Motorcycle Repair: Honda 305 scrambler, honda 305 scrambler, plug caps

Question
Dear Bill  
I am working on 1968 305 scrambler The left side has been fouling
the plug. The plug is black and sooty after each test. Background
new battery, new air filters, carbs cleaned, new plugs, clean tank
new gas lines, floats adjusted, different needle settings tried,
carb orings replaced, carb mounting orings replaced, ignition timing
set, valves adjusted. ignition system is older including points,
condensors, coils etc. Symptoms are when riding bike at stable
speeds from low to higher speeds there is a miss it goes away when
accelerating. The right side seems to be running perfectly. There is little or no smoke when riding. It seems to be running rich.
thankyou for any advice or direction you can give. Garydla8

Answer
Gary, the usual setup for CL77s is:

Timing set dynamically so that neither side exceed the !! marks on the rotor.
Assuming valves are set at .004" and compression is about 175 psi on both sides, then check carbs for 22.5mm float level, #40 idle jets and #130-135 mains, with needles in the middle position.

If you have changed the air filters or exhaust system, your settings may need alteration.

ALWAYS check to see that the carb slides are in the right carb body. The slides ARE LEFT AND RIGHT sided. If the bike was put together from a bunch of parts, you could have two slides of one side type in the carb set.

Ensure that the condenser is well grounded to the chassis, leads are clean and tight, no excessive arcing at the points while running.

If the air bleed ports in the carb body throat are plugged up, no air will be mixed the idle/main jets and you get a lot of richness, due to lack of emulsion of fuel/air. Main jet holder cross-drilled holes must be open/clean.

Check coils for 4.5 ohm resistance across the primary sides. If you have spark plug caps with resistors, they should not exceed 5k ohms. Make sure all the spark plug cap rubber boots are intact. I had a non resistor cap bite me the other day, arcing from the end where the plug wire goes into the cap to the head.

D8HA spark plugs are normally used.

Make sure both slides are synchronized correctly and carb body flanges are not warped.

I have restoration guide CDs available for all 250-305cc models, one for each version. Contact me on my website for more info.

Bill Silver
www.vintagehonda.com