Member Contributer Terry Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 The original rebound shims would have been 3 of the 0.1mm thickness, not 0.15. I've not come across any 0.15mm thick shims in Honda forks yet (and I onto my 4th different model now). I agree with your plan above. Now that you know exactly what you have in the fork, it is time to go riding and be as analytical as possible. Here are some links to Gold Valve instructions that I've received with parts purchased over the years. The compression instruction is the old version which gives specific advice on revalving a stock rebound valve. https://www.dropbox.com/s/cuen74nrsz3dck6/Racetech Rebound Gold Valve Instructions.pdf?dl=0 https://www.dropbox.com/s/c3t3c8ygt00dnxx/Gold valve compression installation.pdf?dl=0 Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 I'll see if I can find my "early" RaceTech Gold Valve installation instructions, but it also sounds like you've got this sorted (thanks to excellent advice from Terry and RC36Rider). I once wrote up a web page on an NC30 Gold Valve install (which I found amusing to read again more than ten years later!) In it, I reference the fact that the FMGVS2040 kit instructions call for the drilling of a 1.3mm bleed hole (and lament that RT hadn't done it already). Ciao, Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 Another thought about your brake dive: Check your sag / preload. If the bike has been pitched forward significantly (frequent change on VFR's) this can have a fairly pronounced effect on the rate of dive. I know because being a sloppy lazy guy, I didn't bother cutting new preload spacers when I changed my fork springs and ended up with the front riding too high (very little brake dive). I subsequently cut new spacers 10 mm shorter and was amazed at how much softer the front felt. I emphasise "felt" because preload does not affect spring stiffness or damping in any way but it still feels like it when grabbing a handful of front brake Just a thought. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 And yet another thought... Having no low speed bleed should (if my thinking is correct ) lead to a sort of "crunch" effect where the forks won't budge at all until a certain threshold of force is reached, then suddenly resume normal behaviour. This could be experienced as pronounced brake dive as the forks would then tend to "catch up". It could also conspire with your bent forks (depending on how badly and where they are bent). In short, the effect would be similar to having a very high amount of stiction. No good. Whether the above is more or less correct or not, I think the best course of action is indeed to fix what is obviously wrong (i.e. drill a bleed and replace fork tubes) and only then start worrying about your shim stacks. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 Another tidbit about rebound valves. The above are RT's classic rebound GV's. The (relatively) small round holes are the rebound ports while the large kidney shaped ones are the refill ports (check valve side). I think it's obvious that they designed the refill ports for max flow. To the extent that the rebound valves have an influence on the compression stroke, I tend to think that it is not really intended, just not always avoidable. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 BTW, if you compare the port geometry of your stock Showa rebound pistons with the GV, you'll see that the rebound ports are larger and the refill ports correspondingly smaller. That's bound to have an impact on your shim stack. The consequence IMO is that the Showas require a stiffer stack to achieve the same rebound damping force and that they are more likely to become restrictive on the compression stroke (but the latter may be of no practical consequence. Dunno.) Also, check very carefully that the check valve plate is as free to move as it can be. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 4 hours ago, JZH said: I reference the fact that the FMGVS2040 kit instructions call for the drilling of a 1.3mm bleed hole (and lament that RT hadn't done it already). They let you choose between 1.0 (racing) and 1.3 (road). Also, some bikes do not need the hole at all (e.g. 6G VFR). I understand that RT will drill for you if you ask and specify what you need. For better or for worse, RT's kits are not specific model dedicated drop-in kits. IIRC, I bought my FMGV S2040 from an Aprilia dedicated website where it was listed for the RS250. Clearance price. Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 The compression valves supplied by DMR for my 4th gen (same forks as later 3rd gens) do have a 1mm bleed valve Never got to install them on my redslut..... You see? Now I HAVE to buy an SP2 for them! Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 44 minutes ago, Dutchy said: Now I HAVE to buy an SP2 for them! Yes, you must ! And I'll ride to Utrecht with a bottle of Champagne if you let me have a go. Joking of course. I know you prefer a good single malt. Link to comment Share on other sites More sharing options...
RhodeMoto Posted November 4, 2016 Author Share Posted November 4, 2016 I second the thoughts on a good single malt. If this all goes well I will have to pick up a bottle. Islay please,.....The cupboard is bare. So - Great to get the RT original instructions. Terry - are those your notes on stack in sidebar? The RT recommended seems a giant leap from stock, but written notes are even greater. How did this work out? What I have and what is indicated here just seems like a huge jump from stock, if stock is 3 @.10. I am basing this all on the thinking that the spring rate is 25-30% greater and therefore the rebound should go up proportionately. Do I use all 10? Drop a few? Heading out to pick up a #55 drill bit. Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted November 4, 2016 Member Contributer Share Posted November 4, 2016 Islay..... Can't go wrong there eh? :-) Back to shims again.... Link to comment Share on other sites More sharing options...
RhodeMoto Posted November 5, 2016 Author Share Posted November 5, 2016 Wow - Similar tastes. Have had all but the two on right. The Ardbeg Ugeandal (sp?) is possibly my all time favorite,... So took my FZ650 for an afternoon fall run to the hardware store for the #55 bit. They were closing and some very well meaning young guy grabbed a bit out of drawer and handed it over. I should have been more alert as when I got home discovered it was way to big. Trip two to a different store and have it in hand. Used some #600 wet / dry on one rod and then polished it on buffing wheel. Get things cleaned up and the holes drilled. assemble what I can so when tubes arrive on Tuesday will be able to button up and see what we have. Still perplexed as to using the entire rebound stack,......I keep was thinking that if the stock rebound was OK (3 x 17/0.10) and the spring rate is increased 30% then to maintain same rebound you should add one shim. Tonight's thought (no scotch) is that spring rate under compression is not relevant to rebound rate. Is it possible that an increase of 30% compression equates to an exponential increase in rebound? So it may be a 60% increase in rebound that I now have to control. That gets me closer to what is suggested by RT instructions. Again - current stack is 10 x 0.10 or three times greater than stock. I feel like this must have been owned by someone who had the right intentions, as there is a FOX rear shock with remote air, as well as these fork mods. But if the bleed hole was not done what else may have been done wrong or incomplete,....? Probably should check the torque on rear wheel before I go too far! There is much to go over before I feel this will be road safe for extended tripping. Next on list is checking the temp gauge. In the short run I did have on this the needle did not move. I read that if you ground the lead to the sending unit and the gauge jumps then gauge is good and most likely the sending unit. Anyone with clues on this? Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted November 5, 2016 Member Contributer Share Posted November 5, 2016 The hand written note was actually for my Suzuki RF900; but I took a punt and followed RT's instructions for re-shimming the OEM rebound (identical to the VFR's Showa valves) and it was great. As RC has inferred above, the same 20mm cartridges get used in a lot of different forks, so you can easily mix and match parts so long as you pay attention to things like fork diameter when choosing springs, and identify where the low speed bleeds are. I also dropped the compression back to C32 in that RF900, and have done the same on my VTR1000, VFR800 and ST1100, as that suits the rough roads that I play on. C33 transmitted too many jolts to my ageing wrists. I also run lighter springs than you, 0.85 in the VTR, 0.9 in the VFR and 0.9 in the ST1100 (which being heavy should use 1.1 which I also have, but the 0.9s are much better for me). With hindsight, there's not much wrong with those 6-port Showa valves, they flow plenty of oil unlike the HMAS valves in the VFR and VTR which have tiny (relatively) ports, and I doubt there is much benefit from replacing them with RT valves. I looked up some specs for the VFR750FV, and that should have had 2 x 17 x 0.15 and 1 x 17 x 0.1 shims on rebounds as standard. 10 x 17 x 0.1 shims is standard for a NC30. Link to comment Share on other sites More sharing options...
RhodeMoto Posted November 5, 2016 Author Share Posted November 5, 2016 Once again many thanks - Now feel I have enough information compiled to know I am not going blindly into this. based on this last info feel the rebound, if not perfect, will be a reasonable start point. If I use a bend factor of 1 for a 0.1 shim then a 0.15 = 3.4 stock - (2 x 3.4)+1 = 7.8 increase spring rate - 7.8 + 25% = 9.75 my current set - 10 x 0.1 = 10 Drill the bleed hole and assemble! Drink scotch! Will report back with results. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 5, 2016 Member Contributer Share Posted November 5, 2016 2 hours ago, RhodeMoto said: Drink scotch! To quote the RT instructions: "Do not take this step lightly." Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 6, 2016 Member Contributer Share Posted November 6, 2016 On 02/11/2016 at 3:44 PM, RhodeMoto said: Would a tapered stack respond better as this is going to be be full on at rebound. A tapered stack would open early with softer rebound and increase with velocity? Yes? According to Shim ReStackor, there is no real difference between a tapered stack and a straight stack in terms of the damping curve they generate. The main difference is that the tapered stack is kinder to the spring material as it spreads the bending forces more evenly. The compression shims flex a lot (very wide spread of velocities) while rebound is much more limited hence a simpler straight stack is deemed good enough. At least that's what I think the rationale is. Stack styles Link to comment Share on other sites More sharing options...
RhodeMoto Posted November 7, 2016 Author Share Posted November 7, 2016 This reinforces my move to go with basically what I have. The compression stack will hopefully be right on, now that I have drilled the bleed hole. I have faith the rebound will be close. Everything clean, assembled, and waiting on new tubes,.... 2 days? Found a length of acrylic tube I had is a perfect fit to make some new pre-load spacers and trash the electrical conduit with cuts that were not square. Any thoughts on discussions I have seen regarding "special" racetech 5 wt. fork oil? Is this a differnet viscosity than other 5 wt. ? I had always thought that oil weight was the visitcosity, and 5 wt. was the same across the board. Also - RT recommended 120mm fill height. That is more than spec. Anybody have opinion, experience weight, volume using RT mod's? Link to comment Share on other sites More sharing options...
Member Contributer Terry Posted November 7, 2016 Member Contributer Share Posted November 7, 2016 You are basically correct, 5W should be a standard, in practice what should be specified is a viscosity at 40C; 5W should be around 16-18 cP, and would be what I'd suggest. Yes run with RT's oil level suggestions. To be clear make sure you have pumped the fork leg a few times to dispel any air, then do the same with the cartridge. It is very obvious to feel when all the air is gone and the damping is smooth over the full stroke. Once at that point, compress the leg fully and set the oil level, before the springs etc are added. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 7, 2016 Member Contributer Share Posted November 7, 2016 7 hours ago, RhodeMoto said: Any thoughts on discussions I have seen regarding "special" racetech 5 wt. fork oil? Is this a differnet viscosity than other 5 wt. ? Sort of. If you pick another brand's 5W, it is likely to be heavier than RT's. As Terry says, go by cSt@40°C if you can find the info. Much more precise than the SAE system of "weight" which was never intended for suspension fluids. The 5W I currently use is on the heavy side at 25.6 cSt@40°C whereas RT's is on the light side at 15-16. That difference can definitely be felt. At a minimum, you want to pick a brand and stick with it otherwise you'll be chasing your tail. Also check your tyre pressures religiously while testing. Quote Also - RT recommended 120mm fill height. That is more than spec. RT use 120 mm for pretty much every road bike. Not really an issue as it is a safe starting point but they certainly over-hype how "personal" their set-ups are.  I'd think it's rather on the high side considering that the 3G has 140 mm of travel and not the typical 120 (just a rough rule of thumb this). NB: The RT springs are almost certainly much smaller in volume than the OEM so that's a good reason to raise the oil height a bit. I'd probably start about halfway between RT's and Honda's recommendations but it's fairly easy to adjust so no big deal really. Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted November 7, 2016 Member Contributer Share Posted November 7, 2016 Yeah, it takes a little digging, but one can find cst info online i.e. http://www.putoline.com/en/search/#!/query:hpx/ http://www.putoline.com/en/catalogue/product/370/hpx-r-15w/1734/ Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 7, 2016 Member Contributer Share Posted November 7, 2016 Case in point: Putoline 4W at 16.90 cSt@40°C is actually slightly heavier than RT's 5W. IMO, it does not matter hugely whether your choice of fork oil is a rather light or rather heavy 5W. My own choice is entirely based on local availability. It does not bother me as long as I know exactly what I have in my forks. Link to comment Share on other sites More sharing options...
RhodeMoto Posted November 8, 2016 Author Share Posted November 8, 2016 Or pick from one of these,.... http://mahonkin.com/~milktree/motorcycle/fork-oil.html http://bmwmotorcycletech.info/ShockOilComparo.pdf then got lost somewhere is this http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid Link to comment Share on other sites More sharing options...
RhodeMoto Posted November 8, 2016 Author Share Posted November 8, 2016 I am going to see if anyone local carries RED LINE. New tubes arrived today! Look very well made. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 8, 2016 Member Contributer Share Posted November 8, 2016 Just found some potentially interesting info on...err... another VFR dedicated board: Stock shim stacks Seems that your rebound stack is actually stock. Link to comment Share on other sites More sharing options...
Member Contributer RC36Rider Posted November 9, 2016 Member Contributer Share Posted November 9, 2016 2 hours ago, RhodeMoto said: I am going to see if anyone local carries RED LINE. Peter Verdone uses Red Line for shocks, IIRC. It has very high VI (temp stability of viscosity) which I'm pretty sure means $$$ for no real benefit as forks do not run anywhere near as hot as monoshocks. Link to comment Share on other sites More sharing options...
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