The Sump Plug FAQ
compiled & edited by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.

Classic Oil Change:
GS Oil Change:

So far, this only afflicts the Classics ...!

Don't Over-Tighten That Sump Plug !
by Steve#001,Flash#412 & Kristian #562
Created 11/28/99, Updated 03/03/02

The Problem

This is MAINLY a Classic Problem! OK, so you recently did your Oil Change and now your sump plug is leaking? Well there a few causes of the problem, but fear not, there is repair kit for this if you have stripped the threads. The best thing however is to avoid stripping it all altogether.

This Photo shows the left half of the crank case for a Classic F650. The stock drain plug is in place, off to the left. In the fingers is another drain plug that Harl made out of a fill plug for a K75 transmission, to which he epoxied some rare earth magnets, being held up next to the case edge. You see that white plastic thing held in by the bolts? That is the edge of the filter screen that occupies the space ABOVE the drain area, which is the space between the screen and the bottom of the sump where the plug goes. (Those bolts also hold a little "windage" deflector in place.). I had thought that the screen was to protect the intake of the primary oil pump. It appears that it ONLY covers the crankcase drain, keeping the big chunks inside the crank sump. I believe ALL the screen does is keep the stripped sump threads out of the rest of the motor.! Flash# 412


This (slightly focus-challenged) picture, shows WHY Harl made the other plug.



The BMW Repair Kit

Q. What is IN the BMW Sump Plug Repair Kit & How do I get out the Old Plug?
A. The BMW repair kit ($110 when I bought it) is a slightly oversized 18 mm bolt with self tapping threads. In the center is a threaded hole and a much smaller bolt with an Allen head. The smaller bolt has a matching crush washer. That's it.


Big thanks to Todd#389

Are there Alternative Plugs ?
by Todd#389 & Flash #412

Q. Are there unused threads in the case when the stock plug is screwed in? i.e. Would a longer plug really work?
A. Absolutely. There are three or four unused threads in the case when the stock plug is screwed in. And CLEARLY there is lots of room, maybe 6-8 mm, between where the screw emerges from the case before it hits the screen.

M18x1.5, max 10mm thread intrusion, max 24mm shoulder - for the Classic, not for the GS. My OEM plug has 4 threads on a 9mm shank and a magnet.

Homemade Plugs: Details of the OEM Plug

Quick Changer Oil Change Plug:


I thought this product looked especially interesting, given the annoying F650 sump plug. I emailed (highly recommended btw, they have very good service) and confirmed that the K plug is 18 x 1.5, and therefore should fit the F (although I did not confirm the shoulder measurement).

Freeze Plugs:


This a universal sump plug. Since it is too long, I will shorten the rubber by 0.5 cm. The instructions say that it is not recommended to reuse. The final plug after a little trimming is shown in the RH pic. It fits perfectly and (so far) no oil leaks. I've tied one of the wings to the frame, but it is not going to be sufficient if it bumps into something serious. To tell the truth, I didn't even remember that the plug was exposed and not covered by the plastic. This is the reason I opened the wings, to make it shorter in case it was. At the present, I am not planning any off road. gim '97 F650, Waltham, MA. gim'97 F650, Waltham, MA.


I bought my 1997 ST used a couple of month ago and it arrived with a rubber plug in it. The type with a bolt inserted into the centreline. When you tighten the bolt it increases the diameter of the plug filling up the already mostly ruined threads. After my first oil change and 2k miles it is still holds drip-free. Maybe I am willing to invest the sum of $10 for a new one.


K-Bike Sump Plugs

Magnets for Sump Plugs

Where is the Oil Pickup ?
by Flash#412

There is a little screen in a plastic frame that is about two inches (~5 cm) square. See picture above. This screen sits in a horizontal plane in the center of a void. The drain plug pokes up into the void below. The oil pickup occupies the void above. There is a little sheet metal piece that serves three purposes bolted to the case half there. First, it keeps the screen in place. Next, it serves to close off the upper void, effectively requiring all oil sucked into the pickup to come THROUGH the screen. And finally, it has an appendage that serves to control oil slosh in the bottom of the crankcase. The mating area on the other half case is... non-existent, except for the outside perimeter. This allows oil in the bottom of the case to freely flow into the void above which is the screen and below which is the drain plug.

The first photo shows the pickup parts in a state of disassembly.

This shows the bits all assembled. I put a red mark on the case for reference.

This red mark more or less mates with the red mark on the case opposite the pickup.


Stripped Sump Plug Feedback

Newly added Section so not many Cases Reported here, but it is fairly common on the Classic