Speedometer reading correct mph on the km/h numbers???

This is odd, an I'm still tryn to figure it out . I just bought a atari box off eBay for my 82' 750 maxim. After installation and a short ride I discovered with the help of gps that my speedometer was reading incorrectly, slower than it should according to the mph numbers, BUT at actual 20, 40, 60 mph (according to gps)the needle fell on the numbers on the km/h side that matched what mph I was going. Can anyone tell me what's goin on here? My only theory is that some one has replaced the internal speedo parts with some that would go into a gauge that had a 120 mph faceplate reading on it , but is there such a gauge for xj's? I'm tryn to research that now, but haven't found any pics of such a gauge. My odometer seems to be accurate but I'm goin to confirm that with highway mile markers soon . Also I made certain that the cable , and the female part on the back of the speedometer the cable slides into operated freely before I put all together. Any help will be greatly appreciated, thanks.

 

Well after further research I am thinking now that I should prolly clean the internal parts of the speedo , bc I figure it has some gummed up old lube in it thats slowing the needle down , at least that's what most of the post on this subject here point to as a cause .... Pretty certain the cable is ok bc I've already cleaned and lubed that up , any other ideas would be helpful though, thanks to all

 

The distance test against mile markers or GPS waypoints should tell you something. If you clean it and re-test the speed let us know how it works out. Maybe it's just coincidence that it seems to be aligning to KPH because it is gunked.

 

Well I broke the atari down and pulled the speedo assembly today cleaned and lubed all the parts of it and seemed to help the needle move more freely by hand, moved easily , don't think it could get more freely moving, but after a drive it is still showing the same reading at the same rpms so it is still way off. Still lands on the km/h numbers the correspond with the mph I'm goin , I've already cleaned an lubed the cable also so Im not sure what to think now, any ideas anyone?

 

Is the MPH scale on the inside(International), or outside (US) of the dial display. you might have gotten a guage for the Canada. Europe, international market, not sure if this would affect the reading or not though.

Ghost

 

Yeah,... I was gonna say. Post a pic, if it's a KPH speedo, you might just be reading it wrong.

 

Well I tried to post a pic as an attachment then also in my gallery with my iphone but can't for some reason, unfortunately this is my only source of Internet here at home , but it's an U.S. Speedometer, the outside larger numbers go to 85 written in white, and the inside smaller numbers are in white also, they are all sunfaded I suppose, which shows the last smaller number listed as 120 an that hits on about 75 mph. MPH is written below the tripometer and kmh is written smaller above the tripometer . I hope that info drew an accurate description for u guys . When I bought the bike awhile back, the speedometer was broken the innerds of the speedo ground up , so this is better than no speedometer, lol , but I still would like to have it correct if possible , thanks for ur input guys .

 

Deffinately a US guage.
Next question.
When you got the guage off ebay. Was it described as a Seca, or Maxim guage?

BigFitz.
Do these guages use a series of switches on the back to calibrate the guage like an automotive guage?

Ghost

 

These gauges are mechanical, there's no way to calibrate them. I'd bet you have an old speedo face in a newer speedo guts.

 

Speedos are indeed mechanical; there IS a way to slightly "fine-tune" their calibration mechanically but I haven't perfected it yet.

Here's what's in there: http://xjbikes.com/Forums/viewtopic/t=15303.html

 

When I got the speedometer from eBay I actually bought the whole atari box , it was listed as a maxim gauge cluster and is one Im sure bc it looks like my original ,and I've looked at a seca atari and they defiantly look different. i took the speedo out of the one I bought an put it into my original atari box , bc it was in better condition cosmetically , and I know that everything else in it works . It may be that I have the guts of a 120 mph gauge , I've looked at bigfitz write up on the breakdown of the gauges , ( helped me alot by the way thanks for that writeup) and there is a pic if the 120 gauge faceplate in there if I did have that faceplate on my setup I would be showing about 10 mph slow on it, but I feel that's pretty close to right, especially since everyone on here talks about the inaccuracy of these vintage gauges anyhow, still not sure though ...

 

Oh and I just wanted to say I have a 100/90 19 tire on it, just replaced my old one actually , thought I'd put that on to save anyone the time of asking if u guys were wondering ..