HL500 Projects

bright eyes 28 volt belt light

Sign by Danasoft -

New! Husky 250 HL500

Roger Landberg's HL500 Project

 HL500 replica using Geoff Morris Concepts frame

Ed Gocek's HL500 Project

Framecrafters Reproduction HL500 frame

Geoff Morris Concepts

GMC frames, & fabrication

175 Davis Road

Broadford, Victoria 3658

Tel: (03) 5784 1446


email: email me if you have 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 the YAMAHA 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

Thumperpilot.com  has a whole section on Halman 500's

Collecting 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.


1979 Yz125tank. 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 as 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 inch 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 what the original HL500 used so they are hard to find. Tank will need mounts welded also.

Progress as of January 3, 2008

I  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 50% bigger.

HL500 handling mods thread reading...Good info on rake and trail for Maico handling.

My HL500

Here below is the HL500 bike I am using for plans. One of the most famous HL500's out there!

cool hl500

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 not allow room for the carb and air cleaner. On the Maico AW 1977 frames this used 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 stronger splice.

Now I bend tubes forward and hold a section of tube in place to tac weld in place.

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 finished

Upper  mounts are drilled and then will be welded in place

Bottom 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 wants!

Update: Feb. 20, 2008

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 found!

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 be a 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.

I also worked on the frame some too. Cut  this tube to be welded in place

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

Next 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 for powdercoating.

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
Terraflex makes one monster tire! Video

Still gowing!

Frame sandblasted.

 Next process is to convert the frame to an oil tank.

August 4 2009
I started working on the project again, too many things around the house to do but I decided to try to enter the AHRMA vintage ISDT vintage enduro race September 18 and 19, 2009 at NATRA land in Westpoint TN  which is 5 week away!

Oil Tank

 Here is a preliminary drawing of the oil tank. Here is a 3d CAD model in eDrawings format(free viewer)I still need to add outlet and inlet ports and fill and drain port. I ordered a 12 inch x 24 inch sheet of Aluminum .100 thick 3003 alloy from McMaster Carr. Looks like I will eed another square foot of aluminum sheet.

I made a cardboard oil tank for a pattern. The back of the oil tank is the rear tire mud guard and the side makes a airbox to protect the air filter from flying mud.

Left is forward.

The cutout is where the air filter fits.

My thumb is on a tab which will mount the lower mud guard

This is the fourth iteration and volume is around 175 cubic inches. Goal is 130-150 cubic inches which is around two quarts. I am still going to try to route the oil through the frame downtubes for cooling. I found a supplier for the fill cap and oil line fittings to weld on. Chassis Shop has lots of good stuff.

To race vintage class I need all drum brakes so I picked up this 1981 IT465 dual leading shoe front wheel and forks.
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 end.
 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.

 Frame: I had a setback, while project was on hold a strong storm blew open my shop door and sprayed the newly sandblasted frame. Now it has a very thin film of rust. THe exhaust pipe hits the right downtube since it was designed for a single downtube craddle. I bought a 1 inch dia tube and bent it with a jog to clear 1.75 inch dia  pipe.

I will cut a 5 or six inch section out of the right downtube and weld this one in. Then grind it all flush and make it look like it came that way.

Front Forks: Another setback. The Maico tripple tree I bought on ebay had the threads on the stem stripped.  I bought another one and should be here August 24, 2009.

Here is a page from Chassis Shop Catalog to make  those tough bends with pre bent tubing.

Swing arm spacers installed. Each spacer is .250 inch thick

First time I have wheels on it. The Maico forks are 38mm so I thought the Yamaha IT465 38mm forks would fit. They dont!  The Maico forks are about .004 inch smaller dia and there is not but about  .002-.003 inch you can spread them. I will have to bore the trees about .005 inch to get Yamaha forks on. So I installed the stock Maico forks just to get it on wheels. My Maico forks are a rustbucket. But hey, it looks good on two wheels! The Aluminum tank has a large dent in it, that is how I got it for $25. A nice tank will run $200-300, I can live with a dent! One day I will figure out how to pop out the dent.

9-11-09  Rear swing arm bushings came in. I will get the rear brake pivot bushing I made welded this weekend. I am real close to getting this frame ready to paint.

9-22-09  Rear Brake

I modified a stock xt500 brake system.

Here is where it will get welded. The bracket also will fasten the front brake stay bar I made from .049 wall 3/4 dia
steel tube. I machined aluminum end fittings for the tube.