Skorpion 660 Lightweight Build

[jpmsteadi]

No worries! The aluminum came in today, but alas I am actually working the next four days! Things are starting to shoot movies again.

But! hopefully the bike gets back on the road in the next two weeks or so.

[DII]

I wonder how the weight of Mastiff/Baghira spoked wheels compares, would they fit?

The Mastiff rear wheel weights 16,7 kg (I made a note about it some years ago but now I don't remember if it was with or without the tire on ).

[jpmsteadi]

So I spent all day in the garage today working with the mill (and the new rotary table I got, though its already broken....) making the brake caliper bracket to adapt the ninja 400 wheel to the MZ swingarm. It certainly looks and feels like its made on a manual mill, but it will work! I am going to go over all of it with a sander tomorrow and get it a bit nicer looking. It is about the same weight as the stock bracket, perhaps a touch heavier. I will weight them tomorrow when I am done. I am also doing the wheel spacers out of aluminum vs the stock Ninja steel ones. Should save some weight too.

[DAVID THOMPSON]

something like that is a bit of work on a manual mill
but it is sure nice to have one in the basement

i use it a lot to make wood parts for things as well as aluminum

wood boat frame parts for a friend is one item i do often
there are 2 wood pieces in his boats that need to be perfect
so every thing else lines up proper when cut to the drawings

Dave

[jpmsteadi]

A bit of work indeed! I am getting faster at it, but this took me about 8 hours today.

It is a handy thing to have around!

[Puffs]

That should be plenty strong! And maybe even allow for some weight saving, as you said.

I envy you guys with equipment like that, and a place for it. Houses in Europe are normally too small...

[jpmsteadi]

The equipment is super handy to have. For work as well; I have made a bunch of little brackets or replacement parts over the last couple months. Doesn't take up that much room really. I think with the mill, lathe, and work table it takes up about 30" (about 3/4 of a meter) by about 12 ft (about 3 meters). I do think we have generally bigger garages over here in the US. I know if I get another place down the road I will get a bigger garage!

Today my plan is to make the other side wheel spacer and try and get some wiring done. I got some nice newer waterproof connectors and am going to do it all up with those.

[breakwellmz]

BIGGER cars = BIGGER garages
I hope you`ve got rid of that radiator overflow tank by now!

[jpmsteadi]

Alas, radiator overflow is still there. Not sure it is going to go if I am honest. Not sure how much lighter I can make that.

Speaking of making things lighter: I woke up this morning with a newfound determination to get this rear wheel mounted. I took a scale downstairs and found that the stock MZ rear brake bracket weights 371 grams. The bracket I made weighed 399. DAMN! I can't be putting something on that is HEAVIER than the stock piece. So back to the mill it went. In two rounds I ended up making two pockets in the backside, and two rounded cutouts on the front side and got the weight down to 372 grams. I can live with basically the same weight. The new wheel spacers take the weight from 133 grams to 58 grams. I also got some titanium brake rotor bolts. Every little gram, right?

[jpmsteadi]

After fighting with some tires this afternoon I have wheel weights. Both of them are without tire, but with brake rotor, sprocket, cush drive, and wheel spacer(s).

The stock MZ:

The Ninja 400:

7.2 lbs (3.26 kg) aint nothing. Especially in rotating mass. Pretty happy with that.

[breakwellmz]

Good stuff!
Those wheels looked so much lighter from the start.
The overflow tube from my radiator (If that`s what that tank is for) just drops (drips) down to the ground, do non USA Skorpions have that tank?

[Puffs]

Nice work!

A saving of 3.26kg is indeed quite a lot, and your Ninja wheel looks a lot nicer too.

With the rotational inertia proportional to R² the biggest gain there is made by using lighter tyres: are you going to use 160's or 150's (as the Ninja wheel was intended for)?

A worry could be strength, the Ninja400 is a parallel twin weighing about 166kg wet, about 49hp/38Nm, and I'm guessing it's aimed at the Asian market (where people are smaller & lighter, say ~60kg).

On the coolant tank: have a good look what it does. The KLX650 I once had, had one too, and if I remember correctly it was an expansion tank. Coolant went both in and out, depending on how hot the engine was (different expansion coefficients).

[jpmsteadi]

I am not too worried about strength. The ninja 400 is actually really popular over here and people hop them up and race them, making more power than the MZ does. In addition, lots of quite large people ride them and I am only 145 lbs (65kg).

The coolant does go in and out. allows the engine to expel some coolant without drawing back in air. If I were going to keep the bike truely naked and not put the side panels back on I would firgure out a better looking solution, but since I am not, I am not too worried about it.

I was doing some research last night, it seems that the amount of weight I dropped is about comparable to how much weight a modern bike drops going to carbon fiber, so it should be a very feelable difference. pretty neat.

[breakwellmz]

I see.
Is that a cheats way of getting a larger coolant capacity without a bigger radiator?
Surprised Mastiff and Skorpion have such different cooling systems, two radiators on the Mastiff.
GO WATERLESS COOLANT! You won`t need an expansion tank then.
You can take the rad cap off a hot engine running waterless coolant as it doesn`t expand with temperature.
I fitted the fan back on mine when i realised it would bolt straight onto the other radiator, even the electrical lead was the right length!

[Puffs]

On the Ninja400: I have never actually seen one... Not sure they were/are imported here. But I'm sure Kawasaki included a sufficient safety margin & with your weight you'll be fine. That's actually quite an ideal weight for a racer, 65kg. Wish I was a bit lighter, but over the years I gained...

On water & waterless coolant, there are 2 effects that play a role: boiling and expansion.

As we all know, clean water boils at sea level at 100°C (one of the gauge points of the Celsius scale, the other being clean water freezing @ 0°C). Dissolving something into the water (like anti freeze) increases the boiling point, and reduces the freezing point. When water (or any fluid) boils, it evaporates & turns gaseous, thereby taking up a much larger volume. Consequently, in a closed system, the pressure rises, which actually increases the temperature of boiling. Engines may run a bit above the atmospheric boiling temperature of the coolant, and the lot is kept in order by the higher pressure. Caps come with different blow-off pressures.
This is not what the expansion tank is for. The volume increase liquid --> gas is (depending on what it is) much greater, in the order of 100 to 1000. So if you have some 2L of coolant, you would need a tank of some 1000L to capture that in the gaseous phase, which is awkward.

A waterless coolant can be a mixture of glycols, and it still boils. But at a different temperature, say 190°C. If the coolant would reach a temperature like that, your piston has long since melted, so yes, you can operate at a higher temperature, but you'll also loose the protective effects of a coolant with more water (boiling at, say, 120°C @atmospheric P). It's a choice. Also/more important than the (atmospheric) boiling point is the heat capacity of the coolant. That determines how much heat you can transport from the engine to the radiators. Finally, note that glycols expand too, see https://www.engineeringtoolbox.com/cubi ... _1262.html. Typically twice as much as water, actually.

A higher boiling point is for instance desirable if you're doing a difficult climb, making no or little speed while using the clutch a lot. That can get the engine boiling (and on my YZ I routed the blow-off tube up, so that I see that happening). But running the engine above the normal design temperature of course also comes with risks.

Expansion is something else. Most (if not all) materials expand when their temperature increases, both solid and liquid (& gas). If the coolant expands more than the metal (barrel, head), you need some room in the cooing system to allow that. It's not a lot of volume, and often a bit of air is sufficient. Or the manufacturer preferred to include an expansion vessel for it, wanting to prevent air in the radiators, for instance. Very common in cars too.