Replacing a leaky oil pan gasket on BMW airhead motorcycles

pangasket.htm
50C

Trick/hint: Using a small 10 mm box end wrench or a SMALL square drive wrench with a 10 mm socket, try tightening the 14 pan bolts, but not over 75 INCH-ounces.
If any of the bolts have bad threads, note which ones, mark the case, so you can fix them after the pan is off.
(You don't want to replace the pan gasket and find you have bad threads at any of the 14 threaded holes)

This first section is a copy, edited, of a short thread on the Airheads LIST. Please read this section, and then read the rest of the article.

"I replaced the leaky oil pan gasket on my 1973 r75/5 with a high quality silicone gasket. I had a terrible time getting the original gasket off (stuck on the oil pan side). After getting the original gasket off I lightly sanded the oil pan with 400 grit sandpaper, cleaned surfaces, and installed. Well I still seem to have a leak (perhaps even slightly worse). I plan on taking the oil pan back off after I try to find the exact location of the leak with talc. I will get a better torque wrench and follow guide lines (6 ft-lbs) I found on other threads. My question: Are there any other tricks to avoid leaks? Perhaps something applied to the gasket besides adhesive?"

Snowbum replied:

"This is a generic reply, for MY method of dealing with pan gaskets.

BEFORE removing the old gasket, I use my personal hand-feel on the 10 mm bolts (you can use a torque wrench) to identify any threads that are being pulled out. Finding out about a pulled thread is best now, and not after you start torquing up the new gasket.

I never EVER use silicone pan gaskets....nor ANY type of sealant, silicone or otherwise, on the pan gasket surfaces (that means engine and pan metal surfaces). I make sure the pan is flat, nick-free, and install a STOCK gasket, on very well cleaned surfaces (some gasket remover products work pretty well, if you are leery (and I suggest you be VERY careful anyway) of using sharp tools in cleaning off any old gasket and sealant residues.

Any sanding of pan surfaces MUST be done on a FLAT surface, such as an old piece of window glass or a real Surface Plate. I use even pressure, and figure-eights, varying my hand position, etc. Don't do sanding unless there is a problem! You can use a lamp or flashlight at the pan-to-flatplate surface to see any problems...or, as I do, with a very thin feeler gauge (.002" happens to be the one I use).

After the pan is known to be flat and without serious nicks (DO NOT nick with your scraping tools!), and ALL old gasket crap is removed from engine and pan surfaces, and the surfaces cleaned (I use ACETONE on a rag), I install conventionally, and I torque very evenly, in a cross-pattern (very important), and for the first go-around, I use a quite low torque. I hold the pan and gasket to the engine, then finger-in all the bolts first.

Then, I use a very small wrench. If you do not have a good feel for torque, use a good INCH-pound or similar torque wrench, after you get all the bolts evenly and LIGHTLY tightened. Always do any tightening in a cross-pattern...this is just plain good practice, and is IMPORTANT at the pan. It is very important to torque evenly, in a cross-pattern, and to do this in STAGES. That means any one amount of torque is done in a cross-pattern until all bolts are at that torque level, then increase the torque a bit, until all are at that next level. The idea is to NOT 'bunch up' that gasket. Of course, the idea is also not to over-torque the bolts and pull threads out of the engine.

Do NOT!! use a big torque wrench like we use for swing arm locknuts or for the cylinder stud nuts.

After you have ridden the bike some, and have a few heat-cool cycles, you can re-torque the 10 mm bolts.

If you find any leaks at any given bolts, you can remove the bolt and apply some common gasket NON-permanent sealant at the BOLT threads and under the bolt (and washer) head. Sparingly is the word on use of sealants.

If you are replacing the pan gasket due to leaks, first be sure that the leaks were from the pan mating surfaces. I have seen pushrod seals leaks, leaks from the oil sender switch, leaks from the high pressure galley, neutral switch etc., all appear to be pan leaks.

You will need a brand-new pan gasket. The early cork gaskets are no longer available and tended to leak anyway. The presently available gaskets are a fiber material, and are much better. They have a side with writing on it, that is coated with a heat-activated glue. That side is UPwards. NOTE: Gaskets have apparently been seen that do not conform to this....so just install the gasket in the correct fitment direction.

How to go about replacing the pan gasket, basics:

Tricks/hints: Using a small 10 mm box end wrench or a SMALL square drive wrench with a 10 mm socket, try tightening the 14 pan bolts, but not over 75 INCH-ounces.
If any of the bolts have bad threads, note which ones, mark the case, so you can fix them after the pan is off.
(You don't want to replace the pan gasket and find you have bad threads at any of the 14 threaded holes)

Bad threads are best fixed by installing Helicoils. You will want the M6 x 10 Helicoil kit.
You will need a 1/4" drill bit, unless your kit comes with the drill bit.

At the next oil change, drain the hot oil. Put a large and soft towel or other item on the floor, as the pan MAY fly off the engine. The pan may have been put on with a sealant, which is WRONG!.. thus, the pan may be difficult to remove. Occasionally even a pan that does not have sealant applied will prove mildly difficult to remove. HEAT a corner area of the pan if not already hot from riding. Check that every pan bolt is removed! There are 14. Use a block of wood and a substantial hammer and give the well-placed piece of wood a substantial whack from the hammer. Do NOT bust fins, ETC. DO NOT be stupid and allow the pan to fly across the area and be damaged. I usually have an assistant to grab the pan so it cannot fly.

With the pan removed, VERY thoroughly clean everything. It is critical that you do not nick the pan and engine mounting surfaces. Any projected nicks you find should be dressed flat. Rarely you may find a nick that needs filling, you can use one of the metal epoxies for that, then after curing, make it dead-flat. To remove the old gasket, if need-be, use a sharp blade on a very flat angle (nearly flat to the surface) to remove any old sealant or other substance found. Use a strong commercial gasket remover, if you wish. The crankcase surface absolutely must not have old gasket material and no nicks that have metal proud of the surface. Clean the area very well! Final cleaning of the crankcase surface should be by a good solvent that does not leave residue. I am particularly fond of acetone for this.