Wednesday 30 December 2020

Ever heard of ... BMW R86?

Attention, here comes a bit of smart kit - a BMW R86. This isn't a typo, but a bit of clever mix 'n' match game. So what we started out with here was a BMW R45, which in its first stages of life grew to a much more healthy R65. As you surely know, a R65 runs a 82 x 61.5 mm bore and stroke combination. Now there isn't much wrong with that. It's a bit bland in stock configuration, the phrase "not quite a powerhouse" springs to mind, but it's a very decent commuter.

Let's just say there's no replacement for displacement and we have a little gander at what else BMW has got on the shelves. A BMW R100S runs a bore and stroke combo of 94 x 70.6 mm. I say I wonder if that could be made to fit... (As this is a blog post on the conversion you obviously know the answer already!)

To be fair, there's a German company who sells it as a kit for such a compelling price that I haven't even bothered putting the same kit together myself. 

Four nuts holding the rockers on plus two more holding the cylinders to the heads.

The pushrod-tube-seals were well and true past their prime. They hadn't started leaking (yet), but honestly it would only have been a matter of time.

Splitting heads and cylinders is easy as there are studs poking out, which only take a gentle tap and then release the lot.

BMW gudgeon pin clips are probably made from the toughest and most springy steel known to man, but other than that, there's not much to installing those pistons and cylinders.

Only a smear of sealant around the two top studs is required, the rest relies on the o-ring. Let's see if this is going to leak.

Nice thing about this job, there's only one actual special tool required and that's a special spanner for the exhaust nut.

Fire the old girl up...

... and run her in gently. 😏

A bit of rejetting and some other carb-work might be due, as it originally had fouled one plug, because of a certain lack of synchronization.

And another shot of the bike as I am actually quite fond of it, but don't let Chris now or he'll take the piss of me forever for that statement.


So what's my verdict: if you already have a high-mileage R45/65 said kit is well smart and if the pushrod tubes are leaking, well not that much extra work to do. I admit with the engine being rather short stroked, it would benefit tremendously from a free flowing exhaust and different carbs and if you wanted it a bit more sporty, you'd probably throw in the right kind of cam and then end up with a nasty backroad-scratcher until the cylinders touch the ground. I admit I have just been checking ebay and some other sites for one of those unloved Dutch army R65 GSes... luckily there aren't any for a reasonable price at the moment.

Monday 28 December 2020

Turbo TR1 - if it ain't blown it sucks

Let's be fair, the last thing I need is another project. But this little gem fell into my lap without asking me for permission.

What you see here is Aisin's finest, an AMR500, named so because it displaces 500cc of air per revolution.

And here it is next to the local standardized gauge vessel for liquids, also holding 500cc.

As the department of motor vehicles only excluded draw-turbo charging, I might just give it another shot with a supercharger and get the old girl on the road this way. Should be good fun either way.

Monday 21 December 2020

The XV sidecar - building the rest of the engine (pt.4)

Last time we left off with me hoping that the courier service wouldn't let me down. Well, it was more than a week, so probably some things happened. Even without immediately having all the parts at my disposal there was a lot more that could still be done. 

First was to assemble the rotor and mark out the correct position on the teeth (you basically do this blind).

Then clean out the oil-pickup on my oil-pump (Gears were fine, yet still...) and install it

As the 750 clutch was missing some parts, it was about time to overhaul that one as well. Springs were overly compressed and the clutch disks completely worn.

As the center bolt on v-star cylinders is longer (M6x100mm to be precise), I had to get a set of those

The other thing was to clean the pistons, as unlike last time on Bumblebee, these were in very good condition, except for the oil-scrapers, which had failed prematurely. A bit of spray-on gasket remover softens the baked on carbon and makes it easier to clean.

But these are just the cosmetics, not pointless, but mostly cosmetics. The important part are the ring-grooves. In order to clean them, you need an old set of rings, of which you clip off a piece or two and then scrape the grooves until they are free of carbon buildup.

Before scraping, after just a light brush with a SOFT brass brush.

And after an hour of thorough cleaning. As a result now the rings move freely in their grooves again.

With the pistons good to go, it was time to focus my attention on the heads. In general the ports on these heads need a mild touchup and not much more, at least not for road use.

I am fully aware, that polishing valves is more or less pointless... but they look too good AND it slows down carbon buildup on them. 

In order to reduce the seat pressure, I mix and match harder and softer valve springs in the hope of getting a bit more life out of the rockers. 

I know these are somewhat debated amongst SR/XT-users, but I love swivelhead valve adjusters as the grant much longer life to the valve stems due to the greater contact patch. Downsides? Heavier and at some point the ball will wear down resulting in the adjuster screw touching the valve and thus resulting in the adjuster breaking. (Ask me how I know...)


6205-Z single sided, metal-shielded ball bearing instead of the stock ally journal. 


Plenty of assembly lube on the cam.

All assembled. The blue line on the bolt means, it's loctited in. If you can't build an engine in a single go, you have to have some signs for yourself which of the jobs have been tackled and which haven't. (Another one would be my habit of painting the alignment dots on the cam-gear with white paint, so I know the corresponding cylinder has been timed up.)

Tapping the spark-plug thread, because there's not a lot like screwing a spark-plug in a freshly cut and oiled thread.

The camchain adjusters needed some attention too. In stock form the v-star adjusters are too short to work in an older Gen1 engine case with the correct tensioner blades. 

The new buttons have a 16mm head diameter, which is 7mm tall (compared to the stock 2mm) and the bit that goes into the tensioner is 8.6 in diameter and you can basically make it as long as you like, but I went with 6mm. Material was slightly better grade mild-steel (St.52), because that's what I had on hand and it machines lovely.

As I plan to run VM38 carbs on the sidecar and the VM38-200 inlet rubbers don't have any provision for vacuum ports I installed them right in the cylinder heads. The tubing used is 6mm ally tube with 1mm wall-thickness.

And one last tip: if you ever want to use your oil-filler cap again, you will have to trim the bottom most cooling fin of the front cylinder. 

And there you have it: a XV and XVS1100 hybrid.

Not going as far as to say it's ready to be bolted in, but it's quite a bit closer now.