Odometer trip Speedo Disassembly

[cineburger]

My speedo was DOA on my newly acquired 1971 Ace 100 B+ thrasher....read 100MPH while I was standing still daydreaming...the cable is good and the sender unit sends; the odometer works; I have removed the bezel and loosened all the observable screws but have yet to pry off the rubber surround on the trip reset knob; anyone have info on further disassembly? How do I remove the reset knob/dial/whoositz? Does the speed indicator pointer just pull off?? Can't seem to find any info links other than the bezel removal....any help would be immensely appreciated...cheers, david.

[hodakamax]

There's a few good discussions in Forum past on this procedure. You might start with a search above. As I remember the chrome ring is methodically and carefully pried off.

Max

[relic]

I hope your speedo looks a little better than mine did...
The trip reset knob is held on by a VERY tiny phillips head screw. To remove the indicating needle I use two spoons, placed at 180 degrees across from one another and gently pry the needle up levering against the face plate. They are a press fit.
The two phillips head screws you see on the face plate secure it to the main frame.
If you use the correct size spoons you can pry against these screws rather than the thin, easily damaged face plate.

Ken

[relic]

What I have learned over the years (and I am no expert and could be wrong on many accounts) is that the drive drum which is connected directly to the cable, ("A" in the photo below) rotates around the driven piece which is connected to the needle. ("B" in the pic) One having a permanent magnet which "drags" the needle around governed by the rpm of the cable.
The most common problem I see with old speedos is that the bushing between the driven piece (connected to the needle) and the bracket that holds it wears allowing the drive drum to contact the driven part.



You can see the pin that the needle attaches to right above the letter "B".

Ken

[relic]

The play is between "B" and "C" in this next photo. In this case any rotation of the cable resulted in the needle wrapping around to the stopper.



I fixed it by buying another speedo that wasn't rusty and crusty and combining the good parts from both to make one.
The Yamaha enduro speedometers are similar in fact my DT400 uses the exact same unit, the only difference being the face plate and the case. So if you need parts that might be a source. I've been into several over the years---I find the trail or enduros usually suffer from dirt and moisture ingestion and the street speedos get the broken glass and dented bodies.
Lots of fun and quite satisfying if you can bring one back to life.

Doubt this has been much help but hopefully somewhat interesting. And maybe the experts on the forum can correct my guesses on all this.

Ken

[Bill2001]

Speedo repair is as mysterious as watch repair. Not only do you have to repair the instrument, you have to calibrate it, too.
For my time and money, I'll hunt up a replacement unit.

[cineburger]

Thanks for all the quick responses...I fixed the beast--and here's what I learned; maybe it will help someone else in my previous shoes...I am obviously no expert in any of this but having taken the speedo apart and put it back together I'd like to share my experience; the reset knob comes off with a phillips head screw on the end; careful taking off the rubber grommet sealer; the speedo pointer is mounted to a shaft (axle) with a pressure fit; you just pry it off gently; some folks use a kitchen fork to apply pressure evenly on both sides; there is a watch-like spring wrapped around the shaft which functions to return the pointer to 0 mph when idle; in my case this spring was broken right at the outside top mounting point to the shaft; the shaft has a small raised "slot" into which the spring end is placed and bent over then glommed with a bit of sealant material; my spring end was floating in the breeze (allowing the pointer to remain at 100mph when idle) and there was a telltale little spring bit still on the slot of the axle shaft. I removed the bit and respun the spring around the shaft then fastened it to the slot and bent it slightly. This shortening of the actual spring length will probably affect the speed calibration slightly, but I am not into micro perfection and a general indication of mph is good enough for me. Make sure that the spring is pulling the needle counter clockwise back to zero, reassemble everything and carefully re crimp the bezel--yer good to go. Good luck all.

[hodakamax]

Ah, good report! I've got one in the shed with the needle loose in the case. With your encouragement I might have to give it a shot.

Max

[cineburger]

A brief followup--the $80 speedo fix....I previously spoke too soon; yeah "I fixed the beast" and got the spring back together but going down the road it now read 0-3 (3 for good vibrations!) instead of 100...musta been the issue Brother Relic mentions above...ebay to the rescue...bought the new 3 light unit (exactly the same as ours only a neutral light added to the mix...changed the bulbs, installed and, cabled--voila--my bike is now brand new with 0 miles and everything speedo-wise works...now I know I'm only going 43 mph when it seems like 75--whudda feeling.....