pattonme

I am thinking about it but I have to do something about the stable I have now (6 bikes). I have a GPR on my KTM motard because at 90mph and going over the hump on Summit/Shanandoah front straight the front gets really light and waggles. I tried a couple sessions with the GPR set to minumum and the bike stabilized itself quickly. A dynamically stable bike will come back to stable on it's own.

sorry @deersSlayer the website prices are USD. I called them and asked. At the end of August the website will be listing both and prices in CAN at least are going up. Today they are 'at par'.

No, the solution is to keep your speed within the design criteria, assuming your suspension is balanced fore/aft. Don't run known aerodynamically unstable objects (top box and side case) at high speed. Look on the lid, it should say not rated above 50mph or something like that. Yes, 50. My givi's had those markings or it was on the website. But even 'clean' I fully expect it's the front fairing causing way too much lift. Take out all the body panels near the forks and gauge cluster so the air doesn't get trapped above the radiator and can flow upward past the headstock. It'll probably buffet you but at least you'll keep the weight on the front tire. If you like 100+mph and do so regularly, buy a different bike.

race bikes are set up for the aggressive end of stability for 'flickability'. And since they get HARD on the power, the front-end gets light even at moderate speeds. They have dampers because the racing organization requires it, because back in the day 70-80's bikes would get out of control since chassis stability wasn't maintained and suspension 'sucked'. And like I mentioned, some bikes (05-06 ZX10 I believe) are like the F-111 figher, unstable at any speed. I expect you could take the dampers off any Ducati in WSB and it would make no difference. Probably the Hondas too. Dampers do serve a useful purpose when landing the power-wheelie crossed up which happens to even Stoner and Rossi. And the guys who do street racing, they've got the bike jumping off berms, hitting man hole covers at 180mph and all kinds of silly. If you're going to do the 'ton' or delve into speeds that the FJ is not designed to handle, then sure, put a damper on there. Suspension balance won't help here where aero has taken over. Just don't mistake the lack of shaking as "alles gut' and keep pushing the envelope. My SV bike would head shake coming out of VIR T10 and down the straight. Shortened the rear shock by 2mm and it has never done it since.

I forgot the 4th and 5th factors: the uneven suspension damping between left and right fork legs and aerodynamic lift. I finally watched the video of that front-wheel where it starts to shake at the 30 second mark. You can clearly see the fork extending longer and longer the faster he goes. This is aero-lift (and short wheelbase) at work. The 115mph top speed limit isn't such a silly idea now, is it... This bike has a big 'pocket' for air pressure to build up at speed (80mph+) and Yamaha has blocked off spillover on the sides and upward flow. If you look at the Z1000 tourer, the old FZ1 and a bunch of others that can (and are) ridden pretty fast, they don't have the shrouds and they have noses that are canted downward. The FJ has it's 'mouth' open wide and angled upward to catch as much wind as possible. What you need at speed is downforce and the Yamaha is designed for lift; never a good idea. If you're going to ride at 90mph+ you MUST ride 'clean', no top box and no side bags. Also I would remove or cut away as much of the plastic in the cockpit area that prevents air from escaping upward. As to the forks, this is what contributed mightily to my Triumph's stability issues. I had 10mm more preload in one leg than I had in the other. At 80mph even with 50lbs of luggage on the back it was no problem. Just steered a little odd - left was easier to initiate over right. With the shock not sufficiently preloaded for the bag contents I was running nose-light which set up and then quickly escalated the head shake once aerodynamic forces had built up enough. But back to the FJ, when you put the damping all in one leg, the other one is able to move faster. It is the front axle alone that tries to keep things in sync. But front axles flex, there is bearing slop, and minute torque moments introduced every time the suspension moves. A steering damper is still a bad idea - you're taking away the bike's ability to warn you that you're approaching dangerous conditions. The FZ09 was designed for hooning and 'moderate' speeds. It's probably perfectly stable at 120mph (despite it's crap suspension) since aero lift is modest. You can't slap on a big-ass, cupped fairing on a short wheelbase bike with front-wheel lofting tendencies and magically say it'll handle the same way at elevated speeds.

If looking at retailer cross-references is sufficiently accurate, the answer is yes. Model YA335 for both. A lot of very naive people just slap in shocks without paying any attention to spring rate, valving, and stroke. Not saying these ZX or other shocks aren't a match (will need to dig up that FZ09 post) but if you do go that route, make sure to check ALL aspects of the fitment and spend the ~$200 to get it fully serviced.

The problem here is that there are multiple seemingly contradictory factors. hard bag are not aerodynamically stable at elevated speeds. I doubt they are rated for anything over 70mph. (I crashed at 128mph with 45L GIVIs on my triumph a few years back. *wicked* tank slapper) Too little rear preload means the weight bias is too far back and while the "raked out" forks would otherwise be more stable because of increased trail, the relative lack of weight on the wheel encourages it to get flighty. Especially since there are plenty of things mounted to the yoke that will catch wind including the operator's hands. Too little fork preload means the bike is oriented nose heavy with decreased trail. Some tires, once worn can have subtle cupping which results in oscillation. I had a front Avon that would shake pretty damn hard but it was small oscillations and never escalated further. Was still a bit unnerving but putting hands back on the bars was enough to stop it. If rider sag is set right at both ends the bike should be stable. Steering dampers only hide/mask the symptoms, they do not solve the underlying problem! Yes there have been bikes (eg. ZX10) that were unstable as hell and would tank-slap by virtue of design choices/errors. But the FZ/FJ isn't one of them.

Please comment for additions and fixes. I will update as often as I can. All prices on the first line of a product reflect known or approximate MSRP. All other prices reflect value at the time of posting but do not include shipping, credit card or merchant fees, and may be subject to currency fluctuations. They are a guide only and not necessarily a final, quoted price. Forum vendors are highlighted in BOLD OE spring is 7 11/16" long, 56mm ID ==> Eibach 0800.225.0550 Ohlins YA335 (S46DR1) aka Parts Unlimited 1310-1148: $575 Length 329mm, Stroke 65mm, Rate 95N/mm=9.7kg/mm=542lb/in product info [ul type=disc][*]Forks-by-Matt : $575 (shipping, Paypal and "gift card" included) [*]Omnia Racing[span style=background-color:transparent] (Italy) : E465[/span] [*]58 Cycle : $634 [/ul] Ohlins YA535 (S46HR1C1) aka Andreani Group SKU (1511): $1100 remote reservoir, compression, rebound, preload product info [ul type=disc][*]Forks-by-Matt : $1100 (shipping, Paypal and "gift card" included)[*]Andreani Group (Italy)[*] [/ul] Penske Sport aka 8900E (PS-89xx-FZ09): $695 Penske 8983 (2-way) : $950 Penske 8987 (3-way) : $1250 product info [ul type=disc][*]StolecMoto : as above[*]Traxxion Dynamics[/ul] Elka stage 2 : $599 Elka stage 4 : $799 Elka stage 5 : $999 product info, It seems they have exited the MC market Matris MY117.1KD : E530 / $560 [ul type=disc][*]PJ's Parts : $573[*]Forks-by-Matt : $500[*]CarpiMoto (Italy) : E424[/ul] Matris MY117.1KF : E920 / $980 [ul type=disc][*]PJ's Parts : $994[*]Forks-by-Matt : $825[*]CarpiMoto (Italy) : E736[/ul] K-tech RAZR-R (279S-014-270-020) : $795 product info [ul type=disc][*]Forks-by-Matt : $700[*]Orient Express[span style=background-color:transparent] [/span] [*]Computrack Boston : $715[/ul] JRi 350 Pro : $699 product info [ul type=disc][*]Forks-by-Matt : $570[*] [/ul] JRi Double : $985 product info [ul type=disc][*]Forks-by-Matt : $860 [/ul] JRi Triple: $1299 product info [ul type=disc][*]Forks-by-Matt : inquire[*] [/ul] Hyperpro YA09-6AD (model 466): $569 emulsion, no length adjuster Rebound, Preload Hyperpro YA09-1AD (model 461): $749 product info, 5yr warranty, free 1st rebuild Comp, Rebound, Preload remote-preload strongly suggested ($200) length adjustment ($70) [ul type=disc][*]Forks-by-Matt : $485 / 640[*] [/ul] Hyperpro Streetbox (SB-YA09-6AD): $699+ product info model 466 shock, fork springs, and fork oil with preload, clicker and ride height recommendations for baseline 180lb rider [ul type=disc][*]http://www.epmperf.com/ Klaus Huenecke; info@epmperf.com; Phone: 732-786-9777[*]http://hyperpro.com/en/wp-content/uploads/sites/3/2015/10/Hyperpro-Shockabsorbers.pdf [/ul] Wilburs 640-1133-00 : $619 product info, 5yr warranty emulsion, no length adjuster Wilburs 641-1133-00 : $849 product info, 5yr warranty Comp, Rebound, Length, Preload avail in -30mm, w/ RPS [ul type=disc][*]Forks-by-Matt : pending[*]Wilbers USA[*]http://wilbersamerica.com/[*]http://www.epmperf.com/[/ul] Nitron Sport (NTR1, BKY 55S) : $699 product info [ul type=disc][*]Forks-by-Matt : $650[*]Norwest Suspension [/ul] Nitron Track (NTR2, BKY 55T) : $1050 product info [ul type=disc][*]Forks-by-Matt : $1000[*]Norwest Suspension[*]ProPilot Suspension[*]Nitron Racing Shocks[*]BikeHPS (UK)[/ul] Nitron Race (NTR3, BKY 55R) : $1200 product info [ul type=disc][*]Forks-by-Matt : $1075[*]BikeHPS (UK)[/ul] Nitron Race Pro (NTR4, BKY 55?) : <price> product info [ul type=disc][*] [/ul] Hagon M620?? : $350 Adjustable rebound and customized spring [ul type=disc][*]http://www.hagon-shocks.co.uk/catalog/partdetail.aspx?partno=M620??[*]http://www.hagonshocksusa.com/[/ul] YSS <model> : $499 Adjustable rebound but no spring customization (go 3rd party) [ul type=disc][*]http://yssusa.com[*]http://epmperf.com[/ul] Cogent Dynamics : $639 product info, forum post Norwest Rebuild : $250-350 [ul type=disc][*]Forks-by-Matt : http://fj-09.org/thread/2876/rebuilt-zx6-zx10-shock-services[/ul] From a purely length, stroke, and spring-rate standpoint the following are swap candidates. HOWEVER!! the clevis and reservoir location may preclude their use without significant alterations. [ul type=disc][*]TBD[/ul][ul type=disc][*][span style=font-size:medium;background-color:transparent] [/span][*][span style=font-size:medium;background-color:transparent][span style=font-size:16px;background-color:transparent] [/span] [/span][/ul]