UPDATE: I've made a bunch of changes to spring specs etc. in the
'FastAce fork oil change / spring replacement, part 2' thread, which you might also want to check out if you're planning to work on your FastAce forks.
After living with the Fox shock & new spring for a while, the FastAce forks seemed increasingly harsh in comparison. The rear was hooking up & tracking straight, but the front end was dancing around and deflecting off everything, and only compressing about 6". After the work below, the bike stopped bouncing and just rolled over everything instead, holding the desired line much better. I found myself deliberately aiming for the nastiest rocks & roots, but instead of being thrown off line as before, there was just a quick 'buh-bump' with almost no direction change at all. The bike feels more stable and 'planted' now, with @ 8" of travel visible on the sliders (I haven't felt the forks bottom yet).
Here's a diagram I put together that's close to what I found inside - it looks like the fork is a 43mm 'cosmetic copy' of the 47mm '04 Honda CR250 Showa forks, with rebound-up internals from the '95 CR250 43mm Showas:
What was done: I replaced the OEM 24.8 lb/in (.44 kg/mm) springs with 18.0 - 23.0 lb/in (0.32 - .41 kg/mm) progressive springs from Cannon Racecraft, along with 7mm preload spacers & Bel-Ray HVI 3W shock oil. Sag went from 20mm (static) 38mm (race) to 32S 56R, and every aspect of the fork improved. The adjustment clickers also became usable, instead of just staying at minimum damping as before.
Spring Dimensions (OEM): 16.56" / 420mm OAL, 1.46" / 37mm O.D., 1.10" / 28mm I.D., 32 coils
Spring Spacers: 1.00" I.D., 1.46" O.D., .28" / 7mm max thickness, aluminum (machine shop), or...
NF14502 nylon washers (1.45" O.D. x .99" I.D. x .12" thick,
www.non-ferrousfastener.com)
Prep: I put the bike on the stand, removed the bars & risers together (riser bolts use 7mm Allen keys), then slightly loosened both fork caps, front axle, & brake caliper bolts while the front wheel was on the ground. To minimize fork-cap damage, I used a modified 34mm Proto impact socket w/.012" shim, aluminum tape, and plastic guard made from an aerosol can lid:
I then propped up the front end at the fender bolts, and removed the front wheel, caliper, and both fork legs.
Fork Cap / Spring Removal: Adjust the rebound clicker to about 10 clicks CCW from full CW, then unscrew fork cap from leg, slide cap/spring up slightly, and slide a thin 17mm open-end wrench (I used one from an old Honda tool kit) between the spring coils to fully engage the two flats on the inner shaft's locking collar. These flats round easily & require a fair amount of torque, so use the widest thin wrench you can find.
While holding the fork cap with the socket, unscrew the locking collar until it bottoms on the shaft threads and resistance is felt, then continue to apply force to unscrew cap from shaft. Leave rebound clicker & slotted setscrew exactly where they are, and the cap may go right back on later. With the cap off, remove the springs (the center shaft may slide down into the fork, no biggie). NOTE: I didn't see any Loc-Tite on anything I worked on.
Oil Change (the forks do NOT have to be disassembled further): I set up a long steel rod with about 6" hanging over the bench edge & the other end weighted. I pumped out as much oil as possible into a pan underneath the rod, then hung the fork leg on the rod to let the rest drain (it took a while). The LH leg had @ 400cc, RH leg 360cc. The oil seemed like maybe 10W, black & 'pearlescent', and looked/smelled a lot like some 70's graphite-based fork oil I have. After a Web search of 43mm-fork oil levels (the lowest I found was 378cc, highest was 410cc), I decided on 400cc of Bel-Ray HVI 3W oil. NOTE: this was for a '14 2.8 FX w/light springs; the 5W HVI might be a better choice for a 5.7 w/OEM springs, although the 3W should work well too.
After flushing out any remaining OEM oil with some old HVI 3W, I poured in the new oil slowly, then worked the shaft up/down repeatedly. At first there was cavitation noise, but after many up/down movements the noise stopped and the shaft had full damping in both directions. The oil level was 130mm from the outer tube top when it was aligned with the top of the center shaft.
Spring / Cap Replacement: OEM or straight-rate springs can go back either way, but progressive springs must have the 'soft' side down so the 17mm wrench can be used again up top. The center shaft will want to slide down inside the outer tube, so I angled the fork leg quite a bit to put some side friction on the center shaft while the spring was slid over it. Once the spring was in, I used the 17mm wrench to snag & move the center shaft up more. I then put the spacer inside the fork cap and screwed the cap onto the center shaft (the spring needs to be compressed with the wrench in place, kind of a PITA). The cap clicker's lower end is basically a super-short flat screwdriver blade which engages a slotted setscrew in the center shaft's I.D.; if the clicker and setscrew weren't moved during the fork work, the cap might go right back on to full thread depth - but I'd assume the worst and screw the cap on slowly & gently, and if it stops moving early try rotating it and/or the clicker back and forth a bit until the clicker blade engages the setscrew slot (if the clicker starts clicking while the cap is being installed, either the clicker blade is jammed against the setscrew or the adjuster needle is bottomed; try backing out the clicker a half-dozen or so clicks). Once cap is on (be sure air venting screw is tight!), invert & rotate fork legs once to oil spring & outer tube, then return quickly to normal cap-up orientation so cartridge stays full of oil.
Misc: The rebound-adjuster setscrews push against long aluminum needles. The needle tapers are short and roughly machined, so it's no wonder they have poor action over a limited range. I smoothed and polished the tapers a little which seems to have helped a bit, and may try having custom needles made at some point (although these are working great with the 3W oil).
Torques used:
Handlebar clamps 15 ft/lb (M8)
Handlebar risers 25 ft/lb (M10)
Triple clamps (all) 15 ft/lb (M8)
Fork caps 15 ft/lb (M46)
F caliper bolts 18 ft/lb (M8)
F axle end cap 15 ft/lbs (M8)
F Axle clamps 9 ft/lbs (M6)
Ray
Author
Topic: FastAce fork oil change / spring replacement (Read 10613 times)