The Yamaha AT1MX Replica Project
Suspen
sion
Left, at the bottom you see a spacer tube.
This comes in the stock forks and sits on top
of the fork spring. Years ago Webco made a
fork kit for the AT1/CT1, which consisted of a
spring to replace these spacers. Webco isn't
around anymore so we used 3 Briggs and
Stratton valve springs per fork with B&S valve
spring keepers in between each spring &         
  stacked on top of the stock fork springs.
Finish off with 4 oz. of 20wt fork oil. This setup
 will have about a half an inch of preload don't
worry, you'll understand why when it's all
together.  The result is a front suspension that
is soft in the first 1 to 2 inches of travel then
gets progressivly stiffer, but is very difficult to
bottom out. This is as good as it gets with 5.5
inches of travel.
Stock Yamaha spacer tube
Briggs&Stratton valve springs&keepers
Stock
Yamaha fork
spring and
washer
Slamming into bumps wasn't what made me
nervious about the 30mm forks. Not being able
to hold a line at speed or while cornering were
my main concerns. This used fork brace made
all the difference. The bike holds a line and
turns like a cat on carpet. The 21inch CT1
front wheel Happy found, fit perfectly. Michelin
S12 does the steering well.
Cycle Gear had the 20wt fork oil, fork seals and locktite.$25
The local lawnmower shop had 6 used Briggs&Stratton valve
springs and 4 keepers. $10 Fork brace on E-bay $15.99  for a
total of $50.99 the AT1 has a front end that works.
The Before front
end with 18 inch
wheel and no fork
brace.
The used Works Performance shocks were a
bolt on. They were off a CZ and were 13.5
inches eye to eye. The mounts fit well and
only needed the bushings bored out slightly to
fit the larger diameter Yamaha mounting bolts.
A drill and a vise was all that was needed.        
The shocks being 1.5 inches longer works out
perfect with the taller front wheel, the bike sits
level and feels good on the track.