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Mystery electronic device on my VFR750

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Pete.
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PostPosted: 09:38 - 21 Sep 2012    Post subject: Reply with quote
Bloody unusual having a domestic 750cc bike come out of Japan but I agree with Sickpup, it's a speed restrictor that most likely used to work off the needle drive in the speedo. A part in the speedo occludes the emitter as the needle swings past a certain speed (180kmh/112mph) probably killing the spark to one or more cylinders.
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stinkwheel
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PostPosted: 09:53 - 21 Sep 2012    Post subject: Reply with quote
That being the case, I could probably replace it with a resistor which would be less prone to failure?

If I measure the current in that orange/blue and divide it by the voltage difference between the black/brown and the orange/blue, I should get the correct value resistor.
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Islander
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PostPosted: 09:59 - 21 Sep 2012    Post subject: Reply with quote
stinkwheel wrote:
_Iain_ wrote:
Could you not put it on paddock stand or whatever & run it up to that wheel speed? Then whack something across the blocks & see if it misfires?


The speedo is mechanical. Were it not, I think that would go so far beyond risky it's over the Darwin awards horizon.


If it works by cutting the spark to two cylinders then you don't need to have it in gear or moving at speed to test it really. Wink
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stinkwheel
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PostPosted: 10:02 - 21 Sep 2012    Post subject: Reply with quote
Just to confirm. Found a picture of one off an NC30 and it's the exact same circuit board.

https://i205.photobucket.com/albums/bb134/Speedy72/NC30/indexedspeedo.jpg
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P.addy
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PostPosted: 10:03 - 21 Sep 2012    Post subject: Reply with quote
What an odd thing.

So "technically" you could just remove the speedo cable.
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Islander
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PostPosted: 10:08 - 21 Sep 2012    Post subject: Reply with quote
stinkwheel wrote:
That being the case, I could probably replace it with a resistor which would be less prone to failure?

If I measure the current in that orange/blue and divide it by the voltage difference between the black/brown and the orange/blue, I should get the correct value resistor.


Measure the voltage on the output lead with the light path free and then again with the light path occluded. One should produce a low reading, the other high. Once you know what voltage the free path produces you can reproduce that with two resistors as a potential divider. You may even find it's 12v and 0v in which case just tie the output lead to either switched supply or ground via a lowish value resistor (say, 1k or so) to act as a current limiter in case of a fault condition.

Another way would be to pot the whole thing in a box with a suitable potting compound (Farnell/RS/Maplin should have this) taking care to ensure that the light path remains clear. That will prevent water ingress.

A third would be to wrap the whole thing in self amalgamating tape and run the tape up along the leads. Thumbs Up
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Islander
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PostPosted: 10:09 - 21 Sep 2012    Post subject: Reply with quote
##Paddy## wrote:
What an odd thing.

So "technically" you could just remove the speedo cable.


Simple methods are often the best ones - in either direction Wink
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P.addy
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PostPosted: 10:28 - 21 Sep 2012    Post subject: Reply with quote
Islander wrote:
##Paddy## wrote:
What an odd thing.

So "technically" you could just remove the speedo cable.


Simple methods are often the best ones - in either direction Wink


I care not for a speedo. Laughing
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Pete.
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PostPosted: 10:30 - 21 Sep 2012    Post subject: Reply with quote
##Paddy## wrote:
What an odd thing.

So "technically" you could just remove the speedo cable.


Nope, I think the 'restrictor' also works when the speedo reads zero. Best way is to modify the wheel so it doesn't occlude the emitter.

Quote:
That being the case, I could probably replace it with a resistor which would be less prone to failure?

If I measure the current in that orange/blue and divide it by the voltage difference between the black/brown and the orange/blue, I should get the correct value resistor.


Pass, I'm sure someone must know but it's all 'magic string' to me. I still don't know how they manage to push all those little copper wires down the middle of such a long plastic tube to make the stuff.
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sickpup
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PostPosted: 09:04 - 22 Sep 2012    Post subject: Reply with quote
Pete. wrote:
Bloody unusual having a domestic 750cc bike come out of Japan.


Not that unusual. Theres been an influx of GSXR750 slabbies over the last few years that are restricted to 77ps for example.
I think it was 1991(could have been later in the nineties) that big bike licenses became easy to get due to appeasing the US trade deficit by making it easier for people to own and ride Harleys so lots more big bikes appeared on the market but all restricted in one way or another.

I suspect thios VFR has a Japanese market CDI as well as the speedo restrictor. It may well have different cams and carbs as well.
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stinkwheel
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PostPosted: 09:42 - 22 Sep 2012    Post subject: Reply with quote
sickpup wrote:

I suspect thios VFR has a Japanese market CDI as well as the speedo restrictor. It may well have different cams and carbs as well.


I'll check the part number on the CDI when I get home from work.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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pdg
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PostPosted: 11:25 - 22 Sep 2012    Post subject: Reply with quote
If this is a speed limiter and it works by a tang on the speedo wheel interrupting the beam, then disconnecting the speedo cable will disable it, the speedo won't move... It can also be 'disabled' by taking the unit out of the speedo head and wrapping it up in loads of insulation tape.

To 'test' it, start the bike and let it tick over in neutral, then put something in the slot that blocks light (cereal packet, black plastic) and see what it does. Three things could happen:

1. Nothing.
2. The engine will run lumpy on less cylinders - if the unit cuts out a coil pack.
3. The engine will slow, maybe misfire a bit. - if the unit retards the ignition.

It's unlikely given the age of the machine and the fact it's a bike that the restrictor will have any other connections (i.e. tacho sensors, gear sensors etc.) I'd be a little surprised if a limiter merely cut the spark though, on a cdi system it's so easy to retard the ignition to reduce power it would be silly to just turn it off.

You can take all the readings you want but they don't mean much unless you either replicate what happens when you reach the limited speed and/or you trace the wiring and actually figure out the operation of the unit.
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stinkwheel
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PostPosted: 12:11 - 22 Sep 2012    Post subject: Reply with quote
pdg wrote:

You can take all the readings you want but they don't mean much unless you either replicate what happens when you reach the limited speed and/or you trace the wiring and actually figure out the operation of the unit.


That's very easy. It has already been disconnected and the speedo replaced but I want to remove it entirely. What would happen when you reach the limited speed is a bit inside the speedo occludes the optolink. This can be replicated using a piece of cardboard.

The answer being when inactive, there is a 10.5v current in that wire. When it is activated, there is no current. So I need to have 10.5v in that wire and it will remain inactive (and importantly, can't be activated by a bit of dust, a spider crawling about or a componant of the PCB failing).

If I've done my sums correctly, to drop the voltage from 12.1 to 10.6 I need a voltage divider with a 140R and a 1k resistor.

EDIT: Or given that there is between 0.6 and 0.7mA current when the restrictor is "off" and no current when it's "on". To get a 1.5V drop in a current with 0.6mA I need a single 2K2 resistor between the brown/black and orange/blue wire.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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pdg
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PostPosted: 12:48 - 22 Sep 2012    Post subject: Reply with quote
stinkwheel wrote:
pdg wrote:

You can take all the readings you want but they don't mean much unless you either replicate what happens when you reach the limited speed and/or you trace the wiring and actually figure out the operation of the unit.


That's very easy. It has already been disconnected and the speedo replaced but I want to remove it entirely. What would happen when you reach the limited speed is a bit inside the speedo occludes the optolink. This can be replicated using a piece of cardboard.


I certainly agree with the 'remove it entirely' idea. The components on that board aren't exactly prone to failure, but it's another 'possible' weak point.

What I meant is what happens electrically, which you appear to have found out. As I said:
pdg wrote:
To 'test' it, start the bike and let it tick over in neutral, then put something in the slot that blocks light (cereal packet, black plastic) and see what it does.


If the voltage/current reading you have are when the engine is running, then you aren't far out. Personally, I'd be tempted to find out exactly what is on the other end of the wires and decide whether it's worth messing with dropping the voltage or just to bypass it at full system voltage.


***edit*** using the single resistor idea may well give you a dropped voltage, but it would also act as a current limiter - find out if that's actually what you need.
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stinkwheel
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PostPosted: 15:21 - 22 Sep 2012    Post subject: Reply with quote
sickpup wrote:
Not that unusual. Theres been an influx of GSXR750 slabbies over the last few years that are restricted to 77ps for example.
I think it was 1991(could have been later in the nineties) that big bike licenses became easy to get due to appeasing the US trade deficit by making it easier for people to own and ride Harleys so lots more big bikes appeared on the market but all restricted in one way or another.

I suspect thios VFR has a Japanese market CDI as well as the speedo restrictor. It may well have different cams and carbs as well.


For fucks sake!

It's a Japanese one and it's restricted. Frame number is RC36 10002** so it's one of the first ones to be made but it's got a 77ps RC35E engine (the engine number on these is a total bastard to read, you need plastics off and a torch and dentists mirror).

This has been the epic fucking failbike from the planet ripoff from start to fucking finish.

When it's finished, I've got half a mind to ride the fucking thing down there, into their showroom through the biggest window I can find, do a doughnut on the carpet, kick over a row of bikes and ride home again.

I do have all the bits off my old one, including a set of already dynojetted carbs, cams and the CDI. I'll see how it rides before doing anything drastic with the engine though.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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RideLimousin
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PostPosted: 16:29 - 22 Sep 2012    Post subject: Reply with quote
Does it seem slower than your previous bike? (assuming they are the same model)
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stinkwheel
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PostPosted: 17:10 - 22 Sep 2012    Post subject: Reply with quote
RideLimousin wrote:
Does it seem slower than your previous bike? (assuming they are the same model)


Dunno yet. Still waiting for my new brake callipers to arrive. I could go and find out how fast it goes but I couldn't stop again.

I also found the orange/blue wire goes straight to the CDI.

For the record. (and the benefit of google)

Bypassing speed restrictor on Japanese import VFR750.

Measured voltage in orange/blue wire with speed restrictor connected but not activated is between 10.6 and 11.8V depending on rev speed. Current in orange and blue wire is a steady 0.6mA.

I've fitted a simple voltage divider in its place using a 976 ohm resistor as R1 and a 6.2kiloohm resistor as R2. This keeps the voltage within the same range and the current remains the same.

I did it by soldering the resistors to the three wires on the original connector block and shrink tubing over them. Remember to put the shrink tube on first!

Not road tested yet though.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Azonicben
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PostPosted: 17:44 - 22 Sep 2012    Post subject: Reply with quote
Scott
Had a bit of deja-vu when I saw this it is I believe a restricted from the clocks as mentioned above.

https://www.bikechatforums.com/viewtopic.php?t=178369&view=previous
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Islander
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PostPosted: 17:53 - 22 Sep 2012    Post subject: Reply with quote
That should work just fine. The current through the divider is only 1.6mA so it won't affect anything but should easily provide the bias current required by the ignition system.

I reckon you'd probably have been ok just tying the ouput lead high through a 1k resistor - just to act as a current limiter in case of a fault condition occurring but better safe than sorry. Thumbs Up
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Old Thread Alert!

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