Torn apart and giving the engine a bath

The manual available for this bike is old, with terrible photos. So I am snapping shots of everything while I take it apart. How would this happen in the film days??? Expensively I guess…
Pixels are cheap.
More Photos to come…

Bridgestone 175 rear brake hub.  Looks like it will polish up OK.

Bridgestone 175 rear brake hub. Looks like it will polish up OK.

Bridgestone 175  rotary 2 stroke engine getting a bath in on the parts washer.  It was filthy.

Bridgestone 175 rotary 2 stroke engine getting a batch in on the parts washer. It was filthy.

Bridgestone 175HS rear sprockets.  I can't wait to clean these up.  They are a nice feature on the bike.

Bridgestone 175HS rear sprockets. I can’t wait to clean these up. They are a nice feature on the bike.

Airhead Oil Change warning and other ‘used motorcycle’ purchase issues

“Ran When Parked”

“Just needs gas and a tune up”

Ahhh… the phrases I am seeing in the ads when people are selling a complete hunk of crap.   I bought the last restoration candidate knowing I was going to do a full rebuild but the owner’s ad and conversations were trying to sell me on the fact that the bike could run with an afternoon’s worth of work.
WRONG.  I found all sorts of surprises when rebuilding that engine (and elsewhere throughout the bike).
The bike was an R75/5.

One issue was a deep in the engine when taking out the cam shaft.  The lobes were severely pitted rendering the cam useless.  The bike still would run but doing a complete rebuild was necessary to make this bike ‘right’.  I have a stash of spare parts and happened to have an extra cam shaft lying around. Here are some photos of the bad cam.  If you ever get this deep into the engine block (or at least have the cylinders off), take a look at the cam lobes.  If they are pitted, the lifters probably need replacing too.



Here is a simple oil filter change fault. 
If you don’t know the history of the bike, it is good to do a complete oil change as soon as possible. When replacing the oil filter, make sure that the entire old oil filter comes out.
In this case, the gasket and end of an old oil filter were jammed into the rear of the oil filter galley. I’m assuming that an old filter got removed, those parts were left inside, and new filters were installed on top of them, thus jamming them in there even further.  It took me nearly 20 minutes to devise chopstick like tools, with hooks on the end, strong enough to pull this stuff out.


Just another reason that the used motorcycle market is overpriced on 30-40 year old machines.  Unless you know the bike has ZERO issues like this deep down inside, the cost of repairing these motorcycles is much too high compared to the asking prices these days ($4000 for an old Honda? why?).

In addition to the engine needing a rebuild, the steering bearings were rusted (which is dangerous), the splines and driving dog were almost gone on the final drive and rear wheel, and LOTS of other repairs were necessary.  Again, I planned on doing all the repairs anyway but beware of the “Just needs a battery and a tune up” ads.

A quick look at Siebenrock pistons for a R75/5

These piston and cylinder kits seem to be the rage right now. I used one on the last build and had very little problems aside from the pushrod seals being extremely difficult to install.
The pistons are made to mate with the R75/5 heads and you can use the same carbs (might need to change jetting).

Here is a quick look at the piston and how it compares to a stock R75/5 piston that i have lying around.


It is a lighter, yet wider piston. The piston on the right has the rings on it still. The siebenrock doesn’t have the rings on it.


I didn’t measure heights when i snapped this photo but they seem close.

The piston in the cylinder. The cylinder wall is very thin compared to a R75/5 cylinder.

I haven’t heard of any issues with these yet. Supposedly they give you a 20% gain in power… so that makes it around 900cc.
I’m pretty sure they are cheaper then replacement BMW parts too.

Skateboards make good dollies

…and wives help when needing to hold it from rolling down the driveway…
And she kept me from breaking my back by trying to lift it out of the trunk by myself.

Dave Gardner at Recommended Service did the assembly.

I can’t wait to fire this thing up…
Siebenrock power upgrade Pistons and Cylinders.
Lightened Flywheel.
Newer oil pump cover.
New BMW valves and valve job.
/6 rockers.
Stainless pushrod tubes (as part of the Siebenrock kit).