bright eyes 28 volt belt light
HL500 replica using Geoff Morris
Ed Gocek's HL500
Reproduction HL500 frame
Geoff Morris Concepts
GMC frames, & fabrication
175 Davis Road
Broadford, Victoria 3658
Tel: (03) 5784 1446
suggestions! Or have or know parts I could use!(replace "at" with @
What is a HL500? The "HL" is for Torsten Hallman, Sten
Lundin, Bengt Aberg and Steffan Eneqvist. Hallman developed
monoshock motocros bikes during the late
1970's. The bike is also known as the Aberg Yamaha. Check
out this link for the
complete HL500 story. Here is a link of photos of
HL500's out there. HL500 VIDEO
whole section on Halman 500's
parts began a year ago: 1978 Maico MC250 frame was selected for this
project. Why Maico? is a good question. Maico engineers nailed
the steering geometry and their bikes had razor steering. Their
frames were the first to use "lay down shocks" and they were the ones
that introduced leading axle forks. They are also lightweight and
strong chrome moly frames. Although it is much more work doing a
HL500 on the Maico compared to a Husky 400 or RM400 frame the handling
and weight is the most important features to me. 1978 RM400
Aluminum swingarm fits with a modified swing arm bolt and a couple 5 mm
spacers since the RM is about 10mm narrower and a RM400 rear
wheel fits the swingarm. The RM400 shocks are 1.25 inches longer than
stock Maico shocks and raise the bike to match the 1.5 inch longer
front forks I am using.
The RM400 Swigarm bolt is 1 mm bigger so I have to drill out the frame
to 15mm or 19/32. The RM400 swingarm is about .50 inch narrower so a
couple spacers will be needed. 1978 XT500motor, Suppertrapp exhaust,
Mikuni 34mm, EX400 oil cooler, Fox Airshox! I spent a day cleaning out
the shop so I can have room to start this one. The KX250 tripple tree
needed a smaller dia lower bearing pressed on the stem. Upper is same
Maico stock. Stem length looks ok! Fox Air shox need re-building and
seals are on order($200). Upper left rear shock mount needs re-done .25
more to outside to line up with lower mount. All stock motor mounts
will be ground off and XT500 tabs welded in place. 1979 YZ125 seat did
not fit so I found an original Maico 250. A 1976-1977 YZ125 tank is
the original HL500 used so they are hard to find. Tank will need mounts
Progress as of January 3, 2008
finally found an aluminum 1976 YZ250 tank! Although the original HL500
used a 1976 Yamaha YZ125 tank it just did not look like it would hold
enough gas for 500 Yamaha engine. Also the 125 tank was for motocross
and this bike is going to be hitting the woods. The YZ250 tank is about
mods thread reading...Good info on rake and trail for
the HL500 bike I am using for plans. One of the most famous
Another great HL500 or Aberg Yamaha
So here is where I start with a 1978
Maico Magnum 250 Frame.
Starting on the Motor mounts, looks
tight! I will start by grinding off all stock Maico engine mounts and
brake lever supports.
FOX Shox parts are available at Thor
Lawsons Fox Parts
Engine Fit October 6,2007
Still having trouble fitting engine in
frame. Front of case is too
close to downtubes. THe 1977 Maico AW frame works much better and no
frame mods are required.
Suspension Fit Check, installed front forks
HL500 Frame mods. Extend engine cradle 1.5 inches
Tubes on this particular frame form an inverted cathedral which does
room for the carb and air cleaner. On the Maico AW 1977 frames this
a standard cathedral tube and engine will fit much better. I have to
cut thes tubes
out and re-weld a cathedral support.
Then clean up and prepare for new tubes to be welded later. I will do
this last after I have carb and air claener installed
Now I will cut downdubes and install a 1.5 inch section of tube
to make more room for the engine. A 45 degree angle cut makes a much
Now I bend tubes forward and hold a section of tube in place to tac
And here is the finished splice
11-18-07. Engine fits much better. Looks about 1 inch lower too.
Engine chain alignment and front wheel installed 11-1-07
Engine alignment and mounts
Case split line must be about 10mm
offset to one side in the frame.
Welded Front motor mounts
Front motor mounts
Upper mounts are drilled and then will be welded in place
engine mounts still need shaving down. To remove engine it must
pass over these mounts and upper bar only allows about 1/2 inch upward
engine movement to clear this mount. My next door neighbor let me work
in his shop a couple months when it was too cold to work outside.
I need to decide where
to place the oil cooler? Most folks comments say put it on the side
Tiger the kitten
killed his first rat today in the shop! He can sleep anywhere he
I decided to look inside the motor, my curiosity got too me,
engine was seized up
from sitting out in a pasture for 20 years with no carb or exhaust
pipe. I pulled the
plug and looked inside and there was no rust! Hmmmm!
I removed flywheel cover and removed the flywheel and this is what I
The side case
had a crack in it and let water in
I tapped flywheel with a
hammer lightlty and it moved!
Engine broke loose and spins freely!
Looks like this engine may
runner! Oil was clean, no trace of water in it!
I have a 10.5:1 piston and cylinder for it but will probably run this
just to see if it will.
A few minutes with the sand blaster and flywheel is back on.
also worked on the frame some too. Cut this tube to be welded in
This makes room for the air
filter and oil tank. I also cut the tank
suports from a section of 1 3/4 muffler pipe
the left rear upper shock mount
needs to move outward 1/4 inch to line up with the RM400 swingarm. The
old mount is ground off and a pattern made. I will be glad when I can
strip all this nasty paint off!
You can see the offset.
I am tack welding all the parts in place and when I have finished
mounting things will take the frame to a friend with a Heliarc welder
to weld them all up. Then the frame will be stripped and sandblasted
The chain roller will need a mount also
The timing advance mechanism was
exposed to the weather for many years
and is beyond repair so a new one needs to be located on ebay.
Found a nice advance and points today!
Found the perfect tire to go on this bad boy! Designed especially for
500cc big bore bikes
makes one monster tire! Video
To race vintage class I need all drum
brakes so I picked up this 1981 IT465 dual leading shoe front wheel and
These are the best drum brakes made.
The forks are 38mm and so is the Maico tripple tree so I will assemble
them next, that is after I paint this bake hub.
August 14, 2009
Swing Arm Mods.
The RM400 swingarm is about .60
inchess narrower than Maico. To make this work we need a
different pivot shaft.
The Maico swing arm bolt is too small for the ID of the RM
Pivot spindle. A XR250 pivot spndle is the correct ID and OD and needs
to be trimmed to 7.536 inches long by removing equal material from each
The top bolt is RM400 which is too short. THe bottom bolt is
Maico or XR250, (same). THen we make two .3 in thick spacers to center
the swing arm.
Sept 5 2009
Cutting off the XR250 swing arm spindle.