And, late spring update!
"That which is worth doing, is worth over-doing." -Anyonymous
Rarely before has that axiom been so true as on this R65 project. . . in addition to the head work mentioned above, I did the following projects this winter.
Bought new Nikasil cylinder from eBay, around $120
Stainless pushrod tubes and new pushrod seals
New exhaust valve, 4 new keepers for intake and exhaust
New head gasket and cylinder base o-rings.
That took care of the head. As mentioned way above, I also did the timing chain, crank sprocket and the rest of the timing chain parts like both tensioner rails, the tensioner piston and the spring. Unlike the later 911 motors, chain tension is set by a helical spring acting on a metal piston which pushes on a metal tensioner with a plastic face. But it works well enough in this application.
"While I was in there" I also decided that the pipes were absolutely trashed, which is where they went. Siebenrock has commissioned new exhausts in stainless steel from a manufacturer out of Italy, so I sourced a set of those and they are both visually and sonically appealing. (There was a set of NOS Zeuna available on eBay but I decided to leave those to a "restorer.")
The headers were sent to Jet-Hot for their 1300 coating in silver. They claim all kinds of benefits for this coating, in addition to reduced pipe temperature it will evidently improve your LDL cholesterol and regrow hair, but it looks nice enough and won't turn blue with heat like a set of new headers will.
Shaun at Tru6 contributed to the project- Cerakote on the timing chest, starter cover, battery box and airbox, with clear cerakote on the front cover. I can't say enough positive things about the quality and attention to detail that Shaun's team puts into the work-- and the Cerakote will be much more durable than powder and thinner besides. The coating was removed from the fins and the B M W script as original.
Once I got it back together there was a little fiddling to get it started-- this bike, being an '81, has the '81- hall effect sensor in the ATU (also called the "bean can.") As such, you can't use a test light to set the static timing the way you could with the "points in a can" version.
The ATU has two ears on it that capture some short allen screws, you can rotate the ATU clockwise or counterclockwise to set the timing. Since the camshaft turns clockwise as viewed from the front, if you rotate the ATU clockwise, you are retarding the timing toward OT (top dead center). Likewise if you rotate it counterclockwise, you are advancing the timing away from OT.
I put a zip-tie to hold the clutch in and used the starter to crank the engine until I could see the "S" or "Spätzündung" (retarded ignition) mark in the timing window. This was enough to get the engine to start. I then let it warm up and revved it to around 3500, and could see the "Z" (Zündung, ignition) mark in the window. That took care of both ends of the timing, and the engine started right up.
I ran it for a bit then adjusted the valves again. The right exhaust rocker is still axially loose and making noise, I need to put a c-clamp on it with some spacers to tighten up the clearance which should quiet it down a bit.
Also over the winter I sourced a good R45 original seat from Germany. The tail trim I had was from a '79- bike so it fits but it's not quite right-- fortunately the part is still available from BMW in Germany and wasn't that expensive with my discount from my buddy at the BMW dealer, so that will be installed later in the summer.
The side stand had been drilled out by the PO to accomodate an SAE bolt, so I found the later retrofit kit for the 81- side stand and installed it with new springs. I am a big fan of the Factory's auto-retracting side stand for safety reasons.
