Hi BS and mandkn,
The other main issue with the kirby is that the main butterfly shaft wears to the point of leaking air in and as such the engine will hunt up and down continuously and this is just not fixable as these shafts have long been discontinued.
The best you can do is buy a full replacement carburetor off the net and use that. This has been the most common fix to keep these old timers running reliably.
Cheers,
BB.
