Speedometer Accuracy

[chicagorandy]

Just for fun, I took a ride the other day and brought along my TomTom GPS. The suction base attaches quite well to the top of the faux gas tank and it's power supply plugs into my new portable power socket.

Up to about 35mph the dash speedo is reasonably accurate (within a point or two) After that through the range up to 75-80mph it reads a consistent 5mph high. So when it reads 70 I am really only going 65, 45mph = 40 mph etc. Great for avoiding speeding tickets I reckon - lol - but it was very good info for me to learn to be able to monitor my 'actual' speed vs what the dial said.

No wonder so many cars passed me by on the slabs - lol

I didn't see anything come up on this topic when I searched "speedometer" though I seem to recall reading other similar posts?

Just a 'for what it's worth' posting on a sunny Saturday before I head off for another near the end of season ride.

[debron]

There have been a number of posts about this. In the Tech Section section of the website there is a blurb about this and a reference to replacing the 25-tooth speedo gear with a 24-tooth replacement. Though most believe their speedos are off "about" 5 mph, I have read and found this to be true on my bikes, that most Japanese bikes are built intentionally to read 10% fast. This was true on my Suzuki 650, Honda Sabre, and both of my XII's.

On both of my XII's, according to my Tom-Tom GPS, the speedo was/is off exactly 10%. This is why it appears more accurate at lower speeds. In other words. at 50 on the speedo, true speed is 45, at 60, true is 54, at 70 true is 63, at 80 true is 72, and at 90 true is 81. I've been to 100 only twice but focused on the road and the bike and didn't take my eyes off to look at the speedo! I tested this many times with my GPS, on flat roads, straight roads, twisty roads, up-and-down roads, sea level, and high elevations. Always 10% off, which is "about" 5 mph at standard highway speeds.

[chicagorandy]

I knew I'd read something about this - lol

Don't know why the search function doesn't bring up anything under 'speedometer'?

The two necessary parts to convert to 24 teeth are on order as I type this. I'd rather not need to do the mental speed conversion -

For reference my '03 Ural Tourist's speedo was so far off that I only used it for the odometer function. I kept an inexpensive Magellan GPS mounted to the handlebars to tell me my speed 24-7-365.

For those who might also be interested in this rather simple looking fix, the part numbers are:

92049-1057 - oil seal - $4.30 from Partzilla
41060-1025 - 24T gear - $9.13

plus ($5.95) USPS shipping to my house.

[debron]

By the way, even though my speedo is off 10% the odo is off only 2-3%

[doug of so fla]

Randy: Replacing the ring gear with a 23 tooth makes the speedo right on, 24 is ok also, and Replacing just the ring gear and not the pinion will make for mismatched gears, (new against old) and will wear fairly fast, pinion will start to skip. and it is not worth it not to replace it. Only a few more $..

[gearheadfla]

It seems to be common on Kawasaki's. My 07 Nomad has the same thing, and on the Vulcan sites seems all the V-Twin's speedo's are off. The nomad don't have a speedo gear or cable, but there in a fix for it with some kind of module, I just don't think it's worth the cost of trouble to do it. In town I'm moving with traffic flow, on the slab I'm using a GPS anyway.

PS, Hey Doug, the Toy Run is the 2nd weekend of Dec this year, we are having the 1st meeting this Wednesday, you interested in coming down again, Victory is going to have the new Slingshot for Demo's. I gotta ride or I guess drive one of those critters.

[chicagorandy]

Thanks for the tip Doug - pinion is on order.

This will be an off-season project....sadly getting pretty close here in Chicagoland. Once the frost and ice start appearing in the weather forecasts it's time for my two-wheeled toys to hibernate - lol

[grumpin]

it reads a consistent 5mph high.


I don't use a GPS but time it with mile markers. I think every speedometer, on every vehicle does this. I just add 5 to every vehicle. Good point about speeding tickets though! One question is, how accurate is the GPS, and how would you check calibration?

[carl leo]

doug is right, mixing new with old never works with the speedo gears, the part numbers for the correct 23t gear and the 19t pinion are.
41060-1107 23t
41060-1016 19t
it is easy to damage the housing trying to disassemble the unit and i see some that look like kindergarten children worked on them. be gentle..............

[chicagorandy]

I already have the 24t gear on order so I'll see how that works out. It was listed in the tech posting before Carl posted. Any tips on disassembly before the parts arrive?

[debron]

So, is it the 24-tooth or the 23-tooth gear that corrects the speedometer error? I may need to correct the Tech Center page.

[carl leo]

i find the 23t gear sets my speedo perfect with my gps, the 24t was still reading several mph fast. this is with a E3 at 38psi...........

[debron]

Thanks Carl! I'll work on the correction.

[chicagorandy]

I have sent a request to Partzilla to change my order to the 23T gear. Hopefully they can accommodate. If not I can always re-order.

Good info to have.

Any special precautions or technique to replace the gear, oil seal & pinion ?

[ghostler]

I've been getting about 3 mph difference at 75 mph on my 2001 XII. Lower speeds are less. This is comparing with my Magellan GPS. I was following advice until I got my GPS. By traveling 5 mph faster, I was 2 mph over the speed limit, potential ticket getter in Texas Panhandle. I haven't counted the number of pinion teeth yet to say if a previous owner replaced one of the gears.

[chevyman1]

The 1996 600 ninja speedometer drive should fit right on and it has the 23T gear

[doug of so fla]

Any special precautions or technique to replace the gear, oil seal & pinion ?

You have to drill a hole (same size as roll pin) in the hsg on the opposite end of the roll pin so you can push the roll pin out. The small hsg that holds the pinion in is pressed in, you need to grip it good and work it out & it is alum so do not bugger it up to bad. The seal will come out fairly easy with a screwdriver just pry in different spots, If you are easy with it it can be reused if need be. I use a marine white lithium waterproof grease, Do not use wheel bearing grease or a thick heavy grease. Check that the lock or collar with the two big notches that fit in the wheel are not chewed up, if edges are dinged up you can file them so they are straight, if real bad you you need to replace and be sure when you put hsg back on that it is set in properly, The housing where the cable is attached should be almost parallel with the floor. The speedo hsg looks like it fits between two stantions on the shock but it does not, Look at the way it goes before you remove it. Cable should go up thru fairing on outside of shock and I always put a small o-ring on bottom end of cable to keep water out and do not loose little washer on the end of cable and ones on the pinion. Actually takes longer to type this than to fix it. Like Carl says some are better off just replacing the whole assy. But I do not think you can get the correct gears that way. If you run into a problem let us know..