weighting....

Here are some weight figures. Each wheel was placed in a like box and weighed on a postal scale... so the weights are likley 1-2 lbs high, but its relative. The rear 7R and galespeed wheels were weighed in the same box, likewise for the front. So the figures are less important than the weight difference.
Configuration. Both front and rear wheels of the 7R and Galespeed wheels were stripped. No rotors, etc. Those accessories were included after.

Rear wheel, cush drive and alloy sprocket

7R                           Galespeed                        Difference
21.4038 lb              18.275 lb                            3.1288 lbs

Front wheel, no rotors. Galespeed with spacers, 7R without

7R                           Galespeed                         Difference
14.00 lb                   11.6138 lb                               2.3908 lbs

total wheel weight savings: 5.519 lbs

Rear rotor

7R                             Braking (9r pattern)                            Difference
2.7236 lb                    1.2496                                              1.474 lbs

So, about 6.9 lbs.

Wheelie Nice...

Proof that you do use math after high school

I'll do my best to explain this, as while I have a BA in English, I don't have one in math.  However, some help from a teacher colleague next door who knows his numeracy guided me through this process.

When I first fit the zx9r swingarm, it appeared that the combination of linkages, dogbones, and swingarms from 2 different bikes resulted in a swingarm with incorrect angle... it pivoted down too far, so the bike would be stood on its nose in this configuration.  I needed to do some measuring to be sure, as my eyes might have been playing tricks.

First step was to reinstall the stock swingarm and take some measurements.  I liked how the bike handled in this guise, so it was a good place to start.  The straight edge ensured my measurements (using the floor as a datum line) were more accurate.  After measuring the swingarm axle distance from the floor, and the swingarm pivot from the floor, as well as the swingarm pivot length, I could determine the swingarm pivot angle in this configuration.

With a diagram and formula provided, I got all scientific...  The unknown angle, or the angle of the 7R swingarm, turned out to be 11.1 degrees.

I now wanted to replicate that same angle with the 9R swingarm.

I installed the 9R swingarm, using the 7R linkage and dogbones.  By plugging in the numbers from the slightly longer 9R swingarm, it turns out my suspicion was right.  The swingarm did sit at a steeper angle, adding 22.5mm more ride height.  This would equate to 40mm over the totally stock 7r configuration... I had added 20mm of ride height with the WP shock

Too much?  I didn't know -- but my goal was to reset things back to how I parked it a few weeks ago.  I needed to ideally get the swingarm "up" a couple of centimeters to mimic the same attitude.

I had been warned off creating/buying longer dogbones to lower the rear end, as I was told it might screw up the suspension travel or rate.  When I looked at the upper shock mount, I saw that there was some room to move...  I ended up removing the nut that fit on top of the upper shock mount.  It was about 3/8 of an inch thick, so perhaps removing that would lower the rear end of the bike.  Considering people add spacers or jack it up with no ill effects, perhaps the opposite will be true as well.

I took some measurements and... I am now much closer.  Right now the rear ride height is only 7mm higher than where I had it set.  A good place to begin.  I also allows me the full range of ride height adjustment built into the WP shock, so should I want to quicken up the steering even more, I have room to do so.

So where I am sees the 9R swingarm, the 7R knuckle, dogbones, and shock, and the spacer removed from the shock.  Another 7mm of ride height shouldn't adversely affect the handling!

Some progress

A bit of spare time has allowed me to test-fit the 9R swingarm into the 7R frame.  I'm going by limited interweb information that others have posted throughout the years.  I realize that with any of this stuff, "Your results may Vary"... so I've decided to check dimensions and weights myself, just to be sure what differences can be established.  To start off in the area of weight:

zx7r swingarm -- 8.785 kg
zx9r swingarm -- 6.755 kg (this is the late model braced one)
Saves 2.03 kg or 4.46 lbs

Caliper bracket
zx7r 493 g
zx9r 269 g
Saves 224g or .492 lbs

So both together is 5 lbs.

The next step will be weighing the caliper itself, as the 9r caliper is a smaller, lighter, single piston model.  There will even be a minute difference in things like the swingarm bobbins... the 7R uses massive 12mm bolts, whereas the 9R uses 10mm.

In terms of the fitment, the first step was to swap the "top hat/shouldered" spacers from one side to the opposite.  So, the threaded spacer pictured is normally on the RIGHT hand side on the 9R.  By switching out the seals from left to right, you can then move this to the LEFT hand side of the 9R swingarm, so it will work in the 7R frame.  There is a special notch/saddle in the 7R frame to accomodate it.  There was also some discussion about 0.125" needing to be removed from this to align the chain.  I noticed that the 9R spacer similar to the one pictured was not as "tall" as the 7R one.  Perhaps this would allow the sprokets to line up?  I used the shorter threaded spacer for now... we'll see if more material needs to be removed.  On the opposite (right) side of the swingarm, I found a spacer that fit UNDER the oil seal, which held it in place, and ensured a snug fit with the frame by spacing out that shouldered spacer enough.  

Once inserted into the frame, I snugged up the pivot bolt to the 14.5 ft/lbs called for in the manual.  The swingarm pivoted freely, so nothing is binding.  I then attached the swingarm linkage.

Everything is still together only finger tight.  With just some eyball guessing, it appears the swingarm might be angled down too far...?  That would mean that the dogbones are too short.  These are the 7r dogbones, and the 9r ones are even shorter.  There are "lowering kits" offered, which are simply longer dogbones, which might bring the ride height back into spec.  Need to get wheels on it first to be sure.  The jacked up reasets might be monkeying with my reference point.  For the record, the swingarm from pivot to front of the axle slots is 1cm longer.  Not sure a rider of my abilities will notice...

Starting some more serious modifications

Along with the Galespeed wheels, I plan to swap out the rear swingarm for that from a zx9r -- a 2000-02 model, which is braced, uses the same swingarm and axle diameter, and is actually 2.2kg (5 pounds) lighter.  It will also necessitate a rear caliper change, but that is to the good as well, as the bracket is lighter, as is the rear caliper itself.  I'll be trying to keep track of the weight savings of the lighter parts as they are swapped in.

At the same time, however, the front end also needed some service, so I decided to send the forks off to Race Tech for a gold valve kit, and new oil and seals.  The ZX7r is legendary for its front end, and I didn't want to bother with a total front end swap, despite the radial brakes, and lighter forks.  So after a couple hours' work, I had the front end off.  While I was at it, I also removed the triple clamps and cleaned and re-greased the steering stem bearings.  There was grease still there, but some fresh stuff will be nice to have in place.

As the new wheels do not have a speedo drive, I will be coming up with some sort of instrument solution as well.  The stock gauges have been removed, with the cable speedo drive as well.  The Koso gauges are a common swap, and I have some experience with them wiring up the race gauge for the ex650.  This will require sorting out instrument wiring as well, but apparently it is straightforward.  I have my eye on a newer model they have released.  More on that later.

For the back end, I was hoping I could use the dogbones and linkage from the zx9r swingarm, as it has grease nipples installed already, and the dogbones are lighter in aluminum, rather than steel.  The first step was to get the rear end propped up securely, without using the swingarm bobbins.  The old peg stands I made for the ex650 came in handy here, but of course will only work with solid pegs.  Some aggro was the need to remove the entire exhaust system, right back to the headers, to remove the dogbones, and linkage.

Unfortunately there were too many differences between the zx9r parts and zx7r parts.  The linkage had smaller diameter bolts in the 9r than 7r, so that wouldn't work.  The lighter alu 9r dogbones were also too short, which would make the rear end of the bike sit too low.  While I could wind in some shock length on the WP shock, I decided not to bother, as I doubt I had enough thread on the collar to give me the length I needed.  In the end, I cleaned up the 7r pieces, and cleaned and greased all the needle bearings in the linkage.  Hopefully this will last for another 40,000km!  I am still waiting on a specialized tool to remove the 7R swingarm from the bike.  Those who have done this mod before indicate some machining of spacers is required to line things up properly.  I'll be sure to continue to take notes and pics for others.

Back home

I guess I have enough followers and vanity to go back to using this blog.  "MB Supertwin" is no longer the right name, as I no longer have a twin cylinder bike... MB Superbike, perhaps?  Hmmm, according to what you can buy today, calling the zx7r a superbike is a bit of a stretch.  Anyway, some pics... first, utilizing some cheap Chinese trackday bodywork at Gimli...

 Thanks to AJ Enns for the great pics...

 The bike handles pretty decent.  Certainly wasn't pushing it that fast, but the power is fun (not always stuck behind a 600 in the straights), and I get all the raving about the 7r's front end... solid is an understatement.















It is a bit of a tank, so I've been doing a few things to shed some weight...

High mount exhaust was a complete system, and shed a few pounds...  Currently playing around with jetting to try to get it right.

Lightweight battery...

Rebuilt WP shock...

EBC rotors (stock ones were warped), Nissin calipers from a GSXR, and venhill lines... brakes much improved.

But again the biggest single complaint about these bikes is the weight, primarily the wheels.  I am trying to really simplify my riding/touring/trackday experience, so I've decided to splurge on some nice wheels, and use some all purpose tires.  Stay tuned...