Topic: I swear I searched!- electrical noob

[karmasevo]

ok so here it is: just got done retuning carbs and installing dyna2000 ignition and dyna 2.2 ohm coils. Bike was running great so I headed to get some fuel. Shut the bike down and when I went to start it back up it blew the 15A main fuse. Put in another one and well it just keeps blowing over and over. So i did some quick testing. With the key in the middle position I can run the headlight/tailight with no problems. As soon as I turn the kill switch on to energize the coil circuit it blows the 15A main fuse. I checked all wires leading to the Dyna and nothing is unshielded ( I was thinking short to the frame ect). I have searched but could not seem to find the right answer. Any help would be a blessing at this point. Thank you very much!!!

[dave500]

coils are drawing too much current?

[karmasevo]

Dave500,

How would I verify this? and what would be the solution?

[Rgconner]

Dave500,

How would I verify this? and what would be the solution?

2.2 ohm draws too much juice for the wiring harness. 5.4amps or 65w to be exact.  Hondaman (search for him) resistor packs to reduce the draw will fix the problem.

Or, put the old coils back on, that should do it in the meantime. The old ones were 5 Ohm and drew 32w or 2.7 amps.

Very likely you have damaged the wiring, you will have to go over it with a multi-meter to be sure.

[karmasevo]

Dave500,

How would I verify this? and what would be the solution?

2.2 ohm draws too much juice for the wiring harness. 5.4amps or 65w to be exact.  Hondaman (search for him) resistor packs to reduce the draw will fix the problem.

Or, put the old coils back on, that should do it in the meantime. The old ones were 5 Ohm and drew 32w or 2.7 amps.

Very likely you have damaged the wiring, you will have to go over it with a multi-meter to be sure.

RG,

If what you say is true how come the bike ran fine the whole time I was tuning my freshly rebuilt carbs? I ran the bike for a significant amount of time and had no issues? Why would this only happen after riding it for about 1 mile but not when tuning in my garage? Thanks for the help

[TwoTired]

coils are drawing too much current?

And/or the dyna2000.
How that thing works and how long and when the unit charges the coils is key to full understanding.

If what you say is true how come the bike ran fine the whole time I was tuning my freshly rebuilt carbs? I ran the bike for a significant amount of time and had no issues? Why would this only happen after riding it for about 1 mile but not when tuning in my garage?

In the garage at idle, the battery voltage could be low.  Out riding, the battery voltage goes up and "should" limit at 14.5V rather than the 12.5V is would see at idle.
So, you need to measure the battery voltage at idle and while revving the bike after a 1 or more mile ride.  You could have Vreg problems.

Or, you might simply be taking too much power through that 15 A fuse.
The stock bike draws about 10-11 amps through the 15A fuse.  Higher wattage headlights and higher power coils can push that average current up an amp or three, putting the fuse near its melt point.

You could also have fuse clip oxidation (transparent or not) that has resistivity and heat with current flowing through it.
You didn't say where the fuse is blowing. If at/near the end caps rather than the center of the fuse, then fuse clip heating is adding to your issues.

FYI:  Ohms law E=I*R, I= E/R, R=E/I.  10 amps at 13 V means the circuit has 1.3Ω resistance.  Use the same resistance and up the voltage to 15 V and you now draw 11.5 Amps through the same circuit, just by raising the voltage.  Adding load on the circuit means you also lowered the circuit base resistance which also upped the current.

Cheers,

[Rgconner]

coils are drawing too much current?

Or, you might simply be taking too much power through that 15 A fuse.
The stock bike draws about 10-11 amps through the 15A fuse.  Higher wattage headlights and higher power coils can push that average current up an amp or three, putting the fuse near its melt point.

Each coil is going to draw 5.45 amps at 12v, and 6.6@14.5.

Not much headroom left there on a 15 amp fuse.

[Rgconner]

What bike do you have?


More info from HondaMan:

This Resistor Pack is used to match low-ohm primary coils to the vintage Honda/Kawasaki/Suzuki/Yamaha bikes with points and coils of (normally) about 4-5 ohms primary impedance.

The Honda wiring for the Ignition Coils is sized to carry about 3.3 amps of continuous current, while the stock coils draw 2.4 amps. The 3-ohm coils from Dyna and ACCEL draw over 4 amps, which heats the stock wiring quite a bit. The connectors, in particular, and the handlebar RUN-OFF switch slowly grow damage from continuous use at this higher current. This Resistor Pack reduces this current to a safe level (2.8 amps) for the bike's stock wiring, while still allowing for a nearly 3-fold spark voltage at the sparkplugs from using these high-output coils.

The Dyna (Green) coils and ACCEL performance coils have 3-ohm primaries: these require a 1 ohm Resistor Pack to match these bikes' wiring (and charging) systems to those coils.

The Dyna 2.5 ohm ultra-high voltage coils (or 1980 and later Honda coils) require a 2.0 or 2.5 ohm Resistor Pack when used on the SOHC4 motorcycles, depending on the bike: contact info@sohc4shop.com for more details. Typically, this is only for off-highway applications, as the alternators on these vintage bikes don't support these high-draw coils very well.

NOTE: On the alternator-challenged CB500/550 bikes, this Resistor Pack can allow the rider to use the Dyna 3 ohm coils, with either stock points ignition or the Transistorized Ignition. It will not, however, reduce currents enough on this bike to allow for BOTH the Dyna S triggers and the Dyna 3-ohm coils: that is just too much load for the mid-sized Four to carry. The CB500/550 rider may use EITHER the 3-ohm coils with this Resistor Pack, OR the Dyna S triggers with stock OEM coils: using both will cause electrical overloads and low battery charge problems, due to the smaller alternator output.

[Duanob]

Well there you go, you're not a nooob anymore. 

I looked up the Dyna2000 on there website and the "technical Specifications" are just marketing BS that don't give you specifics on anything useful. I hope you didn't fry your wiring.

[karmasevo]

RG and twotired,


The fuse is frying directly in the center of the filament. I did notice a couple of wires that had melted the outer plastic insulation but I have no way of knowing if that was caused before or after the coil installation. My bike is a 1974 CB750K4. I also tried a 20A fuse and it blew immediatley. I will contact Hondaman and see what he says but its acting like a short. Meaning the fuse blows instanstly as soon as the ignition circuit is energized. ( Ie.. I flip the kill switch to on).  Also I was revving the bike quite consistently while tuning the carbs. Also I had to take the carbs back off and replace a few odds and ends; then put the carbs back on and tune again. So through all of this tuning and revving of the engine nothing happened until I took it on a ride. I will contact Hondaman immediately. Thanks guys!!

[TwoTired]

Each coil is going to draw 5.45 amps at 12v, and 6.6@14.5.

Yes, in steady state, if the Dyna2000 leaves the coil on all the time, which it doesn't/ can't.  It has to release the coil energy to fire the points at some portion of crank rotation, and there is no info on how long it charges  the coils.
We do not know what dwell the DYNA2000 provides, and therefore cannot calculate what power the system uses.
The stock points use 190 Degrees of dwell.  So, the stock coils are only on during that time of crank rotation.

If the Dyna2000 only powers the coil through 90 degrees of crank rotation, the power draw could be much less.  The Dyna S drives a coil though 270 to 320 degrees of rotation (I forget exact amount, but it been posted on the forum before).  No info if the Dyna2000 works the same way as the Dyna s.

[karmasevo]

RG and twotired,


The fuse is frying directly in the center of the filament. I did notice a couple of wires that had melted the outer plastic insulation but I have no way of knowing if that was caused before or after the coil installation. My bike is a 1974 CB750K4. I also tried a 20A fuse and it blew immediatley. I will contact Hondaman and see what he says but its acting like a short. Meaning the fuse blows instanstly as soon as the ignition circuit is energized. ( Ie.. I flip the kill switch to on).  Also I was revving the bike quite consistently while tuning the carbs. Also I had to take the carbs back off and replace a few odds and ends; then put the carbs back on and tune again. So through all of this tuning and revving of the engine nothing happened until I took it on a ride. I will contact Hondaman immediately. Thanks guys!!



Dyna was contacted directly when this purchase was made and there was no mention about this issue. You would think they would know about this and have a solution posted 

[TwoTired]

The fuse is frying directly in the center of the filament. I did notice a couple of wires that had melted the outer plastic insulation but I have no way of knowing if that was caused before or after the coil installation. My bike is a 1974 CB750K4. I also tried a 20A fuse and it blew immediatley.

With those indications, I'd say you have a short somewhere which may be intermittent.  Possibly a sloppy install.

  Also I was revving the bike quite consistently while tuning the carbs.

The battery doesn't gain voltage instantly when you rev it.  The battery both gains and loses voltage slowly.  That's why it is there.
Unless you held the revs up for 10-20 minutes, the bike may have never fully peak charged the battery in the garage.  But, no matter.  You've got wiring to fix, unrelated to battery charge levels.

I will contact Hondaman immediately.

ok. good luck then.

[Rgconner]

Each coil is going to draw 5.45 amps at 12v, and 6.6@14.5.

Yes, in steady state, if the Dyna2000 leaves the coil on all the time, which it doesn't/ can't.  It has to release the coil energy to fire the points at some portion of crank rotation, and there is no info on how long it charges  the coils.
We do not know what dwell the DYNA2000 provides, and therefore cannot calculate what power the system uses.
The stock points use 190 Degrees of dwell.  So, the stock coils are only on during that time of crank rotation.

If the Dyna2000 only powers the coil through 90 degrees of crank rotation, the power draw could be much less.  The Dyna S drives a coil though 270 to 320 degrees of rotation (I forget exact amount, but it been posted on the forum before).  No info if the Dyna2000 works the same way as the Dyna s.

Don't disagree with that, it is some number less than full power. I did not want to give the poor boy a headache just yet...

I looked it up, the Dyna2000 has a variable dwell. But, if that dwell is more than 90 degrees, then you would have an overlap where both coils are energized at the same time, putting the full load on the wiring.

I am thinking by what he has said that it worked, got hot, started acting like a resistor and now is likely fully shorted from melting wire covers. That would be in the loom somewhere, so it might not be fully visible.

Totally sucks. Whoever sold you that should have known a vintage bike would not take anything less than a 4 ohm coil.

Unless you bought it over the internet, in which case, that is the risk of the internet.  Even some otherwise reputable sites sell the 3 ohm and 2.2 ohm coils without a warning about the load. Like, say, dynoman.net

I only knew what to expect because I researched the hell out of the subject here on the site. Especially since the 550 does not have as good as a charging system as the 750.

[Rigid]

"I am thinking by what he has said that it worked, got hot, started acting like a resistor and now is likely fully shorted from melting wire covers. That would be in the loom somewhere, so it might not be fully visible." 

Yep, first problem too little resistance in coils, now melted wires with a dead short.  If working on these old bikes is fun, he is going to have a heck of a weekend. 

[dave500]

a hell of a weekend.

[srbakker]

So... If these things draw so much voltage, why do the solid state kits always seem to come with 3 ohm coils?  Are you losing anything by just using 5 ohm coils?

Forgive me if it's a stupid question.  I know biology, not physics. 

[Rgconner]

The spark is weaker, that is why the gap is .35.

Is the bigger spark worth the hassle?

Probably. And since 5 Ohm is harder to find, 3Ohm is the most common now.

[TwoTired]

So... If these things draw so much voltage, why do the solid state kits always seem to come with 3 ohm coils? 

For the same reason why some cars have over 300 HP.
It's the "more is better" attitude.

The stock spark gap is about .025 inch. And stock 5Ω coils and ignition components make more than enough voltage and current to fire the stock spark plugs, particularly during the normal run portion of operation.  The stock system is quite efficient doing just what is necessary without stupid excesses.

Are you losing anything by just using 5 ohm coils?

Not with the stock bike.

It's a common misconception and widespread myth, where people think that using race components is an "upgrade" rather than just an unnecessary and wasteful excess.

Race engines can have higher compression that needs more voltage to fire in those compressed environments between electrodes.
If you want to increase the spark gap AND operate with higher compression, you may need that extra voltage potential to avoid misfires.
Race engines may and often do have both, and therefore "need" a better sparking system.

If you put 3 ohm coils (or lower Ω) on a standard engine and don't increase the spark gap, the coils fire at the same voltage as 5 ohm coils, because of the way the Kettering system operates.  It's the spark gap distance that determines the voltage needed for it to fire as the coil energy builds.  Once the plugs fire, the plasma channel behaves as shorted outputs which prevents further build up of voltage.   Any, excess current during the spark event only serves to erode spark plug electrodes (making the gap bigger over time) and shortening their life.

I should note that you can't ONLY consider the coils alone, as the way they are driven and triggered can make a huge operational difference.

Cheers,

[srbakker]

Wow.  Thanks - that was a greatly useful answer!

[wrenchmuch]

Putting larger fuses into a circuit with a existing problem is not a good idea . Don't damage the harness any further . In terms of trouble shooting a short in the ignition system , I'd start with the headlight shell . Look for the wires coming from the kill switch ( see electrical schematic ) . Test the kill switch for a short . On 750's with higher draw ignitions I've found problems here when they happen . The switch isn't designed to take the extra load . Same goes for the key switch . Many have run a fused circuit from the battery to the coils via an automotive relay , triggering the relay from the existing ignition circuit . This takes a great deal of load from the stock system and switches . Many on the site run Dyna 2000 on 750's . M Reick for one . I don't know if they run 2.2 Ohm coils though . I would think if you intend to keep this system the relay mod is a necessity . Maybe the Hondaman resistor pack as well . On Dyna's coil page they show 3 ohm for use with 2000 systems . Did they tell you to use the 2.2 Ohm coils ? The 2.2 ohm coil shows no specific use info next to it .

[karmasevo]

Each coil is going to draw 5.45 amps at 12v, and 6.6@14.5.

Yes, in steady state, if the Dyna2000 leaves the coil on all the time, which it doesn't/ can't.  It has to release the coil energy to fire the points at some portion of crank rotation, and there is no info on how long it charges  the coils.
We do not know what dwell the DYNA2000 provides, and therefore cannot calculate what power the system uses.
The stock points use 190 Degrees of dwell.  So, the stock coils are only on during that time of crank rotation.

If the Dyna2000 only powers the coil through 90 degrees of crank rotation, the power draw could be much less.  The Dyna S drives a coil though 270 to 320 degrees of rotation (I forget exact amount, but it been posted on the forum before).  No info if the Dyna2000 works the same way as the Dyna s.

Don't disagree with that, it is some number less than full power. I did not want to give the poor boy a headache just yet...

I looked it up, the Dyna2000 has a variable dwell. But, if that dwell is more than 90 degrees, then you would have an overlap where both coils are energized at the same time, putting the full load on the wiring.

I am thinking by what he has said that it worked, got hot, started acting like a resistor and now is likely fully shorted from melting wire covers. That would be in the loom somewhere, so it might not be fully visible.

Totally sucks. Whoever sold you that should have known a vintage bike would not take anything less than a 4 ohm coil.

Unless you bought it over the internet, in which case, that is the risk of the internet.  Even some otherwise reputable sites sell the 3 ohm and 2.2 ohm coils without a warning about the load. Like, say, dynoman.net

I only knew what to expect because I researched the hell out of the subject here on the site. Especially since the 550 does not have as good as a charging system as the 750.

Well I did find a melted cover on the red power wire that goes to my ignition switch factory harness). I could very well have other melted wires in the loom. I guess I have no choice but to take it apart. SOB!!!!!!! I bought this from a well known shop here in town who called dyna to make sure the 2.2 ohm coils were the right ones since that is what Z1 was selling with their Dyna2000 setups. RG, thanks for trying to keep it simple for me. Its helpful to learn slowly and in a simple fashion rather than being bombarded with info. I can beleieve I have to rip this whole harness apart to see whats going on now.

[karmasevo]

Putting larger fuses into a circuit with a existing problem is not a good idea . Don't damage the harness any further . In terms of trouble shooting a short in the ignition system , I'd start with the headlight shell . Look for the wires coming from the kill switch ( see electrical schematic ) . Test the kill switch for a short . On 750's with higher draw ignitions I've found problems here when they happen . The switch isn't designed to take the extra load . Same goes for the key switch . Many have run a fused circuit from the battery to the coils via an automotive relay , triggering the relay from the existing ignition circuit . This takes a great deal of load from the stock system and switches . Many on the site run Dyna 2000 on 750's . M Reick for one . I don't know if they run 2.2 Ohm coils though . I would think if you intend to keep this system the relay mod is a necessity . Maybe the Hondaman resistor pack as well . On Dyna's coil page they show 3 ohm for use with 2000 systems . Did they tell you to use the 2.2 Ohm coils ? The 2.2 ohm coil shows no specific use info next to it .
[/quote



I will test the switches this morning thanks!!

[karmasevo]

Anybody know someone for sure that is running the CB750 with a DYNA2000 that I can contact for sure to see if they have found a solution. I guess what I"m saying is let's assume that I fix the wiring harness(assuming that I find more burnt wires) then I still have the same issue with the 2.2ohm coils creating too much draw. Hondaman claims that it is impossible to use the 2.2ohm coils on a 1974 CB750K4 ( my bike).  It would be great to get some feedback from some guys/gals who are currently running the Dyna2000

[Rgconner]

There are replacement looms available. Dave Silver spares I think?

You probably have only damaged the ignition part of the loom, it is not that hard to replace those wires. Take your time, do a good job, find a buddy who knows how to solder and ply him with <favorite adult beverage>.

Which ones to replace? Obviously the melted one if it is visible. Check the others at junctions with a meter and if they show resistance, replace them. Use 16AGW, since we know you have a high load and you are dealing with high draw parts of the electrical system. Apparently, the "stock" wiring is somewhere between 18 and 16, so I say if yer gonna go, go big.

I would also go back to the shop, politely and nicely explain the issue, don't place blame on the shop, laugh about it... then ask them to swap for the 3ohms. They might do it.