Sight glass

[mhallman]

Was able to change it out quite easily. Melted the plastic with soldering iron and used a screwdriver to pry it out in about 5 seconds. Probably the easiest thing I've done on the bike. It was certainly not far from letting go...

 

[DavidEBSmith]

Look into the bottom of the airbox, If you over fill it will pump the excess into the airbox. Bad things can happen to overfilled BMWs sightglass can leak and even pop out and seals can be blown and begin to leak. If oil is in the airbox, dump the oil and start again.

There is a drain plug in the bottom of the airbox (rear left as I recall) that you can remove and allow any oil to drain.

Also years ago somebody posted this this cutaway of the Oilhead motor showing just where the sight glass is with respect to the crankshaft and how much room there is for "excess" oil:

 

[fbt80]

That's correct, at least on my R1100s there are drains with caps on each side of the airbox to drain oil from, it comes into the airbox via the breather tube when the oil level is too high. The breather tube cannot be obstructed or pinched off in any way. If the tube is holed then out sprays a fine mist of oil over everything.
Not the greatest idea IMHO but what we have to deal with.

 

[dieselyoda]

Yeah, bad design.

Face flush seals have been around before I was born, a long time ago.
Anytime, rarely, I saw a face flush seal popped from it's bore and it was always due to excessive pressure.
Occasionally, a comeback from poor installation but that happened quickly, with a few hours of the repair.
If you wanna know how certain I am of that, crimp the breather tube on your differential.
Not a bad design. Just not enough preventative maintenance.

 

[BC1100S]

Not a bad design. Just not enough preventative maintenance.

Yes, a bad design, as witnessed by the updated and improved circlip-secured system on the Wetheads. Which doesn't require any "preventative maintenance" - whatever that might be.

 

[Omega Man]

Yes, a bad design, as witnessed by the updated and improved circlip-secured system on the Wetheads. Which doesn't require any "preventative maintenance" - whatever that might be.

“Preventive maintenance” would be checking to make sure the crankcase ventilation system is working. There is a lot of crankcase pressure generated by the pistons moving. The pressure has to be vented somewhere, frequently into the air cleaner intake system.
This pressure change even has to be taken into high-rise buildings with the elevator movement.
OM

 

[dieselyoda]

Yes, a bad design, as witnessed by the updated and improved circlip-secured system on the Wetheads. Which doesn't require any "preventative maintenance" - whatever that might be.

Kinda funny this topic has come up.

I gotta travel drive from a 65K tonne excavator that keeps blowing the motor seal. Pressure relief is set at 3200 psi.
The seal itself never blew out of the bore but this is it's second go in 3000 hrs.
We went in like a plastic surgeon. Very hard to ask the customer to give up $16k twice.
Slipper rings were a bit so-so. Shaft, a bit so-so. We will eat those costs as goodwill. That be a quick $4k out of budget.

Why now a snap ring on newer bikes?

I'm no engineer and never call me a technician.

But your comments have me wondering if the quality of mechanics on an assembly line has dropped or that there is another factor that made hegineers know and won't share.

 

[pglaves]

Voni's "1994" R1100RS was built in March of 1993 and we bought it for Mother's Day in May, 1993. It was almost, if not quite, a beta bike. With only a few thousand miles on the bike it blew out the sight glass near Salt Lake City, BMW got a new sight glass from Germany to the SLC dealership in less than 48 hours primarily because she was a damsel in distress with a new bike and because the VP head of BMWNA motorcycles in the US was there to sell a new bike to a well know movie actor.

Those sight glasses are/were a friction fit and the recess for it was machined just a hair too big on her bike. She had a second one blow about a year later. When I installed the replacement I could push it into place with my thumbs, no driving required. I didn't trust it so wasted it removing it and got another replacement. I got an adhesive black rubberized super glue (I forget the name) that BMW had earlier specified for use on the then two-piece crankshaft pulley and used it on the backside of the sight glass rubber - not the circumference - where it contacted the engine case. I didn't have to replace it again until it had discolored with age.

Now at 31 years old and 416,000 miles it is on its 4th or 5th sight glass - all but the first two stuck in place with adhesive.

 

[tangoalpha]

Voni's "1994" R1100RS was built in March of 1993 and we bought it for Mother's Day in May, 1993. It was almost, if not quite, a beta bike. With only a few thousand miles on the bike it blew out the sight glass near Salt Lake City, BMW got a new sight glass from Germany to the SLC dealership in less than 48 hours primarily because she was a damsel in distress with a new bike and because the VP head of BMWNA motorcycles in the US was there to sell a new bike to a well know movie actor.

Those sight glasses are/were a friction fit and the recess for it was machined just a hair to big on her bike. She had a second one blow about a year later. When I installed the replacement I could push it into place with my thumbs, no driving required. I didn't trust it so wasted it removing it and got another replacement. I got an adhesive black rubberized super glue (I forget the name) that BMW had earlier specified for use on the then two-piece crankshaft pulley and used it on the backside of the sight glass rubber - not the circumference - where it contacted the engine case. I didn't have to replace it again until it had discolored with age.

Now at 31 years old and 416,000 miles it is on its 4th or 5th sight glass - all but the first two stuck in place with adhesive.

Voni has 416,000 on her ‘93 RS? That’s absolutely incredible. What about you Paul, what kind of mileage do you have on your bike(s)?

 

[pglaves]

Voni has 416,000 on her ‘93 RS? That’s absolutely incredible. What about you Paul, what kind of mileage do you have on your bike(s)?

My '86 K75, "Old Smokey" was totaled after a crash in 2005 with 369,000 miles on it. My R1150R was sold with 189,000 miles on it. My current 2 K75s have 135,000 and 46,000 or so. Voni sold her other R1100RS when it had 172,000 miles on it. These things last a long time when they are properly taken care of.

 

[tangoalpha]

That’s incredible. BMW should hire you and Voni to be paid spokespeople for the motorcycle division.

 

[r0ckrat]

That’s incredible. BMW should hire you and Voni to be paid spokespeople for the motorcycle division.

But then they'd sell fewer new bikes... LOL! Everyone would start keeping them for 3-400k miles instead of trading them in for "new and shiny"!