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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: JR67 on June 03, 2017, 11:29:02 AM

Title: fork springs - sleeve too long? and other motorcycles that use the same springs
Post by: JR67 on June 03, 2017, 11:29:02 AM
Hello folks,
A quick question: I am replacing my fork springs for racetech FRSP S32340090 springs and was wondering if the sleeve is being re-used.
The reason for my question is that when the sleeve is fitted over the original springs, there is 7" of spring exposed which exceeds the maximum fork travel. Fine.
But with the shorter racetech springs there is only 3.5" of spring exposed which is less than the maximum fork travel which makes me think the forks would bottom out on the sleeve. Not good.
So is I my assumption that I either discard the sleeve, or cut a piece of preload spacer that fits under the sleeve and add more pre-load spacer on top correct? It would explain why racetech includes 6 washers instead of the 4 needed according to this link http://www.largiader.com/tech/k11forks/ (http://www.largiader.com/tech/k11forks/)
I see that they call the sleeve(BMW speak) a spring cover.
Here is a pic of what I am talking about.
Thanks in advance for your insights!
Title: Re: fork springs - sleeve too long?
Post by: JR67 on June 03, 2017, 11:59:05 AM
To answer my own question; since I am in the middle of this and eager to finish the job I decided to go with the original BMW preload spacer under the sleeve, on top of the spring, and add some length of racetech supplied pvc spacer on top. This way the exposed spring length is near to what it was originally. Perhaps discarding the sleeve is no problem at all, I have not seen this part in other forks, but I my best guess is that it was designed to keep noise down, so better leave it close to original...
Title: Re: fork springs - sleeve too long?
Post by: JR67 on June 03, 2017, 04:42:17 PM
So I did a test ride, all works well with the original preload spacer on top of the springs and the sleeve over it. I added a washer on top of the sleeve and 85mm of racetech spacer to give it approximately 20mm of preload. Used 10W BelRay fluid and that's it. By googling the Racetech 32430090 number(32mm outside diameter, 340mm long, 0.9kg/mm spring rate) I found out that the K1100LT springs fit the following motorcycles as well, funny enough no mention of BMW's in that list.......

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