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Author Topic: Ultralight Dirt Bikes  (Read 14193 times)

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Offline Daryl Jones

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Ultralight Dirt Bikes
« on: April 30, 2015, 12:34:44 am »
The New Zealand designed FX lightweight (57 kg.) dirt-bikes have been around for a few years now. (  http://www.fxbikes.com/   )



I liked the concept a lot, but the use of lots of Downhill/Mountain bike components seemed a bit expensive & delicate for a full-sized,
mature age rider, such as myself. Just the front forks cost $2000 alone.

Years ago, I had a RM80H big-wheel, it was an absolute blast to ride in the bush.
So, I designed & build my own new lightweight, using readily available, S/H, ‘China Cheap’ components.
Wet weight is around 66 kg. with plenty of opportunity to lose some flab, check out the front disc.



Funny thing, FX has now come to the same conclusion. The 2015 FX5 uses trials and other motorcycle components.
The handlebars appear to be the only bicycle bits still in use. Weight is up a touch (60-62 kg.) depending on the Spec.
They will be built in Italy with prices ranging from US$4,000 - $12,000.
( info sources:  http://www.gizmag.com/fx-bikes-mountain-moto-fx5/30113/   and   http://www.fxbikes.com/  )



Here are the latest specs:      2015 FX5 Series | Specifications*
•   Weight (ready to ride): top end models starting at 60kg / 132lb
•   Frame/swing-arm (chassis): Chrome Moly steel, tube and sheet down to 0.9mm (0.036?) wall thickness, TIG welded, made in Italy
•   Suspension, front: trials motorcycle forks, 40mm stanchions, 165mm / 6.5? travel, by Formula’s Tech Suspension, made in Italy
•   Suspension, rear: motocross/enduro motorcycle shock, coil spring, 165mm / 6.5? travel, top end models with Ohlins TTX36, Sweden. 
•   Engine: 4-stroke, single cylinder, 125cc (FX-Works 125cc engine makeover upgrade available on premium models. 
        150cc and Daytona-Japan 190cc upgrade kits available later)
•   Transmission: 4-speed left-foot-shift (automatic clutch and manual clutch options)
•   Carburetor: Mikuni
•   Ignition: CDI, NGK spark plug, kick-start (easy on 125cc, decompression assist for Daytona 150-190cc)
•   Exhaust/muffler: USFS-approved with spark arrester, industry standard 94dB loudness or less
•   Tires, front and rear: Kenda 19? motocross/enduro 70/100-19
•   Rims, front and rear: RK Takasago Excel motocross/enduro 19? x 1.40?, made in Japan
•   Drive chain: RK Takasago Excel 420 motocross/enduro, made in Japan
•   Brakes, front: Formula 4-piston hydraulic trials/enduro brake set, made in Italy, with trials motorcycle disc
•   Brakes, rear: Formula 2-piston hydraulic trials/enduro brake set, made in Italy, with trials motorcycle disc
         (left-hand control on auto-clutch models, right-foot control on manual-clutch models)
•   Fuel capacity: 1.85 US gallons / 7 liters
•   Fuel economy: 125cc up to 125mpg (est. max range 200 miles / 360 km)
•   Maximum speed: 125cc estimated 60mph / 100km/h
•   Wheelbase: 1350mm / 53? (similar to KTM Freeride 350)
•   Seat height: 812mm / 32? (Honda CRF230 is considered low at 34?)
•   Ground clearance: 300mm / 12? (similar to trials motorcycle)
•   Seat to footpeg distance: 512mm / 20? (similar to KTM Freeride 350)
•   Rider to handlebar reach: (similar to KTM Freeride 350)
* Final specifications subject to change.

My Comments:
Only 6.5” travel F&R with 40mm tubes seems a bit ‘tame’ by post ’75 standards.
I notice also, that they have returned the engine back to a more horizontal position than the earlier bikes had.
It looked ‘cooler’ before (ie. less Postie), but would have raised the C.o.G. and probably messed up Mr Honda’s oiling system,
and that’s never a good idea.

I would find a fully street registerable one, for around say AU$3,000, very appealing.
But for US$12,000!!….Well, as Dr Hibbert says: 
“Hillbillies would like to be known as ‘Sons of the Soil’…...but it Aint Gonna Happen!”

Cheers, Daryl.
P.S.  Perhaps something (nicely) built around a Postie bike Compliance Plate could be a way to go?
Or a big wheel, big bore SL70……or I maybe I could just finish the big-wheel TC90 in the shed.


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Offline Mike52

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Re: Ultralight Dirt Bikes
« Reply #1 on: April 30, 2015, 07:51:55 am »
Saw Daryl's one at Murphy's Creek.
Interesting
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Friend  struggling up a hill on a old bike at MTMee .http://www.youtube.com/watch?v=cjj6E2MP9xU.

Offline Nathan S

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Re: Ultralight Dirt Bikes
« Reply #2 on: April 30, 2015, 08:05:38 am »
Any guesses on what a typical BW 85cc MXer would weigh with either an XR100 or a pitbike motor in it?

A mate has been building serious electric powered DH MTBs - fast enough to beat his YZF450 to 80kph. They're a ~$10k exercise, but at least you get the electric bike's benefits of noise and perceived legality.

For $10k, I'd be buying a Beta X-Trainer (noting that they're not the same type of bike, but when it comes time to lay down the cash, 99% of people will buy the most versatile product).
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Offline Daryl Jones

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Re: Ultralight Dirt Bikes
« Reply #3 on: April 30, 2015, 09:19:21 am »
Quote from: Mike52 on April 30, 2015, 07:51:55 am
Saw Daryl's one at Murphy's Creek.
Interesting

The base bike cost $70. It needs a set of rings before I'd take it out of sight of the pits.
Not bad for Mozzy control, but. ;D

Mine is just a test of the concept. 
As Nathan S has indicated it is the ability to be "legal" or at least the perception of "legal" that will make it useful/valuable.
I'd like to see pics of the electric MTB.

Street legal, Very quiet & lightweight opens up so many riding opportunities.

DJ
« Last Edit: April 30, 2015, 11:07:06 am by Daryl Jones »
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Offline sa63

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Re: Ultralight Dirt Bikes
« Reply #4 on: April 30, 2015, 04:38:16 pm »
look at:
http://www.stealthelectricbikes.com.au/

not cheap, but a total urban hooligan machine and quiet
id love to have one, but tied to my petrol dinosaurs!
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Offline Daryl Jones

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Re: Ultralight Dirt Bikes
« Reply #5 on: April 30, 2015, 09:44:25 pm »
The Stealth looks great.



Unfortunately,  5,200 Watts, which would provide Excellent performance, is 26 times the power allowed
for a "Low Powered / Except Vehicle" (200W Max.) for use in/on public areas in Qld.

Still looking for an economical "street legal" lightweight solution.

cheers, Daryl.
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Offline Mike52

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Re: Ultralight Dirt Bikes
« Reply #6 on: May 01, 2015, 07:47:31 am »
Quote from: Daryl Jones on April 30, 2015, 09:19:21 am
Quote from: Mike52 on April 30, 2015, 07:51:55 am
Saw Daryl's one at Murphy's Creek.
Interesting

The base bike cost $70. It needs a set of rings before I'd take it out of sight of the pits.
Not bad for Mozzy control, but. ;D
DJ
;D ;D

Saw the stealth at CD10.
The yellow one is the hotter version and goes like a stabbed rat.
Wanted one straight up till I asked the price  :o
Can buy a couple of old bikes for $8000 so I'll just keep dreaming.
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Offline sa63

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Re: Ultralight Dirt Bikes
« Reply #7 on: May 01, 2015, 08:02:45 am »
yes wish id tried one, I didn't as I had no intention of buying one..stupid me!
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Offline Tex

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Re: Ultralight Dirt Bikes
« Reply #8 on: May 01, 2015, 10:51:58 am »
Interesting thread, thanks Daryl. Those FX bikes, and indeed your prototype would be a real experience to ride!

Tex
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Offline Nathan S

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Re: Ultralight Dirt Bikes
« Reply #9 on: May 01, 2015, 12:01:25 pm »
Quote from: Daryl Jones on April 30, 2015, 09:44:25 pm
The Stealth looks great.



Unfortunately,  5,200 Watts, which would provide Excellent performance, is 26 times the power allowed
for a "Low Powered / Except Vehicle" (200W Max.) for use in/on public areas in Qld.

Still looking for an economical "street legal" lightweight solution.

cheers, Daryl.

Yes. There's a point where you can't meekly claim that it's only 200W - like when you're in the bike lane on a slight uphill, and moving faster than the cars.

http://the-riotact.com/faster-than-a-speeding-car/101665
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Offline Daryl Jones

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Re: Ultralight Dirt Bikes
« Reply #10 on: May 01, 2015, 12:05:28 pm »
Hi Tex, They really are Fun to play with.

If you read the reviews by some of the US gun riders who have tried them, they all agree.

The big advantage is that you don't need a whole lot of space for a couple of hours of fun.
If you were stuck in only an acre of bush on a full size Enduro or MX bike you would be bored pretty quickly.
Straights need to be long enough to wind them out, jumps big enough to be challenging, etc.

On a Lightweight, every obstacle is challenging/interesting & fun, fast or slow.
Think like trials riding, but where it's OK to put your foot down, pick up the front wheel and do a pivot turn,
throw a roost and mono toward the next challenge.

Driving around, I'm always stunned by how many great riding areas have been lost over time.
There are still some good opportunities around but, you are bound to get some trouble unless you're very Quiet & 'Legal'.

Now, something like this can be retailed in Australia for $1,749.



That's really a  'lot of Bike' for that sort of money.
I want Much Less Bike (component size & most particularly weight) PLUS a compliance plate, and I'd happily pay $3,000. (plus rego.)
You wouldn't think that's too much to wish for???

Of course, there are unicorns in my world and the sky is green and full of rainbows & dolphins.

Cheers, Daryl


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Offline Daryl Jones

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Re: Ultralight Dirt Bikes
« Reply #11 on: May 01, 2015, 12:36:16 pm »
On the Compliance Plate thing, here's a question.

When we no longer have a car building industry, the Aussie Govt. will/should lose it's ability to dictate ADR's to the International manufacturers.
We will need to accept "internationally recognised standards".

Perhaps that will flow on to motor cycle compliance as well.
The door might open for us to be able to register bikes that satisfy  "road worthiness" requirements without the need for ADR testing & certification?

Any-one got some knowledge in this area?

DJ
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Life's too short not to try to do Everything.

"First they tell you you're wrong, and they can prove it.
Then they tell you you're right, but it's not important.
Then they tell you it is important, but they knew it all along."
Charles Kettering.

Offline Nathan S

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Re: Ultralight Dirt Bikes
« Reply #12 on: May 01, 2015, 05:22:40 pm »
I keep hearing this. In hindsight, the whole ADR thing seems to be a mix of industry protection and government "make work scheme".

Apparently, a reasonable number of ADR requirements can already be met simply by compliance with international standards: hopefully that number will only increase.
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Offline Daryl Jones

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Re: Ultralight Dirt Bikes
« Reply #13 on: May 01, 2015, 08:38:33 pm »
Yes, 40 years of number plates relocated from the highest visibility position, in the middle of the back doors of 4WD's, down on/into bumper bars which need to be cut & shut to make this work, ( loosing their strength in the process). Highest prices for imported vehicles anywhere in the world.

DJ
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Life's too short not to try to do Everything.

"First they tell you you're wrong, and they can prove it.
Then they tell you you're right, but it's not important.
Then they tell you it is important, but they knew it all along."
Charles Kettering.

Offline 80-85 husky

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Re: Ultralight Dirt Bikes
« Reply #14 on: May 03, 2015, 09:46:29 am »
a mate and I seriously considered racing a couple of big wheel rm' s in the 84 vic enduro series years ago but we could get around the rego issue. the whole idea of a bike you could pick up if your stuck appealed...
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