My bike ('98 FLHTC) is eating speedo drive units.

My speedo cable snapped about a foot from the bottom inside the casing.

While changing it, I did it wrong. I unscrewed the set screw in the drive unit to get the cable out and while doing so, the worm gear came out of the drive unit, and cannot get it back in. (I was not aware that the cable just unscrews from the drive unit...a lesson I learned in my next attempt to repair it)

I purchased a new cable and drive unit from the local HD dealer (that is when the parts guy showed me how the cable was SUPPOSED to come out). I replaced the drive unit on the axle, and installed the new cable. Before torquing the axle nut, I wanted to see if everything worked, so I spun the front wheel. Big mistake. The drive unit spun and hit the fork, and SNAP!, the bottom of the drive unit blew out, and kinked the end of my new cable.

Hoping I could still use the new cable, I got another drive unit. Installed it, torqued the axle, and gave it a test spin. When I did, the tab (the tab that goes into the brake rotor and turns the gear inside the drive unit) bent and came out of the rotor. Only thing I could figure is that the slight kink in the speedo cable was just enough to lock up the worm gear, and caused the drive unit to bind and lock up a little, which bent the tab.???

I got another new cable, replaced it, bent the tab back into place on the new (now third) drive unit, and very slowly tested it. No kinks, no binds, everything was good, speedo worked again, odo worked again, turns signals self cancelled again, all was right with the world.

Well...all was right with the world...for 72.4 miles, and the tab once again popped out of the rotor and bent.

I am obviously doing something wrong, but I have no idea what it could be. This is not rocket science, its more like "see spot run" mechanics. I have thrown my hands up in the air and called my local indy to tell them its on the way for them to figure out.

In the meantime... what the hell am I doing wrong?

 

You could try bending the tab back into place and leaving the cable disconnected from the drive unit. I know you replaced the unit with a new one but if you drove the bike without the cable connected you could verify that it is not a problem with the drive unit. You also mentioned that the old cable broke in the casing. Was the new cable a cable and casing? Did you route the new cable the same way as the broken cable, no kinks? I probably haven't helped and I'm out of ideas. Good luck, post the fix.

 

A stiff or kinked cable will ruin a drive unit fast. I guess you know that now. Anyway, put a new cable and drive unit on (I know they are not cheap, believe me, I've gone through six or them at least) and make sure the cable is routed with as little of any bends as possible. Big radius curves.

 

OK - question - when the axle was loose and you installed the unit what did you do to keep the axle from turning

a - tightened the bolts on the axles left side and then torqued the nut

b - held the axles left side with a drift and torqued the nut then tightened the 2 bolts on the left side

???????

 

Very good point/question.
There is a different answer to my two bikes. One needs the 7/16" drill bit, the other don't. One has two discs, the other got one only...

 

I've broken them by tightening the axle nut and not holing the axle with a drift like John noted. I've actually done it twice.

 

answer - unless the axle is tightened while holding the axle ( un attached on the right side ) the drive unit is not held in place correctly and the wheel is actually off its center just a bit

 

Three or four years ago I snapped the speedo cable so when I got the new one I took the cable out of it's cover for inspection and it looked like there was hardly any grease on the thing.So I gave it a generous coating of wheel bearing grease then some for the worm gear installed the cable and no problems since.

 

Only grease a new speedo cable inner for the lower 2/3rds, otherwise there is a risk of grease finding it's way back up into the speedo head.

 

Johnjzjz--The answer is (b). I have had the axle off many times (repacking bearings and new seals, etc.), and I always torque the axle nut first (with a big phillips head screwdriver through the slot in the axle to hold it in place) then I torque the axle cap nuts.

14GP-I did bend the tab back in before, but did not drive it without the cable attached. Yes...the new cable(s) came in new casing.

Dr. Hess- big radius curves...Yes. The only thing I did not put back exactly like the old one was was zip tie it around the brake hose, so basically it was "free floating" from the drive unit to the head unit.