Bruce -

Welcome aboard !

► Generally, if one sticks to a solid plan to change the oil every 5000 miles, and is using a name brand oil, then there is no need to drain the oil cooler system. The oil in the cooler represents ~2% of the total oil, and when mixed with 98% new oil after an oil change, means it simply doesn't matter. Consider that 2% of the oil in your car is also trapped in hydraulic lifters, oil galleries, and oil puddles atop the cylinder head... but no one looses sleep over that!

Issues with the oil cooler come from other sources:

• There is a on-going need to get into the engine's front cover. There is a particularly troublesome electrical connector that will shut down your engine without warning. There are also 2 alternator brushes that need replacing every ~50K. To get to these items the cooler must come down, and this can end in a tangle of hoses if not done in conjunction with an oil change.

The white ignition connector often disintegrates with age

• Another issue (it is not a problem) is that the cooler is higher in elevation than the filter, and oil can tend to drain over night. (To prevent drainage, I purposely look for cars and motorcycles where the external oil filters are mounted hanging down.) So you might want to carefully listen to your engine for metal-on-metal just after the first start-up of the day. That first 10 second is critical for engine longevity.

• Excessively noisy startups can point to a bad thermal valve inside the oil filter cover. And these valves do get stuck in a half-way position allowing oil drain down at night and very poor oil cooling during the day.

• Then there is the simple issue of the age of the hoses and sealing washers themselves. Continued flexing during maintenance and a never-ending barrage of stones thrown up by the front wheel. Replacement hoses are offered with steel braid exteriors. 

• Lastly there is the easy mistake of inserting the wrong dang oil filter! The minor differences between oil cooler and non-oil cooler filters can be lost on the novice.

To tell you the truth, if the oil cooler gives me any problems (real or perceived) I simply remove them and revert back to the pre-cooler cover and filter. I can do this in the mild climate of GA, NC and TN where I ride. Not recommended for 100°F summer ambient in AZ or west TX !

► I cannot speak to the differences in the 2 Spectro oils you mentioned. Spectro is not sold in my area. I use Valvoline VR-1 20W50 which has the appropriate API rating of SF/SG/SH with the "zinc package". This is sold locally in auto parts stores in 5qt jugs for ~$20. With oil changes every 5K miles, synthetics are not really needed. 

However, I would most definitely look for synthetic gear oil for the gearbox, drive shaft and final drive, and change those once a year. In those applications, synthetics result in better shifting and cooler running temps.

Hope this helps.

@wobbly I very much appreciate your reply. I've been waiting as patiently as I can. So, you believe that the spectro heavy duty 20w50 is ok I take it?  Read alot about the need of zinc in the oil on our bikes. The oil cooler did hang overnight while I figured out the correct number of shims. Filter assembly is back together now. So, just add the oil ( not sure on exact quantity)  3.? Quarts. And crank it with the carbs dry and petcocks off for 2 - six second intervals and then crank it up?  Also, where would I source the alternator brushes?  My bikes at 51,000. Any other maintenance you'd suggest. Drive fluids I assume. Suggestions on brand and types of drive fluids would be greatly appreciated. thank you in advance 

Posted by: @bruce-suehr

So, you believe that the spectro heavy duty 20w50 is ok I take it?  Read alot about the need of zinc in the oil on our bikes. 

That is NOT what I said. I have no opinion on Spectro.

So, just add the oil (not sure on exact quantity) 3 quarts? And crank it with the carbs dry and petcocks off for 2 - six second intervals and then crank it up? 

Fill according to the dipstick, crank the engine and re-check. The dipstick is NOT screwed in for checking oil levels on an Airhead.

Also, where would I source the alternator brushes? 

At a dealer. I like Max BMW, but Bob's BMW is also delightful. They both have on-line parts fiche to verify part numbers.

The only dealer I do not like is Capitol.

My bikes at 51,000. Any other maintenance you'd suggest.

Bruce, I listed everything in my first post. You may wish to re-read it. I don't answer the same question twice.

Drive fluids I assume. Suggestions on brand and types of drive fluids would be greatly appreciated. 

• Gear oil: Valvoline 75w140
• Per BMW, DOT4 brake fluids are changed once a year. (If you completely evacuate the system you can convert to DOT 5 Silicone (ala Harley-Davidson) which is good for ~10 years.)
• Fork oil: BelRay 7W fork oil
• All grease points, including wheel bearings and head post bearings

Thank you for your help

@bruce-suehr You're certainly welcome, sir.