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So, I work just down the street from Race Tech in so cal. My forks have been leaking horribly, so I took them in on Monday, and got them back today (Thursday). Kept the stock springs, but did the top-out spring conversion, compression and rebound valves, polish the tubes, and a rebuild, all for standard street riding. My first quick ride tonight was fantastic, less dive, easier to point and hold a line, and better feedback. I'm a very happy customer so far, thanks Race Tech!!
 

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Hey, that's good to hear Agent. I'm going to do the same thing in a few days. My local shop is WestCoast Motors. I've talked to Rob the owner a few times now, and he seems pretty cool. He's owned a couple RC51's and seems really familiar with them.

So, I'm not aware of the top-out spring conversion. Gonna search that. My seals are fine, but with almost 19,000 on the forks and not knowing any history of the bike prior to my rescuing it....

I think it was madbuyer that once said, 'and for god sakes, change that fork oil'. Kinda got me thinking :eek:
 

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Discussion Starter #4
The top-out conversion puts shorter springs in with some spacers, it allows you to get a proper sag setting. The OEM springs are longer than most for some reason. If you put the bike in the air on a stand so the front wheel is free, you can actually pull the front wheel down out of the forks about another inch. I was told that makes setting a consistant sag nearly impossible. Either way, I'm really happy so far, need to put more miles on.
 

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I think on bumpy real life streets that top-out spring helps maintain contact. For race track use I suspect it is just added weight.
 

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So, I work just down the street from Race Tech in so cal. My forks have been leaking horribly, so I took them in on Monday, and got them back today (Thursday). Kept the stock springs, but did the top-out spring conversion, compression and rebound valves, polish the tubes, and a rebuild, all for standard street riding. My first quick ride tonight was fantastic, less dive, easier to point and hold a line, and better feedback. I'm a very happy customer so far, thanks Race Tech!!
Hi Clark, I just got a RC51 2006 model, i just rebuilt the front forks last night as they were both leaking.

I need to put fluid in the forks, I do not know what grade of fork oil and how much vloume of fluid per fork? can you help. There standard Forks on the bike..thank you
 

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I think on bumpy real life streets that top-out spring helps maintain contact. For race track use I suspect it is just added weight.
The RC51 has the longest top-out springs of any bike, around 115mm.

Most bikes have much shorter top-out spring of varying degrees of stiffness.
On some bikes, you can pull on the fork bottom and see the fork extend as the top-out spring compresses.
On others, the top-out spring is so stiff it's practically immovable.
On average, the usual top-out spring length is around 20-25mm.

A shorter top-out spring allows the forks to extend and maintain contact with the surface under hard acceleration instead of lofting the wheel.
It also keeps the forks from topping out harshly which can affect handling at speed and damage the forks.

Your shocks have top out springs as well (at least my Ohlins does). They're just not used much, unless the whole bike is in the air.
 

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This is a really good video explaining the top out springs, kinda long but it goes into the details:
http://www.ustream.tv/recorded/6349484

Agent Clark: Correct me if I am wrong, but isn't the spacer that they put into the forks actually for the fork spring, and not the top out spring? Putting a shorter top out spring and a spacer in there would negate the benefit of shortening the top out spring.
 

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This is a really good video explaining the top out springs, kinda long but it goes into the details:
http://www.ustream.tv/recorded/6349484

Agent Clark: Correct me if I am wrong, but isn't the spacer that they put into the forks actually for the fork spring, and not the top out spring? Putting a shorter top out spring and a spacer in there would negate the benefit of shortening the top out spring.
The spacer is for the fork spring.
The top-out spring is inside the cartridge.

This is a photo of the Race-Tech cartridge.
The top is with the cartridge assembled and the bottom shows the damper rod and rebound valve out of the cartridge tube.
The two shiny cylinders are the fork spring spacers.
The small spring is the top-out spring, which is next to the rebound valve assembly.
The compression valve (non-RC51) is above the rebound valve assembly.

 

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The RC51 has the longest top-out springs of any bike, around 115mm.

Most bikes have much shorter top-out spring of varying degrees of stiffness.
On some bikes, you can pull on the fork bottom and see the fork extend as the top-out spring compresses.
On others, the top-out spring is so stiff it's practically immovable.
On average, the usual top-out spring length is around 20-25mm.

A shorter top-out spring allows the forks to extend and maintain contact with the surface under hard acceleration instead of lofting the wheel.
It also keeps the forks from topping out harshly which can affect handling at speed and damage the forks.

Your shocks have top out springs as well (at least my Ohlins does). They're just not used much, unless the whole bike is in the air.
This refers to the SP2. The SP1 are much shorter. There isn't a need to shorten the SP1 Top out spring.
 

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The spacer is for the fork spring.
The top-out spring is inside the cartridge.

This is a photo of the Race-Tech cartridge.
The top is with the cartridge assembled and the bottom shows the damper rod and rebound valve out of the cartridge tube.
The two shiny cylinders are the fork spring spacers.
The small spring is the top-out spring, which is next to the rebound valve assembly.
The compression valve (non-RC51) is above the rebound valve assembly.

When Dan Kyles cuts the SP2 spring he installs a spacer to take up the difference. If you do not, the fork will be longer and require them to be set higher in the clamps.
 

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Do you have photo of the top-out spring spacer and shortened spring?
I tried to remove mine but it was in there pretty tight, and I didn't want to risk damaging the cartridge interior.
 

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Right after I asked what the top out spring conversion was, I found this in the firehawk forum. Here's the link, it's about a SP2 rebuild with lots of good pics. http://www.superhawkforum.com/forums/members-rides-35/rc51-track-bike-project-17434/

This is also somewhat related, since many people install RC51 and CBR forks on their Super Hawks.

The '00 and '01 forks have short top-out springs. Top-out springs on the '02-up forks are about 3 times longer and softer. This is the primary difference between the forks.

There are 2 schools of thought on this. The argument for longer top-out springs is that the forks don't extend as far on the gas, so the steering angle remains steep, when accelerating off corners, so the steering rate doesn't change as much. I believe the other reason is to "use" the unsprung weight of the front end to make it less prone to lifting. Simliar to using too-soft springs in the stock VTR forks.

The argument for short top-out springs is that the spring rate remains constant, so that the contact force of the tire with the road surface stays higher, when the front end is light under acceleration. Keeping the fork off the top-out springs maintains a constant, linear spring rate at all suspension positions.

Here is a picture of the SP-1 top-out spring (right), the standard SP-2 top-out spring (center) and shortened SP-2 top-out spring. Another subtle difference is the profile of the slow rebound needles:​

SubSailor, is this what you meant?
 

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Right after I asked what the top out spring conversion was, I found this in the firehawk forum. Here's the link, it's about a SP2 rebuild with lots of good pics. http://www.superhawkforum.com/forums/members-rides-35/rc51-track-bike-project-17434/

This is also somewhat related, since many people install RC51 and CBR forks on their Super Hawks.

The '00 and '01 forks have short top-out springs. Top-out springs on the '02-up forks are about 3 times longer and softer. This is the primary difference between the forks.

There are 2 schools of thought on this. The argument for longer top-out springs is that the forks don't extend as far on the gas, so the steering angle remains steep, when accelerating off corners, so the steering rate doesn't change as much. I believe the other reason is to "use" the unsprung weight of the front end to make it less prone to lifting. Simliar to using too-soft springs in the stock VTR forks.

The argument for short top-out springs is that the spring rate remains constant, so that the contact force of the tire with the road surface stays higher, when the front end is light under acceleration. Keeping the fork off the top-out springs maintains a constant, linear spring rate at all suspension positions.

Here is a picture of the SP-1 top-out spring (right), the standard SP-2 top-out spring (center) and shortened SP-2 top-out spring. Another subtle difference is the profile of the slow rebound needles:​

SubSailor, is this what you meant?
Not quite. It shows the SP2 OEM top-out spring in the middle and the shortened one on the left (the SP1 cartridge is on the right).
What I was referring to was the top-out spring spacer mentioned that isn't shown.
 

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I need to put fluid in the forks, I do not know what grade of fork oil and how much vloume of fluid per fork? can you help. There standard Forks on the bike..thank you
After putting in my Ohlins valves it was recommended to me that I use Ohlins 19 cSt. oil P/N 1309-01. I can't remember the level it was at, I will check when I get home today. I know it was 525ml. per fork.
The Ohlins oil was quite expensive I might switch to the Bel Ray(19.50 cSt), or the Redline (18.40cSt) next time.
 

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The service manual says that the Fork fluid level should be 135mm.
Mine is at 137mm. I have removed my hydraulic stop in order to get to my rebound valve.
 
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