QuestionSo, I've broken out my 1983 Honda CM450E, and noticed after I had replaced the battery (what an improvement on starting and night riding!) that the speedometer was doing something strange.
While first increasing speed, upshifting normally, I found the speedometer would eratically jump between 40 mph and 55 mph, almost as if it was reading RPMs and something was missing. After setting into 4th or 5th gear for a short while (30 seconds or so) it would settle down and speed would be constant. Is this a problem?
Normally when cruising at highway speed, the need is pretty constant, but fluctuates normally as I go up and down hills. On the flat straight-aways, the needle is very steady.
Also, After filling my 3.25 gallon tank with fresh gas this week, I was expecting to get 200 miles out of the tank. About 140 miles, the engine started missing at 60 mph... and I instinctively reached down to rotate the fuel petcock. That seemed to straighten things out. It ran smoothly, but I panicked as it meant I would only top out near 180 miles, at best, and I was currently 30 miles from a stop near a gas station. I made it 60 miles round trip and stopped to fill up... 3.40 gallons, so I know I cut it close.
What might have caused this drop in mileage? The bike is in good running condition. I'm just getting back into Springtime riding and don't abuse it.
Thanks!
AnswerKirk, the speedo cable is probably dry and binding in its sheath. Disconnect it from the speedo end and squirt some light machine oil into the end and let it soak its way down. If this doesn't make it better, you may need to replace the entire cable.
A sudden drop in fuel mileage could be caused by a dirty air filter and/or contaminated furl in the tank. Check and replace the air filter if necessary and try draining the carb float bowls and the gas tank, then filling with fresh fuel. If the problem persists, the carbs may require cleaning and synchronising.
