1990 750 Sport fork oil

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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Nunodeo
Posts: 13
Joined: Tue Jan 21, 2014 2:28 am
model: 750 Sport
year: 1990
Location: South S.F. Bay USA

1990 750 Sport fork oil

Post by Nunodeo »

Thinking about replacing my fork oil, so I need a little help deciding how much oil to buy to refill both of my forks. Also wanted to know if you guys are running 5wt oil on your bikes. And, does anybody know exactly how much oil goes in each fork?
Any help would be greatly appreciated. Thanks
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paso750
paso grand pooh-bah
Posts: 5558
Joined: Sun Jul 18, 2004 12:00 am
model: 750 Paso
year: 1987
Location: southern Germany

Re: 1990 750 Sport fork oil

Post by paso750 »

You`ll need approx. 350cc per fork leg but how much oil goes in is not that important as the correct airgap. That`s 150mm (to the liner). All info that is mentioned in the manuals btw...

G.
Nunodeo
Posts: 13
Joined: Tue Jan 21, 2014 2:28 am
model: 750 Sport
year: 1990
Location: South S.F. Bay USA

Re: 1990 750 Sport fork oil

Post by Nunodeo »

Thanks G. I did see the 150mm airgap, and just wanted to confirm that was still holding true these days.
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bmw851
Posts: 322
Joined: Tue Mar 13, 2012 9:02 am
model: other
year: 1988
Location: The Blue Mountains, NSW, Australia

Re: 1990 750 Sport fork oil

Post by bmw851 »

Have replaced mine twice now in 2 years, used Repsol 15W first time and 300cc per leg on advice from my mechanic, and this time Belray 15W and 360cc which gave the 150mm air pocket as per the manual, I had replaced the fork seals so it was a complete fork legs off and cleaned out dry fill.

The strange thing is can't feel any difference in how the forks are working with the extra fluid, have a black cable tie on one fork leg to check travel and it is in the same position as before after road testing the bike.

And the ride is still the same, not soft or harsh, just does what is it meant to.

Cheers

Peter
So long, and thanks for all the fish...............

https://www.facebook.com/PDBCustomGuitars
Nunodeo
Posts: 13
Joined: Tue Jan 21, 2014 2:28 am
model: 750 Sport
year: 1990
Location: South S.F. Bay USA

Re: 1990 750 Sport fork oil

Post by Nunodeo »

Thanks Peter
My local shop said to use 5W and I thought I should use at least a 10W like my othe bikes.
However, he said you get better feel using 5W because it's thinner and starts working faster. I don't know if this is true, but I'll give it a shot and see how it works out.
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paso750
paso grand pooh-bah
Posts: 5558
Joined: Sun Jul 18, 2004 12:00 am
model: 750 Paso
year: 1987
Location: southern Germany

Re: 1990 750 Sport fork oil

Post by paso750 »

your shop is right. I`ve used 7.5 in the past as I didn't know if the fork would become to bouncy with a 5W oil.
Then I got progressive springs and those came with a 2.5 and it works fine.
As the fork already is rather stiff I wouldn`t go with thicker oil. Peter, I wonder if the fact that you`re in a hotter climate has impact on the oil and how the fork reacts to/with it.
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bmw851
Posts: 322
Joined: Tue Mar 13, 2012 9:02 am
model: other
year: 1988
Location: The Blue Mountains, NSW, Australia

Re: 1990 750 Sport fork oil

Post by bmw851 »

It's an interesting subject, like Nunodeo I've always used 10W in most of my bikes over the years except in the various BM's which were either 5W or 7.5W or my old '78 Honda 750/4 which ran 20W :lol:

I was a bit wary when advised to use 15W thinking it would make for a very harsh ride indeed, but it is actually quite supple over bumps.

I've got a video I'll post on Dropbox or You Tube and post the link in this topic, which was a road test with a camera strapped on the frame and all you can see is the forks and the range of travel, and it is with 15W in them, I got a shock when I watched it, never realised how hard the forks really work :shock:.

We do tend to have a warmish climate, I say that laughingly as it's meant to summer here and it's raining and around 15c outside.

Cheers

Peter
So long, and thanks for all the fish...............

https://www.facebook.com/PDBCustomGuitars
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paso750
paso grand pooh-bah
Posts: 5558
Joined: Sun Jul 18, 2004 12:00 am
model: 750 Paso
year: 1987
Location: southern Germany

Re: 1990 750 Sport fork oil

Post by paso750 »

it's meant to summer here and it's raining and around 15c outside
hey, that sounds like our current winter except for the rainy part :)
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bmw851
Posts: 322
Joined: Tue Mar 13, 2012 9:02 am
model: other
year: 1988
Location: The Blue Mountains, NSW, Australia

Re: 1990 750 Sport fork oil

Post by bmw851 »

You Tube link, test ride after fork oil change to 15W but was mainly trying to figure a reasonable place to mount the borrowed camera I had at the time.

The M1B's certainly do what they are meant too.

http://youtu.be/P8DihhXBcrM

Cheers
So long, and thanks for all the fish...............

https://www.facebook.com/PDBCustomGuitars
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