Speedo drive rotating

Hi,

I went for a rather bumpy ride this morning and noticed my speedometer stopped working. The pressed on end on the drive end of the cable housing had come off. I've had this happen a few times, but not in a while, usually when going over a bunch of bumps.

In the past I've peened the cable end back on. I've been able to prevent it I'll by making sure my cable routing doesn't tug. I like to tie it to the cradle, not the frame.

This time it looks like the drive has rotated 270 degrees. The drive is just starting to bulge. I just greased it and based on previous experience I wouldn't expect any problems for a few thousand more miles (I'm on at least my sixth Speedo drive counting the ones I've cobbled together from other drives). I can't see how the drive could rotate unless it was seizing. It didn't seem to move in the ten miles or so from when I noticed it until I got home.

Eric

Yes Eric I-we understand but what is your point? W/o reenforcing the rivets I get & expect about a drive chain wear of mileage ie: 10k miles so keep a spare of those known wear items on hand. I suspect turns on rough surfaces tend to distort swingarm ends in shock absorber rubbers putting binds in the speedo drive.

I buy them up whenever I see one with a good body at a swap meet. Usually the innards outlast the body, although I've also stripped the teeth off the worm gear and the ring gear before too. I've reduced the torque on the axle to 65 lb ft to slow down the bulging process. I still torque the dummy axle to 80.

Does anybody know what causes the speedo drive to rotate? I have observed the rotation of the drive pulling the end off the cable. Seen this on other bikes, fortunately not on mine (yet).

Stephen Hill

Parts wear out, like the top hat spacer, the body where the spacer attaches is soft and prone to bending, it's very weak metal. What makes them turn is the body contacts the hub cover and binds up on it. Make sure the speedo drive is not touching the hub cover. When it happens you can see all the witness marks on the hub cover.

Make sure that you have the little top hat spacer in place Item # 34 Part Number N-M.13270 Spacer Speedometer Gearbox.
Make sure you have the cable routed correctly. It goes inside the crossover tube under the engine.
Make sure you do not over tighten the ties near the swing arm (Two fingers space not tight up against the s/arm). Leave things a little loose is better.
Angle the output of the speedometer gearbox with rider weight for best line then tighten the rear axle to fix the position.
Cheers,
Thomas
CNN

DogT said:

Parts wear out, like the top hat spacer, the body where the spacer attaches is soft and prone to bending, it's very weak metal. What makes them turn is the body contacts the hub cover and binds up on it. Make sure the speedo drive is not touching the hub cover. When it happens you can see all the witness marks on the hub cover.

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In my case I don't run a hub cover.

Being a simply complex commando means a number of things by themselves or in combination can cause speedo shell to torque twist or fully turn to snatch cable out the clock and wrap around wheel for short stops> generally the rivets get loose to ring gear does not spin centered and the wear game is on it earnest after than> then its common to follow norton over torquing on both dums asxle and long axle and many have missing top hat bushes to semi help prevent shell holding ring gear distorting extra loading on thin meat loose rivet snydrome> installing with the block teeth not in the drive notches just once may bring on shell distorion syndrome after re seating right> ed the tomato man number OONINE CNW Cdo wrote me this week his long axle would not come out and the speedo drive was turning but the dumb asxle nipped up fine just could not bet the tight turning long axle to back out a withworth> finally sawed through rh axle and spacer to find long axle rusted to spacers inside wheel and drum and could not bash out once cut out of swing arm< >> came to conclusion his power washing with strong detergents had intruded to corrode to a show stopper> if ya can not live with well known commando factory part weaknesses one can always jump fence and unnortonize till putting norton part vendors in a pinch>>>

next will be bitch on short rear tire life after getting a good tune down>>

ewgoforth said:

In my case I don't run a hub cover.

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Something is binding somewhere. Look here http://www.oldbritts.com/1971_g16.html parts 29, 31, 34 and of course 5 should not rotate with the wheel. If they do something's worn out, crushed or something has gotten between something else. I'd pull it all apart and replace anything that doesn't look good. It's about all you can do.

After 85K miles, mine twisted up, gouged and distorted the hub cover, and bulged its center. On removal, I found the ring and worm to be so worn that they jammed at certain points in the rotation. This is an explanation for severely worn speedo drives.

DogT's explanation for drives not so severely worn is worth reading again. There is something about the soft body metal, and the top hat spacer that causes the center to bulge allowing the body to drift toward the hub cover.

FWIW .... After mine twisted up, I went about rebuilding the rear wheel, brakes, new speedo drive, etc. On reassembly, I was not able to get the last spacer in place, lacking 0.140 inch. Further inspection, and with help from DynoDave and Madass, I determined my swing arm had a bow in the drive side arm. Removing the bow allowed the last spacer to go in with the fingers, like it used to every time I previously removed the rear wheel.
Did the development of the bow cause the speedo drive to bulge in the center? I know two other guys who lacked about 1/8 inch getting the spacer in. They just forced it. Maybe this is a factor. Check that last spacer clearance .... something is wrong if the swing arm has to be sprung apart to get it in.

Slick

I had an issue with not enough clearance once, but it was because I powder coated the brake cover, and the swing arm. All those surfaces added almost 3/8" to the inside parts of the assembly. I ended up grinding the powder coat off where needed. Where it really showed up was getting the single piece rear axle from madass and the axle nut would not completely seat. Nothing to do with the speedo drive.

I still have my orginal drive it has well over 140,000 miles on it, it only gets greased when I think about it and I also have the orginal cable, have never had any problems with it rotating, I only tighten my axles up with a big shifter spanner so no toqure wench at all, have never over tighten my axles, I ride on bumpy roads as well a lot of dirt roads, my cable runs freely with no ties on to the frame or cradle so I don't understand why so many have problems with this happening, could it be from the axles out of line :?:

Ashley

ashman said:

.......... could it be from the axles out of line :?:

Ashley

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Or over tightening.

ashman said:

I still have my orginal drive it has well over 140,000 miles on it, it only gets greased when I think about it and I also have the orginal cable, have never had any problems with it rotating, I only tighten my axles up with a big shifter spanner so no toqure wench at all, have never over tighten my axles, I ride on bumpy roads as well a lot of dirt roads, my cable runs freely with no ties on to the frame or cradle so I don't understand why so many have problems with this happening, could it be from the axles out of line :?:

Ashley

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Be curious to see you what you're torque value would work out to be. I have just under 100,000 miles on my bike and the longest I've had a speedometer drive last was maybe 25,000 miles. This is the first time I can recall having a drive rotate. I generally change then out when the bulging is worse than what I'm seeing here. Like the other guy wrote when they bulge badly they rub on the cover.

Eric

DogT said:

ashman said:

.......... could it be from the axles out of line :?:

Ashley

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Or over tightening.

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What do you tighten the spindle to? I'd read 80 lb ft in the Commando Service Notes, I believe. I've reduced it to 65, but that still might be to much. Of course the spindle is fairly greasy so the clamping pressure is higher than with clean dry threads.

Eric

Eric

Nothing needs 80 lbs trq on Commandos ugh. There is not mush force trying to spread the assemblly so 50 ish lb is more realistic protective and really only needs tight enough not to loosen on its own. I think the over tightening of long axle adds to the tendency to pop off at dumb asxle. Check shock bottom bbers in case they are loose worn which I think adds to binding twists of each end of swing arm.

One of the most common problems is incorrect alignment (usually several times) between the two speedo drive dogs and the two slots cut into the wheel based speedo drive; repeated miss alignment and over tightening makes the two slots smaller (peened over, bent) so the speedo dogs don't have sufficient free depth such that they are not wedged. Naturally the spacers (both sides) have to be properly oriented and of the proper length, but they are almost inert. If the speedo drive's metal sealing ring protrudes beyond the drive such that it makes contact with the "hub cap", assuming you have one (you stated that you didn't have one), that will add enough friction to make things interesting. When the wheel is fitted and properly torqued it should spin with very little effort.

The fix is just a matter of cleaning up the slots with a file or a Dremel, if you have a steady hand; the drive should just about fall onto the wheel based drive slots with a very small amount of seal friction.

If the "system" that includes the speedo drive, the right side axle, the inboard and outboard spacers are in good nick then torqueing the axle to factory specs should be a non-issue.

RoadScholar wrote:

"If the "system" that includes the speedo drive, the right side axle, the inboard and outboard spacers are in good nick then torqueing the axle to factory specs should be a non-issue.]"

I agree. I think RoadScholar has the best explanation of the cause of the bulge. The right side spacer bears against the top hat, the inside of the top hat against another spacer and so on thru the hub. The body of the drive should not have any pressure on it regardless of the torque value.

My lock ring slots were buggered from using a punch to remove/replace it. Per RoadScholar's explanation, this may have caused my twist up. I used a new lock ring on the rebuild and crafted up a tool to tighten the nut.

@ewgoforth: Want to sell any of those bulged out drives you changed out at less than 25K miles? I'll apply a little heat to the body and using a socket bearing on the top hat, squeeze them in a vise and remove the bulge. There's probably lots more life left in them.

Slick

I use 80 ft lb. but over time it will crush the top hat spacer. I keep spares around. I'm using a single piece axle now, but I doubt it will change anything. I also don't put miles on like you do.

ewgoforth said:

DogT said:

ashman said:

.......... could it be from the axles out of line :?:

Ashley

Click to expand...

Or over tightening.

Click to expand...

What do you tighten the spindle to? I'd read 80 lb ft in the Commando Service Notes, I believe. I've reduced it to 65, but that still might be to much. Of course the spindle is fairly greasy so the clamping pressure is higher than with clean dry threads.

Eric

Eric

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I use a 10" shifter spanner but when using it I don't put to much force on the axles I just tighten them up, I also put a smear of grease on my axle before fitting it on the wheels and have so for nearly 40 years, and the slots that the drive sit in are as good as the day I brought my Norton from new.

Ashley