Faulty Speedometer

Speedo needle fluctuates wildly!

Generally it is reading very low.

I know its electrical, but where do I start to try & fix it?

This on a 1999 Fi-X with 50k miles.

Andy

Sent from my SM-A310F using Tapatalk

First thing to check is the plastic cup on the sender. 2 8mm bolts on the sprocket cover. 

MBRane is correct, had this fault myself. There is a plastic cup on the end of the speedo sensor that screws into the sprocket cover. The cup sits over the sprocket nut and drives the sensor. If the hex in the cup is not lined up with the sprocket nut when the cover is installed it gets pushed back up the shaft and will no longer engage with the sprocket nut consistently. Best is to buy a new plastic cup, they are about $6 IIRC, and fit a lot of Hondas so will be easy to get. Part number 44808-MR7-013

1 hour ago, Terry

MBRane is correct, had this fault myself. There is a plastic cup on the end of the speedo sensor that screws into the sprocket cover. The cup sits over the sprocket nut and drives the sensor. If the hex in the cup is not lined up with the sprocket nut when the cover is installed it gets pushed back up the shaft and will no longer engage with the sprocket nut consistently. Best is to buy a new plastic cup, they are about $6 IIRC, and fit a lot of Hondas so will be easy to get. Part number 44808-MR7-013

This happened to me on the way to the last SumSum. Luckly, Hispanic Slammer diagnosed this and fixed it for me. Thanks HS. A new mechanic at my Honda shop screwed a new chain installation when reassembling the left crankcase cover.

It turned out that the former owner had installed an aftermarket drive sprocket, which was thinner than oem. The Honda OEM sprocket has a rubber dampener on it's outside surface to reduce noise and vibration. When the wider sprocket was installed it left the speedo engagement nut "unengaged". Hence inaccurate or no speedo readings. 

21 hours ago, MaxSwell

It turned out that the former owner had installed an aftermarket drive sprocket, which was thinner than oem. 

I do wish people would leave things alone.

3 hours ago, M1962

I do wish people would leave things alone.

Especially when they do not know what their doing. The bike in question, when I bought it, came with a Staintune can and a PCII. So original owner could have also put a different-tooth drive socket hence the difference in the sprocket width. This would all be consistant with a person wanting the fastest acceleration possible. I don't fault the original owner for this but the mechanic involved should have known what needed to be done when putting in the thicker OEM sprocket for me. 

There is/was someone on eBay.com (but in Hong Kong) selling aluminum versions of the plastic cup.  I bought one, but found that it was just slightly too tight to fit onto the bolt head.  It's fixable with a Dremel, and some patience, but I haven't yet done it.  Great idea, though!

Ciao,

Often you can simply slide the cup out on the shaft a bit, and it will be fine. If it is worn a little silicone or some tape can do the trick too if you're poor/cheap.

MBrane Often you can simply slide the cup out on the shaft a bit, and it will be fine. If it is worn a little silicone or some tape can do the trick too if you're poor/cheap.

9 hours ago, An9dy

Thanks for the guidance.
Yes the problem was the plastic cup.
The cup had the sensor spindle push through the plastic;
hence the cup had slipped back along the spindle and disengaged from the sprocket nut.
Solution:
3 or 4 small washer spacers behind the cup, on the spindle, moves the cup back to its normal position.
Works fine now!
Andy

Sent from my SM-A310F using Tapatalk
 

This is exactly what happened in my case. We put the nut in the proper position on the shaft; it has been fine since that. No extra parts added.

It's worth replacing once you see it compared to a new one:

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