Brian, the previous owner, explained that the Honda XR500 was severely leaking oil out its exhaust and this prompted the complete disassembling. Taking apart the engine revealed a broken piston ring, among other things. A friend gave Brian a spare engine as a donor and this engine is part of the Basket Case. With Brian as the information source, it is as far as I can get deciphering the history of this bike. Let’s investigate further by inspecting the Basket Case parts.
A little bit of XR500 history, facts and references
The Honda XR500’s engine is a 4-stroke air cooled 498cc single OHC, 4-valve, single cylinder, with 2 head exhaust pipes, and 5-speed transmission. This dirt/enduro bike was manufactured by Honda in Japan between 1979 and 1984. Some significant changes were introduced in 1981 and, starting that year, all XR500 models were designated as XR500R. The following can help identify an XR500 model year (describing here the main changes between production years):
1979: The XR500 initial production year. Bike color is Tahitian Red. Metal tank with a red “Honda” tank decal. The top of the tank, side cover panels, and headlight cowl are black. The “XR500″ side cover graphic is red and white, the front wheel is 23″ while the rear is 18”.
1980: The gas tank shows now a Honda wing decal. The control levers and kick starter arm are black, and the muffler is smaller.
1981: Some significant changes introduced that year: The number plate panels are now black, the “XR”side cover decals are black, the engine color is entirely solid black, the former dual shock rear suspension is replaced with a single shock Pro-Link design, the gas tank is plastic, front wheel is down to 21″ while the rear is down to 17”. The engine has reed valve induction which improves low end performance. The model designation is now XR500R and the side of the black seat displays a white “500R”. Click here to display a 1981 Honda brochure which shows the entire Honda lineup for that year (PDF file).
1982: The number plate panels are now white and the “XR” side cover decal is also white. The engine color is still black but with polished cylinder head fins.
1983: The bike color is now Flash Red, the number plate panels are yellow, the seat and tool bag are blue, the fork boots are black, and the “500R” swingarm decal is also black. Larger diameter front suspension tubes and a single disk brake at the front replaces the earlier models drum brake. The engine is upgraded and referenced as RFVC (Radial Four Valve Combustion) with a dry sump, fueled by two carburetors. The side of the blue seat displays a white “XR” and the seat is elongated at the front covering part of the tank.
1984: The bike now includes plastic handguards. The “500R” swingarm decal is red and white.
1985: Introduction of the XR600 which replaces and terminates the XR500 production.
From a VIN perspective, the XR500 model year can be determined with the help of the following table:
|Honda XR500 year||VIN numbers start at|
So what model year is this bike?
The hand-sprayed-over VIN reads: JH2PE0100CM300### (where ### is a 3 digit serial number). Referring to the above table, we can deduct that our specimen is a 1982 Honda XR500R. Further analysis of the VIN confirms this identification:
- JH2 –> manufactured by Honda, in Japan
- PE## –> model code:
PE01 –> XR 500 Z-A / RB-E
PE02 –> CR 450 RB / CR 480 RC-D / CR 500 RE-T
PE03 –> XR 500 RD-E
PE04 –> XR 600 RF-T
PE05 –> CRF 450 R2
- C –> 1982 (the eighth digit from the right end of the VIN identifies the model year of the vehicle, starting with A for 1980, B for 1981, C for 1982, etc. Check a VIN decoder table for reference)
And what about the engines?
The Basket Case came with two engines, one that the previous owner mentioned was leaking significant oil out of the exhaust and a spare given by one of his friends. At first glance it is clear that neither are 1982 or post-1982 engines as they are not painted black (they are both plain aluminum). This immediate observation has decision consequences for this restoration project as what we have here is a bastard Basket Case with parts from various model years (the seat is blue for instance and blue seats were introduced in the XR500R series starting the following year, 1983). So I can either go on an eBay crusade to find a correct engine or look at this project as a free-for-all-let’s-have-some-creative-fun restoration. I’m leaning towards the latter, let’s create a nice restoration, a bike I can take off-roading and not worry too much about scratching some paint – and maybe along the way I may even get a bit creative with the restoration.
The previous owner dismantled engine shows a serial number starting with PE01E, which indicates that it is an XR500 engine. The spare engine, which is also disassembled, displays a serial number starting with PD01E which indicates that it is an XL500 engine.
Looking more attentively to specific details of the oil leaking XR500 parts reveals devastating damages, likely due to running the engine with little to no oil in basically oil starvation mode. The cylinder head journal bearings for the camshaft for instance are showing seizure traces and so is the camshaft itself. The rocker arms show abnormal advanced wear on the faces which run along the cams. Similar observations can be made on parts belonging to the engine bottom end. Ouch! This PE01E XR500 engine is unfortunately pretty much a write off.
My focus switches thus to the spare engine which parts don’t show wear damage or alarming signs. This is an XL500 engine though, what are the differences between an XL500 and an XR500 engine? Let’s find out.
XL500 versus XR500
The Honda XL500 is introduced in 1979 as a direct competitor to the Yamaha XT 500. From 1979 to 1981 the model designation is XL-S and with the introduction of enhancements starting in 1982 and to 1984 the designation becomes XL-R. For the U.S. market, Honda releases at the same time a sportier variant designated as XR500 which includes a solo seat, a tool kit, a smaller integrated headlight (6V 25/25W), a round speedometer, foldable brake and gear levers, longer travel front and rear suspensions (0.8 inch) and slightly higher engine performance. The sportier XR500 is lighter and doesn’t include a battery, blinkers, tachometer or ignition switch.
XR and XL engines are very similar – same piston, compression ratio, valves, cam cut and timing. The main differences consist of:
- The XL rotor/flywheel is heavier than the XR.
- The XL stator coils are different than the XR and output higher electrical power.
- The XL500S outputs 6V and so are the XR500 and XR500R up to the end of 1982. The XL500R and the 83/84 XR500R are 12V.
- The gear ratios are the same between the XL and XR. However, the gear cogs are cut in a stronger steel for the XR and the XR 5th gear cog is a couple of millimeters wider.
- The final drive ratio is different between the XL (XL500S 2.785 [39/14]; XL500R 2.733 [41/15]) and XR (3.429 [48/14]).
- The XL has a sensor for a neutral position light which the XR doesn’t have.
- The carburetor main jet size varies between models and location (US-49 states versus California).
- The XR carburetor emulsifier tube appears to have more holes than the XL carburetor emulsifier tube.
- The manual carburetor choke handle is operated remotely via cable for the XL whereas the choke handle is directly mounted on the carburetor for the XR .
So the remaining question is which XL engine serial number corresponds to which model year?
|Engine number from … to||Model year|
|PD01E-5008864 … PD01E-5010504||XL500SZ (1979)|
|PD01E-5106436 … PD01E-5112191||XL500SA (1980)|
|PD01E-5205212 … PD01E-5216142||XL500SB (1981)|
|PD02E-5000030 ….||XL500RC (1982)|
Comparing my spare XL engine, serial number PD01E-5212###, with the above table we can see that it belonged to an ‘81 XL500S. Its 6V output is the same as the ‘82 XR500R bike it will be mounted in. I’ll use though the lighter flywheel and stator from the discarded XR engine as I won’t need significant power for the headlight, blinkers or other electrical systems and want a more responsive engine at lower RPMs. The final drive sprockets are the same (14 teeth) so no changes there. On the carburetor side, I’ll rebuild the XR carburetor. Cool, looks like we have a keeper!
Next: what’s this performance piston found among the pile of parts?