Saturday, 28 July 2018

Carburettor Rebuild

After what I imagine is 35 years without disassembly I took the carburettors off the bike and rebuilt them. I replaced:


  • All the O-rings. 
  • The diaphragms. Both were inflexible. 
  • Cap screws. These had corroded somewhat. 
  • Vacuum Blanking screws. These were damaged from repeated removal. 
  • Throttle shafts and screws. The peening of the original screws meant that they damaged the brass threads on removal. 
  • Gaskets on cold start and float chamber. 
  • Main jet washer. These were a bit corroded. 
  • Throttle and cold start return springs. 
A few pics of this:

two dirty carburettors before cleaning

Before: 35 years of gunk. Note the carburettor on the left has the cold start spring replaced with a pair of other springs.

dirty carburettors showing the darkened piston

Before: The carurettor on the left, with the darkened piston, is the one with the damaged diaphragm.

carburettor diaphragms showing tear

Diaphragms. The one on the right is so badly damaged I'm surprised I was able to tune the bike at all. 


clean carburettors following rebuild

After: all clean, ready for reattachment. 

A few comments: 

  • One of the main jet holders was difficult to remove, there was so much gunk in it that it wore the threads down as I removed it. It reassembled okay, despite this. 
  • I couldn't adjust the idle down on the LHS carburettor far enough to be able to set the idle mixture. I removed it from the bike and reseated the throttle butterfly, being more careful this time to ensure a good seal against the throat. 
  • I had no device to remove the peening on the throttle butterfly retaining screws, and damaged the threads on the shaft when I removed them. I replaced the shafts and screws and used lock thread on reassembly. 
  • I crimped the fuel hose attached to the LHS carb on reassembly and it got no fuel. Replacing that section of hose fixed the problem. 
  • I don't have a compressor so I used a can of compressed air and a can of carburettor cleaner. 
  • I found this youtube clip from "Boxer2Valve" immensely useful: ·         https://www.youtube.com/watch?v=MpBA6wimjLc&list=PLXo0yJ7WoKfvSNxo1uZU3qupxkkf9xU4w&index=5 

  •  Probably I should've done this 20 years ago. 

The bike is running much better, it pulls better and I think that the range has increased 20%. 



Hand Guards

It's winter in Oz so I've gone looking for a way to stop my fingers from freezing. These handguards are black versions of ones fitted to R80GS models. I sourced them from Munich Motorcycles.

Part number is 71609062160. The white equivalent is BMW: 71 60 2 303 496. I'm not aware of any bike for which these guards are standard equipment. 

Installing the guards was straightforward but fiddly: I needed to loosen the handlebar retaining bolts and cut a couple of cable ties before I could wiggle the RHS one into place. 

They help considerably on cold mornings.  :-)


r65ls with black hand guards