Which to rebuild? - SP1 or SP2 forks? - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 18 (permalink) Old 07-23-2013, 05:11 PM Thread Starter
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Which to rebuild? - SP1 or SP2 forks?

So I just bought a 2002 RC51 that came with a set of SP1 forks rebuilt by traxxion dynamics and sprung for a 180 lb rider. The problem is, the stanchions are pitted and rusted. I want to replace them and install the correct springs for my weight (~170 with gear). I have two sets of stock SP2 forks in good condition.

Ideally, what combination of tubes, stanchions, caps, springs, spacers, valves do I use??

Riding style will be city with occasional canyon carving, rear will be controlled by a penske shock.
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post #2 of 18 (permalink) Old 07-23-2013, 06:50 PM
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Spring rates will be much the same for you as for a guy 10 lbs lighter...

Just take the SP1 forks off, undo the top, drain out the oil then use an impact gun to remove the bottom allen bolt. Remove the stanchions & replace with some SP2 ones. You'll need some SP2 caliper carriers too, as they're not the same as SP1.
Then re-fill the oil to the correct level using a suitable tool. I've done this with the springs already in place before, with no problems. Easier than disassembling the spring and checking the fork oil level, then re-assembling.
Be sure to fit the correct grade of oil as used by Traxxion Dynamics.

I have a pair of good SP2 caliper carriers if you're missing some.

Euro RC51 SP2: HRC WSB Ti Hi-Level, T1 Airbox & Snorkel, PCIII, Dymag CA5 Carbon Wheels, Ti64 Spindles (F, R & Swing Arm), Mori Link, Maxton GP7 Shock & Ohlins 832 Forks, Brembo GP Calipers & SBK narrow track (F), Braketech Disc (R), Brembo billet Underslung x 2 Brembo RCS, Tyga Triple, 7075 Stem, Probolt Titanium all over, Babyface rearsets, MR Complete Carbon Lineup, Custom Undertail & CBR 1000 LED, Watsen LED Indicators, Harris Brace, Giles clip-ons, Corbin seat, etc. 2013 BOTY.
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post #3 of 18 (permalink) Old 07-23-2013, 07:42 PM Thread Starter
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I have a set of SP2 caliper carriers ready to go. But thanks for the offer!

As far as spring rate goes, I'm just taking the previous owner's word for how they're sprung. He didn't recall the exact rate, but he says he weighs around 180. Not sure if he told TD his actual weight, or his weight with gear. Either way, I'll inspect the springs for an indication of spring rate.

I know the SP1 and SP2 forks are built differently, and there has to be an advantage to using one or the other as a base. I've heard that the SP1 offers more travel because of a shorter top out spring(which sounds better), but is also physically longer overall(not sure how this effects things). I know the fork caps/preload adjusters are different, but does either one offer an advantage over the other besides aesthetics?

I know it seems like I'm being nit-picky, but if I have all these parts sitting in front of me, I might as well put them together in the best possible combination, right?
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post #4 of 18 (permalink) Old 07-24-2013, 11:20 PM
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http://www.speedzilla.com/forums/hon...sp2-forks.html


Post 5.

2001 Honda RC51 SP1
1996 Honda CBR 900RR
2003 Aprilia RSV Mille R
1999 Aprilia RS50
2012 Triumph Daytona 675R (Sold)
2010 BMW S1000RR (Sold)
2005 Yamaha R6 (Sold)
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post #5 of 18 (permalink) Old 07-24-2013, 11:27 PM
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Aparently there are more differences too, i would go with the SP2 forks.

2001 Honda RC51 SP1
1996 Honda CBR 900RR
2003 Aprilia RSV Mille R
1999 Aprilia RS50
2012 Triumph Daytona 675R (Sold)
2010 BMW S1000RR (Sold)
2005 Yamaha R6 (Sold)
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post #6 of 18 (permalink) Old 07-25-2013, 12:50 AM Thread Starter
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Thanks for the link. Good info there. Here's another that I found:

http://www.superhawkforum.com/forums...project-17434/

also Post #5


I can see the reasons for wanting a longer top out spring on a stock bike, but with upgraded suspension, I'm not so sure. When it comes to suspension, I'm officially in over my head!

I guess the question comes down to longer or shorter top out springs?
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post #7 of 18 (permalink) Old 07-25-2013, 12:28 PM
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yeah, suspension is tough....at least for me. i have a few really good books on it, if you are interested. sorry i couldn't help you more.

http://www.kyleusa.com/

Call these guys and ask for Mike, or shoot him a PM on the forum. His name is LDH, he will be able to answer any questions you have.

2001 Honda RC51 SP1
1996 Honda CBR 900RR
2003 Aprilia RSV Mille R
1999 Aprilia RS50
2012 Triumph Daytona 675R (Sold)
2010 BMW S1000RR (Sold)
2005 Yamaha R6 (Sold)
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post #8 of 18 (permalink) Old 07-25-2013, 02:26 PM
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Were the forks re-valved or were the AK-20 cartridge kits installed in the forks?
Check what the rebound adjuster looks like.
If the AK-20 cartridge kits were installed, the rebound adjuster should be aluminum vs brass (or it is on my SP2 forks).
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post #9 of 18 (permalink) Old 07-25-2013, 02:50 PM Thread Starter
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Rebound adjuster is brass. Guess I'll have to open up the forks this week to see what's inside. I thought traxxion only made cartrige kits, but I could be wrong. FWIW, I've been finding alot of great info on the subject. Here's a link to a video talking about nothing but top out springs. They even bring in an RC51 to use as an example.

http://www.ustream.tv/recorded/6349484
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post #10 of 18 (permalink) Old 07-25-2013, 08:39 PM
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Scott,
I currently have on my bike a set SP1 forks with Traxxion Dynamics compression and rebound valves and 280mm 1k springs and short top out springs.
To my knowledge Traxxion did not make a AK20 for the SP1, but I could be wrong.
There is nothing wrong with the SP1 forks. I agree that you will need to open them up to see what you have inside.
I like these forks better then the SP2 with the ohlins valves and springs. They were just to aggressive for the street for me. Probably better on the track. The Traxxion are a bit "softer/plush" on top but have plenty progressive support as you get into the travel. I have recently had them serviced and reshimmed by Traxxion.
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