I have a 1976 92908 on a Victa of the same age. It has been becoming a bit erratic lately, and needed to be sorted out. Because Joe Carroll commented a few days ago that people have all kinds of trouble with the carburetor involved (PulsaJet with automatic choke) I thought I'd post on how I went about it.
The symptoms were a bit ambiguous: lack of power, hunting at maximum speed and load, black spark plug, and idle speed gradually dropping despite the speed screw being locked with loctite. There seemed to be two main possibilities: high speed ignition breakdown, or a carburetor fault. After checking that the spark was blue and regular, I followed my preferred procedure: I just swapped the entire carburetor and fuel tank with the ones on my spare mower (a 92508 from 1983). This instantly fixed everything, the mower suddenly was Ferrari-powered and silky-smooth. So, I had to deal with a dodgy PulsaJet with auto choke. I began in the obvious way, by removing the carburetor from the fuel tank, and finding that the fuel intake filter was fairly well clogged with grass. However when I unclogged it and reassembled the carburetor to the tank, I was in deep trouble: it ran best with the mixture screw all the way in, and no fuel going through the main jet. I began to see why the automatic choke isn't all that popular with repairers.
The key to the solution to this problem is here:
http://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_98.htmUse the Next button to page forward. Briggs and Stratton have laid out in great detail, what is likely to go wrong with that carburetor and how to fix it. They give a list of possible causes of the problem, from A to K. I quickly found that my carburetor was fine except that it had fault J: the top of the fuel tank wasn't all that flat. Briggs say you mustn't be able to fit a 0.002" feeler gauge between the tank top and a straight edge, adjacent to the vacuum chamber, and I could - though barely. I could see that some previous repairer had fitted the very crude repair kit Briggs sold: a roll pin and a tiny teflon washer in the most vulnerable spot. However the teflon washer had disappeared, and I hated that solution anyway, so I had to flatten the top of the tank. This was accomplished in about 5 minutes of draw-filing.
http://armyordnance.tpub.com/Od16218/Od162180135.htmWarning: unless you have been taught the technique by an expert and practised it for years, don't try it on a fuel tank you want to be able to keep using.
When the tank top was flat I reassembled the tank and carburetor, carefully, using Briggs' detailed instructions in the manual quoted above. I put the assembly on the spare mower, and fired it up. Faultless, of course. I switched it back to the original mower and put the spare mower back into storage. Then I unnecessarily mowed the back yard just for the pleasure of it with such a sweet-running mower.
All this was easy stuff once I had read the manual carefully. I would not like to have attempted it without that manual, though.
