CBX250 Speedometer Gear Repair

Erratic Speedometer Reading

I noticed something strange on the speedometer when I was riding the CBX250 Twister last week. The needle was moving unsteadily. It was rising up and down even though my speed was constant. Additionally, the speedometer was under reporting the speed I was traveling. At about 8,000-8,500 rpm, the speedometer should be pointing at about 80 kph, but was only showing 60 kph.

Speedometer Cable?

My first thought was that the speedometer cable was on the verge of breaking again. This phenomena occurred previously when the cable was about to break and went away when I fixed a new cable. I went to buy a new speedometer cable but after fitting it, the problem remained.

Speed Sensor? Digital Speedometer Panel? Electrical Connections?

I thought next that perhaps the speed sensor was faulty or that the electrical connections needed cleaning. I removed the speed sensor, cleaned it and also cleaned the connections to the main speedometer/rev panel, but that didn’t help. I was already checking with the Brazilian parts shop for the speedometer sensor (as usual the local agent did not have it).

Before buying the sensor from Brazil, I decided to try disconnecting the battery for a few minutes to see if it helps. I was thinking that perhaps the speedometer panel may be faulty. That did not wotk either.

Speedometer Gear Assembly

As I was going to remove the sensor again to open it up, I spun the wheel again to see if the needle on the meter moved. It was then that I noticed soft clicking sounds coming from the front wheel’s hub. Intrigued, I spun the wheel again and traced the sound to where the speedometer gear assembly was.

When I removed the connection of the speedometer cable to the assembly and spun the wheel, the little tab at the assembly turned but it turned for half a turn, stopped and then turned again. The tab was spinning and that was why I did not realise that this part was faulty previously.

Worn Gear Teeth

Removing the speedometer gear assembly and taking the parts out revealed that one of the gears was worn out. There were teeth all around the circular spacer like item, but on closer inspection, I saw that a portion of the teeth was worn and could not engage the small gear spinning the tab connected to the speedometer cable.

Worn Gear
Worn Teeth on the Faulty Gear

The next day, a call to a Honda parts store returned with good luck. They have the gear in stock and I ordered one. This little plastic thing cost $20 and was even more than what the whole speedometer gear assembly cost in Brazil.

New Gear
New Gear with Good Teeth

With that fixed into the gear assembly, the bike’s speedometer was showing correct speed again. This fix could possibly help to show better gas mileage for the bike. My guess is that as the gears worn out, the odometer was under reporting the distance traveled. I have reset the trip meter to zero and filled up with a full tank. We will see if there is any “improvement” in the gas mileage.


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