Speedometer 1982 XJ750 Maxim

It was suggested to me by a fellow member "MercuryMan" to start a new thread so that this may help others. Thank you for the advice as I am still learninig.
I am having a speedometer issue. Already replaced the speedo cable but it did not correct the issue. At speeds above lets say 30mph the speedometer is about 12-15 miles below the correct speed. I have used a gps strapped to my handles to verify. The needle is smooth and not jerky. At speeds below 30 mph it seems to be correct. At 60mph it reads 45. Even at 70 never seems to get past the 45-47 mph range. Question ? do I need to change the Head or the speedo nut/ sensor on the front wheel. Can the speedometer unit itself be fixed or cleaned? My XJ seems to gain speed pretty fast so a good speedometer is important to me. All suggestions welcome.

Is it easier to replace the entire Control display as it would be just to replace the speedometer?. Thanks!. I have my ideas but there's no substitute for experience.

 

Hey, I have a 83 maxim xj750k and am having the same issue that you were having. I also did the gps thing on the handle bars and got about the same readings you did. Did you find out what was wrong and a fix for it. I replaced the speedo cable and the speed sending unit. When I went to fit the speed sending unit on the axle the hole was not big enough for the axle to go through so I had it machined out. I do not know if the speedometer was correct before changing the parts out because the speedo cable was broke in half and the speed sending unit would not accept the new cable. I am leaning in the direction that the whole front end is not stock due to the controls and master cylinder not looking like the other xj750k's that I have seen. Any help would be greatly appreciated.

 

I too have a Maxim with a similar issue.
There is a write up by BigFitz in the FAQ section on cleaning and lubricating the speedometer internals. Like most of his stuff it is very detailed and complete...if memory serves me though...it's for one of his 550 Seca's and not a Maxim, but it should get you "in the ballpark".
Good luck

 

My writeup applies to any of the mechanical instruments regardless of what bike they're on. The only "caveat" is accessibility; it's easier to get to the speedo guts on some models than on others.

I did do another piece more specific to the 550s, on how to remove and disassemble the cluster.

 

The 83 maxim clusters are much easier to disassembles than the 'canned' ones are........

Dave

 

I don't mean to hijack this thread, but I just pulled my cluster off my XJ750 Maxim (because this thread motivated me!!)...How do I get to the Speedo? Before I go pulling things apart...I'd like a little guidance. My service manual has an exploded view, but does not give and accurate depiction of screw locations.
The main idea is to clean the speedo and lube the bearings.
Any help is appreciated.

Pat

 

Make sure you remove/loosen the TINY set screw holding the trip reset knob on BEFORE you try to remove the rear cover of the atari!!!

After that taking apart the guts of the atari are pretty straightforward (from memory).

 

Try this: Breakdown of the 750J Gauge Cluster