Yeah... we'll get there.
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Points to GN250 Electronic Ignition Conversion
- Thread starter Jim
- Start date
If it keeps up try a 700 ohm resister across the pickup. Will drop the impedance and voltage level.
Jim, you have the same workshop safety shoes as me...
Is the rotor powered up?
I powered up the alternator and it kept running. Was running rough at the time so I couldn't tell what affect, if any it had.
Interesting setup
On the video there is a evident difference in Throttle response
And can see it shooting back in the carburetors
As well as a difficulty to start
Indications that timing is off.
Which is found via the strobe light
Thinking out loud Can the spark plugs be a factor .doing a quick googling it appears to be different for
GN250
On the video there is a evident difference in Throttle response
And can see it shooting back in the carburetors
As well as a difficulty to start
Indications that timing is off.
Which is found via the strobe light
Thinking out loud Can the spark plugs be a factor .doing a quick googling it appears to be different for
GN250
Hopefully removing the magnet from the pickup will fix it. I wonder about the the effect of which pole faces out on the rotor.
That eliminates noise from the rotor from causing it.
polarity of the various magnets involved.
and /or
possible overdrive of the coil. perhaps raising the flying height would help. That was why I suggested the 700 ohm resister to shunt some of the power of the input pulse to the Gonzo lady.
Got a little play time in this evening. Swapped pickup leads... no help; still hard starting and rough running.
Removed the magnet from the pickup; bingo!! Starts easily and runs smoothly... bearing in mind the carbs were just tweaked enough to make it run. A better way to say it would be the smoothness is identical 'tween the points and GN systems now.
On to the next dilemma.... only gettin' about 5 to 10° advance. ... scratches head...
Removed the magnet from the pickup; bingo!! Starts easily and runs smoothly... bearing in mind the carbs were just tweaked enough to make it run. A better way to say it would be the smoothness is identical 'tween the points and GN systems now.
On to the next dilemma.... only gettin' about 5 to 10° advance. ... scratches head...
Oh... and running with the alternator on didn't seem to have any adverse affects. It'll be interesting to put the o-scope on it and see how noisy the trigger signal is in the real world with and without the alternator.
Got a little play time in this evening. Swapped pickup leads... no help; still hard starting and rough running.
Removed the magnet from the pickup; bingo!! Starts easily and runs smoothly... bearing in mind the carbs were just tweaked enough to make it run. A better way to say it would be the smoothness is identical 'tween the points and GN systems now.
On to the next dilemma.... only gettin' about 5 to 10° advance. ... scratches head...
Mr Jim I hear a ticking sound ..That sounds a bit worrying I don't believe it is ignition related
Perhaps a Valve play or something. I would not ride a bike sounding like that before investigation.
It's the valves Jan.... on a junkyard engine... that prolly ain't see a feeler gauge in 20 yrs or more. For what I'm doin', it'll be fine. 
Try swapping pick leads
700 ohm in series or parallel It affects the advance on my test stand.
700 ohm in series or parallel It affects the advance on my test stand.
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Yeah, I'll try that. Don't think it's gonna make a difference though. It did on the TCI pickup. But that was just because one lead was center tapped to two different sensor coils. Worth a shot though. I'll also swap the box in from my SG. That's a known 16-18° advancer. At the least I'd like to eliminate that as a possibility.
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Got a link to that? I didn't remember you doin' it.
Swapped the pickup leads.... no joy. I think I see the problem. @Paul Sutton theorized (in your thread Jack) that the "amount" of advance is dependent on the relationship between the pickup coil and the size of the iron target. At the time I was thinkin' along those lines also. In the case of the GN250, the pickup is the reluctor (magnet) and the iron target is rectangular shaped.
I've taken the magnet out of this Yamaha pickup so it's not a true reluctor, it's more in line with what we're running on the TCI systems.... a magnetic "target" and a non-magnetic coil to sense the target. So I backtracked a little and reinstalled the magnet in the pickup. That brings us back to rough running, but the advance curve didn't change. It was the same 5 - 10°.
Did some measuring. The Yamaha pickup core is 6mm dia. Compared that to the TCI pickup... it's about 8-1/4 mm. On my SG (TCI) I'm getting about 16-18° advance (Suzuki advertises 25°, so neither one is close to that). I'm seeing a correlation here between the two as far as amount oftime.... no actually, degrees of rotation the coil and target interact with each other vs. amount of advance. That's telling me Paul was on the right track with it being the degrees between the start of the pulse and the end that determines amount of advance.... which explains why Suzuki used an elongated rectangular target when a simple round iron screw would have otherwise been just fine.
I'm mulling over some ideas... but I think this Yamaha pickup leads down a dead end. Keep in mind my two overriding principles here are cost and KISS... keep it simple. For that reason I'm not gonna go down the road of adding resistors, capacitors or what have you, unless there's absolutely no other way.
EDIT: Just realized I forgot to swap the boxes. I've already put everything away 'cause there's rain clouds about. I'll try that tomorrow.
I've taken the magnet out of this Yamaha pickup so it's not a true reluctor, it's more in line with what we're running on the TCI systems.... a magnetic "target" and a non-magnetic coil to sense the target. So I backtracked a little and reinstalled the magnet in the pickup. That brings us back to rough running, but the advance curve didn't change. It was the same 5 - 10°.
Did some measuring. The Yamaha pickup core is 6mm dia. Compared that to the TCI pickup... it's about 8-1/4 mm. On my SG (TCI) I'm getting about 16-18° advance (Suzuki advertises 25°, so neither one is close to that). I'm seeing a correlation here between the two as far as amount of
I'm mulling over some ideas... but I think this Yamaha pickup leads down a dead end. Keep in mind my two overriding principles here are cost and KISS... keep it simple. For that reason I'm not gonna go down the road of adding resistors, capacitors or what have you, unless there's absolutely no other way.
EDIT: Just realized I forgot to swap the boxes. I've already put everything away 'cause there's rain clouds about. I'll try that tomorrow.
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Thinking out loud again
If i understand it right the Yamaha stock uses 2 points for signal collecting and determine rpm and advance
I have read somewhere that a Micro controller can be triggered on rising flank or falling flank of the signal
So if the rising flank is detected and then after a rpm dependent time the falling flank is also used.
iron target is rectangular shaped.
Perhaps that time between triggering can be used inside the Gonzo box for calculating and setting the advance
If i understand it right the Yamaha stock uses 2 points for signal collecting and determine rpm and advance
I have read somewhere that a Micro controller can be triggered on rising flank or falling flank of the signal
So if the rising flank is detected and then after a rpm dependent time the falling flank is also used.
iron target is rectangular shaped.
Perhaps that time between triggering can be used inside the Gonzo box for calculating and setting the advance
No news yet from the have a go day test as I haven't caught up with my mate but I am assuming no news is good news.
Here is a link to the pick up I am using. I selected it more for its size, it is also is used on a few other bikes.
https://www.aliexpress.com/item/1005002239112684.html?spm=a2g0o.cart.0.0.11b03c00WXJYGb&mp=1
Here is a link to the pick up I am using. I selected it more for its size, it is also is used on a few other bikes.
https://www.aliexpress.com/item/1005002239112684.html?spm=a2g0o.cart.0.0.11b03c00WXJYGb&mp=1
Just putting this here so I don't lose it. Nothing to see here folks... move along....
1 magnet= .3 grams
Radius= 1.55"
Rpm= 7500
Centrifugal force= 1.6 lbf
https://www.omnicalculator.com/physics/centrifugal-force
Typical tensile strength of phenolic sheet... 6000-12,000 psi
1 magnet= .3 grams
Radius= 1.55"
Rpm= 7500
Centrifugal force= 1.6 lbf
https://www.omnicalculator.com/physics/centrifugal-force
Typical tensile strength of phenolic sheet... 6000-12,000 psi
