Yep, so I did it. I rebuilt a 1998 CBR600F3 shock with new internals and spring, and stuck it on my 2007 Honda 919. It's great. Here's the whole saga in short version and long:
Doing all the work myself, I rebuilt an F3 shock with new internals, new spring, and new fluid. I installed it on my 919, and now know what mcromo means when he says "nothing short of transformational". It's a new bike. It handles well, rides well, feels great.
For the parts list, scroll to the bottom.
Like pretty much all the rest of you, I bought a 919 last year because
1) I love motorcycles
2) Its looks
3) Its supposed driveability
4) Its price
5) I like to tinker with stuff, and the 919 seemed a good blend of technology (no fucking carbs) and simplicity (no fucking traction control).
Pretty much from day one, I was dissatisfied with the bike. I wanted something with good driveable torque, but nimble handling. My 919 had the first point in gobs, but the second was so lacking that it made the thing all but irritating to ride. It didn't help that the previous owner had ruined the tires (when I bought it the tires were <20psi) and the suspension setup was totally wacky.
Last year I installed RaceTech fork springs (1.0kg/mm for my 6'6", 220 pound self), low flat handlebars, and new tires (Pilot Power 3). These things helped the handling situation, but things were far from ideal. Hell, they were barely acceptable. I put 3,000 miles on the bike, all the time feeling like I'd bought the wrong bike. Woe was me.
I played with the setup of the bike weekly. I used a lot of the info on offer here on WT, was pleasantly guided along by a number of folks (shout out to mcromo in particular!), and took copious notes in my handy-dandy composition notebook.
Despite repeated attempts to square away the bike, the handling was just atrocious. It was unnerving to push hard, unsettling to ride on rough roads, and gave absolutely no sense of confidence. I loved my motorcycle, but it sucked. Think parenthood.
As we all well know, the shock seems to be the root of all evil on the 919s. I was hesitant to put any dough into the shock, knowing that if it didn't fix my problems, I was probably going to sell the bike anyway come spring. I pondered on it a bit, and last fall figured I kinda owed it to myself and my bike to give the shock a good try.
Being a 919 owner (and thus a broke-ass), I wasn't able/willing to a spend a bunch on a fancy Ohlins or Penske shock. I had seen the posts on here about using an F3 shock (mtnniceguy and a couple others sorta paved the way here. Nice work, fellas.). I liked the notion of the cheap shock, but I also recognized that the stock internals that were designed 20 years ago for a linkaged sport bike were not appropriate for the 919. Even though I wasn't going to spend the dough on a big name, I definitely wanted my shock to at least be valved correctly. Also, I knew that any shock I picked up would likely be in desperate need of a rebuild simply from sitting God knows where for the last two decades. Together, that spelled P-R-O-J-E-C-T to me.
I got in touch with RaceTech about their Gold Valve for the F3 shock I got off eBay. It sounded like they would need a lot of input and whatnot from me to build a special piston/stack combo for the F3 that would make it appropriate for the 919. That didn't sound like fun to me. If I was going to be the development monkey, I sure as hell wasn't going to pay them for the opportunity. With that in mind, I determined to make my own shim stack and piston modifications.
From here, it was research time. I researched linkages, ratios, valving, shims, rebound, compression, pistons, tuning, fluids, blah blah blah. I went nuts. I spent half my spare time on Borynack and Verdone's sites, and the other half on WT and IBSF. I learned a shit-ton about shocks and valving and whatnot. Mostly I learned that I don't have nearly the experience nor the expertise to properly develop a good valving setup for my bike from scratch. I might (MIGHT!) be able to squeeze into the ballpark, but it wouldn't be right and I would never be confident that I was getting out of the new-to-me shock what could be got.
With all of my internet stumbling and "research"ing, I ended up in contact with a pretty well-regarded one-man company who does a lot of tuning and rebuilding of shocks for Hondas like ours. He doesn't specialize in 919s, but he's worked with them and has done lots of work with very similar shocks/bikes/problems. He sold me a new piston of his own design/production with a shim stack developed for the 919. Just like that, I saved myself a crap ton of time and energy, and got an excellent product that gave a high degree of confidence in the eventual result. Bingo. This, my friends, was the right way to do it.
Once I had the valving and had received a new spring and Schrader valve for the re-charging of nitrogen, it was just a matter of reviewing and re-reviewing the methods for assembly/bleeding of the shock, and the procedure for installing the thing on my bike.
The step-by-step directions for the disassembly/reassembly of the shock are readily available elsewhere, so I won't go into the details. For all you guys who think it's complicated: it ain't. It's a pretty simple process (just follow the directions!), and as long as one takes ones time, pays attention, and ensures the methods being used are what's recommended, there's not a lot to go wrong. I have a little 10'x12' basement shop that I use for all my projects; home improvement, motorcycle, bicycle, etc. My handiness is mid-level, and I'm definitely not one of those types who seem to be able to work magic with their hands. I have to focus carefully and really ensure I do things well/right and don't get ahead of myself or impatient. In other words, though I've always liked tinkering with stuff and have some experience behind a wrench, I'm not a natural engineer. So if I can do it, you probably can too.
I used a homebuilt spring compressor (the threaded rod/bar stock type), a bench vise w/ padded jaws, a drill press, a torque wrench, a thread tap that I bought for this project, and the usual hand tools that every Real Man probably has multiples of. I also wore safety glasses the ENTIRE time I was fooling with this stuff, and often made use of a rubber apron to keep my filthy shop clothes from getting soaked through with shock fluid. With the exception of the drill press (a hand drill would have been fine), I don't think I could have done without any of these tools. I tried several automotive spring compressors, and none of them fit. Thus the decision to just make one. It worked out totally fine.
I took the shock to my local moto shop/suspension guys to get charged with nitrogen through the Schrader valve I installed. No problems here.
The install onto the bike was equally easy. I hung my bike from the rafters, and used the method outlined by mcromo in post #18 of this thread: https://www.wristtwisters.com/forums/...ild-32389.html
I did take a bit of time to position the way-too-long reservoir hose so it wouldn't kink and to secure the new reservoir in a position that will allow easy access to the compression adjustments.
I set sag as outlined in the Sportbike Rider articles. Setting Static Sag | Sport Rider
I wasn't able to ride the bike for a few days after the install/completion. I was pretty excited/nervous to see how the thing would do. When I finally got to put in a couple days of solid riding, all my fears were quickly put to rest. This shock has absolutely transformed my motorcycle.
It handles turns very predictably, including my special "testing" turn that has a huge pavement lip across the entire two lanes right after the apex of the turn. In the past, this has unsettled the bike to a scary degree; now it's not a biggie. The bike "tips" in quickly and controllably. Changing lines in the turn is now much less of a challenge. Accelerating hard out of the turn is now actually a possibility that doesn't strike a bolt of fear straight through my heart.
The bike feels like a rocket; it fires straight forward. No more of that "squish, wiggle, squat" with vagueness in the rear. No more "God- am I pulling a little wheelie, falling off the back, or just pulling away from a stoplight?!" It's fantastic.
: Speedbumps and rough pavement are still there, but the bike now takes them on with grace. Gone are the butt-tossing hops and spine-chilling shakes over little bumps or potholes.
Yes, the compression and rebound adjustments work. I've been playing with them, and have a reasonable setting at 1/2 turn in on rebound and 3/4 turn in on compression. I'm sure this will change. Almost as exciting is that the spring preload adjuster on the F3 shock is on the BOTTOM of the mounted shock, thus allowing extremely easy access with the spanner. Like crazy-easy access. I can't fathom why the original shock had it on top. What a PITA.
In short, this project was fun, rewarding, inexpensive, and extremely effective.
Here are the prices/details on most of the parts:
- Used 1998 F3 shock. $35 shipped on eBay
- New piston/shims and main seal. $142 shipped from a known specialist
- Eibach 600.225.1100 spring. $73 shipped from ultrarev.com This is 6"long x 2.25" I.D. x 1100 lbs/in. (( Contrary to a couple things I read, no grinding was required. It fit like a glove. ))
- Schrader valve with 1/8" NPT threading. $7/pair on Amazon.
- Silkolene RSF Pro 5wt shock fluid. $23 from local shop.
Total: $274 for parts. Also spent $6 on the thread tap tool and $11 on welding bar stock, nuts, and washers for the spring compressor.
Here are some links to sites I used for research and guides for disassembly and reassembly and shock selection:
- The site you're on.
- Peter Verdone's site.
- The IBSF
- mcromo's install guide
- jnich77's thread
- I also spent a lot of time on forum sites devoted to other inadequate Hondas. VTRs, Hawks, old CBRs, etc.
I hope this helps anyone who's interested in undertaking this project themselves.