Honda-SOHC

Other Stuff => Misc / Open => Topic started by: Athame57 on June 13, 2026, 02:45:26 PM

Title: Why might my speedo be failing?
Post by: Athame57 on June 13, 2026, 02:45:26 PM
A couple of weeks ago my speedo stopped. Time for a new cable I thinks, so I got one on fleabay. After fitting all was well a few hours, and it stops again. I figured I had bought a naff one, but also observed my routing wasn't very good.
Okay, so I get another speedo from a different source and went to change them over but couldn't find anything wrong with the one I'd just taken off. Fit new one anyway and all was well for a few hours and zunk, it stops again. I take off cable, check it and refit but nothing.  Any ideas what might be happening?
Title: Re: Why might my speedo be failing?
Post by: Oddjob on June 13, 2026, 03:07:24 PM
Speedo drive gears stripped?

Speedo drive not engaged onto drive plate properly?

Second is more likely. Take off the front wheel, pull the spindle out and check the drive engages on the tabs of the drive plate. If it's been like that for a while expect some damage, may be bad, may be just some scraping.
Title: Re: Why might my speedo be failing?
Post by: exvalvesetdabbler on June 13, 2026, 03:12:12 PM
Is the inner part of the cable  still in one piece? It should just pull out from the front wheel end.  Other than that is the inner too short and not engaging in the Speedo properly.

Also if you whittle down a pencil or round bit of wood with a square end  to fit in the Speedo and spin it anticlockwise the needle should respond.

Regards
Dave
Title: Re: Why might my speedo be failing?
Post by: exvalvesetdabbler on June 13, 2026, 03:29:34 PM
Check that the rubber bonded coupling hasn't disintegrated 182 in the image below.

[attachimg=1]

For the drive gearbox , 184, you will see two pegs inside just below the seal, you should be able to spin/push that round with a small screwdriver or 3m. Drill bit. Should be smooth and the flat blade that engages with the cable should rotate with it.

Regards
Dave
Title: Re: Why might my speedo be failing?
Post by: Athame57 on June 13, 2026, 04:46:58 PM
Thanks for the answers guys. I have notice the snail has a lot of grease around it's lower parts, unusual.  :-\
Title: Re: Why might my speedo be failing?
Post by: Bryanj on June 13, 2026, 05:53:15 PM
The easy answer is just like me old age and infirmity!!

I have seen cables where the inner is a bit short and does not engage the square in speedo properly, i have also seen some drive plates, usually on 550, where they are made in two parts and rubber bonded together presumably for damping and the bonding has let go, early ones are one piece steel and dont do that.

Otherwise as said the drive gearbox could be failing or the speedo itself, the pencil is an idea but most of us now have a least one battery drill that will go backwards!
Title: Re: Why might my speedo be failing?
Post by: exvalvesetdabbler on June 13, 2026, 06:21:04 PM
The snail or worm  drive is usually well greased and it can go hard and gum things a bit. When I have  refurbed one in the past I have washed out all of the old grease with a solvent, while spinning it around, dried it out  and packed in a bit of fresh grease.

On the 400 drives that I have the coupling is two metal parts bonded with rubber, if the `snail` seizes up it can rip the rubber bonding.

Regards
Dave
Title: Re: Why might my speedo be failing?
Post by: exvalvesetdabbler on June 13, 2026, 06:55:41 PM
Or connect the taco cable to the Speedo

4000 engine  rpm with 7:1 drive ratio = 571 rpm on the tacho cable

60 x 571/2240 = 15 mph reading on the Speedo.

Dave
Title: Re: Why might my speedo be failing?
Post by: Athame57 on June 13, 2026, 07:38:38 PM
Or connect the taco cable to the Speedo

4000 engine  rpm with 7:1 drive ratio = 571 rpm on the tacho cable

60 x 571/2240 = 15 mph reading on the Speedo.

Dave
I'll definitely try that one out Dave!  ;D
Title: Re: Why might my speedo be failing?
Post by: Athame57 on June 17, 2026, 05:40:00 PM
It really looks like I had fitted the broken cable on instead of the new new one  :o  and put the good one to one side. A correction of that has my speedo up and running again, but not before I'd already started searching the web for rarish spare parts. Senior moment ::)
Title: Re: Why might my speedo be failing?
Post by: Bryanj on June 17, 2026, 08:30:40 PM
Been there, done that
Title: Re: Why might my speedo be failing?
Post by: exvalvesetdabbler on June 17, 2026, 09:01:59 PM
Good job you hadn't tossed it in the bin and the bin men had already been down your streer
Title: Re: Why might my speedo be failing?
Post by: Athame57 on June 18, 2026, 01:57:17 PM
Good job you hadn't tossed it in the bin and the bin men had already been down your streer
SSSHHH.... It's only been a week since I accidently threw out six nicotine replacement patches.  ::)  I'll be putting my dog in the bin at this rate.  :o
Title: Re: Why might my speedo be failing?
Post by: Bryanj on June 18, 2026, 02:50:50 PM
You mean your dog doesnt raid the bin anyway?
Title: Re: Why might my speedo be failing?
Post by: Oddjob on June 18, 2026, 03:01:05 PM
Sorry George but how could your speedo start working again for a few hours if the inner cable was broke because you refitted the old cable. Something else going on. Either that or you really are losing your marbles 😀😀
Title: Re: Why might my speedo be failing?
Post by: TrickyMicky on June 19, 2026, 08:06:36 AM
Maybe he has decided to stop pulling long 'wheelies' now that he's realised the speedo only works when the front wheel is turning???
Title: Re: Why might my speedo be failing?
Post by: K2-K6 on June 19, 2026, 08:44:55 AM
If one breaks down near the wheel end, then the "floating" upper part can "snaggle" the still fixed end to give intermittent drive sometimes.

Had a once in a lifetime (well I expect it to be) headlight builb low beam go out at over 5000rpm on a Kawasaki triple, but on again below that, which turned out to be the bulb's filament detached from one of the main posts, to "wiggle" up out of contact as vibration increased.

Less vibration or static, and it remained on  ;D
Title: Re: Why might my speedo be failing?
Post by: Athame57 on June 19, 2026, 12:05:55 PM
If one breaks down near the wheel end, then the "floating" upper part can "snaggle" the still fixed end to give intermittent drive sometimes.

Well actually that's what it has been doing today, working when it feels like it. Some meddling with the cable on the move ( bad idea!  :o ) can get it going again. I haven't pulled the cable out for inspection yet, I'm getting a bit cheeses off with it.
Title: Re: Why might my speedo be failing?
Post by: florence on June 19, 2026, 03:24:49 PM
I've been through so many speedometers it is beyond belief.  One wouldn't go above 50MPH, another developed an alarming squeal above 30MPH, another, the odometer stopped working and another was so vague, it waved + or - 20MPH whenever it felt like it.  I have consoled myself by coming to terms with the fact that speedometers are largely a cosmetic addition to the area above the headlight and now rarely look at it  ;D
Title: Re: Why might my speedo be failing?
Post by: Athame57 on June 19, 2026, 04:19:53 PM
I have consoled myself by coming to terms with the fact that speedometers are largely a cosmetic addition to the area above the headlight and now rarely look at it  ;D
Well, actually I've thought of giving up with it for a while too!  ;D
Title: Re: Why might my speedo be failing?
Post by: Rayzerman on June 20, 2026, 01:40:15 PM
You may want to dive in deeper and do a full refurb........
https://www.youtube.com/watch?v=PLU2sCFx6qU&list=PLSL5PUw3f6df2_9SmyiV7tF9XH_jnxlhj&index=14
Title: Re: Why might my speedo be failing?
Post by: K2-K6 on June 20, 2026, 02:24:07 PM
Undo the cable from speedo end, zip tie it so you can see it when riding, stick a tape "flag" to the cable end and then see if it turns all the time.

Separate the system into two parts, then look at each section on that analysis.