first oversize. However today the pistons are scarce and very expensive, plus we now have the technology to plate with Nikasil and continue to use your existing pistons which generally do not wear. This provides a harder Nikasil bore and it is less expensive at $450.00/pair. You will need to use Nikasil appropriate rings which we sell at $76.55 each, two sets required.
Of course one step better than this would be to install a set of Siebenrock 1000cc cylinder/piston kits


So how do we fix this mess?  I’ve put it out to the Airhead Community and I’ve come up with a few options…

  1. New R90 cylinders and rings – $$$$ not an option
  2. Used R90 cylinders with pistons – I’ve seen sets on and Ebay from $300-$500 of unknown mileage so a bit of a gamble. Also I have a 1976 and only a set from another ’76 will fit.
  3. Used R100 cylinders with pistons – I had incorrectly assumed that any R100 cylinders would be a direct swap for my ’76.  I learned from Ted Porter that “you could look for a good used set of BMW 1981-on Nikasil cylinders and pistons which will require a minor modification to the cylinder base to be used on your 76-on block. There is a small step of metal inboard of the base oring groove that is designed to fit into a chamfer in the 81-on block which your 76 model does not have. We just remove this step for $70.00/pair and the cylinder fits the 76-80 block just fine. Keep in mind the 81-81 Nikasil pistons were low compression at 8.2:1, the 1988-on Nikasil pistons were 8.5:1 so they’re a little more desirable.”
  4. Bore to next size with new pistons – A local shop has quoted me 50 bucks a side to bore them and their machinist was pretty confident that one size up would take care of the pitting, [Motobins has first and second over pistons for £154 ea] [ Motoren-Isreal has Wossner pistons for 349 Euros a set ]
  5. Have cylinders restored, bored and nikasil coated and reuse existing pistons with new rings for nikasil – I heard about this process also from Ted Porter who carries the rings “at $76.55 each, two sets required” and got a quote from PowerSealUSA “From the looks of the photos we should be able to fix them by honing to accommodate the plating thickness then plate/hone to size. Price to plate a steel/cast iron liner is $225 per cylinder.”
  6. Siebenrock kit – from  Motoren-Isreal – 817 Euros with shipping to the US. From Motobins it is more but comes with a gasket set.

I think the first 3 are not an option, at the going rates for questionable used parts I can get new pistons and a rebore. I’ll still keep an eye out for a really good deal on a post ’88 R100 set though.

Wossner pistons and a rebore look like my cheapest option for new parts. The downside here is I really want nikasil cylinders that will last forever.  A few guys that have gone this route that replied to my forum threads have been very happy with the results though.

Having my existing cylinders nikasil plated is a very intriguing option that I was not previously aware of and roughly the same price as the others.

I really think the Siebenrock kit with the horse power boost is my best option with this bike being built up for a sidecar tug in the future.  Unfortunately $930 is a big expense that I was not expecting, the good news is with the dollar surging this option is $270 cheaper than it was just a few years ago if you buy from Europe.

UPDATE:  Several other unexpected expenses that also added up to $1000 have pretty much killed this restore project for the time being so I’m going to go with plan G: hone the cylinders myself, re-ring and call it good for the time being.  It’s run decently with plenty of pull all this time in this condition so I don’t think it will hurt to leave it the way it is for another 6 months until tax return season rolls around and I can revisit this then, along with getting heads done.


Road Karma

A group of guys traveling cross country from New Jersey made an emergency pit stop at the house over the weekend.  I saw a post on a Facebook page from the previous day that Marco’s BMW R90 had a wheel bearing go out in Gallup and gave him a call to see if they still needed help. He thought it was a loose axle and fixed it by tightening the nut but by the time they rolled through Albuquerque it turns out it actually was the bearing and it had grenaded on the way here.

I swear these old Beemers are very reliable bikes once you go through and fix all their weak points. I read the blog they have been keeping of their trip, , and sadly it seems like the BMW has been having every textbook failure in the book,  charging system, ignition system, starting system, front and rear wheel bearings..  Good thing his bike has a beefy reinforced subframe carrying all that weight so he shouldn’t experience the broken frame problem as well.   Just think, by the time you get home you’ll have a well sorted rebuilt bike that can go anywhere.

The bearing on Marco’s bike must have gotten super hot as it was destroying itself and part of it was seized on the axle making it impossible to remove to get the rear wheel off.  Unfortunately my Dremel tool, and also my grandfathers hammer, were stolen in a breakin and both would have come in real handy.  I had to call in some help from my neighbor to cut the bearing off.

Originally I had planned on just swapping out the bearing from my wheel to his and calling it a day but since it took an hour and a half just to get his wheel off so we decided to just swap the whole wheel instead and deal with getting parts back to the right owners later.  It is only fitting since he’s already changed out the front wheel along the way too.

I was very impressed that little Robert who had been sick and fussy for several days thought all of this was fascinating and amazingly watched the whole thing for a couple of hours which was the longest he’d gone without crying all weekend. Even when he is not sick he won’t sit still for that amount of time. We’ll make a motorcycle mechanic out of him yet.

I thought I’d write this post after a friend asked Why? the next day after explaining how I’d smashed my thumb with a roofing hammer helping some motorcyclists that I’d never met before they rolled up in my driveway.

I’m not sure why I do what I do, even before I got into motorcycles I’d helped over 100 stranded motorists.  At the time living out in the country and frequently traveling dirt back roads with a less than reliable Jeep I had to become proficient in fixing my own stuff to keep going and had to carry a full set of necessary tools with me at all times.  As you experience new problems that you weren’t prepared for your tool kit grows, like after the time I overheated and had to hike back and forth to a windmill for water with only an empty soda can to carry it in I started carrying a gallon of water and antifreeze with me at all times.  With a rolling mechanics shop in the back I knew I could fix most common issues and get people to their destination so why not?  Helping those in need makes you feel good after doing your good deed for the day.

When I drove my Jeep pickup I did everything from countless jump starts to replacing a thermostat in the grocery store parking lot and more than once more than once having to do CPR on a crash victim before emergency responders arrived. Back then cell phones were a rare item and even after they became more common there was no coverage outside of the bigger towns so if you broke down between towns you were screwed. Learning to be self sufficient and prepared was a necessity.

I am a firm believer that what goes around comes around.  You shouldn’t expect it but many of those that I have helped have returned the favor later on, I got invited to a wedding reception for fixing a thermostat and even got out of a speeding ticket when the officer remembered my truck as the one that had helped a family member a few months earlier and occasionally had a few 20’s forced on me here and there. One rider gave me $100 for fixing an oil leak her bike, when I refused payment I found she had stuffed the money in my saddlebag.

After I got the V Star and used that as my primary vehicle and really couldn’t carry all the tools I had before I got a little bummed that I couldn’t help people like I used to, I had to pass by all those cars with hoods up in parking lots waiting for a jump start.  It was then that we started going on motorcycle trips that I discovered a whole new level of Road Karma, helping fellow cross country travelers.  When you give a soccer mom a jump start in the grocery store parking lot her day has just been slightly inconvenienced, when you help out someone on a cross country bike trip 2000 miles from home who’s already been on the road for several weeks you can be a god send!

Unless you have broken down thousands of miles away on a road trip without knowing anyone to call for help for several time zones you really don’t know what it is like. You are stuck, there is no going anywhere until you solve the problem and most of the time you’ve already gone way over budget by then too so a really expensive repair could be the end of the trip. Those that have been there will usually drop everything to help a fellow rider in need and bend over backwards to help someone in the middle of a trip. It is also a neat way to meet fellow travelers and hear about where they’ve been and in a small way become part of their trip.

I’ve also found that you are far more likely to run into road trippers that you’ve helped again. After you’ve saved their butt in the past they are happy to be able to return the favor and fellow road trippers like to travel a lot so you are more likely to meet them on the road and at gatherings.

Who knows, that random person you helped field strip and repair their bike in your girl friend’s mother’s driveway …

may offer you a bed to sleep on in Texas.

Or the guy who gave you a free stay at a nice hotel they’d won at a poker run in Arizona

you may run into at a meet up in Texas where you can give them an inflatable mattress you didn’t need.

If you decide to go on road trips eventually you will need the kindness of strangers so it is good to have lots of Road Karma points in the bank. Even if you don’t break down you’ll need a new tire or maintenance item along the way and getting your bike in for a quick thing without an appointment can still be a problem.  More than once we’ve been told by dealerships that their schedule was booked and we’d have to come back a few days or a week later and have had techs sneak us in under their foreman’s nose to do a quick tire change and get us back on the road.  Thanks guys at Adventure Motorsports !

We’ve also had to deal with asshole managers at oil change places and had techs step in to save the day.

Sometimes it is nice just to get out of the tent and have a couch or bed to sleep on without paying for a motel.

So don’t think that you’ll never need help along the your trip with your super reliable bike.

Whether you’re packing light and traveling by sweet Excelsior-Henderson …

or petal power …

or taking everything with you …

including the kitchen sink …

or traveling by well used and abused classics …

or brand new rides for a father/son cross country trip, eventually you’ll need help from someone.

So what can you do to earn some good road karma?

  • Offer your trade skills:  If your frame breaks you aren’t going anywhere until you find a welder …

  • Being able to fabricate new parts from scrap metal instead of having to wait for an overnight or a back ordered piece is great!

  • If you are mechanically inclined or just have a good set of tools to borrow that may be enough to get someone back on the road.

  • Write a repair article. If you don’t want to host your own blog other sites will welcome guest posts for your content and you may even get paid for it.

  • If you don’t know how to work a screw driver you can still carry a set of jumper cables, if you don’t know how to use them chances are the other guy does and sooner or later you’ll need them yourself, it’ll save you an hour wait for AAA to show up.  Any basic set will do, I have the heavy duty extra long 25 foot kind after my truck had a dead battery in a downhill space in the corner of a lot and we had to find 3 pairs of cables to daisy chain together to reach.  With these ones I can park behind someone and still give them a jump, the downside is they are heavy and bulky and don’t fit in my car I drive now.

What if you have no mechanical ability at all?

  • You can still offer your garage, spare bedroom or couch as a place to stay:

  • Recommend some amazing hole in the wall eateries you think they might like, like this sadly now out of business Greatful Dead themed pizza joint that had wall to wall memorabilia of the band and played the Greatful Dead channel on a big screen TV up front, my friend who was passing through on a Greatful Dead themed bike thought it was great!

  • Do a tour of the local sights around your town.

  • Or do a longer tour and show off some of the best motorcycle roads.  I have taken days off work to lead travelers through the best back roads to the Colorado border.

  • Throw an epic BBQ and get together to welcome a fellow forum member on a long trip. This is how some annual meet and greets got started and now people come from several states away to attend.

  • Or arrange a behind the scenes tour of a gator farm.

  • Or a behind the scenes tour of an aquarium to show how dolphins are cared for.


I am thankful that we have not had a major breakdown on any of our trips that I was not able to fix on our own.  Not to say we haven’t had a few scrapes to get through, there was the time that my auxiliary light broke off and destroyed my fender in the process on the Texas coast …

Or the frustrating time in Washington state that it took me over an hour to figure out that a mosquito had gotten into the carbs while I was changing jets and caused us to loose one cylinder a while later.

Or overheating issues in Utah.

Or the time a lady backed into the bike in Oregon

Or an Excursion crashed into us in Albuquerque.


It is practically impossible to plan every detail of an epic road trip ahead of time, you may want to spend longer in one place or less in another and lets face it, shit happens.  You may not make your motel reservation due to a wind storm that shut down the interstate, or it may take 3 days to ride the 101 across Oregon instead of 1 because you didn’t plan on being there on the 4th of July and getting stuck in 6 hours worth of parade speed traffic.  You have to be flexible and roll with the punches.

I’ve always said if everything went according to plan life would be too boring. Getting through those obstacles and deviations from the plan is what life is all about, you will always remember the time your engine exploded on the way to Grandma’s on Christmas Eve and you and your future wife nearly froze to death waiting for help, you probably won’t remember the same routine trip when nothing happened.

When you break down and things are looking dim just remember someone will be along to help you out of the jam and think of it as another opportunity to meet more interesting people.  When things are at their lowest it can only get better right?

Look forward to what you’ll see over the horizon when you get back on the road and what a great story this will be when you get home.

Ride Safe.