12 June 2020
After using WD40 and an impact driver I was able to remove the battery box and air box, and discovered perhaps why there was an idle problem, as the above photo shows.
This is a common problem with the XT500, the connection from the box to carb cracks and brakes off, sometimes because the owner tries to squeeze in the carb without loosening all the mounting points of the air box. But maybe also due to the vibrations of the engine, the joint could be under stress as the carb does not fit square on to the air box. I always felt that the joining rubber should be more flexible. Anyway, if you still have the piece that snapped off (or a piece of plastic tubing of the correct size) then it is possible to plastic ‘weld’ it back on. In my case I didn’t have it. I would avoid reusing the rubber connection if it has lost its flexibility due to age.
The air box cover bolts were badly corroded with the cross heads so chewed that I had to replace them, one had to be drilled.
In the end I used the air box from the spares bike which I had bought to dismantle and use for donor parts. It also needed restoring but at least the joint was just cracked and not completely sheared off. Using a flat screwdriver heated by a heat gun, I was able to melt the plastic together along the crack, on both sides. I did the same for a small hole in the cover. I could also have done it with a soldering iron but the risk of it being too hot, and melting too much, wasn’t worth the risk.
The three mounting brackets were added to the collection of parts for re-plating, they were removed by drilling out the rivets. These brackets were originally zinc plated using olive drab passivation. Similarly the internal plates securing the air filter were also to be zinc plated.
As with all plastic and rubber parts, I cleaned all dirt and grease using a petroleum-based cleaner. The rubber vents I used came off the original box, into which I had massaged vaseline before reinserting into the main box.
The olive drab passivate didn’t work out and so the final restoration seen here was with black passivate. The reason for this will be documented in a section about zinc plating, coming soon.
Shopping List
- Air filter
- Air filter oil
- Set of allen screws and washers
- Rivet gun
- Rivets
