fork oil clarification, please - K-Bikes.com - Excellence in Motion
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post #1 of 12 (permalink) Old Nov 26th, 2010, 8:39 pm Thread Starter
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Question fork oil clarification, please

1992 K75RT.
I am confused on how much fork oil to put in my bike. I have a Clymers and a Haynes and they don't agree.

The Haynes says that the K75 has a Fichtel & Sachs forks from 85-92 and gets 330cc. From '93 on it says the bike has Showa and gets 410cc.

The Clymers doesn't even agree with itself or the Haynes. On page X it says '86-'89 gets 330cc and '90 on gets 410cc. On page 560 it says '92 on gets 410cc.

Does anyone know which manual to follow? Is there a marking somewhere on the bike that I can look to find a brand or capacity?

thanks in advance for your help.
wayne
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post #2 of 12 (permalink) Old Nov 26th, 2010, 10:37 pm
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Your '92 should have a Showa fork. It is easily identified by a flat front section at the bottom front of the sliders and a fork spring plug with 17mm flats. These forks take 410cc per side.
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post #3 of 12 (permalink) Old Nov 28th, 2010, 10:19 am
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belt and suspenders here, drain the old oil into a ratio-rite measuring flask. The 2 forks should release just about the same amount of oil. Unless they're leaking, that amount should be very close to what you need. My forks both released 11 oz. of old oil, and that is the recommended amount to use in the Owner's Manual...which I trust a lot more than Clymer's or Haynes.
Steve
1990 K75RT
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post #4 of 12 (permalink) Old Nov 28th, 2010, 11:28 am
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Quote:
Originally Posted by stevemac829
belt and suspenders here, drain the old oil into a ratio-rite measuring flask. The 2 forks should release just about the same amount of oil. Unless they're leaking, that amount should be very close to what you need. My forks both released 11 oz. of old oil, and that is the recommended amount to use in the Owner's Manual...which I trust a lot more than Clymer's or Haynes.
Steve
1990 K75RT
However be careful with this method.

The PO of my bike DOUBLE filled the crank case. I found this out when I drained it to take off the sump as I wanted to have a good look at what had collected there and make sure the screen was clear. I was concerned because the sight glass looked black with grunge but it was only that it was full past the top with very dark oil. Almost ran over the drain pan I had in place.

Lucky me, other than a light sediment, the pan was very clean.

When I drained the forks, I got a few ounces of black nasty watery oil from them.

I went with clymers numbers for this year bike but upped the weight to 20 and she rides fine.

Tony G

'87 K100LT "Her Teutonic Majesty"
'79 XS750 "The Triple"
'72 A65T "The T-Bolt"
'68 B25 "The Blue Bike"
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post #5 of 12 (permalink) Old Nov 28th, 2010, 7:37 pm
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post #6 of 12 (permalink) Old Nov 28th, 2010, 8:12 pm Thread Starter
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Quote:
Originally Posted by FlyingDuck
thanks guys, and thanks for that link, Flying Duck. I, like the poster there, am very much not happy with the front suspension currently. I'm thinking there is something "rotten in the state of Denmark" and perhaps the P.O.'s mechanic got confused with this transition year problem.

I will keep you posted if I find an improvement (won't happen until next spring though).
thanks again.
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post #7 of 12 (permalink) Old Feb 13th, 2011, 8:32 pm Thread Starter
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So, it finally was warm enough today to work in my garage and I drained the old fork oil. Only around 300 cc per side. I've determined that these forks should have 410cc ('92 K75RT).
I think this explains why I've been so un-happy with the ride on this bike. It has been very rough.

I still have at least two months until enough snow melts that I can try it out on the road. But I feel good that I am on the right track.

thanks again.

Last edited by WayneDW; Feb 13th, 2011 at 8:59 pm.
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post #8 of 12 (permalink) Old Feb 17th, 2011, 3:21 pm
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If you're still not happy with it, a set of progressive springs makes a big difference. I have Hyperpros in mine and it make the front end a 100X better. Any after-market ones are going to preform better than stock. IMHO.

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post #9 of 12 (permalink) Old Feb 18th, 2011, 5:17 am
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Fork Oil

Quote:
Originally Posted by WayneDW
So, it finally was warm enough today to work in my garage and I drained the old fork oil. Only around 300 cc per side. I've determined that these forks should have 410cc ('92 K75RT).
I think this explains why I've been so un-happy with the ride on this bike. It has been very rough.

I still have at least two months until enough snow melts that I can try it out on the road. But I feel good that I am on the right track.

thanks again.
All the K75(s) after the 1990 model year had the Sport suspension of the "S" model and therefore should have 280cc of fluid which would about corrospond to the 300cc you drained out. I personally don't like the softness of the forks and replaced the 7.5 wt with 10 wt and found it to be much better. Good luck!

kwhiner
'90 K75 STD
"94 K75S
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post #10 of 12 (permalink) Old Feb 18th, 2011, 8:11 pm Thread Starter
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Quote:
Originally Posted by kwhiner
All the K75(s) after the 1990 model year had the Sport suspension of the "S" model and therefore should have 280cc of fluid which would about corrospond to the 300cc you drained out. I personally don't like the softness of the forks and replaced the 7.5 wt with 10 wt and found it to be much better. Good luck!

kwhiner
'90 K75 STD
"94 K75S
OK, thanks, but just to clarify. I do not have a S bike I have a RT which has Showa forks which takes 410cc. This confusion of model and year transition must be why the PO's mechanic put in 100cc short of fluid and is why the ride was so rough.

1992 K75RT
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