cally4x4 Posted January 8, 2020 Share Posted January 8, 2020 Hey all going to change fork oil again but was going to try another weight oil I’m using 10 weight atm but was thinking of 7.5 or maybe 5 weight. I’m 6ft ,14stone and the roads around me are terrible bumps and holes everywhere I’m also thinking of lowering air pressure to 37psi from 42psi to see if that helps any thoughts or suggestions would be appreciated Quote Link to comment Share on other sites More sharing options...
SwampNut Posted January 8, 2020 Share Posted January 8, 2020 Helps in what way? What problem exactly are you trying to fix? Lighter oil will reduce damping, which I'm sure you knew. Rebound damping should generally be predicated on spring rate and unsprung mass. If it's too light, the fork will bounce out too fast and create bounce. If it's too hard, the fork will compress over repeated bumps and/or fail to keep the tire connected to the ground. On compression you want enough to keep the tire on the ground. The ProfessionalTM will surely correct me on all of my simplification of the process, and proceed to explain how my island origins are to blame for me not being 1/100th of the suspension engineer he is. Quote Link to comment Share on other sites More sharing options...
poida Posted January 8, 2020 Share Posted January 8, 2020 blackbird forks are undersprung and over damped.if you go to this site https://www.racetech.com/ProductSearch/12/Honda/CBR1100XX Black Bird/1997-2003 and find the right spring rate.i have a stiffer spring with 7.5w oil and it improved the handling.bought the springs from sonic springs.they can recommend the oil weight and air gap with the new springs. 1 Quote Link to comment Share on other sites More sharing options...
cally4x4 Posted January 8, 2020 Author Share Posted January 8, 2020 (edited) 2 hours ago, SwampNut said: Helps in what way? What problem exactly are you trying to fix? Lighter oil will reduce damping, which I'm sure you knew. Rebound damping should generally be predicated on spring rate and unsprung mass. If it's too light, the fork will bounce out too fast and create bounce. If it's too hard, the fork will compress over repeated bumps and/or fail to keep the tire connected to the ground. On compression you want enough to keep the tire on the ground. The ProfessionalTM will surely correct me on all of my simplification of the process, and proceed to explain how my island origins are to blame for me not being 1/100th of the suspension engineer he is. Cheers Swamp the problem I’ve got is the forks spring back to fast so with the crap roads most of the time the front wheel doesn’t feel planted to the road Edited January 8, 2020 by cally4x4 Quote Link to comment Share on other sites More sharing options...
cally4x4 Posted January 8, 2020 Author Share Posted January 8, 2020 1 hour ago, poida said: blackbird forks are undersprung and over damped.if you go to this site https://www.racetech.com/ProductSearch/12/Honda/CBR1100XX Black Bird/1997-2003 and find the right spring rate.i have a stiffer spring with 7.5w oil and it improved the handling.bought the springs from sonic springs.they can recommend the oil weight and air gap with the new springs. Thanks podia I’ll have a look Quote Link to comment Share on other sites More sharing options...
SwampNut Posted January 8, 2020 Share Posted January 8, 2020 22 minutes ago, cally4x4 said: the problem I’ve got is the forks spring back to fast so with the crap roads most of the time the front wheel doesn’t feel planted to the road You're describing an oversprung/underdamped condition. At 190 pounds you're probably a bit heavier than the average rider, so you'd tend to compress the springs more. Do you know if the springs, valves, and oil are stock now? Quote Link to comment Share on other sites More sharing options...
cally4x4 Posted January 8, 2020 Author Share Posted January 8, 2020 3 minutes ago, SwampNut said: You're describing an oversprung/underdamped condition. At 190 pounds you're probably a bit heavier than the average rider, so you'd tend to compress the springs more. Do you know if the springs, valves, and oil are stock now? Yeah everything is stock I did a oil change 18 months ago with 10 weight oil this past year I’ve wacked a few stone on but the bike has always had this feel of a light wheel on the road Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted January 9, 2020 Share Posted January 9, 2020 Forks bouncing back might be a lack of rebound damping, excessive compression damping, or under-sprung and bouncing off the bump stops because it bottomed out. If what you're feeling is a sharp upward hit it's likely that the suspension bottomed or there's too much compression damping. I can feel and understand car suspension better than bike so don't assume I'm right. From what I recall these forks are properly sprung for someone around 150lbs and the rear is good for about 180lbs. It's up to you to convert our real weight measurements to rocks. 😊 Everything I know says that the recommended tire pressure is higher than ideal. I run 36F and 38R solo and many say that that's on the high side. Dropping pressure will help soften small sharp bumps. I've seen 36F 42R being the recommended pressures on every 2 seater sport bike I've checked and the pressure is always for riding at the maximum gross vehicle weight rating so obviously you don't need as much for solo riding. On 'super sport' bikes like Ducati the recommended pressures are quite a bit lower using the same size tires. Getting it sprung for your weight is probably the easiest improvement that can be made to the forks and I've read that dropping the oil viscosity does wonders for these. Unfortunately the number on the bottle can be very misleading and the only way to really know what the viscosity is is to check the specs on the oil. I don't know why that is, but checking the specs on several brands in the same stated weight reveals several different viscosities. Quote Link to comment Share on other sites More sharing options...
XXBirdSlapper Posted January 9, 2020 Share Posted January 9, 2020 You need to be correctly sprung for your weight. If you have original springs they're trash. Spring it as a base line. My stock suspension up front was undersprung and underdamped. It dove HARD on braking. Quote Link to comment Share on other sites More sharing options...
cally4x4 Posted January 9, 2020 Author Share Posted January 9, 2020 2 hours ago, superhawk996 said: Forks bouncing back might be a lack of rebound damping, excessive compression damping, or under-sprung and bouncing off the bump stops because it bottomed out. If what you're feeling is a sharp upward hit it's likely that the suspension bottomed or there's too much compression damping. I can feel and understand car suspension better than bike so don't assume I'm right. From what I recall these forks are properly sprung for someone around 150lbs and the rear is good for about 180lbs. It's up to you to convert our real weight measurements to rocks. 😊 Everything I know says that the recommended tire pressure is higher than ideal. I run 36F and 38R solo and many say that that's on the high side. Dropping pressure will help soften small sharp bumps. I've seen 36F 42R being the recommended pressures on every 2 seater sport bike I've checked and the pressure is always for riding at the maximum gross vehicle weight rating so obviously you don't need as much for solo riding. On 'super sport' bikes like Ducati the recommended pressures are quite a bit lower using the same size tires. Getting it sprung for your weight is probably the easiest improvement that can be made to the forks and I've read that dropping the oil viscosity does wonders for these. Unfortunately the number on the bottle can be very misleading and the only way to really know what the viscosity is is to check the specs on the oil. I don't know why that is, but checking the specs on several brands in the same stated weight reveals several different viscosities. Thanks superhawk I’ll have a go with new springs and lower tyre pressures first of all. I’ve hit an age where 150 lbs is never coming back lol 165lbs or just under 12 stone will be a target for me. I know my bike was dropped at low speed before I got it so might get the chassis checked for pease of mind it checks out ok with the string around the wheel test but still Quote Link to comment Share on other sites More sharing options...
tomek Posted January 9, 2020 Share Posted January 9, 2020 (edited) Stock fork springs are perfectly fine for your weight, you just need slightly thinner oil . If you change springs you gonna have to fuck wirh spacers. Anyone who claims otherwise has no clue about suspension. Quality5wt works very well, 10 wt is totally unsuitable for modern cartridge forks. Not all fork oil is equal, I recommend Maxima Race 5wt, blue label. Lastly, what tire do you run ? Some are better then others as far as absorbing bumps. 42 psi for the front is overkill, 36 is better. Edited January 9, 2020 by tomek Quote Link to comment Share on other sites More sharing options...
tomek Posted January 9, 2020 Share Posted January 9, 2020 Couple more notes. Even with straight rate springs the fork is progressive rate anyway because of the air gap between oil and fork caps. The factory recommended level is more of a starting point and can be changed. Increasing oil level will make fork more progressive. So if you feel it bottoms too much or dives excessively on the brakes increase level by 10mm. The fork has to be completely disassembled during oil change and every compont cleaned very well. Otherwise it is pointless. Setting oil level is critical, just follow workshop manual instructions. Quote Link to comment Share on other sites More sharing options...
SwampNut Posted January 9, 2020 Share Posted January 9, 2020 +1 on the new springs, and what Oscar said. What I'd like to suggest is that you pay more attention to what the bike is actually doing, as I believe what you're describing may not be exactly what is happening. That may be your perception or the words we all use to describe things, which vary. Springs and a valve kit made a massive difference for me, and well worth the cost and effort. Some of what you may be feeling is just the fact that the spring and valves are utter trash on this bike. What other bikes do you/did you ride that you may be comparing this to? Quote Link to comment Share on other sites More sharing options...
cally4x4 Posted January 9, 2020 Author Share Posted January 9, 2020 Thanks all so before leaving for work this morning I lowered the front pressure even with the wet roads it felt better then lowered it a little more to 36psi and 38psi rear again felt better. I will pull the forks apart and do a full clean and try some 7.5 weight oil. Im running Michelin Road 5 tyres front and rear. Previous bike was Honda cb500 then Zx9c1 Ninja, Zxr750L1, Yamaha diversion 900, Honda Ntv650, Honda cb1 400 plus a few 125’s after passing my test none of the previous bikes have ever had the same feel from the front I get from the bird I’ve always felt planted to the road bends on the bird are taken with care with the ride I’m getting it’s not a fun bike to ride. Before I left work I checked the travel of the forks by rocking back and forth forks don’t seem to be topping or bottoming out but very hard and slow to move. I’ll get a pal to have a look at get a second hands on description for what’s going on 👍🏻 Quote Link to comment Share on other sites More sharing options...
SwampNut Posted January 9, 2020 Share Posted January 9, 2020 You mentioned some much lighter bikes, so your perception on this bike will certainly be different. Some of those are sure to have had better forks. I think your tire pressure range now is what most of us run, 36-38 front and 40-ish rear. Quote Link to comment Share on other sites More sharing options...
tomek Posted January 9, 2020 Share Posted January 9, 2020 (edited) Valves are on this particular bike perfectly fine. You can't tell the difference between honda's hmas and let's say, similarly sized (20 mm iirc) Ohlins units. It is matter of shim stack. If some tells you they are trash they have no clue. Suspension places rather sell you 400 bucks valves then 5$ worth of shims. I've duplicated traxxion dynamics shim stack on friends old 07 cbr1000rr and you could not tell the difference between my old 04 r1 equipped with ak20 full cartridge kit. ymmv. Edited January 9, 2020 by tomek Quote Link to comment Share on other sites More sharing options...
cally4x4 Posted January 9, 2020 Author Share Posted January 9, 2020 44 minutes ago, SwampNut said: You mentioned some much lighter bikes, so your perception on this bike will certainly be different. Some of those are sure to have had better forks. I think your tire pressure range now is what most of us run, 36-38 front and 40-ish rear. Your right the bird is the heaviest bike I’ve owned with only the zxr and diversion coming close with any luck the lower pressure and a fork clean up will see an improvement. Don’t get me wrong I like the blackbird and I like the linked brakes but if I can enjoy it then it’s time for a swap why Honda never gave its A list bike more features is beyond me a sports tourer that needs a garage of tools for suspension adjustment lol Quote Link to comment Share on other sites More sharing options...
SwampNut Posted January 9, 2020 Share Posted January 9, 2020 Yeah, no question you have to enjoy it or it's not worth keeping. The Racetech valve kits are cheap though, and a tremendous improvement, so keep that in mind. Quote Link to comment Share on other sites More sharing options...
tomek Posted January 9, 2020 Share Posted January 9, 2020 Racetech is hardly an improvement over stock. It is still too harsh on high speed dumping for my taste. Traxion Dynamics is imho better for street riding. If you wanna go racetech route uou can simply duplicste their c34 valving on oem valves. http://www.mahonkin.com/~milktree/re-shim-project/racetech-shim-stacks.html Quote Link to comment Share on other sites More sharing options...
jon haney Posted January 9, 2020 Share Posted January 9, 2020 (edited) Racetech was a huge improvement for me. Maybe because I was 210-215 lbs. suited. Picked up about a second per lap at the next lapping day. Of course, this was like12 years ago. Edited January 9, 2020 by jon haney Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted January 10, 2020 Share Posted January 10, 2020 (edited) There is actually a completely free and fun way to make the front suspension not hinder your riding, use as many of the 1,137 cubic centimeters of lifting power needed to fully relax the forks. As a bonus, the front tire lasts forever. Back to real help...if you don't know about lifting the rear suspension for better handling: insert about a 4-5mm spacer between the upper shock bolt and frame, some use a bit more. The other option is to lower the front, or a combination of a little at each end. It makes it much more neutral in turns without making it unstable. In stock form the bars are always trying to push toward straight while in a turn, with the change it becomes neutral. Different tires may act a little differently, but all three of mine have benefited from the lift. As a bonus, it makes it easier to get onto the center stand and decreases the likelihood of scraping the header on speed bumps. Edited January 10, 2020 by superhawk996 Quote Link to comment Share on other sites More sharing options...
jon haney Posted January 13, 2020 Share Posted January 13, 2020 On 1/9/2020 at 8:19 PM, superhawk996 said: There is actually a completely free and fun way to make the front suspension not hinder your riding, use as many of the 1,137 cubic centimeters of lifting power needed to fully relax the forks. As a bonus, the front tire lasts forever. Back to real help...if you don't know about lifting the rear suspension for better handling: insert about a 4-5mm spacer between the upper shock bolt and frame, some use a bit more. The other option is to lower the front, or a combination of a little at each end. It makes it much more neutral in turns without making it unstable. In stock form the bars are always trying to push toward straight while in a turn, with the change it becomes neutral. Different tires may act a little differently, but all three of mine have benefited from the lift. As a bonus, it makes it easier to get onto the center stand and decreases the likelihood of scraping the header on speed bumps. I did that too. Worked great, but a 4mm shim was about all my modest inseam could handle. Side stand could be a little longer as well. With a 6mm shim, I doubt you could spin the back tire while on the center stand on level ground. Quote Link to comment Share on other sites More sharing options...
John01XX Posted January 14, 2020 Share Posted January 14, 2020 6 hours ago, jon haney said: I did that too. Worked great, but a 4mm shim was about all my modest inseam could handle. Side stand could be a little longer as well. With a 6mm shim, I doubt you could spin the back tire while on the center stand on level ground. I may be wrong but I didn't think the shim affected the rear tire clearance while on the center stand. I sold many hundreds of 5mm shims to BlackBird owners all over the world. I supplied Jaws with them for a few years. Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted January 14, 2020 Share Posted January 14, 2020 The shim definitely changes tire to ground clearance when on the stand, the shim is moving the tire downward away from the bike whether loaded or not. It also changes how much effort it takes to get onto the stand by very a noticeable amount, especially if standing it while on the bike. One of my birds felt like it wanted to fall into turns and I didn't know why, as soon as I put it on the center stand I knew. The tire was on the ground indicating too much rear suspension lift. I adjusted it to about where my other bird was and it became neutral. Changing the fork height will also change the rear tire/ground clearance. Quote Link to comment Share on other sites More sharing options...
John01XX Posted January 14, 2020 Share Posted January 14, 2020 10 minutes ago, superhawk996 said: The shim definitely changes tire to ground clearance when on the stand, the shim is moving the tire downward away from the bike whether loaded or not. It also changes how much effort it takes to get onto the stand by very a noticeable amount, especially if standing it while on the bike. One of my birds felt like it wanted to fall into turns and I didn't know why, as soon as I put it on the center stand I knew. The tire was on the ground indicating too much rear suspension lift. I adjusted it to about where my other bird was and it became neutral. Changing the fork height will also change the rear tire/ground clearance. I do not understand the geometry of a motorcycle and may have been told wrong. It was explained to me that the shim is placed above the shock resulting in the raising of the subframe. I do know for a fact from hundreds of applications that a 5-6mm shim will not put the rear tire on the ground while on the center stand. Quote Link to comment Share on other sites More sharing options...
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