Yep.. reading the plugs is very telltale..
whiteish-ashy is lean
black and powdery/sooty is rich
black an oily could be a combination of rich and worn rings.
tan is about correct.
Runs for a few seconds and shuts off. Try this. Pull the air cleaner tube off and get a can of ether. Start her up.. if it starts to die, give a small whif of ether.. if you can keep her running on short bursts of ether, it is a fuel delivery problem.. like a blocked mainjet, or dry bowl, or blocked/gummed up float needle.
If the ether doesn't help it, pull a plug and turn it over to check for spark... you need a nice snappy blue-white spark. Gap plugs at .025.. oem spec was a champion H10 / al 216.. but we like to use champion H12 or AL 437 as it is a hotter plug, and helps with the deposits left by modern gas. If your plugs are fouled.. don't try to save 6 bucks cleaning them.. toss them and grab new plugs. That 48' will have a front mount distribuitor.. the pointsgap will be .015... try cleaning the points. An easy way to do this if you don't have an ignition file is to take a piece of coarse brown paper bag, and repeatedly run it through the points contacts while you hold them closed. Don't use sand paper... only an ignition file.. or coarse paper... or just replace them.
Check the cap and rotor as well, for cracks or carbon arcing. Spark plug wires need to be copper core wires.. not modern anti-radiostatic wires. Also ensure that the battery connections including ground are clean, the power to the key switch and ballast resistor are clean, , and that you have a good wire and contact at the top of the square ignition coil. Might also remove the coil and make sure the flat KV contact is intact and clean, and that the pigtail points passthru contact is not burnt or broke. Sometimes we gently stretch the pigtail contact to help it touch the screwhead better.
Air, fuel, good spark ( at the correct time ), and compression is needed in this engine. If it starts and runs, compression is low on the list to check... fuel and spark are next.
Also.. remember that system is 6v positive ground.. hooking it up negative ground can reduce the spark output of that front mount coil anywhere from 25% to 40%, and there is no practical way to orient that square coil to work with a swapped polarity, as you could with a round can coil.
Also.. the front distribuitor removes easilly with 2 bolts.. it's a 15 minute job to pull the distrib, replace and gap points, and replace cap.. etc, and re-install. And the distrib is offset tang driven from the cam.. so as you put it on, use your fingers to spin the rotor cap till the tang falls in the slot onthe cam... so there is no way to install the distrib back in out of time.. unless you use a hammer.. etc.
fire order is 1243 CCW ( the cap is numbered ).
Soundguy
