Speedometer Slow to Respond

[D0wn5h1ft]

So I decided awhile back to put a set of special gauges on my '79F and I'm having an issue with the speedo. The tach works great and all of the lights (neutral, oil, hi beam, etc) all work but the speedo is very slow to respond to changes. I will take off from a stop sign and cruise at ~25mph and it take a good 60 seconds before the speedo even responds. Once it does get up to roughly where my road speed is it is often 5-10mph lower than what those radar speed sign clock me at. When I stop again it take a good 30 seconds for it to fall back down to zero/sometimes it never gets all the way back down.

The gauges look to be in really good shape and the chrome on them is great but for some reason the speedo won't clock properly. I'm pretty sure the odometer is function properly since when I was riding it steadily went up like it's supposed to.

Here's what I've tested: I know the cable is in good shape as well as the speedo gear because I've spun the wheel and watched them turn and I also know that my wiring up to the "standard" harness was done right because everything else works just fine.

Any ideas?

[wingnut]

Sounds like it may have been sitting for a while as a spare and the lube in the unit has dried up, There's a discussion here some where that a member posted with the disassembly process for the unit. It involves bending rolled sheet metal to get the unit apart. I got lucky once and did it but it was not easy. Before I went to that trouble again I would just run that unit a while and see if it frees up. You can take it out of the bucket and try and spray some lithium up there but its a hit and miss process.

[D0wn5h1ft]

Sounds like it may have been sitting for a while as a spare and the lube in the unit has dried up, There's a discussion here some where that a member posted with the disassembly process for the unit. It involves bending rolled sheet metal to get the unit apart. I got lucky once and did it but it was not easy. Before I went to that trouble again I would just run that unit a while and see if it frees up. You can take it out of the bucket and try and spray some lithium up there but its a hit and miss process.

I did buy it from a guy who just had it as an extra set. I was really hoping it wouldn't be that hard to tear apart. Maybe when this ice age is over I'll put some miles on it and see if it wants to cooperate.

[BA80]

The speedometer on the SF I just sold was slow like that when I first started riding it. It had sat for several years before being put back on the road. I rode it to Wisconsin for the lost rally last summer and it loosened up on the trip and worked fine after that.

I did shoot some lithium grease up into the cable connection on the head also.

[IanDMacDonald]

Yeah, speedo on my GS did the same. Shot some contact cleaner in there, then some white lithium like Greg said.

[skids]

I bought a standard speedo off of fleabay a long time ago. Same thing. It eventually worked the bugs out on its own.

[TADracer]

You should not need to disassemble to fix this.

This is common and an easy fix. The problem stems from gumming up between the drive that the cable turns and the bushing. Remove the gauge from the bike and turn it over and you will see the drive and the bushing. Use some liquid graphite type light oil between the drive and the bushing. It is helpful to have a piece of an old cable about 6" long with the squared off end and a drill motor. Work it in both directions until it is free and loose. Then lubricate again with the graphite oil and reinstall the gauge. That's it!

I do this each Spring during my major tune-up that I do each year.