VFR CARTRIDGE FORK SERVICE Part Two of Four ---------------- Version: 1.1 of this Part. Clarified exposure of C-clip for removal of valve stack assembly. Added another person's observations of internal conditions. Author: Robyn Landers, rblanders@math.uwaterloo.ca Copyright (c) the author, 1996 Distribution: May be copied as long as this header is retained. Improved versions will appear on my web page. --------------- In Part One, I described removal of the forks as I embarked on the project of cleaning the cartridges and changing the oil. Recall that my bike had about 17,000 km and has almost certainly never had the oil changed. In Part Two I describe the procedure for disassembly of the fork and cleaning of the internals. Comments on the condition of my forks are interspersed. 4. Fork Disassembly and Cleaning -------------------------------- I had removed the forks after slightly loosening the cap bolts, drained the oil via the drain bolt at the bottom of the fork legs, and then took them to my friendly neighbourhood shop so they could remove the damper rod bolt from the bottom of the fork leg. This required the fork to be clamped in a vise and the bolt was extracted with an air impact wrench. Remaining disassembly was left to me. If you don't have a shop manual, make notes on the orientation and location of all internal parts, and the order in which you removed them. (I highly recommend buying a shop manual! How can you spend thousands on a new bike and not be willing to cough up another $50 for the manual?) To disassemble the fork, finish unscrewing the cap bolt from the fork tube. (With the fork fully extended there is very little pressure from the spring so this is easy. You can make it even easier by reducing the preload setting on 92+ models.) The cap bolt remains attached to the internal damper rod. Use two wrenches, one on the locknut and one on the flat surfaces provided on the cap bolt, to unscrew the cap bolt from the damper rod. (If you backed off the preload, you'll have to turn it back in so as to expose enough of the bolt flats to get your wrench on it.) Both the cap bolt and the locknut are threaded normally. (Some bikes apparently use reverse (left-hand) threads.) Set aside the cap bolt, the notched spring seat, and the flat spring seat. Now you can pull the damper rod assembly up out of the fork. Remove the oil lock piece (little aluminum cup) from the bottom of the damper rod assembly. This piece just slips off the end. The cartridge will still be full of fork oil even though you drained the fork via the drain bolts on the bottom of the fork legs. Pump the rod slowly with the bottom end in a jar until you get all the oil out. Careful or you'll squirt oil onto your pants and shoes. Have a look at the condition of this oil. On my bike, it was not disgustingly filthy but it was well-laced with fine metallic sediment from bushing and other parts wear. Inspect the Teflon(R)[1] bushings on the forks to see if they still have a good layer of grey Teflon(R) on them. If they're chewed up or the Teflon(R) is worn down enough that you can see the underlying metal, get new bushings. Next I submerged the cartridge in a jar of fresh Varsol and pumped it some more to clean out the remaining oil. The shop manual does not discuss removal or disassembly of the cartridge. To do this, first push the valve stack assembly up into the cartridge a little in order to expose the C-clip. Then use something like a dental scaler to carefully pick out the C-clip from just inside the lower end. Thread a bolt into the end of the valve assembly. Say, the damper rod bolt just happens to fit :-) Hold onto the bolt and carefully pull the valve assembly straight out. It will offer resistance because of an O-ring. Once you have it out, examine the O-ring for damage. This part is not sold separately by Honda, so if you damage it you'll have to find a replacement yourself. My local shop had an assortment on hand. This valve assembly is the compression damper. Clean it with Varsol and examine closely to look for trapped debris. I found a piece or two of metal flashing wedged between the washers in both of mine. Other than that they weren't too dirty. (If you were going to attempt to change the damping behaviour of the fork, you would need to proceed to disassemble the valve assembly and replace the washers. I didn't. This is where people such as Lindemann work their magic, in knowing what washers to select to produce the desired behaviour.) With the compression valve out, the damper rod can be slid out of the housing after you remove the locknut from the upper end. There's another valve assembly on the lower end of the damper rod. This is the rebound stack. Clean and inspect it as you did the other one. Examine the housing itself. There are several sets of holes drilled through it. I found more metal flashings on these holes and scraped them off. This is probably the source of the bits that were stuck in the valve assemblies. I damaged the O-ring on one of the valve assemblies due to a nick in the groove where the C-clip sits. With some 400-grit sandpaper I smoothed off the nick to prevent damage to the new O-ring upon reassembly. With a lint-free cloth, wipe off the fork spring thoroughly. Switching now to the fork, clean out residue of thread locking agent from the threads in the bottom of the fork leg. Remove this residue from the damper rod bolts as well. Clean out the fork tube and stanchion by reinstalling the fork drain bolt and plugging the bottom hole with your finger and then pouring some Varsol into the fork. Slosh it around and then let it drain. Wipe remaining Varsol off all parts and set aside to dry off while you go take a break. :-) Now some editorializing. At 17,000 km, the fork oil in my bike was definitely dirty enough to warrant changing. The cartridges themselves weren't too bad, and if it weren't for the bits of metal flashing trapped in them they mightn't have needed this full procedure. But how is one to know until you get inside to look? The magazine article I used as a guide suggested that a new streetbike should have its fork disassembled and cleaned like this after the first 40 hours or so of use. After that, change the oil yearly (simple drain and refill), and do the full disassembly as recommended by the manufacturer. Well, Honda does not specify a service interval for this. Judging by the filth in my oil, I'd agree with the full treatment early on for a new bike, and then perhaps again every valve adjustment interval (25,000 km). I would also recommend doing it right away if you buy a used bike. Then you can start off with the fork in top condition and you have a reliable basis for judging future performance, rather than basing your opinions on a fork with unknown amounts of crud and misadjustment. More editorializing. Another rider, Bill Mekeel, reports that at 17,000 miles his bike's fork oil had some metallic specks in it but the cartridges were satisfactorily clean. Next, reassembly. --------- Footnotes: [1] DuPont's lawyers have warned that this footnote must be shown. "Teflon(R) is a registered trademark of DuPont for its fluoropolymer resins."