Front suspension ??

1985 R80;

I drained out my old fork oil, (no telling when it had last been changed by p/o's)
boy was that stuff nasty looking and smelled bad !

According to the info I received when I bought the bike it has a set of Progressive springs installed.

I was unable to find any "specific fork oil" at a 3w or 5w so I replaced it with ATF.

I added 10 oz in each leg, via the small hex bolts in the top caps on the forks.

The front feels softer and more compliant now, but now I notice a sort of knocking sound over a series of bumps.

I cannot compress the forks all the way with the front brake applied and rocking the bike forward at a stand still , and do not hear the knock , only when i was riding ???

I am also curious about tire pressure ?
Motorcycle is fitted with Pirelli Sport Demons, I have been running 33lbs front and 38lbs rear.
The bike seems to ride a bit hard or harsh to me.

Thanks, Doug

You can use Bel Ray 5wt, or the BMW 7.5wt fork oil. I use the BMW since it is recommended for R bikes, and it is not very expensive. I think it was about $5 for my R90.

My forks were sticky and creaking, and the oil was like you said: NASTY!

I don't have any experience with ATF in forks. I'd consider the ATF as a wash and flush, try the BMW oil, and see what happens.

If you still have problems, tearing the forks down for an inspection rework would be my next step if it is bothering you or affecting the ride.

I will look again to see if i can find some fork oil locally ( tried a couple mostly dirt squirt shops, no luck)
I think you are correct that the ATF is a good flush product , but i wanted to try it and will probably go to a specific fork oil if i can find it.

You're in the Piedmont of NC. That's like what, Winston Salem area? I think there is a BMW shop in Charlotte? Certainly one here in Raleigh. And Advance auto carries motorcycle stuff. And you can get Bel Ray on line. I know we have a lot of independent shops in RTP area so I'm sure you can find it. Heck, if you can't, I'll buy you a bottle from Capitol BMW and meet you half way for lunch. I ride for fun all the time, so it's not a big deal to actually have a destination.

Let us know how it goes. I really hate tearing down forks. Probably more than rebuilding a transmission.

And make sure you let the fluid drain out for a good 15 minutes or so so that you are not overfilling by leaving old oil in there. My manual shows something like 9.8 to 10.2 oz oil, maybe try 9.8.

Thanks,

I found some BelRay 7w at a small Suzuki dealer close by today.

I will drain out the ATF in the next day or so and replace it with the fork oil.

I put in about 10 oz of the ATF just takes a while because the port is so small and i do not have a wrench large enough to remove the actual fork caps.

I had planned to ride down to the Charlotte dealer this Sat, they are having some sort of an event, but the weather looks like it may be a bit funky.
I am usually up for a ride, lets try and hook up in the next couple of weeks.

Doug

There are two different ways to measure the amount of fork oil, volume and level. When I replaced the springs on my bike, the level was specified. In my case, it was with the top caps removed, along with the springs, and the forks fully compressed, then add oil until the level was 5 inches from the top. Stroke the forks a couple times then measure again, add to achieve the 5 inches. Then put the springs and any spacers in along with the cap. I'd recommend checking with Progressive for specifics for your bike.

manicmechanic said:

There are two different ways to measure the amount of fork oil, volume and level. When I replaced the springs on my bike, the level was specified. In my case, it was with the top caps removed, along with the springs, and the forks fully compressed, then add oil until the level was 5 inches from the top. Stroke the forks a couple times then measure again, add to achieve the 5 inches. Then put the springs and any spacers in along with the cap. I'd recommend checking with Progressive for specifics for your bike.

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I never had any luck with the volume method. It never balanced between forks.

Level from the top of the fork is much easier. Steal the turkey baster from the kitchen, mark the tube with a marker or tape and use the baster to remove any excess fork oil. Keep the baster with your tools and blame the dog when your wife is looking for it on Thanksgiving.

BTW, big difference in oil viscosity between brands. One brand's 10W is not the same as another's. The info is out there if you search.

ATF fluid

ATF fluid - which is a hydrlic fluid about 5 to 7 w is good to use in forks.

Dextron is a little lighter than Ford type F or Mercron.


ATF fluid was what was called for before there was special fork fluid.


My guess is they can charge more for special fork fluid.

tommcgee said:

BTW, big difference in oil viscosity between brands. One brand's 10W is not the same as another's. The info is out there if you search.

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Yep, I was told the Bel Ray 5 is the same as BMW 7.5. So Bel Ray 7.5 might be too viscous?

knocking noise

I have an 85 R80RT that made that same noise, the cure is shims that take up a small amount of free play. The shims are about a half inch thick. That knock was a problem with 85's only. MY 86 R80 never had that issue.

97077 said:

the cure is shims that take up a small amount of free play.

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Is part #16 the one you refer to?? They come in thickness from 0.1 to 2.0 mm. Did you really mean 1/2 inch??

RoboRider said:

Yep, I was told the Bel Ray 5 is the same as BMW 7.5. So Bel Ray 7.5 might be too viscous?

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Here's a fork oil wiki with a long ton info: Suspension Fluid Wiki

shim

I looked at the fiche photo on Max BMW parts and that's the shim but I thought it was thicker, sorry. I put that shim in and that took care of it. That little knock is annoying but fixable.