(It all depends on what is wrong with it.) I suggest you send it to a repair shop. search the web for "Airgun repair" and locate a shop near you for repairs.
Not meant to be disassembled
There are 4 variations of the Daisy model 99 BB rifle, not gun. Your best bet is to contact Daisy directly. They offer a free service to evaluate Daisy antiques. See the link below.
There are 4 different variations of the Daisy Model 99, starting in 1959 to 1979. Daisy offers a free service to tell you more about your old BB gun. See the link below
I've gone through several air gun catalogues and have been unable to locate a Daisy model 170 bb gun that has ever been made. I did find a Daisy BB gun model 5170 and a BB rifle model 1170 along with a BB rifle model 107 but "NO" model 170. However I suggest you search the web for "Daisy Air gun Repair" or "Air gun repair" and locate someone near you who can help you.
I suggest you go online and do a search for 'Air gun repair." and locate someone who fixed Daisy's.
Daisy offers a service for older BB guns see the link below.
This BB rifle was made for Sears by Daisy air gun company. It's really a model 1894 and possibly one of the hardest BB rifles to repair. I suggest you look online for "Daisy air gun repair" and locate a shop near you to have it repaired. There are shops that make a living repairing outdated air guns and rifles.
Do a search online for "Air Gun repair." There are several independent shops that repair older air guns. SEE the Link Below.
No published sn data.
It was only made in 1967.
I suggest Crosman Pellgun oil or RWS pellet gun oil.
I suggest you go online and do a search for 'Air gun repair." and locate someone who fixed Daisy's.