Last year, I suffered from the usual K0 problem of black sooty plugs.
Over the winter I lapped in all the valves, installing new guides & valve to make sure everything is good.
I cleaned the carbs, including the small brass air bleed at the carb intakes. Did this with a carb cleaner wire until I could just see fresh brass. No dirt left there. The next thing was to junk the keyster stuff & put a full set of Honda jets, needles and float valves. Set the float height to 26mm.
Replaced the Boyer ignition with points and the K0 advancer.
Wow this thing really goes now!!
But, even with the needles in the highest position the plugs are very light, almost white. Yes thay are all the same (guess that's good)
The head has been skimmed to take out a warp - let's say ten thou, and I'm on +.5mm pistons. This gives a compression of just over 9.6 to 1, according to my calcs.
Any ideas out there as o how to get the plugs a little browner? Put the floats up 2mm?
thanks
David
Raising the floats will definitely darken the plugs, across the whole RPM range. If it's OK in town, with darker plugs, then white on the highway, also try this: remove the gas petcock from the tank and take it apart. Inside, you may find that the passages have narrowed from crud that we've all had in the gas for about the last 10 years. You should be able to pass a 5/64" or 3/16" drill through all the holes, or use it to clean them out.
A particular problem on the K series with petcocks is the front feed tube: it runs leaner than the rear tube when on RESERVE, causing the 2 cylinders attached to run a little lean. That's why your manual says, "...run at reduced speed while on reserve tank setting...". I know of at least one K0 that burned the #2 exhaust valve over this issue, because we used to tour together at 100+ MPH, and one day his turned up with a power loss after his reserve was almost empty in Arizona. That winter's teardown showed the valve.
An associated problem with the lean tube is crud buildup: it builds up faster in the slower-moving tube, making the situation worse.
After you have checked this out, here's a little "performance tip" that we Production Roadracers used to use on the "big four": drill 2 holes in the lower front of the airbox that will tightly fit the air balance tubes from the carbs, on the front side, toward the left side of the box (away from the inlet slot) (I'll try to get a pix of mine on here.). These 2 tubes come out of the 2 center carbs, where they are all connected together, and end up in short hoses that usually go over the top of the airbox. Sticking the hoses into the airbox instead will pull a little vacuum in the float bowls at high engine speeds and raise the float levels, which also raises the top end power...
