Hey Pete, I learned more as I was finalizing this question for publication in the magazine. The upgraded text follows:Hi Pete;
First off, your Janitrol should not be streaking black smoke clear to the tail. I expect you need to get into the heater and check the spark plug (or just replace it), check the spray pattern of the nozzle, check the fuel pressure (7.5 psi) and the output of the combustion blower. If any of these components are not correct, the resulting rich mixture will cause a sooty exhaust. You can download a Janitrol heater service and parts manual from Janitrol at: https://janitrol.aero/wp-content/uploads/2017/04/99M90-I-Series-Owners-Manual-New-s2.pdf.
This may not be the exact manual for your heater it will give you an exploded view of the heater parts and procedures to test the components.
Kristin Winter, who also writes for the Piper Flyer magazine and flies a PA 30 Twin Comanche reports that Easy Off oven cleaner is the quickest and most effective belly cleaner. She cautions that it must be used in a well-ventilated area, must be rinsed with water and wiped off immediately after application and then rinsed again.
Others say that Easy Off is very caustic and that they would never use it on bare aluminum, but only on a good painted surface. Since it is caustic it MUST only be used on a painted surface and MUST be rinsed immediately with plenty of clean water. It will attack bare aluminum.
Responders have also suggested using other less toxic cleaners such as GOOP hand cleaner (without pumice) and rags, Aviation Simple Green (must get the aviation kind) mixed 50/50 with water; Sportys and Aircraft Spruce sell a product called Aero Glaze Dry wash that others recommend.
There have been quite a few upgrades and improvement in light airplane combustion heaters recently. It might be time to pull the heater and send it in for an overhaul.
While there are built in safeguards on these heaters to prevent problems, there’s a lot of comfort to be had when you know the flaming fire in the nose of your airplane is in top notch shape and all the safeguards have been tested and are working properly.
Overhauls can be done at http://www.Janitrol.aero. Most West Coast flyers get their heater overhauled and serviced at http://www.aircraftheaters.com in Redding, California.
Happy Flying.
