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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: mister_anger on May 31, 2020, 04:42:41 AM

Title: speedo only works when in gear
Post by: mister_anger on May 31, 2020, 04:42:41 AM

hello,

I am rebuilding a 1985 K100. Have done this before so I have some experience but this one has a problem that I don't  get.
removed the lunch box and replaced it with a BEP 3.0 and acewell dash. Everything is working fine only the speed indication is acting up.
it will only work when the bike is in gear. This is weird as there, as far as I know, is no link between the 2 circuits of gear indication and speedo.
Maybe I am missing something?

When I turn the rear wheel manually on my other K100 it will indicate speed when in neutral but this one doesn't.

maybe someone has some feedback on this.

Title: Re: speedo only works when in gear
Post by: Laitch on May 31, 2020, 08:24:00 AM

Does "done this before" mean that you've have experience installing a BEP and aftermarket instrument on another moto?

Title: Re: speedo only works when in gear
Post by: mister_anger on May 31, 2020, 09:34:18 AM

that is exactly what I mean. I already have a K100 cafe racer fully modified. There are a some differences between the two bikes. On this new bike I removed the BMU, replaced the flasher with a modern LED flasher and installed a motogadget dash. I also upgraded the controls to the controls of 2010 triumph speed triple. This took some electrical work but all works fine. Just this speedo thing is the only thing that is weird. There is no direct link between the gear indicator and the speedo so I don't get why the speedo only works when I put the bike in gear. Unless I am not sseing it.

this is a link to a picture of my previous build :
https://www.facebook.com/photo?fbid=10217035061251459&set=a.10213025926985608 (https://www.facebook.com/photo?fbid=10217035061251459&set=a.10213025926985608)
this is a link to the bike I am building now :
https://www.facebook.com/photo?fbid=10222045249463033&set=a.10220335267674557

grz, M

Title: Re: speedo only works when in gear
Post by: 850Commando on May 31, 2020, 08:01:27 PM

I'm wondering  it is a bad earth - Maybe that would happen if the brown {earth) from the speedo sensor was not connected so the signals had to find  a different path to earth..  Just a guess

Title: Re: speedo only works when in gear
Post by: Stumpy on June 01, 2020, 06:30:06 AM

Quote from: 850Commando on May 31, 2020, 08:01:27 PM

I'm wondering  it is a bad earth - Maybe that would happen if the brown {earth) from the speedo sensor was not connected so the signals had to find  a different path to earth..  Just a guess

This is what I was thinking as well. the speedo has a brown wire feed from pin 23 on the plug, it could be mixed with another brown from earth.

Title: Re: speedo only works when in gear
Post by: mister_anger on June 01, 2020, 10:38:54 AM

already checked pin 23 and it is fine. In fact as far as switching to ground there is no difference between neutral and any gear. As there is always, in some combination, something connected to ground via the same wire. It is a mistery to me. I'll try and contact the guys that make the BEP3.0 but they are not so great in communicating. ;-)