Vintage BMW Motorcycle Owners




Knowledge Base




Snowbum's BMW Motorcycle Repair & Information Website

The ads above are Google-sponsored.
Clicking on them at every visit helps support this website.
Clicking on something in an advertisement helps even more!

How to replace an oil level "sight glass"
on early Oilhead and K bike BMW motorcycles
O12   K24

I claim no copyright for this method of using a red-hot screwdriver.   This method is simple, easy to do, and leaves no bits of plastic in the oil pan; and, NO DRILLING REQUIRED.

The idea for this method was provided to me in May 2012 by Tom Cutter,; located in Yardley, PA.  Tom is a well-known expert BMW motorcycle repairman. I liked the simple idea so much (why had I not thought of it myself?....) that I asked Tom for permission to post it here .....and I removed my old recommendations (screw method or knocking out from inside if pan was off).

I have edited Tom's information; but, want him to get full credit for his idea.  I also want to note that this method is, in MY opinion, applicable only to the old Oilhead and old K bikes, which do not have retaining clips for the sightglass.

Every 'oil level sight glass' I have worked on, so far, except for some very old antique, or industrial engines, has been plastic.

Use an old wide flat-blade screwdriver about a foot long, DO NOT use a Phillips type.

You will need a method of heating the tip area of the blade to red hot.  A propane torch is fine, so is an oxy-acet outfit. You will need a small piece of wood as a fulcrum for the screwdriver.  You can use an old screwdriver or hammer wood handle for this, or whatever you have.

Draining the the motor oil is NOT necessary; but, if the sight glass weeping or dark discoloration is not serious, you might consider waiting until oil change time.

The first two steps (1) and (2) ensure that actual oil level is well below the sight glass.  If doing an oil change at the same time, (1) and (2) are not needed.

(1)  Tilt the bike to the right for Oilheads.

(2)  Put the bike on the side-stand on Classic K bikes (K1, K75, K100, K1100).

(3)  Heat the screwdriver blade tip until it glows red for about 1/4" back.  Immediately push the heated tip right through the center of the plastic 'sight-glass'  ...and then immediately pull the screwdriver out ...and let it and the plastic cool.

(4)  With the screwdriver now approximately back at room temperature:
Use the piece of wood, etc., as a fulcrum with the screwdriver, and lever the sight glass out.  DO NOT dig into nor scratch the case bore by ham-fisting the removal, be careful of the depth and angle of the screwdriver tip!!

(5)  Clean the seal bore area using a clean rag & evaporating solvent;  then, dress the bore with a bit of 600-grit Wet-Or-Dry paper that is wetted with solvent or light oil to remove both any old stuck-on rubber and to remove any burrs at the bore edge.  I suggest you leave a faint radius at the edge for ease of installing the new sight glass.

(6)  Clean the bore again with a decent evaporating solvent.  You do NOT want the surface oily in the slightest.

(7)  Smear some spit or water on the new sight glass seal OD; and also on the ID of the bore. Push the new sight glass into the bore.  Do this squarely, straight & even, until it bottoms.  You can use an old socket or other round object that fits the O.D.

Press evenly onto the OD without your socket tool overlapping onto the engine case.  Install squarely to correct depth.  Don't let the sight glass go in crooked, and do not press on the plastic sight portion.

(8)  Refill with oil if you drained it.

(9)  Start the engine and test for leaks ...go for a ride ...check for leaks during the ride.

07/22/2012:  Revise to show tilting the bike to right for Oilheads, and that using the side-stands are for K bikes.
10/14/2012:  Add QR code, add language button, update Google Ad-Sense code.
 2013:           Remove language button coding, it caused javascript errors in some browsers.
10/04/2014:  Clean up article and make it exactly a step-by-step procedure.
03/29/2016:  Update metacode.  Clean up layout, fonts, colors.  Minor improvements in the text.
11/18/2016:  Metas, scripts, and large cleanup of excessive HTML codes. Minor clarity improvements.
04/25/2018:  Reduce HTML, colors, fonts a bit more.  Add 10 pxl margins.  Minor improvement in instructions.
06/12/2020:  Minor editing for wording and grammar.

Return to Technical Articles List

Return to HomePage

Last check/edit: Monday, December 07, 2020