Remove burner tube...clean with small bottle brush
Unscrew orifice from gas valve....soak in alcohol then blow dry (low air pressure and no poking anything thru hole
Remove spark electrode and clean soot/carbon from it using emery cloth
push a wire thru combustion chamber out exhaust...tie rag to wire then pull back thru doing a 'chimney sweep' of the 'U' tube
Reassemble and fire it up.
Adjust air shutter (slotted sleeve) open/close to achieve a strong blue flame with 'slight' roar (too loud...to much air/orange-sooty flame---not enough air)