Hello all, I recently purchased a 96 smokin Joes bike and have ridden it about 500 miles now. I noticed early on that the speedo was incorrect and have compared it to two GPS units and both are consistently telling me that the speedo is fast by 5 miles an hour. Its almost purfectly 5miles an hour at any speeds. I have checked tire size and they are stock size, I have not looked at the fromt gear but the rear geear is stock and as far as I know the entire bike is stock.

Does anyone know if this is a known issue or have some ideas on what to look for. I was thinking that airgap on the sensor may be potential but I don't see that having such a consistent reading. any ideas would be great.

Secondly, I have been given a Scotts steering damper, and am looking for hte mounting bracket but I can not find one in the Scotts site. Anyone have any ideas on where to get a bracket for this thing. AS you know these are not cheap dampers and would love to use it but with out hte bracket its useless. I am calling them tomorrow but thought I would throw this out here.

Thanks
Keith

 

Speedo error is usually a percentage of actual speed: 3 off at 20mph 6 off at 40mph. Never heard of one being 5mph off everywhere. At what speeds are you comparing your speedo to the GPS? And remember, almost all GPS units are about a second behind so in order to get as close as possibe you should maintain a steady speed for a few seconds and then compare.

 

I checked it at variouls speeds. 15mph, 30 mph, 65 mph 80, all of them are alomost exactly 5 miles off, some times 4 but consistnetly 5 miles an hour off. Each test was done at steady speeds for more than 10 secods a piece. Its got me as I know speedo's and their relation to actual speeds vary this one is not a variable its a consistnet 5 miles an hour. When it say5 15 on the speed I am doing 10-11 mph on the GPS. I checked it with two differnet GPS units and both were the same results.

I may just have to live with it and its errored on the right side of the equation if you ask me.

 

Given the construction and functionality of your speedo system, there is absolutley no way for it to be off by exactly the same amount regardless of speed. Are you sure its not magic? How's the GPS do in the car?

Even police radar dectors have a +/- 5 MPH innaccuracy quotient, which is why you'll almost never get a ticket for speeding less than 10 MPH.

 

maybe a fault in the gauge from the factory? like the placement of the MPH numbers are off? does it sit at 0 when its in the driveway?

 

I was thinking that also. The speedo could be right on but the needle is off by 5. If so that's an easy fix. Pull the speedo, run the needle to 60, use a small clamp (like a surgical clamp) to hold the pin. Use a spoon on either side of the needle and pry it up. Make sure the pin does not move. Press the needle back on 5mph less and you should have a speedo that's dead nuts. Had to do this to a Jeep one time when I changed the speedo design. Didn't think about having to hold the pins in the correct position and wound up pulling the thing apart 3 times to get all my gauges correct (temp, oil, speedo, tach ... ugh what a pain)

 

You know the bad part about this is I am not a stupid guy that does not know cars or bikes. I used to teach automotive for Honda in their training center and still work for Honda in a different capacity. My entire background is engineering and technical. But this one has got me baffled. I never thought about gauge number or needle placement. I will look into that. I am telling you that no matter what speed its exactly 5 miles an hour off. I have never seen this in my 17 years of working on Honda’s that’s why I am posting this. Give me the hardest problem with an Accord and I can figure it out but this one has got me stumped. I have a call into a buddy of mine at Techline motorcycle division to see what he thinks but your thoughts and ideas are appreciated. More heads and better than one.
And the quote you’re not a real mechanic until you tasted gas is absolutely true, try some brake clean its even worse, it burns.

I appreciate the help, if there is anything I can do to help anyone here please let me know.

Still looking for a damper for the bike.

One more question, head shake, I get it above 30 mph and above free hand and one handed. Does not get real bad as you get higher speeds like highway, but I had the front tire balanced and still no change front tire is clean tread wise. I am leaning towards head bearing preload being loose, what are your thoughts. Has anyone see this, apart from that I am not sure what more it could be, except a harmonic phasing problem with the tire in the second or third harmonics of the tire.

thanks
Keith

 

Yeah but if that's the case, the needle would be off by 5, even when the bike isn't moving.