Shortening front forks.

Hi all,
returning to motorcycles after several decades of not motorcycling.

My present project is restoring an old motorscooter.
(make probably not relevant as it was a New Zealand product)
Step #2 is upgrading the motor so that I can keep up with modern traffic.
Step #3 has to be fitting modern disc brakes.
Step #4 then has to be upgrading the front suspension, which is where I
will run into big problems. The headstock is rigid enough and can be
further braced, but the forks are an inverted "Y" folded back slightly
with leading arms and short spring/damper units (parts bin engineering
from the manufacturer's motorcycle rear suspension)
My current thought is to make a more conventional motorcycle front end
with two triple plates only with much shorter sliding tube forks.
Has anyone got experience with front forks (say 250cc-350cc size) and
the possibilities of shortening them?

Regards,
Greg.P.
NZ

 

If you can find some forks that will fit the yokes, you don't have to
shorten them in order to make the motorcycle 'sit' correctly.

Just lift the forks through the yokes so you have an inch or two (or
whatever) protruding above the top yoke.

 

Intrigued now. Any chance of some pictures?

Your wallet, but is it viable?

A well setup drum brake, and very good forward planning ;-)

Have a scout round a breakers and see if anything vaguely modern could be
adapted to fit. Once you have a stem/bearing set that fits, look very
carefully at the yoke offset needed from the stem.

 

Step #1: SELL the old motorscooter to somebody who likes that
particular brand.

Those people are definitely OUT THERE, in more ways than one.

Step #2: Buy an old motorcycle that you can afford, preferably one
that was mass produced in Japan and imported by the millions into NZ.

Step #3: Fix it up, using aftermarket repair parts that you can easily
order from the interweb.

Step #4: Next time you have such a creative thought, JUST LET IT GO.

Sure. You could install shorter stanchion tubes, shorter springs and
maybe even shorten the damper rods.

But it wouldn't be worth your time if you have the money to buy a real
motorcycle that does what you want.

And, if you don't have any money, the project will be just an exercise
in futility if some engine part or rear drive part gives you trouble.

Then you'd be back in here asking about motorcycle engines that you
could easily adapt to motor scooter style rear drive, or how to adapt
a motorcycle swing arm and a motorcycle engine to an old scooter.

 

Typical bad advice from a fake.

 

Or you could do what I suggest, which is raise them through the yokes.
As long as you don't mind maybe a couple of inches of stanchion poking
up.

 

I don't feel like instructing Greg about the importance of matching
the front spring rate(s) to the rear spring rates and why that's
important to the overall ride comforts as well as traction balance.

And, if he found a set of forks for a more modern motorcycle which
used a 17-inch front wheel, he would still have a handling problem
because the rear wheel is probably a 12 or 14-incher.

The rider of a two wheeled vehicle with such a wheel/tire diameter
mismatch feels like the bike doesn't "want" to turn into a corner and
then it feels like the rear end is falling out from under him is the
turn.

 

Who said he would?

 

Boy are you stupid. It's a motor-scooter NOT a 125cc street bike you
stupid git.

 

uh, dude your senility is creeping in methinks...he's talking about a
motor-scooter.

 

Some scoots, such as a Honda CH250, could probably handle small bike
forks if the right sized races could be found, the fairing and inner
bodywork would probably have to go and then it would be a rat scoot.

 

My bad for not reading the post properly. That said, grafting a
conventional front fork end on wouldn't be hard: just a waste of effort.

 

Hi Older Gentleman,

the machine currently has an upside down "Y" made of welded tube - no
triple yokes and motorscooter superstructure around the head.
I'm a bit nervous of it's strength if I install better brakes and more
horsepower. The superstructure can be braced easily inside so I can keep
the external appearance.

Apologies for delay, my provider seems only to download about weekliy!

Greg.P.

 

Google "NZeta". Way back when New Zealand had strict fanancial rules
and most (90%) of our exports went to Britain. UK owed the US umpteen
times it's total worth so the UK pounds could only be spent back to
the UK or Commonwealth countries.
Motor vehicles had huge duties and sales tax but the duties were dropped
from NZ built vehicles. As we only had 2-3 million people the result was
a few types of vehicles partly manufactured here, based on existing brands,
eg Volkswagens; imported components 60%/NZ manufactured 40% - 40% of duty
knocked off.

Haven't bought it yet - have put in an auction bid though.

Well, the motor concept came first - scooter from teenage memories.
No wallet mostly used as moth repository, but have machine shop.

My guess is I would have a 50/50 chance of survival WITH perfect brakes, 50
minute survival with drums.
(that might be a joke, might not)

No problem machining up yokes as I have the gear - the only forks I've
seen that might be near the length are childrens offroad bikes. They
wouldn't
take the weight.

 

I'm definitely "out THERE" ;-)

I want a scooter because I lost right leg in a motorcycle accident ..
years ago. no real circulation in the bit I have left so need shelter.
So much family stress m/c out but apparently scooters are acceptable.
(I'm going with the flow for now)

No, can't find such a beast!

I can make those.

There's the basis of the idea - the particular scooter has a proper
swing arm and a conventional unit construction motor.
Almost anything not too tall in the way of engines could be slotted
in - width about 350mm inside body.

 

Can't do it - the body/front skirt surrounds the head.

 

Let's put it this way - I started tuning bikes in the mid 60s,
started building frames and engines in the late 1960s. Racing bikes
1969. (eyesight not up to racing speeds so I retreated to building/tuning)
End of 1970s m/c accident ended m/c career.
1990s worked with John Britten on engine concepts.

I can design a motor, I can design a frame.
I don't know the current and recent motorcycles.
I don't have deep pockets.
Have lathes and mills, CNC and conventional.

Regards,
Greg.P.

 

Adapting "X" axle and wheel to "Y" forks is no problem.
I could equally design completely new forks and machine them,
but if existing forks could be shortened it would cut costs drastically.

 

I don't mind wasting effort - retired with more sense than money

 

In that case, don't buy it, look for something that does what you want
without
having to make major modifications.

Personally, I was thinking about buying a 3-wheeled bicycle and adding
a 49cc moped motor to it if I ever deteriorate to the point where I
can no longer balance a 2-wheeler...