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General Category => General Discussion => Topic started by: Petrus Rocks on March 18, 2019, 03:51:38 PM

Title: Fork oil for 45mm right side up forks
Post by: Petrus Rocks on March 18, 2019, 03:51:38 PM

I just transplanted a set of 45mm MG adjustable forks onto my 85 Tonti frame.  I see 485cc per leg as a spec but no height measurement.  Also MG calls for 10wt oil.  Anyone use something different? 
Pete

Title: Re: Fork oil for 45mm right side up forks
Post by: John A on March 18, 2019, 04:05:29 PM

actually I like to use motor oil.  I learned from some racing types that forks cant read so they don't know if you don't put in high zoot fork oil or not.  Ive been using 15/50.

Title: Re: Fork oil for 45mm right side up forks
Post by: Perazzimx14 on March 18, 2019, 04:06:26 PM

ATF also works a treat

Title: Re: Fork oil for 45mm right side up forks
Post by: Rough Edge racing on March 18, 2019, 06:14:42 PM

 Fairly big gap between 15/50 and ATF , usually described as a 7.5 weight oil....considering forks run much cooler than an engine or transmission...it's still a big difference...

Title: Re: Fork oil for 45mm right side up forks
Post by: Perazzimx14 on March 18, 2019, 06:37:13 PM

Quote from: Rough Edge racing on March 18, 2019, 06:14:42 PM

Fairly big gap between 15/50 and ATF , usually described as a 7.5 weight oil....considering forks run much cooler than an engine or transmission...it's still a big difference...

15/50 might be a bit excessive or have all dampening and slooooooooooooooooo ooo rebound. I've run straight 30w oil in the forks of my Eldorado with success.

Title: Re: Fork oil for 45mm right side up forks
Post by: Rick4003 on March 18, 2019, 10:25:01 PM

I just looked into getting some new fork springs for mine and Wilbers recommend 7.5w oil with their fork springs.

Title: Re: Fork oil for 45mm right side up forks
Post by: Rough Edge racing on March 19, 2019, 05:08:08 AM

 Pete, since the forks assembly on the bike now is from a heavier machine than your "cafe" Tonti, perhaps a slightly lighter oil might be better to prevent harsh dampening...Maybe 5 weight fork oil instead of the slightly heavier ATF.. I'm assuming the 45 mm forks were not under dampened on the original bike...
  For those interested, the 45 mm later forks on the 80's Tonti frame bike look very nice, a more balanced look with the large Guzzi engine...The original 35 mm forks look like they belong on a 250cc bike in comparison... :grin:

Title: Re: Fork oil for 45mm right side up forks
Post by: Petrus Rocks on March 19, 2019, 08:10:47 AM

Good point Tony.
(https://i.ibb.co/0Y3rQzR/20190216-102007.jpg) (https://ibb.co/0Y3rQzR)

(https://i.ibb.co/t35sL06/20190318-150300.jpg) (https://ibb.co/t35sL06)

image uploader (https://imgbb.com/)

Here's a before and after.  Steering stem triples, and bearings all fit right on.  Using the old Borrani rims I will have to make a spacer to center the wheels.  A simple bracket will allow me to use the old calipers.  I have a set of four pot Brembos that will go well with larger discs.

Title: Re: Fork oil for 45mm right side up forks
Post by: Petrus Rocks on March 19, 2019, 08:17:30 AM

Didn't realize that was a such a crappy picture...
(https://i.ibb.co/SBHY1Zd/20190319-091514.jpg) (https://ibb.co/SBHY1Zd)