Analogue Tachometer

FAQ tech questions, please check if the answer to your question is in here before posting elsewhere.
hendy
registered user
Posts: 859
Joined: Mon Jul 07, 2014 10:34 am
Main scooter: lambretta li 125
Location: Tyne and Wear
Contact:

nellyboyo wrote:Ha, no I don`t have varitronic and I don`t think it is reading double as it will only go up to around 7k revs with a big handful .
It just gets there way to quickly .
It was sold a for a single cylinder 2 stroke but its not the end of the world if I can`t get it to work some shape .
That's good then. I may have misunderstood your original post. So it shows the right number but just the needle spins round to the correct point too quickly, yes? If so does it overshoot then settle back down?
nellyboyo
registered user
Posts: 325
Joined: Wed Sep 22, 2010 10:28 am
Main scooter: Lambretta
Contact:

Yes , I really need to damp the action down a bit . cheers
User avatar
diesel
registered user
Posts: 201
Joined: Sat Jan 14, 2012 4:43 pm
Playstation gamer tag: speilekorps
Main scooter: lambretta li 150 s1 1958
Contact:

A koso rpm signal filter could tidy up the performance. Have you tried wrapping the signal wire on the HT lead ? What's the reading like there? Resistor or non resistor spark plugs can make a difference as can the routing of the signal wire keep it away from the magneto. I've had issues with my tachometer and I'm thinking of purchasing the filter
nellyboyo
registered user
Posts: 325
Joined: Wed Sep 22, 2010 10:28 am
Main scooter: Lambretta
Contact:

NO I didn`t try wrapping it around the HT lead . The old leads are quite thick and have metal connections on the end . I was guessing that a pulse from the green on the CDI would work , and it did. It would be something really thin for wrapping around the HT I would think .
I`m only guessing but the Koso unit is only a ferrite choke probably.
You can get clip on ones dead cheap if you want to try one of these first on yours .
I don`t think they`ll work on this type
hendy
registered user
Posts: 859
Joined: Mon Jul 07, 2014 10:34 am
Main scooter: lambretta li 125
Location: Tyne and Wear
Contact:

I've never bothered thinking about this properly, so I can't give any advice on whether it makes sense or not, but it's a fact that MAY help you.

Anyway, most tachos that connect direct to the input to the coil (that I've come across) are connected to the negative or ground side not the 'pulse' side.

Intuitively I'd say that is wrong, but it works. It sounds to me like you've connected to the other side.

Give it a go; it'll cost you nowt.
nellyboyo
registered user
Posts: 325
Joined: Wed Sep 22, 2010 10:28 am
Main scooter: Lambretta
Contact:

So if I put it in parallel between the white and the red it may work ?
I`m away at work now so I can`t give it a go mores the pity as it`ll bug me for the weeks to come ....... :evil:
hendy
registered user
Posts: 859
Joined: Mon Jul 07, 2014 10:34 am
Main scooter: lambretta li 125
Location: Tyne and Wear
Contact:

I don't know what the white and red are, and I'm too lazy to go into the garage for a manual at the moment. But, I'd try 12v dc onto the Red and the black wire to the low tension side of the coil (either terminal).

If you don't like the result move the black wire to the other low tension terminal.

All of this is guesswork based on experience. If your house burns down as a result, I accept no responsibility. :-D
nellyboyo
registered user
Posts: 325
Joined: Wed Sep 22, 2010 10:28 am
Main scooter: Lambretta
Contact:

Ha, don`t worry , The cave is made of concrete.... :)
User avatar
mawso
registered user
Posts: 411
Joined: Wed Jan 07, 2009 8:47 pm
Location: Harrogate
Contact:

Where do you get the Koso filter from? I've a Koso GP MK1 analogue rev counter that reads odd readings...def for a two 2 stroke but I've an M-Tec box fitted, not sure if that will effect things? But does show about 12K when doing about 60mph and needle bounces around all over. In two minds whether to get shut of it!
User avatar
mawso
registered user
Posts: 411
Joined: Wed Jan 07, 2009 8:47 pm
Location: Harrogate
Contact:

I've got the wire wrapped around and insulation taped to HT lead approx 10 x wound round the lead, I was looking at other ways to attach it, but if people are confident that's the right way I'll leave it as is.
Post Reply Previous topicNext topic
  • Information
  • Who is online

    Users browsing this forum: No registered users and 8 guests