Hello,
The good folks at VFRWorld pointed me this way in search of some Honda 3 port fork valve advice and general suspension guru wisdom.
I’m rebuilding the front end on my 1990 VFR750 and aim to address the damping issues by delving into the world of re-shimming the 3-port Honda valves which I know isn't strictly Hawk related but I believe they are similar / the same as those from certain CBR600’s of a similar age and a common upgrade for the NT650.
My current, underdamped, setup is as follows:
Rebound :
9 x Ø17 x Ø6 x 0.1mm
1 x Ø8.5 x Ø6 x 0.2mm
Compression :
5 x Ø17 x Ø6 x 0.1mm
1 x Ø8.5 x Ø6 x 0.2mm
My main issue with this setup is the lack of low / mid speed compression and rebound damping. I’ve gone up to 15wt oil, can’t remember brand for cSt rating, with not much improvement. My goal is to improve the aforementioned damping issue without creating an overly harsh ride.
As a starting point I’d like to confirm if my current setup is indeed standard. The rest of the fork internals were standard when I got the bike and the damper rod was neatly mushroomed over the rebound valve retaining nut, as if from factory, so I’m guessing that it is standard but any knowledge would be useful.
I like the look of the setup with the pre-load shim described in the thread : Interchangeability of Hawk/F2/F3 forks. It seems to address the low-speed damping issue without creating high speed harshness which I think will be well suited to my less that perfect road conditions and riding preference. I am tempted to start with a slightly lighter version of this but with a more typical ≈ 7.5wt / 30cSt oil. Can anyone comment on this setup or similar?
Lastly does anyone have experience with porting valves to reduce turbulence? What is the specific goal here, is it to reduce overall friction losses in the ports (i.e. maximise effective port size) or is it to limit the onset of turbulence over a greater velocity range for a more consistent damping effect (i.e. avoid damping ramping up on high speed hits)? This is probably getting beyond the point where I’d notice any real-world difference but I like to play around with the theory. Since maximum fluid velocity occurs during high-speed compression events it make sense to focus on any active ports during the compression stroke, I see no reason not to chamfer the inlet-side of the compression ports and both-sides of the rebound by-pass ports, the added advantage of the later being to reduce the impact of the rebound valve on compression damping and potentially reduce the occurrence of cavitation.
Any help or advice on the above would be greatly appreciated. I plan to document this as I go so will keep posted with results for future reference.
Cheers, Lewis
The good folks at VFRWorld pointed me this way in search of some Honda 3 port fork valve advice and general suspension guru wisdom.
I’m rebuilding the front end on my 1990 VFR750 and aim to address the damping issues by delving into the world of re-shimming the 3-port Honda valves which I know isn't strictly Hawk related but I believe they are similar / the same as those from certain CBR600’s of a similar age and a common upgrade for the NT650.
My current, underdamped, setup is as follows:
Rebound :
9 x Ø17 x Ø6 x 0.1mm
1 x Ø8.5 x Ø6 x 0.2mm
Compression :
5 x Ø17 x Ø6 x 0.1mm
1 x Ø8.5 x Ø6 x 0.2mm
My main issue with this setup is the lack of low / mid speed compression and rebound damping. I’ve gone up to 15wt oil, can’t remember brand for cSt rating, with not much improvement. My goal is to improve the aforementioned damping issue without creating an overly harsh ride.
As a starting point I’d like to confirm if my current setup is indeed standard. The rest of the fork internals were standard when I got the bike and the damper rod was neatly mushroomed over the rebound valve retaining nut, as if from factory, so I’m guessing that it is standard but any knowledge would be useful.
I like the look of the setup with the pre-load shim described in the thread : Interchangeability of Hawk/F2/F3 forks. It seems to address the low-speed damping issue without creating high speed harshness which I think will be well suited to my less that perfect road conditions and riding preference. I am tempted to start with a slightly lighter version of this but with a more typical ≈ 7.5wt / 30cSt oil. Can anyone comment on this setup or similar?
Lastly does anyone have experience with porting valves to reduce turbulence? What is the specific goal here, is it to reduce overall friction losses in the ports (i.e. maximise effective port size) or is it to limit the onset of turbulence over a greater velocity range for a more consistent damping effect (i.e. avoid damping ramping up on high speed hits)? This is probably getting beyond the point where I’d notice any real-world difference but I like to play around with the theory. Since maximum fluid velocity occurs during high-speed compression events it make sense to focus on any active ports during the compression stroke, I see no reason not to chamfer the inlet-side of the compression ports and both-sides of the rebound by-pass ports, the added advantage of the later being to reduce the impact of the rebound valve on compression damping and potentially reduce the occurrence of cavitation.
Any help or advice on the above would be greatly appreciated. I plan to document this as I go so will keep posted with results for future reference.
Cheers, Lewis
Comment