Question I have a 1966 CB160 that I am trying to get running after about a year of sitting. First of all let me say that I am not much of a mechanic so my terminology might be a little off. One cylinder on this bike is running great but the other is completely dead.
Here is what I've checked:
-I removed the fuel line going into the carburetor and the gas flowed freely.
-The spark plug has good spark.
-The compression was good, at least by the feel of my finger.
My suspicion:
When I first put gas in it, fuel came trickling out of the bottom of the float bowl. I removed it and cleaned it which stopped the trickle but there seemed to still be some leaking out of the top of the bowl. I have held off on totally taking the carburetor apart, hoping I could fix it less invasively.
Can any guesses be made with this limited information? I really appreciate your help!
BA
AnswerBrett, there is complexity and simplicity in this machine, but they are very sensitive to any overlooked details.
Finger compression checks are not too accurate. When in doubt about the condition of an engine, adjust the valves to .004" cold (intake and exhaust) on the respective TDC compression strokes. Valves that have insufficient clearance will lose compression when they get warm and/or damage the valves.
All the fuel must be fresh and all fuel system components have to be clean. There are air passages as well as fuel metering passages that need attention. Hard to do when they are still attached to the bike, but you can do quite a lot with them in place. You just have to have a watchmaker's mentality and dexterity to do it successfully.
The carbs have a little series code stamped into the carb body. C code carbs have a 19.5mm float level setting and the LD carbs are using 21.mm level settings. Doesn't sound like much, but the 2mm = .080" which can make a big difference in a small capacity engine with tiny carbs. Anyway, determine what the float level is supposed to be for your bike and adjust the float so that it measures the indicated setting when the float has just closed the needle against the seat, but not compressed the spring loaded needle tip.
The ignition system is fairly easy, with just one set of points for the two cylinders. The gap needs to be set around .014" at the widest setting, then the point backing plate is moved until the points just open when the F mark on the flywheel aligns with the marker on the stator. Check spark with both plugs grounding to the cylinder head. Because of the double-ended coil, the spark jumps from the center to the side electrode on one side and reverses on the opposite spark plug. Use new, fresh plugs to do evaluations. Run the bike for a few minutes. If it is still dead on one side, remove the plug, check for spark and evaluate whether the plug is getting no fuel, too much fuel or is oil fouling.
If there is smoke from the mufflers and/or the breather tube coming from the cylinder head cover, then there is a problem with piston ring sealing. That will require a top end engine teardown to verify what needs to be fixed.
Remember, a running engine/cylinder has to have compression, spark (at the right time), fuel mixture (correct ratios) and air.
Bill Silver
