Today I started work on the carburettors. The R65LS had later style Bing CV carburettors with a 32mm diameter. I should mention that the Boxer2Valve YouTube video on R90/6 carburettor rebuild was amazingly helpful for this part of the project, despite there being a few minor differences between the two carbs.
Carb rebuilding is like a mini version of the entire bike project really- there are so many parts that you will do well do keep everything very organised as you disassemble, taking a lot of photographs of where things go. It’s also a great idea to work on the carbs one at a time. This way, when you invariably get confused at some stage you have the other one to use as a reference.
Following the instructions in the video I started by removing the float bowl and the float. Removing the float pivot pin requires identifying the end that is knurled and then using a fine punch to tap it out from the other end.
After the float was removed the needle valve could be gently withdrawn. It hangs on a little wire clip off the float pin as shown. The valve and floats weren’t in terrible condition but I have ordered replacements anyway.
Next I removed the springs on the choke and throttle assemblies and then removed the top of the carb taking care not to damage the diaphragm. After that the carb can be flipped upside down on the table providing a stable base for removing the jets.
After removing the choke cover I discovered a problem which is apparently quite common- the choke cover gasket had deformed and sucked in a little around one of the screw holes. This is a common cause of vacuum leak in these carbs. The bike seemed to run ok prior to this project so I’m unsure whether this was a problem or not.
The last thing to disassemble was the throttle butterfly and spindle. This is principally so that the o-ring on the spindle can be replaced. The two screws in the spindle which hold the butterfly valve plate in place are meant to have been peened off to stop them backing out. The solution for this is to cut the end of the screw off with a Dremel or small hacksaw blade prior to removal. On mine however, the screws weren’t flattened off- maybe they had been replaced at some stage. I still managed to slip with my screwdriver and scratch the plate…
Next entry will be cleaning all these parts up, replacing the rubber parts and rebuilding!
EDIT: I have now pulled apart the other carb and there a couple of things I would add about the process:
- Both my carbs had stuck atomizers (diffusers) which required gently tapping out from the inside. And I mean really quite stuck.
- Neither of my carbs had the throttle butterfly screws peened off on the back-side as per the factory however I think they had both been rebuilt with some loctite. One of the screws was impossible to get out and I ended up having to put the carb in a vice and very carefully drill the screw out. This was scary but I seem to have managed to not damage anything.
