Part of my build design for the Honda XRC520 restoration was to have the ability to convert from VMX to enduro in less than 15 minutes.
I grew up on a farm in Reid’s Creek near Gayndah in Queensland watching my father engineer farm equipment. I annoyed him from a very young age asking him to teach me how to weld. He said when I started Grade 8 I would teach me, which he did. Over those years on the farm together we made many farm implements and my father became well known in our district for his excellent work that spanned decades. This is where I leant my engineering skills, I will never forget those years with him as they taught me how to do this Honda XRC520 restoration.
Now we fast forward 15 years and I bought my first XR500RC in Mt Isa in 1982. Mount Isa has a vast range of shale rock hills that seem to go on forever, and the XR500RC was the perfect bike to tackle those tricky hills. It was absolutely the funnest bike I have ever owned with power on tap and torque to match. Sure, it gave the occasional kick back but it was a pretty easy starter.
I kept my XR500 for several years and eventually retired the bike to the farm and unfortunately it was eventually sold off. I tried to find my original bike but was unable to do so.
In 2021 I bought an old and beat up 1982 XR500RC and proceeded to restore it back to the original factory specifications. Every nut, bolt and part I used was original and tracking down the correct original parts was a time consuming and costly task. I ended up buying parts from all over the world as many that were needed I couldn’t source locally.
During this restoration I bought a second XR500RC but the motor was in a million pieces as the bike had essentially been sitting for years in boxes in a shed. I used it as a donor bike from which I removed all the hard to find parts I needed for my first build, it then sat in the corner gathering dust. I walked past this donor XR500 for months and finally decided to build a twin shock VMX/Enduro bike from it.
My primary aim was to keep the VMX XRC520 as a “Honda” as much as I could and not use other manufacturers’ parts which I achieved. I wanted to build a show room VMX with performance to match. I also wanted to keep this bike as much an XR500 as possible. I retained the original engine, frame, rims, hubs and brakes as well as the seat.
Part of my build design for the XRC520 was to have the ability to convert from VMX to enduro in less than 15 minutes. A lot of trail rides and forestry tracks require your bike to be registered. I spent considerable time adding the electrical requirements to register this bike in Queensland where it currently is. The XRC520 runs a full 12 volt LED system, so has plenty of lighting power using the original layout with the distinctive headlight above the number plate.
Having the flexibility to ride a vintage motocross on Saturday and then participate in an enduro event on Sunday gives this bike a unique quality. It took many months of research and planning to work out exactly what I wanted the end bike to resemble. Honda introduced the Pro-Link single shock rear suspension on the 1981models so the frame was stripped and modified to take the upper mounts for the twin shocks.
I painstakingly started to collect parts for this build, such as a CR250 fuel tank and a CR480 front end and swingarm. I had to engineer those parts to fit the XR500RC frame. The frame was stripped and after weeks of planning I started cutting the frame to make way for the twin shocks and the rear upper frame was cut away to make room for the CR rear mudguard. Quite a few modifications were made to fit the CR250 alloy fuel tank which turned out to be a good challenge.
A CR480 front end was fitted with 43mm Showa forks which pretty much bolted straight up to the XR500. The CR480 swingarm took the longest and was by far the most challenging part of the build needing to be heavily modified to fit to an XR500 frame with the original XR500 hubs and rims.
I then added lower shock mounts for the dual shock setup to get the desired suspension travel to match the 280mm of travel I had in front end. I manufactured the rear axle and swingarm pivot bolt from scratch as there was no way I was finding these to suit. I cut the threads on my lathe and made an exact copy of the original XR pivot bolt but larger to suit the CR480 swingarm.
When I originally bought the bike the engine was in a million pieces, but luckily mostly there. I decided to increase the stock engines performance whilst retaining the reliability that XR500 motors are known for as I wanted a strong motor with a nice mix of power and torque.
The cam was very worn as were the rockers, so I had the rockers built up to original specifications. I decided to change the cam to a Tighe Cams mild performance cam which has greater lift and duration over stock and the decision proved right. The head was ported and polished and new larger valves and valve seats were fitted and a K&N air filter installed. The barrel was bored to 91mm and a WiseCo piston was fitted for a capacity of 520cc from the original 497cc.
New clutch plates and a clutch band were also fitted to strengthen the clutch basket. It now makes more power than stock and the twin shocks fitted at the moment will be replaced with a pair of Ohlins shocks when I have the money.
I then changed the standard two into one exhaust for a twin system with a pipe each side fitted with SuperTrapp mufflers. I chose twin exhausts with SuperTrapp mufflers for something different and to keep the “old” school looks. The twin exhausts allow the exhaust gases to flow with better efficiency.
My TT500 also had a SuperTrapp muffler which I loved, so these exhausts were a no brainer. I had both exhausts ceramic coated for looks and better heat absorption, and the cost and turn-around time was reasonable.
I spent many hours on the lathe turning bushes, and many, many, more hours on the TIG welder re-designing the frame and swingarm. I zinc plated all the nuts, bolts and bushes myself. By far the most time was dedicated to planning the build and problem solving along the way but I was very pleased with the end result.
The bike handles like a dream and has ample power to burn but the modifications to the suspension were the biggest improvement.
The standard XR500 Pro-Link suspension gives around 205mm of travel and the twin shocks and 43mm Showa forks increased that to around 280mm. That’s probably a bit short for modern day bikes but never the less it transformed this bike. The power to weight ratio has been greatly increased due to the modifications coupled with the 38 Mikuni. Brakes are more efficient as a lot of weight has been saved with non-essential parts removed and an alloy tank and swingarm fitted.
I did all the manufacturing myself, including the side panels and all the decals and it certainly helped to have all those skills that my father taught me early on in life.
I would like to dedicate this build to my father Ken, RIP Dad.
Honda XRC520 Special Bits
Wiseco 520cc 10.5:1 piston
Mikuni VM38 carburettor
Tighe performance cam
Ported head
Larger valves
Strengthened clutch
Custom twin SuperTrapp mufflers
K&N air filter
17.5” Twin Shocks (to be replaced with Ohlins when I can afford them)
Custom side panels
WORDS AND PHOTOS | KEN MACDOUGALL