Speedo reading when sitting still

[mdkuni]

Last year I had a problem that happened when I would rev the motor at a stop. Before I ever hit engagement the speed on the display would start climbing. It would get as high at 10mph. As soon as I reached engagement the speed would drop down to the actual speed and started reading correctly. I cleaned the sensor and wheel and did not have a problem since. Now after my pre season prep it is acting up again. Both the wheel and sensor appear to be clean.

Any ideas?

 

[john10toe]

 

[JROCK]

Check the connection on the back of your speedo! I know yours is an apex but this happened to my RX-1 from the connector being loose. Something easy to check!

 

[guardrail]

Sounds like a bad ground

 

[mdkuni]

Thanks for the ideas. I will inspect the wires, ground, and display further.

 

[RTXZIGGY]

I had the same problem on my '06 Apex RTX and it took a new speed sensor to fix it. Replaced it at around 11000 miles, now has 13000 and all is well...

 

[mdkuni]

This has been a nightmare. Dealer reseated all connections, tore the wire harness apart to inspect the wires, replaced the speed sensor, replaced the joint (the gear wheel the speed sensor reads), and replaced the pod. Still did not resolve the issue.

They ended up grinding down the teeth on the joint and drilled the hole out in the joint to move it farther away from the sensor. I am being told this fixed it. I will test it tomorrow.

 

[mdkuni]

This seemed to have resolved the issue. I went for a test ride yesterday and it did not act up. I found out the bolt holes in the sensor were enlarged, not the bolt hole in the joint. So, enlarging the speed sensor holes along with grinding the joint down seemed to do it.

 

[Blue Dave]

drilled the hole out in the joint to move it farther away from the sensor.

You had said earlier that what you are calling the "joint" is the toothed "gear" bolted to the end of the drive shaft that the sensor reads.

Drilling out the mounting hole for this part and moving it farther from the sensor would cause it to no longer be centered on the end of the driveshaft and would only temporarily result in the teeth being farther from the sensor.

Once the drive shaft started rotating this would actually result in the teeth being closer to the sensor every half of a revolution because of it being offset from the center of the drive shaft.

 

[Blue Dave]

I found out the bolt holes in the sensor were enlarged, not the bolt hole in the joint. So, enlarging the speed sensor holes along with grinding the joint down seemed to do it.

That makes more sense. However I am questioning why the dealer ground down the teeth and moved the sensor. It would seem to me that just doing one or the other to a greater degree would have accomplished the same thing which was to increase the air gap between the teeth and the sensor.

The bigger question for me however is why was this required? What is different about your sled from everyone elses that it requires a non standard air gap between the teeth and the sensor?

 

[mdkuni]

I found out the bolt holes in the sensor were enlarged, not the bolt hole in the joint. So, enlarging the speed sensor holes along with grinding the joint down seemed to do it.

That makes more sense. However I am questioning why the dealer ground down the teeth and moved the sensor. It would seem to me that just doing one or the other to a greater degree would have accomplished the same thing which was to increase the air gap between the teeth and the sensor.

The bigger question for me however is why was this required? What is different about your sled from everyone elses that it requires a non standard air gap between the teeth and the sensor?

Doing both does not make much sense to me either but it worked... It was probably unnecessary.

I noticed this problem at about 8,000 miles. It does bug me not knowing what changed.

 

[Zakre]

hows the bearing on the driveshaft clutch side?

 

[Crewchief47]

It's possible the drive shaft is magnetized. Did you have a bearing go south before this started happening?

 

[mdkuni]

This season I replaced all bearings in the chain case and the "speedo bearing". I also installed a new drive shaft. This problem happened before and after these parts were replaced. I did not have any bearings fail.