Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Speedometer Drive Failure?

Speedometer Drive Failure?

Moderators: Curt!, Pa

Post Fri Apr 29, 2011 4:32 am

Posts: 10
Is there any tricks or tips on why speedometer drives last such a short time? The one before last was in there for years then one day it failed, I replaced the gear end on the drive shaft and that one stripped within a few miles. Both were the brass type.

The rear hub is a fairly new genuine part and I can't see anything wrong with the drive gear. The cable and the speedometer both turn freely by hand.

Any ideas what's wrong? These drives ain't cheap so I want the next one to last more than a couple of miles!!

Post Fri Apr 29, 2011 6:31 am

Posts: 386
You need to carefully check the alignment and depth of engagement on the gears. If the spiral geear on the drum is pressed on too far or not far enough it will eat gears. Also the depth of engagement of the drive unit. Is the retaining clip in the right place?

Post Fri Apr 29, 2011 6:51 am

Posts: 10
Thanks for the reply Robbie.

Had the retaining clip bolted down okay, it's in the slot so I guess it's okay.

Any tips on how to check the gears alignment and depth of engagement?


Post Fri Apr 29, 2011 11:20 pm

Posts: 975
Location: Markt Einersheim, Germany


I have had several problems with my WLA doing the same thing. Do a search for my posts and the answers.

I got photos of my NOS rear drum showing the gear completely seated on the drum and the staking...

The drum that I did have on her was not even close to being right.

Make sure, gear seated on drum, NO burrs on the gear.

I also got a pic of the gear on the drive and its postioning. And replacing just the speedo drive gear is easy and cheaper than looking for a complete drive.

If you want the photos send me your email addres.


Post Sat Apr 30, 2011 5:37 am

Posts: 377
Location: madison wisconsin usa

i had the same problem when i put my wla into service. all nos parts except the drive itself.

here are a couple of tips once you find out if your spiral is installed correctly.

first, make sure your cable and drive are well lubricated and not binding. it should turn free with little resistance. the drive gear doesn't stand a chance if the cable is not turning!

second, carefully examine the spiral gear for any debis from previous gear failures. any bits left in the gear will quickly destroy the next one you install! i used a dental pick to clean the bottom of the spiral.

third, you might try using one of the brown fiber gears instead of the brass ones. they seem to be able to hold lubrication better. i used white lithium grease on the spiral and drive gears.

and finally, check for any binding with the rear on a stand before you attach the cable. you may be able to detect any problem before you run it and wreck yet another gear!


Post Sat Apr 30, 2011 6:37 am

Posts: 323
Location: north central Ma.
Try "painting" the gears with a sparpie marker or Dychem then assemble and spin a few revs take it apart and look at the gears to see how the marker came off and adjust as best as possible for center to center wear.

Seems like there should a a sticky note at the top of the forum for speedo drive fixes it come up atleast twice a year.

There must be some junk aftermarket stuff out there....
"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
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Post Sat Apr 30, 2011 11:53 am

Posts: 10
Thanks for all the replies guys.

I did do a search on this subject but I mustn't have got it right as I found nothing!

I'll follow up with my progress...


Post Mon May 02, 2011 1:28 am

Posts: 52
Location: London, England
Have you tried looking at the spindle in the speedo head where the inner cable fits in ? Have you been get any strange noises from that area that sounds a bit like a dry bearing?
I had a problem where I was stripping OEM & nylon drives within a few miles and fitting a brass one gave me the time to find the problem,by puttingthe bike on the rear stand, running it in gear and listening.
The spindle in the speedo head was dry. It would still turn but when compared with another speedo you could tell that it was tight. It is lubricated by a grease filled wick that you can only access by pulling the speedo apart. It is possible to oil this wick by carefull drilling from underneath and dripping in oil. Palmers book has an exploded view of the speedo. That cured the problem.

Post Mon May 02, 2011 12:38 pm

Posts: 10
Thanks Ron. The speedo is a fairly new repop but it could be causing problems. The cable end at the rear wheel turns freely enough by hand but a closer inspection is a good idea.

I'm waiting for some parts then I'll have a go. Please keep 'em coming lads...

Post Sun May 08, 2011 4:43 am

Posts: 176
Location: Carmarthen, Wales, UK
Worth checking too that your speedo cable isn't being trapped. Might seem to be turning fine, but a little bit of resistance at low speeds may not be noticeable, until it multiplies as you go up the road. Ask me how I know! :oops:
72 Ironhead, goes better than it stops!



2005 XL1200R.... well ya gotta have a rat-bike!

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