76 R90/6 - progressive suspension question and oil choice

found someone locally who has brand new rear progressive suspension P/N 12-1203B for sale. is that the right choice for a 76 R90/6? a couple of websites say it's right for a R90S or just "R90" but then a couple of websites say otherwise, something about series 412. they're 13.5" eye to eye shocks.

also it's about time for me to do my first oil change in this bike. what should i use? thanks y'all.

As for oil, there's a recent discussion of oil here:

https://forums.bmwmoa.org/showthread.php?96310-81-r65-proper-oil

From some quick looking I did, it suggests they're not right for the basic /6. Seems strange...if the eye-to-eye length is right and there's enough adjustment range in the shock, it should be OK. If it was good enough for the R90S, should be OK for the R90/6.

Of course there are plenty of alternatives. Ikon (rebranded Koni) makes a nice shock. Tom Cutter and Ted Porter offer shocks that can be built to suit your specific bike, riding style, and touring loads on the bike.

According to the Max BMW parts fiche, the R90/6 and R90S part numbers for the rear shocks are the same for both bikes.

The oil question will get you several responses. My longtime German BMW mechanic says conventional 20-50 motorcycle oil in any airhead.

k12lts said:

According to the Max BMW parts fiche, the R90/6 and R90S part numbers for the rear shocks are the same for both bikes.

The oil question will get you several responses. My longtime German BMW mechanic says conventional 20-50 motorcycle oil in any airhead.

Click to expand...

That said, high ZDDP (aka Zinc) is a critical oil component for these bikes. Many "conventional" 20-50 oils do not have this at sufficient quantities to protect the valve train.

Read this for recommended oils that protect airhead engines. --> https://bmwmotorcycletech.info/oilcansimple.htm

I hope that helps.

Best.
Brook Reams.

Methinks conventional as used in k12lts post means dino oil, and most 20-50 "conventional" and synthetic motorcycle oil includes a zinc component.
This is an oil thread darn it!
While synthetics now have modifiers that allow use with older type seals, I still use dino oil in the engine/transmission/final drive on Airheads.
Bill

brook.reams said:

That said, high ZDDP (aka Zinc) is a critical oil component for these bikes. Many "conventional" 20-50 oils do not have this at sufficient quantities to protect the valve train.

Read this for recommended oils that protect airhead engines. --> https://bmwmotorcycletech.info/oilcansimple.htm

I hope that helps.

Best.
Brook Reams.

Click to expand...

I agree on the Zinc, that's why I specified "motorcycle" oil. Conventional means non-synthetic.