Swingarm gear oil - does some "hide"?

[aj.bauer]

Hi there,

I am looking for a sanity check: I set out to replace the fluids in my 1965 R50 /2 today given the riding season is starting to run out in Minnesota, and noticed only 70ml came out of the swingarm. I have exactly 120 miles on this machine since finishing restoration, and my notes say I originally filled with 150ml per the Barrington Motor Works guide. Does anyone have similar experience draining the swingarm oil where less than expected drains out, or did I screw up filling it?

The final drive drained 150ml as originally filled, and the transmission drained 800ml as expected so fluid migration isn't likely the cause. I wonder if, perhaps, some swingarm oil doesn't drain completely as it may rest behind and beneath the swingarm drain hole within the mating final drive housing. Looking at the layout it seems most oil should drain out, but I could be wrong. Your input would be helpful as I do not want to overfill the swingarm.

Any help out there?

[Twocams]

I have got more out the swing arm but not less. I would turn the rear wheel a couple times and leave the drain plug open. Is it possible there could be some in the rubber boot? Sorry I dont have a book in front of me to look at. If it will fill to the right level with the 150ml then it will be full. Without running all over your shop floor of course. Just my thought but it is late in the day.

[aj.bauer]

Thanks, I'll try turning the rear wheel and massaging the rubber boot with the drain plug out. In the mean time, I did manage to refill it with 150ml, without a mess, but my assumption is the swingarm would hold much more than that before topping out at the fill hole. If I did lose 80ml and now added 150ml it will be at 230 total which probably isn't end of world.

[schrader7032]

IIRC the correct fill amount is 100cc...it went to 150cc in the /5 models because the volume of the shaft was bigger. I do think you can't drain it all out because of the orientation/angle of the drive shaft. So if it were me, I'd only put back in what you drained out. In reality, only a small amount is needed, something like 50cc or so. It moves back and forth when accelerating and braking. Plus the oil doesn't breakdown quite the way engine oil does. There's no contamination and no heating, although there might be some shearing of the molecules. But changing it isn't as critical as the engine oil.

[aj.bauer]

Thanks for that input as well Kurt. I will drain and refill more conservatively.

Only having 120 miles on the original fill wouldn't normally prompt me to change the swingarm oil, but I realized the gear oil I originally used was in fact GL-5. There is some popular advice out there to avoid GL-5 in favor of GL-4 so decided to switch to the GL-4 throughout as long as I was separately changing engine oil at this time. A good project for a cool, fall day in Minnesota.

Cheers!

[schrader7032]

Are you still having "cool, fall days" in Minnesota? I'm originally from St. Paul, but it's been a while since I spent any time there except during the summer months. As my Dad often says (also born in Minnesota), weather there is 9 months of winter and 3 months of poor sledding!

[Discogodfather]

Are you sure there is no transfer going on to the rear diff? That's usually where oil ends up going and why there is less than normal oil in the swingarm.