Yamaha Neos 50cc build

that makes sense. not sure I'll get time to test tomorrow but hopefully Sunday otherwise so will report back. cheers for the help, much appreciated. I tend to get 'dog head' with wiring

 

Wrap the wire round the HT thats what ive done in the past, its how a lot of companies get the tacho reading as standard.

 

I've picked up the pulse from the stator pick-up wire and coil connections before now.
If you go from the pick-up wire, you can trace it all the way back to the cdi plug and link in there.
Or, use the wire that sends the pulse FROM the cdi to the coil.
Fairly straight forward when you start to think about it really.
As the flywheel turns it passes over the pick-up head, which sends a signal to the cdi which tells it to send a signal to the coil to send a spark to the plug.
So either in or out of the cdi should give you a result.

 

Yeah that. My brain is fried from meds.
Fuck.

 

Less words more pictures dammit!

 

lots of options, cheers guys

Steve - good idea re the pickup IN wire, I'll see if I can find that on the wiring diagram and test that too - one of these will work I'm sure

 

After doing some sums, rather than getting the local machine shop to work the adapter bits for me I just bought a small lathe \o/. Watch this space for lots of custom scooter bits. Am thinking it opens a world of possibilities in terms of making adapters to fit crazy rear wheels..for starters! 20s on my scoot coming up..

 

took a lead from the pulse IN to the cdi and that seems to work perfectly I figured less chance of random back emf form the IN side of the cdi than the OUT wire to the coil. maybe the cdi has protection from that but the tach prob doesn't.

sorteed

 

OK so tacho runs fine, however the fuel level meter not so much.

Initially I wasn't really getting any consistent readings from it so took it to bits, cleaned all the contact areas for the potentiometer part and now it reads a nice, consistent variable resistance on the multimeter, but still no dice on the multi-function gauge. I tried running one wire to positive and the other to the fuel level wire on the gauge, same but to negative etc..no difference.

Gonna do some digging on youtube/google to see if I can find any useful info but if anyone has ideas/experience/input it would be welcome

Since the tach has no low-oil level warning but it does have indicators for which gear you're in, and since the scoot has no gears I figured I'd try and rig something up to the "N" gear..originally intended to mean neutral but now meaning "NO OIL". I've got a spare indicator relay so hoping I can even make it flash as a warning. That's a whole other set of wiring issues though but at least I know what the tach expects by way of an input, unlike the fuel level wire.

EDIT: think I've figured the fuel gauge thing - to some extent at least. Will have to do some tinkering with resistors to get the range right but should be doable.

 

So I got the fuel gauge mostly working - I did a bit of measuring with the multimeter and it turns out the yamaha fuel sender gives a range of roughly 0-100 ohms and the gauge expects a reading between 0-520 (or thereabouts) ohms so that's something of an issue, but I think I've managed a workaround to adapt the fuel sender from 100 ohm range to the 500 ohm range needed by the gauge.

A bit of googling revealed that some people in the same position have used a little potentiometer in series with the fuel sender which lets you "trim" the output to match the 500 ohms (i.e. the 100ohms from the sender plus ~400 from the trim pot), but that really only lets you use one end of the fuel scale - i.e. tank full or tank empty, which means the rest of the slider becomes irrelevant. I hoped we could do better than that.

Since I had a spare fuel sender on the donor scoot I took that to bits and did a little bit of experimenting. As you'd expect, to give the reading it has a resistance wire wrapped around a form and there's a copper "finger" which slides up and down that wire to give the resistance reading (fuel level) as the float goes up and down.

As it happens on this sender there's a space below where the copper "arm" travels which is just big enough to squeeze a resistor in, so with a hot needle I made a couple of holes in the plastic case and poked the legs of a 470 ohm resistor through so that the resistor legs made contact with the resistance wire as they exited the fuel sender casing. Then I cut the resistance wire in between the legs of the resistor and folded the stray bits of wire back so they didn't come loose or get in the way. I added a couple more holes to secure the resistor without the need for soldering.

The gamble there was whether the wound resistance wire would be springy - in which case when I cut it it would have "sproinged" and unravelled itself completely and I'd be SOL, but luckily that didn't happen. The resistance wire seems to be quite malleable and pretty much stayed where it was supposed to (result!).

I'd tested trying to solder the resistance wire beforehand which would have made things a bit easier but it didn't want to play so I figured it needs to make contact by mechanical means only...not ideal but it is what it is.

The end result actually works surprisingly well...I tested it wired up to the donor scoot and filled the tank up on that, then drained it back to the canister while watching the gauge. When the tank is full the fuel gauge reads full. As it starts to empty you get one or two bars of movement on the gauge and then there's no further movement until the tank is nearly empty, at which point the gauge reads correctly again, just giving you enough reserve to find a petrol station.



I'm currently using just one 470 ohm resistor, which along with the ~80-90 ohms from the wire by that point in the slide gives roughly the 520 ohms the gauge seemed to need, but inspired by how well this worked I've ordered a few resistors with smaller values (~120, ~100, ~220 ohms) and I reckon I can push my luck and squeeze either one or two more resistors in there so that the gauge should read more or less correctly across the middle of the range too - it should at least give full, 2/3 full, 1/3 full and empty which tbh is better than a number of the OEM gauges have worked in my previous cars!

Once it's working I reckon a few blobs of araldite or JB weld (depending on which is less conductive) should keep everything nicely in place for ever more \o/.

I know it's fiddly and quite a lot of time to spend on a little detail but I want everything on this scoot to *work* as it should, no bodges.


Once that was sorted I looked into the low-oil light warning situation - or lack thereof. The tach/gauge does indeed have a separate LED for "neutral", whereas the gears 1-6 are displayed in the lower part of the LCD panel. Having the separate "N" led is perfect since it's a lot more noticable than just the gear indicator in the LCD part.

The wiring to get it to light up is a little funky since the "low oil" sender seems to be an on off switch which (presumably) sends 12v when oil is low, in order to light up the "low oil" warning light. However on the tacho to light up the "N" you have to run a wire to ground rather than a positive lead and it only seems to output about 5v which isn't enough to power the indicator flasher relay thing I'd hoped to use.

I tried to figure something out using transistors but couldn't get anything working reliably (and may have fried a few) so in the end what worked was a good old mechanical relay, which also negated the issues of voltage, polarity etc.

Since the signal from the low oil sensor (should be 12v), it's enough to operate the indicator flasher unit, which then switches the relay on and off, and in turn makes the "N" flash on the tacho...letting you know there's "(N)o oil!".

I didn't have the time or inclination today to pull the fairing bits off to check that the signal from the low-oil sensor is actually 12v but I'll check that when I get chance.

The progress today means there's really only the speedo left to figure out and then the wiring is pretty much done \o/ and was a LOT less complex than I thought it would be (esp compared to even a basic car loom). The air-ride bits will need a few electrical odds and ends but it should be very basic and I can pretty much mock all that up off the bike and only fit it once it works.

Apaprently the lathe should arrive tomorrow so then I should be able to get onto the fun bit - making the fat rear wheel fit and actually stretching the back end, which is really what this has all been leading up to!

Just as an aside I had a 15x7" golf rim laying about and offered it up to the back of the scoot, and whilst I think 15" might be pushing it, I reckon a 14" rim would *possibly* fit as long as you had a suitably lower profile tyre. I may have to do a little experimenting once I'm done with this scoot

 

Does anyone happen to know how the oem yamaha neos speedo sensor works? it's got wires not a mechanical cable but is it magnet/s inside there? The tach/gauge came with its own sensor which uses 2 magnets but if I can use the oem one I'd prefer to do that, but there doesn't seem to be a lot of info on how they work, and I'd prefer not to have to disassemble it to find out if possible. cheers

 

Mechanical if i recall? If you take the front wheel off you will see what i mean. Its only one bolt to take the wheel off..

 

it has electrical wires not a rotating cable thingy like the older ones...it's not taking the wheel off I'm trying to avoid, it's disassembling the sensor unit to find out how it works (which may mean it doesn't go back together again )

 

Its a nechanic gear thing with a magnet and hall effect sensor, dont see why the magnet isnt just part of the wheel really...

 

aha, thanks so likely does work with a magnet then (what I hoped) - so I might be able to use that sensor rather than having to fit the aftermarket one. Though I think the gauge expects to see 2 magnets for some reason so it may not read right.

 

i think they are three wire pickups .

unsure of how they would be wired as im unable to find a pin out guide to the newer electro speedo hubs.
usually its a magnet and a hall sensor like scuba mentions, as the magnet spins its picked up by the hall sensor and fed to the speedo .

i have also seen what looks like an electro mechanical conversion ( after markets ) where the cable is still used but the spinning is converted to electrical pulses, its possible this type are optical with a small spinning disk and slots cut into it, a set of optical sensors are placed either side and when one sees the pulse of light from the other it send that info to a small ic for conversion to a digital pulse. a bit like how the old computer mice worked

 

hmm ok well I guess I'll have to do a bit of experimenting with the speedo in situ and see if it reads at all, but if it only has one magnet and my gauge expects two or three I guess it'll read wrong or not at all so I may have to see if i can modify the oem one or fit the aftermarket one. The aftermarket sensor also has 3 wires (like the yamaha one) so hopefully I can use the pinout from that to figure out the wiring on the oem one, so it looks like it'll boil down to the number of magnets in play.

Thanks for the assistance

 

They're easy to strip out, the speedo tongues are held in with a circlip, just pop it out, pull the gear off the middle, clean the inside well and you'll see the pickup at the bottom of the drive housing.
The two tangs pass over it with the wheel spinning and send a signal to the dash.

 

aha - "two tangs" was the crucial bit of info there I think. My gauge looks to expect at least two magnets/whatever so whilst the "whatever" part may or may not be compatible, if there's only one of them then it almost certainly won't be..if that makes sense?

whether they send the same type of signal is something I guess I'll find out next session...but as long as there's two of them I may be able to make it work...

thanks that was exactly the info I was after

 

If your after market speedo has two magnets, one should be fixed, normally to the fork leg, and the other is fixed to the brake disc.
So as the moving magnet passes over the fixed magnet it creates a pulse that goes to the speedo read-out.