Buzzy's Revival: 1982 XS650SJ Heritage Special

[Boog]

I added a cellphone holder to Buzzy last night. Today on the way to work (at 27°F), the GPS speed shows 68-69mph while the speedometer shows 60mph. As I got up to 65mph on the speedometer, the GPS speed indicated 74mph.

While I not too worried about the big delta, it is nice to know a little more closely what speed I am actually riding at and the reason why I am passing some people when I do not think I am going as fast as indicated.

Should I be worried that something is about to break?

 

[Ishrub]

I added a cellphone holder to Buzzy last night. Today on the way to work (at 27°F), the GPS speed shows 68-69mph while the speedometer shows 60mph. As I got up to 65mph on the speedometer, the GPS speed indicated 74mph.

While I not too worried about the big delta, it is nice to know a little more closely what speed I am actually riding at and the reason why I am passing some people when I do not think I am going as fast as indicated.

Should I be worried that something is about to break?

Nah, if you like speed ice skating, your obviously doing fine!
Next move........ a pirouette as you become a figure skater too!

Either you need a thinner viscosity grease for your speedo gears and cable or you've gone all Quantum on us as your brain's perception of speed is faster than your body's and your actually in more than one place in time and space simultaneously!
Simpleness.... no?

The mechanical speedo gears and/or other bits maybe worn and slipping.
Even without excessive wear if the drive housing or parts are loose in any location the drive may slip too.

 

[idk]

Speedometer cable may need lubrication.

 

[atomsplitter]

Speedometer cable may need lubrication.

+1. The speedo cable is a wound spring and the friction between the cable housing and cable will cause it to tension the cable showing a slower speed on the dial. Unscrew the speedo cable at the back of the housing and squirt some cable lube down the cable. Thread it back on and give it a test ride. Simple.

 

[Boog]

Thanks guys!

 

[Bigjaype]

Thanks guys!

Unfortunately, lubrication of the speedo cable will not solve this.

As a measuring instrument that is several decades old, it's accuracy is determined by several factors.
Wheel diameter - is the correct size tyre fitted?
Needle Spring - this will definitely have softened over time, causing over reading
Is there particles of dust between the speed cup and plate, causing additional friction - probably unlikely if its around 10% error
I have had several vehicles with 10% over read error. My current Titon UTE has a 9% error.

 

[Boog]

Unfortunately, lubrication of the speedo cable will not solve this.

As a measuring instrument that is several decades old, it's accuracy is determined by several factors.
Wheel diameter - is the correct size tyre fitted?
Needle Spring - this will definitely have softened over time, causing over reading
Is there particles of dust between the speed cup and plate, causing additional friction - probably unlikely if its around 10% error
I have had several vehicles with 10% over read error. My current Titon UTE has a 9% error.

I will research the needle spring you mention. That is new to me. Exterior wise, the gauges are in top notch shape for a 40 year old bike. Mileage is low thus I assume the bike had sat for decades of no use in some sort of a covered room. I do believe the bike will need a deep dive on every system once I get eh gumption to do it. Dust inside the gauges is quite likely.

 

[Ishrub]

Unfortunately, lubrication of the speedo cable will not solve this.

As a measuring instrument that is several decades old, it's accuracy is determined by several factors.
Wheel diameter - is the correct size tyre fitted?
Needle Spring - this will definitely have softened over time, causing over reading
Is there particles of dust between the speed cup and plate, causing additional friction - probably unlikely if its around 10% error
I have had several vehicles with 10% over read error. My current Titon UTE has a 9% error.

Good info, but it is under reading not over, so a dried up cable drive does seem most likely, the beauty is they are a piece of cake to lubricate/clean out with a pressure can WD or similar followed by your preferred lubricant.
The old mechanical ones usually have a manually threaded cable mount socket out of the instruments. remove and squirt until it gushes out the other end and look at what is flushed out to indicate if any grunge, spiders, wasps etc have crept in over time. Old bikes can have things like that disconnected for years until sale having raised generations of spiders, wasps in the mean time.

 

[atomsplitter]

The speedo drive comes from the front wheel at the hub. Accuracy is affected by tire diameter, that said if the tire is a stock size speedo error should be no more than about 7%. Lubing the cable certainly won't fix some problems, but eliminates the source of one.

 

[Boog]

So there I was, minding my own business on the way to work. Coming off the expressway, I down shifted from 5th to 4th. BANG! Engine drops to a normal idle but my clutch is limp and the shift lever does nothing. I see the neutral light is illuminated. I safely coast to the side of the road by the traffic light. The bike is running, I get off and see oil dripping from the transmission area. I shut the bike off, dang it! I call AAA, be here in 2 hours, right...
A workmate pulls up, and we call a few more strong lads from work and lift it into his pickup. While lifting the bike, I see the chain is missing. I look back down the road and there it is. I have not determined what damage it caused under the engine to cause the oil leak yet.
4 hours later and AAA has still not arrived...