KZ650 B2 Light Weight rebuild

I think the differentiation between "sprung" and "un-sprung" weight is probably more important that "total mass" in effecting the way the bike will ride.
The way I used to explain this to apprentices I trained was this:
Strap a 25KG weight to each foot and run a slalom course around some cones (un-sprung weight)
Now remove the weights from your feet and put 50kg in a rucksack supported by your legs and knee's (sprung weight) and run the course again
Which do you think would be quicker and easier to make the direction changes ?

Sixten post=908656 userid=57394That drag bike looks great. Very long intake runners? Did that improve midrange or top end?

About saving weight on axles. I tried once to drill out axles but it was difficult. I found it was easier and cheap to buy hollow axles from a scrapyard.

For the engine mounts I put helicoil in the engine and short screws instead of the long bolts all the way thru.

Long runners make more torque, good for a "small" engine like mine. Most large drag engines use very short stacks for more top end HP.

There are intake track length calculations you can do but the math is very complicated. I tried to get a University Professor to do it (1994) but it never happened. It has something to do with Helmoltz Resonance Frequency. Honda motorcycle wrote a SAE paper on it when they were doing early F1 stuff developement. If you look at those older Indy cars the exhaust is like a bundle of snakes!

Those Hilborn injector "stacks" came stock in that length, same length used for a 4 or 6 cylinder car engine (motorcycles as well) it seemed a shame to cut them, so I just made flanges to weld to the tubes. Again look at those tiny high revving Indy cars.

The hollow axles may be looked at but I need to calculate if its worth it on a street bike (probably not)

As for the long 650 engine mount bolts they discontinued those for shorter ones a few years into production life probably due to cost. I will probably be using short bolts as they don't add too much "stiffness", all the engine power goes thru the top rear mounts anyways.

I shelved the Mark Zero disk for now as I found a ready to go semi floating 300mm rotor on Ebay for $60.



Its off a 2014 Ninja EX650, just needs a adapter fabricated. I roughly measured pic of rotor and front hub to see if it was kosher before purchasing. Stock B2 rotor is 275mm so placement might not be that far off.

Also bought a wet front master and caliper off a 2007 Suzuki Boulevard cruiser (big heavy beast) on Ebay for $50.

Should be strong enough to stop better than the old stock stuff, that was my main goal. Cheap is also good because I am on a budget, was looking at other brands but they want way too much for them. This stuff should clean up fine, plus only pads needed on the caliper.



It may end up to be a lighter setup. Plan is to mount the disk on RH side of wheel to shorten the brake line, and get rid of stock brake splitter (hate those!)

Still have to source some aluminum wheel rims.

I designed this fork brace a bunch of years ago...



Its a copy of the one on my drag bike I paid so much cash for back in 1986! Pretty simple design, the inner fork fender mounts may need to be milled down if I remember correctly.

Here is the 19" glass front fender I bought at the swap meet for $10, sitting on a stock 650 C mag wheel.



So for the raw alloy cost, and my time, the front end is just about there

This is my buddies KZ900, he has the same Mark Zero disk but its been cut out to "flex" as its rigidly mounted. There was a issue with them bending after a while with those rigid Grimeca calipers.



Same setup as my old street bike, we got the chassis work done at the same shop in 1986.



I think this was the hot setup back then, the "road racer" look

My old shocks are on his ride now, should have kept them... also miss that V&H pipe (not on his but gone somewhere)

I keep on find parts I forgot about... all the project bikes are in RubberMaid bins so I need to dig thru them to find stuff.

Found these cheap little amber signal lights (plastic shell) and Cateye tail lamp, the packaging says I paid $9 for the signal set and $7 for the tail lamp.



That small Chinese 60mm tach I bought for about $35, it was going on a drag bike but I sold that during Covid. I did find a matching KPH speedo but its in Germany. I might have to wait till our dollar rises a bit before thinking about purchasing it. It might be cheaper to buy 2 new black face chrome gauges as there available one town over from me at a good price. No rush. 

I also have a bunch of small idiot lights to make a custom dash panel, bought them because I am planning the same thing on my DFI project. 

These are parts I already paid for so why not use them, they are lighter than stock and will keep me road legal.

I plan to do the same thing I did a couple of years ago and put all the stock equipment on to pass the Government safety check .

The only thing they mentioned last time was a slight brake fluid "weep" from one of my rear brake piston. It passed because I agreed to fix it, it would have failed if I was certifying to sell it. 

I do know here in Canada the cops will take any chance to pull you over. I once got pulled over for only having a LH mirror, got a warning. I also got pulled over and a warning for having no signal lights.  

Funny that I have never got a speeding ticket on any of my bikes all the times I was over 100 MPH

I bought this '83 GPZ305 front fender for $40 because I remembered the last time I saw one at the swap meet it was $60. It has the integrated sheet steel hoop just like the GPZ750 Unitrak has, so no fork brace required (may save weight) and way lighter than the stock chrome steel unit.



I have a '83 GPZ750 front fender to look at for comparison so I shoved it on top of a 19" front wheel... looks OK. Since the 305 and 750 use a 18" front wheel it should be fine, the tires are 100 and 110.



The design is slightly different and the 305 part is probably a bit thinner (the 750 requires milling the mounts on the fork legs) I also like keeping it Kawasaki if I can  

This means that the $10 white fender goes back on my DFI build... I think the days of finding fenders for $10 may be gone for good (:

Can't beat a cost effective solution - you don't have to blow the grandkids inheritance to have a cool ride

wrote:

Can't beat a cost effective solution - you don't have to blow the grandkids inheritance to have a cool ride

The first grandkid is still in the oven, but were spending more money on a girl who isn't here yet than my project bike

I thought I was done buying parts, but you never really are...

What can I say, I am living in a Winter wonderland just trying to pass these miserable "snow" months!
 

Could be worse, living with summer days in NZ at 27degrees, and the bike not on the road🤪

Puttering around inside today weighing parts that are stored in the basement.

Not going crazy with a super accurate scale either, just using a pretty accurate digital fish scale (up to 50 lbs) for the large parts. I do have all kinds of scales in the house (home brew guy) but I find the fish scale super easy to use.

Came up with some preliminary weight findings :



A lot of the bigger stock parts are stored out of the house, too cold and snowy to access right now.

Parts not on there that I did weigh for comparison :

RS34 Mikuni flat slide carbs : 8.50 lbs
MAC 4 into 2 exhaust with 17" chrome universal mufflers : 16.38 lbs
Vintage "Smokin" Joe Charron 4 into 1 canister exhaust : 13.94 lbs

I was online and I found a new 4 into 1 pipe on WeBike Japan web site. Nice pipe but no baffle, looks to be lighter than the one I currently have (no weight listed)

Pipe and baffle delivered to me all in about $520 Can. Possible weight savings over the MAC 4 into 2 exhaust is only about 3 lbs.

The aluminum rims conversion is another thing I looked at. Aftermarket rims vary by design and thickness so hard to guess but I figured about 6 lbs total. The rims delivered to me all in about $440 Can. Possible weight savings over the steel rims is only about 6 lbs.

I have to think carefully about spending $960 to save 9 lbs!

I found out that the stock turn signal indicator set weighs 4.12 lbs, so looked into cannibalizing the plastic mini signals I have here. Took those tiny buggers apart, and I can reuse the lens and guts but the rest is shite, even the M8 thread was plastic!! The stock indicators are huge by comparison.





Glad I did not pay any real $$ for them. Good for taking sizes off to make my own design that I can fabricate.

Whipped up a CAD design that I can turn on my lathe.





The only things that will be steel are the M10 studs and nuts. There are also some washers and spacers that can be made from alloy.

Also found this Pingel petcock taken off a Kawi Triple drag bike.



It is ON/OFF only, no reserve (around town bike) and 3/8NPT. Looks like I already plugged one spigot, now with these carbs will have to plug another. Will fabricate my own alloy mount plate.