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2008 cbr1000rr
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Discussion Starter · #1 ·
When installing new fork seals, there is a ring (called a backup ring) that sits against the seal. On mine, one side of the ring has a groove machined into it and the other side does not. I've done endless research and cannot find a definitive answer as to what side of the ring sits against the fork seal.

Whoever did the fork seals before me had the ring in one fork one way, the other fork was the other way. So I can't go by how I pulled them out.

Also, I'm 99% positive I'm putting the seals in correctly, but to be sure- does the chamfered side of the seal face down towards the wheel or up towards the handlebars? Again, endless research and no definitive answer.

Please if anyone knows for 100% sure, let me know. You'll be helping me immensely.

I've attached some pictures. First one is the back up rings, shows both sides- grooved and not grooved. Second is both sides of the oil seal, labeled A and B for easy reference. Third is the oil seal from a side angle, showing the chamfered side.
 

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A1 SuperMod!
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Install back-up ring with the groove side facing the fork and smooth side facing the oil seal. It has to do with how the bore for the fork seal is machined in the outer fork tube. There is a slight shoulder so a ring with sharp 90 degree edges won't seat fully.

As for oil seal, remember the letters face out, towards the bottom of the bike. You can see the letters in "B."

Grease the bore and fork seal with silicone grease (bulb grease at auto store) to ease installation and later removal. Do not try to install them dry or with oil alone.

Put a sheet of paper between the seal driver and chrome tube or you will scratch it. Let me know if there are other questions.
 

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Discussion Starter · #3 ·
Thank you so much 09_Blade !!

I see what you mean about the bore on the outer fork tube; it makes sense now why the back up ring goes in the way it does.

I'm glad you told me to use silicone grease for install; I was going to use oil only.

As for seal driver, I have a 6 inch piece of pcv tubing I cut in half and will secure to the fork tube with zip ties. Seems like it'll work just fine, I guess I'm going to find out lol. I'll be sure to use a piece of paper between seal driver and fork tube. Do you mean just a regular sheet of notebook paper?

Also, how accurate does the oil height have to be? Service manual says 17.5 ounces with a 3.7 inch air gap. Problem is, I bought a quart (32 ounces) which will be 3 ounces short (1.5 ounce short per fork). So I filtered the old fork oil and am planning on re-using 3 ounces. Would you recommend doing this? Or will it be ok to come up a little short on oil?
 

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An upside down fork is very sensitive to oil level. Unless you completely strip the fork and get all the residual oil out of the damping piston, the proper way is to add oil, bleed the fork, then add oil until the oil measures whatever the service manual specifies.

It's okay to come up a little short. That will make the fork less progressive. However, you must never add too much because it can lock the fork near maximum stroke.
 

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Discussion Starter · #5 ·
Thanks for your reply.

I'll follow your instructions when adding oil. I made a tool that measures the air gap between the top of the oil & top of the fork. That should allow me to be dead on.

The only other thing I'm worried about, is when I put the spring back in, I know there is a measurement between the top of the lock nut & top of the threaded portion. I measured it and marked it with a paint marker, but it's probably going to move when I lock it down. Any suggestions on how to keep it from moving and maintaining an accurate measurement?
 

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At the time you tighten the lock nut and fork cap, the lock nut will have a stopper plate under it with spring tension holding it in place against the lock nut. At that point, you screw the fork cap on finger tight taking care not to rotate the lock nut, then once the two are in contact you can jam the lock nut against the fork cap. The position won't change any appreciable amount at that point.

If you have Loctite 271, you can use it to secure the nut in place at exactly the right height and never worry about it again for future service.
 

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Discussion Starter · #7 ·
I'll try the loctite. I might loctite the nut in place beforehand, then tighten the fork cap onto the lock nut.
 
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