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jackonz wrote: ↑Fri Feb 18, 2022 9:45 pm Right am going to pull the front forks out of the bike and clean them up, while I am at it I will of course drain the fork oil and replace with new, trouble is what oil and grade should go back in, most of the brands listed in the shop manual are either not made any more or not available in NZ, we are a small market you see.
As the grade of oil make a huge difference in damping and I have only ridden the bike about 10klm from where I picked it up to home it was really not long enough ride to assess the damping, NZ roads are quite bumpy and the national speed limit is 100kph (62mph) and here in the south island hilly and twisty, add to the fact am now 70 years young I really don't want to be riding like a racer, had I wanted to do that I would have kept the Ducati Monster.

So if anyone can advise on a good weight of fork oil given the above I would be most grateful, I do know we can get Spectro oil.

Stay Safe all

I've used Ravenol 5W fork oil in my '74 R90s (similar front suspension as your R80) with excellent results. You can buy it online. https://www.ravenolamerica.com/motorcyc ... -light-5w/

So here is an update having stripped off one fork leg and drained it and found it has either the original BMW Red oil or ATF fluid and measuring what came out it had the correct volume of fluid, I doubt it is the original oil given the bikes age and the fact the oil seemed clean and did not smell burned.

Checking on Snowbum's reveals a lot about the original oil BMW used as well as it's specifications and have found an oil I can purchase here easily that closely matches the original oil, I have always believed that before you make radical changes to start with the original settings and work from there, the oil is not expensive and is easy to replace should I need to shall we say stiffen it up a bit later on.

Interesting to note that the original oil has a measurement of 13.2 Cst @ 40 deg C and the oil I have purchased Silkolene RSF 2.5 has a Cst of 13.6 @ 40 deg C so it is quite close in spec.

In order to ensure a complete flush of the old oil I stood the leg inverted with the cap and spring out overnight pumping the leg several times and then flushed out the leg twice with new oil, then filled it with the correct volume of oil and setting the level as per Snowbum's data.

There is an interesting table on Snowbum's site on the fork oils and reveals just how confusing it is for people to be able to pick the correct oil they need to have the suspension working correctly, it will be interesting to see how it performs when I get my project completed.

So an update on the fork oil has resulted in more more work required, the Silkoline oil was filled to the required level in one leg and without the spring I pumped the fork leg against the floor and and pulled it back, not much damping really.
So after checking the net it became clear than the bottom bump stop in these forks are known to break down and turn in to crud, so I pulled off the bottom plug and yep all crud and what was there was no longer any form of cushion just a sold whatever it was originally.

So the question is if that's the case is all the guts of the damper going to be the same and need a full tear down.

I see Boxer 2 Valve Parts can do a full kit to overhaul the forks an has anyone used these if so are they any good, or is there a better option out there.