Tom Posted July 10, 2023 Share Posted July 10, 2023 I'm looking for advice on setting up those good old forks on the Blackbird. To put things in a bit of perspective, I posted about my last years "big service" where I was recommended a shop by a "friend" which ended up in fiasco, none of the bearings were installed on the bike (so the guy stole dozen of Koyo bearings I bought for the bike) and the fork was botched and leaked the same day I got the bike from the shop. Without going into that topic, this year I decided to service the forks before my little trip to Italy. I went to a local garage where I used to go few years ago, figured the guy would be decent enough to put together something as complex and the damper rod prototype high tech Showa shocks on the Bird. The bike was finished day before my trip, I didn't have much time to test it, I had specific dates and places to get to and I hoped that the forks would work better than the seal-busted-after-100-meters forks of last year. The guy told me everything was top notch perfect, he changed the steering bearing as well the main one on top of the steering, and he told me he mixed oils to get the perfect oil viscosity for my weight. Sounded good in theory, but... My trip to Italy was the worst I had with the Bird, I have never ever experienced a bike so jittery, no damping whatsoever, every single slightest bump in the road and the bike would jump, or fall into a punched-in part of the road, it was hell, I thought about turning back dozen of times but I just didn't want this fucker to spoil my "holiday". So now I just want to know, what would be the best idea to sort this out, I'll travel 500 miles (and 500 more :D) to find a decent shop I don't care, I want it done. I'm 230lbs, I'm running linear 10 N/mm springs, I have a brand new Nitron R1 (no piggyback) made to my weight and ride habits in the back, never touched the +/- dial on it or anything, and I would like to know which cSt oil should I put, how important is air gap, manual says 142mm and Hyperpro said 120mm, and what should I do also to set the sag on the bike and dial the suspension for once in my life, have the bike ride normally and nicely on weekend twistys that I usually go to. That's all I want ffs :D Quote Link to comment Share on other sites More sharing options...
SwampNut Posted July 10, 2023 Share Posted July 10, 2023 4/7/02 by Carlos Alvarez Also see the tuning notes, updated 4/12/02 See this great article by RaceTech about setting preload The suspension is the XX's weakest link. With a smooth, powerful motor, reasonably stiff chassis, great brakes, and the addition of good tires, there was just one thing that was still a problem... The front end is very softly sprung but overdamped while the rear is non-adjustable and mediocre, plus it wears out fast. There are a few options for upgrades. I chose a mid-level route. For the rear, I transplanted a shock from a CBR900RR, replacing its spring with one of the appropriate stiffness for the heavier bike. In front, I went the RaceTech route. The results are phenomenal. The front end hardly dives under braking, doesn't bottom out any more, and transmits so much more feedback. The rear is far more solid, and my wheelies are much more stable. Compliance over sharp or repetitive bumps like expansion joints is nearly perfect. Overall comfort is improved along with the huge improvement in handling. Shock The early and mid CBR900RR's had the same length shock as the XX does. This means you can transplant a shock very simply--it's just a bolt-on. However, the spring from the 900 is far too light. RaceTech steps in with a spring that is still not as stiff as I'd like, but very close. The spring has to be replaced by someone with a press or heavy-duty spring compressor. In one case, one of our readers made his own. This may be an option, but there is some danger involved and you'll need a couple of odd pieces of metal. I preferred to have a local dealer do it for me for $30. Once you have the right spring on there, the swap is simple and is detailed in the service manual. You'll then need to mount the remote reservoir. I found that it ended up right next to a very large wiring harness, so I zip-tied it to the harness. This results in a solid mount where it is accessible for adjustment but up out of the way. I bought the 900 shock from a local shop for $50. Many others have reported paying anywhere from $50 to $125, which is still reasonable. You will need a shock from a '93-'95 model; the later years won't fit. This will carry one of the following part numbers: MWO-003 MWO-0132A MWO-0132B MAE-0032B The Showa part numbers starting with "MAS" are the wrong part and will not fit (it is 3/4" too short). Forks Honda used a very light spring in the forks, and then compensated for that by over-damping with small valves and thick oil. This results in excessive brake dive, bottoming over large bumps, and harshness over most bumps. The cure for this is two-fold; replace the springs, and replace the damping valves/shims. The springs are easy and cheap; the valves are a little more involved. To replace the springs alone, you can simply remove the top caps and replace the springs. But if you've got a few miles on your bike, you may want to just do the fork oil change anyway, which I detailed here. You will need to adjust the preload by cutting the RaceTech-supplied spacer to the desired length. I started with a size that would make the spring/spacer combo the same length as the stock spring/spacer combo. This is pretty good for me (220 pounds), or possibly just a tiny bit too much. I'm still working on the tuning. The valve replacement gets far more involved, and requires disassembly of the forks. It is well-detailed in the RaceTech documentation, so I won't go into it here. Expect to spend 5-6 hours doing the job, or pay your dealer 4-5 hours of labor. One important note is to consider the damper rod bleed hole size. RaceTech recommends a 1.3mm damper rod bleed hole for street use, and a 1.0mm hole for racing. I found that the 1.3mm hole left the rebound a little on the soft side. If you ride aggressively and trail hard brake into corners, this causes the front to bounce back too much as you release the brakes in the apex. In which case, I'd recommend you go with the smaller hole. If you don't ride like that, the 1.3mm hole will suit you. Parts & Costs (suggested retail price): RaceTech rear spring (SRSP S5717 160), $99 RaceTech front spring pair (FRSP S3732), $99 RaceTech Gold Valve kit (FMGV S2040), $149 RaceTech Rebound Valve Kit (FRGV S02), $139 Fork oil (5 weight), $15 Fork seals (see part numbers below), $21 each You can buy all of the above products from Motorcycles Unlimited. He will ship free for XX group members; just tell him I referred you. You can also send your forks to him if you want the job done for you, and he'll ship them back within a few days. He does a better job than RaceTech themselves, at a lower price. The suggested retail on the shock is probably about $270. You should be able to find a good used one for less than half that. Unless you got unlucky and found a high-mileage one, I suspect most 900 shocks got few miles and are "spares" due to the bike being crashed. Quite a few others were replaced straight off with high-performance models. You can also have the shock rebuilt or send it in for re-valving. RaceTech and Traxxion both offer this service. I've been told Traxxion charges about $150, which seems very inexpensive.. You can rebuild and revalve the shock yourself also, with RaceTech's Gold Valve kit (SMGV S4602, $179). If you do rebuild it, you should also replace the seals, bushings, and of course, the oil. Those extras will run you $50. Fork seal part numbers: All of the following part numbers are for identical fork seals, in case your dealer doesn't stock the specified XX part number. Honda 51490-MR7-305 51490-MZ1-305 51490-KA3-711 51490-KA3-731 51490-KA4-831 Suzuki 51153-14D00 Yamaha 39W23145-LO-00 4NK-23145-00-00 RaceTech sag adjustment instructions sheet General suspension FAQ and definitions: http://www.progressivesuspension.com/documents/suspension_101.html Information on adjusting preload: http://www.factorypro.com/tech/Suspension_Setting.html http://www.foxracingshox.com/motorcycle/pdf/MCManual.pdf Some problem/solution charts: http://www.venomexhausts.com/suspen.htm http://members.ozemail.com.au/~kenrussell/suspension/racemoto.htm http://www.yft.org/tex_vfr/tech/setup_2.htm 1 Quote Link to comment Share on other sites More sharing options...
poida Posted July 11, 2023 Share Posted July 11, 2023 setting up multi adjustable suspension is way out of my league. for me the simpler it is the better.on my 99 blackbird i had the rear oem shock rebuilt by a company here in aus to suit my weight .they revalved and resprung it.the beauty of it is i still just have the soft or hard adjustment so with just me on the bike i have it set to soft.when touring i turn it towards the harder setting till i am happy with it. with the front i bought stiffer springs from sonic springs in usa.they told me what weight oil to use,7.5w and the air gap. i toured europe with that set up loaded with top box,panniers and tank bag for 3 months with no suspension issues. on my 06 blackbird ,which had much lower mileage than my 99,i have only replaced front springs with sonic springs and 7.5 weight oil.i toured europe with the 06 for 3 months with no suspension issues. im wondering if your handling problem could in part be the rear shock being to hard and skipping across the bumps.when ive had a pillion on my 99 blackbird i will have rear shock set to hard.if i forget to turn it back to soft when riding solo again im all over the road. Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted July 11, 2023 Share Posted July 11, 2023 23 hours ago, Tom said: I have a brand new Nitron R1 (no piggyback) made to my weight and ride habits in the back, never touched the +/- dial on it or anything, and I would like to know which cSt oil should I put, how important is air gap, manual says 142mm and Hyperpro said 120mm, and what should I do also to set the sag on the bike and dial the suspension for once in my life, have the bike ride normally and nicely on weekend twistys that I usually go to. A new shock that was made for you shouldn't need a different oil, talk with the manufacturer about it being too soft. Are the forks also too soft? I couldn't really follow your rambles. Quote Link to comment Share on other sites More sharing options...
tomek Posted July 13, 2023 Share Posted July 13, 2023 On 7/10/2023 at 9:12 PM, Tom said: I'm looking for advice on setting up those good old forks on the Blackbird. To put things in a bit of perspective, I posted about my last years "big service" where I was recommended a shop by a "friend" which ended up in fiasco, none of the bearings were installed on the bike (so the guy stole dozen of Koyo bearings I bought for the bike) and the fork was botched and leaked the same day I got the bike from the shop. Without going into that topic, this year I decided to service the forks before my little trip to Italy. I went to a local garage where I used to go few years ago, figured the guy would be decent enough to put together something as complex and the damper rod prototype high tech Showa shocks on the Bird. The bike was finished day before my trip, I didn't have much time to test it, I had specific dates and places to get to and I hoped that the forks would work better than the seal-busted-after-100-meters forks of last year. The guy told me everything was top notch perfect, he changed the steering bearing as well the main one on top of the steering, and he told me he mixed oils to get the perfect oil viscosity for my weight. Sounded good in theory, but... My trip to Italy was the worst I had with the Bird, I have never ever experienced a bike so jittery, no damping whatsoever, every single slightest bump in the road and the bike would jump, or fall into a punched-in part of the road, it was hell, I thought about turning back dozen of times but I just didn't want this fucker to spoil my "holiday". So now I just want to know, what would be the best idea to sort this out, I'll travel 500 miles (and 500 more :D) to find a decent shop I don't care, I want it done. I'm 230lbs, I'm running linear 10 N/mm springs, I have a brand new Nitron R1 (no piggyback) made to my weight and ride habits in the back, never touched the +/- dial on it or anything, and I would like to know which cSt oil should I put, how important is air gap, manual says 142mm and Hyperpro said 120mm, and what should I do also to set the sag on the bike and dial the suspension for once in my life, have the bike ride normally and nicely on weekend twistys that I usually go to. That's all I want ffs Have you adjusted/checked preload on your brand new shock? The sag should be adjusted with you on the bike off the center stand, you most likely would need somebody to help you with this. Once the sag is correct you can play with -/+ dial, that in your particular case is basically rebound adjuster. That would be the start to pin point your issues. Good link, skip the part about the fork becouse XX no adjustments on the front. BTW, you say it has non stock 10N/mm springs, but what about spacers? https://www.cycleworld.com/sport-rider/ask-geek-set-your-static-sag/ Quote Link to comment Share on other sites More sharing options...
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