Frame Modification - Starting to look
like a chopper now
Frame Cut: Cut the backbone close to
the seat mount. We are taking the stock
"dip" out of the backbone and replacing
it with a clean straight tube.
The upper tubes are then marked and
cut. We leave a little extra tubing
just before the curve. This will allow
us to set the proper angle after the
backbone length is finalized.
Frame Cut: After the stock neck is
disconnected, all the old stock tubing
from the cast iron neck is removed.
This is were the new tubing will be
The remaining frame connection points
are then cleaned and prepared for welding.
Backbone Fabrication: Based on the
computer drawing, the new backbone tube
was cut for a total backbone length
of 27". The new 7 degree triple tree
was assembled and attached to frame
neck and the fuel tank set on the backbone.
The final backbone length was marked
and cut Holes were drilled through the
seat mount and backbone for a spot welds
to hold the inner tubing in place.
Setting the final Rake: The new 10"
over fork tubes are attached to the
triple tree with the front wheel installed.
This is how the final rake will be determined.
Before the final weld is applied, the
front tire will be deflated to simulate
the weight of the engine installed.
Down Tube Fabrication: With the front
forks attached, the down tube length
and angles can now be finalized. Small
inner tubing is also cut, the upper
connection inner tubing will have a
Frame Assembly/Alignment: The new downtubes
and inners are installed. Small holes
are drilled through the outside for
spot welds to connect the inner tubing.
The backbone alignment is set to the
original position using a plum-bob.
Spot and stitch welds are used to hold
the alignment in place.
Frame Assembly/Welding: With frame
locked down and aligned, stitch and
spot welds are added. During each weld,
the plum-bob for the backbone center
line is checked. After the backbone
is locked in, the plum-bob is moved
to the neck and the more welds are applied.
Additional checks are performed to insure
the neck is true. After the frame is
stitched welded together, the final
plum-bob position is dead center.
Frame Assembly/Testing: After the stitch
welds were inplace, the rolling chassis
was pushed up the hill and ridden down.
The frame road straight and felt pretty
good. Only getting to about 20 mile/hour,
it was hard to tell if the 3.5in of
trail is enough. If it is not, the 7*
degree tree will be replaced with a
Completion of Frame Modification Phase:
The frame modification phase is now
completed. After the test ride, the
frame welds were finalized. The end
result is 4in stretch in the backbone,
7in in the downtubes and 40* degrees
in the rake.
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