Ok, I got the bike back together, I sent out a bunch of stuff for powder coat including the fork lowers. The mods were to cut about 0.460 inches from the spacer and change over to 5 wt oil. (Ended up using Spectro 5wt) One thing to note is that the m8 forks really only have about 3 1/2 inches of travel. Old 41mm forks are close to 4.75 inches. This assumes about 1/2 inch hydraulic stop for each. Total travel is about 1/2 inch more.
I've only gone about 10 miles so far and the forks seem work much better on the big stuff. With some of the spacer removed, I only get about 1/2 inch of sag, primarily due to it still having 2.8 inches of preload. For me even with the light springs, I probably only get about an inch of dive under braking. Close by, I have about a 3 inch step from the dirt to the asphalt. For me it's a good test of the higher speed fork function. Rolling over it now is way better than before. The only thing I've noticed that is on a bad rippled road I get what seem to be a little chatter on the front tire. I'm running 40 PSI in the front so I plan to drop it down and do a longer ride tomorrow. I suspect that I will have to fill one of the low speed compression holes in the lower part of the damping tube to correct that issue. Tire pressure first.. Other than that I'm liking the way this is going.
Some Pics.
The other lowers are for 41mm tubes.
Less Chrome One fork tube was leaking but both got a little polish with 600 grit. Lowers ready to go 12mm allen was tight Disassembled.
I just installed Legends up front and heading to Tail of the Dragon. Im staying at Deals Gap Motorcycle Resort if any one is in the area. Cant wait to see how my investment paid off. Btw I have 13" premium ride rear shocks, soon I'll get Legends for the rear.
I was wrong about the preload in message 1. That was with some compression on the rebound spring. With the fork sitting statically in the vice, and the rebound spring not compressed other than the weight of the lower, preload was 3.2 inches. Rebound spring compression probably adds 1/2 inch to the overall travel.
I've only gone about 10 miles so far and the forks seem work much better on the big stuff. With some of the spacer removed, I only get about 1/2 inch of sag, primarily due to it still having 2.8 inches of preload. For me even with the light springs, I probably only get about an inch of dive under braking. Close by, I have about a 3 inch step from the dirt to the asphalt. For me it's a good test of the higher speed fork function. Rolling over it now is way better than before. The only thing I've noticed that is on a bad rippled road I get what seem to be a little chatter on the front tire. I'm running 40 PSI in the front so I plan to drop it down and do a longer ride tomorrow. I suspect that I will have to fill one of the low speed compression holes in the lower part of the damping tube to correct that issue. Tire pressure first.. Other than that I'm liking the way this is going.
Well checked the tire pressure and it wasn't 40 psi, only 33. Bumped the pressure up to 38 and the chatter stopped.. The forks are likely still a bit on the stiff side for some but I on roads that are pretty rough with an random pothole. Was able to feel the forks bottom slightly but not hard. The suspension does not float and I can still feel the small bumps. The transition from low speed to high speed compression seems to be at a higher force than a good shim type cartridge damper. Those that like a cushy ride, should probably change to an aftermarket damper. For me , it is bit smoother and the change is good enough at least for a while.
This is the first Harley I have left the suspension alone. It feels good enough for me.
agree, 17 RK works fine..we have pretty good roads and highways out West here, and after spending half my riding life on dirt bikes I guess this seems like a Cadillac
IMO the compression damping is still way too stiff for me so time for some mods.
If you look at the system, there is a bending valve for both compression and rebound. The low speed damping is set by the hole in the bottom. With this setup, it's possible to make a progressive damping system by adding a row of holes in the damping tube. You need to figure where the fork tube to damping rod seal is and work from there. I then added a 4.5 mm / 3.5mm / 2.5mm 2.5mm set of holes 13mm apart. The total area of the holes is slightly more than the original 6mm damping holes.
With less compression damping, I figured I needed more spring so I went with 1.0kg/mm RT springs and stayed with light 5 wt oil. Preload was set to 32mm which gave me 32mm of sag. While RT recommends only 28, 32mm sag iis borderline too much. probably could have used 35mm. The damping feels better, Still using 5wt. May try some lighter still. Brake dive is much better.
I need to get the rear shocks revalved again as the damping on them is still way too stiff.
I may be living under a rock but you are the first person I've ever heard say the front suspension is stiff. My '17 with just about 20k miles dives so hard I feel I may bottom out if I brake too much harder at times.
04-30-2019, 11:05 AM
Bumped the pressure up to 38 and the chatter stopped.. The forks are likely still a bit on the stiff side for some but I on roads that are pretty rough with an random pothole. Was able to feel the forks bottom slightly but not hard. The suspension does not float and I can still feel the small bumps. The transition from low speed to high speed compression seems to be at a higher force than a good shim type cartridge damper. Those that like a cushy ride, should probably change to an aftermarket damper. For me , it is bit smoother and the change is good enough at least for a while.
