Dyna Mini coils?

I read the guide to installing Dynas on an '85 XJ700N on the XJCD (also available here), and it seems like a hassle. Doable, but a hassle.

So, I wonder if anyone has any experience with the Dynatek Mini Coils. Seems like they might fit a lot better, but the secondary resistance is only 11,500, whereas it's 12,000 on my stock coils.

Any idea if they'd work?

 

It doesn't matter what the secondary resistance is as long as the primary is about 3 ohms and they put out enough voltage to produce a good spark.

 

Okay, so it's time for new coils! I checked the resistance (primary) and it's 2.5 ohms on the 2/3 coil and 10.5 ohms on the 1/4 coil. So I guess the 1/4 coil is toast, which probably accounts for some of the problems I've been having (documented extensively on a few other threads).

Okay, it's a '82 XJ650J (Maxim), stock carbs & exhaust, I guess I'd like to upgrade the coils to something better. So, what's my choices and what are the pros/cons of each one? Fitment? Connectors? Plug caps? WThe Haynes manual says my coils should be 2.5 ohms (+/- 10%) primary resistance and 11K ohms (+/- 20%) secondary.....is this what I need to stick with on the aftermarket coils?

Helpful advice muy appreciado........thanks!

 

Any 3 ohm Dyna or Accel coils will work, even stock Harley coils. Being poor I usually go with whatever is cheaper. The Accels are a bit hard to mount though.

 

I have been 'told' that OMC marine coils from '90 on are compatible (physical size and resistances) with Yama Cdi's and provide Double the output voltage of the Oem units. But then these don't have flashy stickers on them though. Dunno about price.
I believe that Bosch Automotive Coils could work 'fine' but are a bit large to easily fit... worth looking into ? certainly cheap enough at a wreckers.

 

I can't find my info right now, but I'm pretty sure the Dyna mini coils have been looked into and WILL NOT work on our bikes -- something to do with the ignition system our bikes use that will cook the mini coils.
I'll try to find the messages, but pretty sure it was HAP on the email list that contacted Dyna to ask about the mini's, and was told they would burn out on our bikes.

Anyway - it's the Dyna DC1-1's you want, or Harley dual-fire take-offs.

 

On the secondary, remember to take into account spark plug leads when measuring resistance. I forget the details except that it threw me at first. It was Haynes I believe, where I had to "interpret" their intent........
Jim W

 

The DC1-1's are the ones that, in my original post, seem like a pain to install on the later XJs. How would the dual-fires work? It looks like the either have one or four outputs, no other options.

 

Here's the DYNA Link. I can't remember where I read the notice and disclaimer about DYNA Products not working with stock Yamaha Ignitions.

I don't think it was related to the coils, now that I think about it. It's their Rev-Limiter Boxes.

You can't put a DYNA Limiter on an XJ-Bike without adding the resistor kit they send you when you tell them you have a Yam.

http://www.dynaonline.com/english/dyna_minicoils.htm

 

The mini coils should work as long as they are 3 ohms. Auto coils will not work since none of them are 3 ohms.

 

Hey guys, thanks for the input. I talked with tech at Dyna and he actually suggested using their 1.5 Ohm (grey) coils and adding a 1 Ohm/20-25W resistor to the input lead, giving you a 2.5 Ohm coil that would actually be fatter than their 3 Ohm coil, and within Yamaha OEM specs (which is the 2.5 Ohm value). Any thoughts from the assembled crowd about doing this?

Also, as far as ignition wires and caps, any thoughts on using non-resistor wire/caps/plugs? Will "no" resistance from the coils-forward cause any problems? In other words, do I NEED to have some level of resistance in that part of the circuit? Pro/cons?

Thanks again, you guys are great!

 

All Systems GO!

I hope this solves the case. You'll be getting ... what? -- 13,000 ohms with those new coils!

That ought to get you firing on all cylinders ... so to speak!

 

I believe the Bosch Coils designbed for Hall equipped Distributor Systems ARE the 'correct' resistance.. check it out for yourself

 

I don't recommend using the Dyna 1.5 Ohm coils with a 1 ohm resistor instead of the 3 ohm coils. It will work in a pinch if nothing else is available but the resistor cuts the current to the coil so the output will be less than it's supposed to be. The output is normally much greater than a stock coil so that's why it works but it won't be the best. Also, you have to worry about wiring in a resistor that can get broken and leave you stranded.

 

Actually the resistor cuts the voltage to the coil, not the current, but the point is correct - the output will be reduced by 40%. I would consider another coil. No point to getting a high output coil, and having to put out effort only to reduce it.
Resistors in the wires/caps/plugs are there to reduce radio interference. Theoretically not having them should give you slightly better performance but I think you'd be hard pressed to notice a difference.
Jim

 

Okay, guys, you know far more about electronics than I do!

But doesn't using a 3 Ohm coil (where the stock coil is 2.5 Ohms) also cut the current to the coils?

So I could use a 1.5 Ohm coil with a 1 Ohm resistor, a 2.2 Ohm coil with a 0.3 ohm resistor, or a 3 Ohm coil with no resistor. Which do you electronic guys recommend for getting the highest coil output?

Just for grins, it would be nice if you ran thru the math (simply) so this thread can be sort of an educational tool for all of us who skipped physics class. I re-title the thread Electrons For Dummies.......!

 

A good analogy is plumbing. Imagine water under pressure, flowing through pipes of different diameters. Pressure is like voltage (volts), flow is like current (amps), and skinniness of pipes is like resistance (ohms).
In our example here we have two skinny pipes, one after the other (in series). The flow, or current, is the same at the "input" as the "output", but the pressure, or volts, has dropped after one of the skinny pipes (resistors).
The math: Current = voltage/resistance. More resistance, less flow. If the voltage is 12 volts, and we have a total of 2.5 ohms, then we have 12/2.5 = 4.8 amps flowing through the resistors. The 1.5 ohm resistor will have 1.5 ohms x 4.8 amps = 7.2 volts across it, and the 1 ohm resistor will have 1 ohm x 4.8 amps = 4.8 volts across it.
A coil is really two coils of wire. The ratio of the turns in the secondary divided by the turns in the primary gives how much the input voltage will be multiplied. So for example if a coil is advertised as having 12,000 volts output with a 12 volt input, it has a turns ratio of 1000.
So, if you put a resistor in series with the primary side of the coil, thus dropping the voltage the coil primary sees, it is only multiplying that lower input voltage by its turn ratio now so - lower output voltage. To use the example here, our 1.5 ohm coil would output 7,200 volts instead of 12,000.

Wow, I started out trying to make a short description and look what it turned into. I hope someone benefits from this!
Jim

 

Hey Jim, that's wasy enough to follow, but.........

Given all the above, how do I figure which Dyna coil will output more secondary voltage give: 12V coming out of the TCI (assumed), and then running into a 3.0 Ohm Dyna coil, OR running into a 2.2 Ohm Dyna coil with a 0.3 ohm resistor in-between the TCI (12V) input and the 2.2 ohm Dyna coil?

Both the 3.0 and the 2.2 Dyna coils are advertised as having a secondary resistance of 14,000 ohms. But my question is what is the difference in the primary voltage that the coil "sees" from the TCI, in once case a 3.0 primary coil with 12V out of the TCI versus a 2.2 primary coil with a 0.3 ohm resistor throttling back the 12V from the TCI?

Sorry if I'm not being clear enough. I'm afraid I think I understand more than I do........

 

First I have to correct something I wrote there. The output voltage is the turns ratio times the input voltage alright, but - the turns ratio isn't necessarily the output resistance divided by the input resistance (because the primary and secondary wires are not usually the same diameter). No matter, the turns ratio is the specified output voltage divided by the input voltage.

So, this is more complex. Here goes:
Both coils have a 14,000 ohm output, hmm.. OK so the turns ratio is different between them, by a factor of: 14000/2.2 divided by 14,000/3 = 1.3636... In other words, with the same input voltage, the 2.2 ohm coil gives a 36% higher output.
But you are not applying the same input voltage. The 2.2 ohm coil with the 0.3 ohm resistor will see 2.2/2.5 = 88% of the input voltage. The combination of this and its higher output is 0.88 x 1.3636 = 1.20.
So there you go, the 2.2 ohm model with the 0.3 ohm resistor will give a 20% higher output voltage.

 

Hey Jim, u da' man!

Okay, Jim, so I got something wrong, too! The output voltage is rated at 40K PER OUTPUT; the secondary resistance is 14K ohms.

http://www.dynaonline.com/english/dyna_coils.htm

This is for their part number DC1-1, the 3 ohm versions.

So according to your calculations, using this 3 ohm coil with a supposed 12V output from the TCI results in 2.5/3.0 = 83% of the designed output...since the Yamaha specs are for a 2.5 ohm coil......or 40,000V x .83 = 33,332 volts per output.

That seems like a lot.........!

Just out of curiosity, does anyone know what the stock Yamaha coils are rated at?

Thanks for all your help!

 

I spoke to the DYNA Technician. Get the GREEN ones!

 

And Yamaha specs 3 ohm coils for our XJ's folks, not 2.5 ohm.
For Dyna's, the "GREEN ones" are the DC1-1 3 ohm coils. That's the ones pretty much everyone is using, and certainly the ones I'm planning on using.

 

Chacal,
Using the 3 ohm coil with 12 volts across it won't give a reduced output, because the full 12 volts is across the coil i.e. there is no resistor dropping the voltage. So you will get the full 40 kV.
Same thing if you used the 2.5 ohm coil with no resistor; you would get the full output.
The difference between these would be the current flowing through the primary of the coil, which is where you need to see what our bikes were meant to handle. And it sounds like they would like a 3 ohm coil.
Jim

 

Okay, I'll use the 3.0 coils.....just wanted to investigate, thank you everyone for your input. Altus, why/how/where did you determine that Yamaha specs the coils at 3.0 ohms. In the Yammy service manual and the Haynes manual under the coil testing section it says that the coils should be 2.5 ohms primary resistance +/- 10% (2.25 - 2.75)???

 

Well lookit that, I stand corrected. Will ya look at that - the service manual actually DOES say 2.5 ohm

I've always relied on the 3 ohm figure and it's what I've always been told - probably because no one makes a 2.5 ohm coil, so the 3's are the closest fit.

 

Go for the DC1-1's!

I installed the DC1-1's in my '85 Maxim-X 750. It's not as hard as it sounds. I can't find the website that helped me through it right now...

Anyway, it's maybe 2-3 hours start to finish. No real setbacks. All you need is the DC1-1 coils, a small length of brass / stainless steel rod, and a cotter pin that you can punch through the rod. New ignition wires to go with the new coils are nice since the old wires are pretty much attached to the old coils permanently. I used Dyna wires.

- Take out the old coils and the bracket that holds them.
- Mount the front (headlight) of the coils to the bracket as usual. This causes the back of the coils to slant away from each other, preventing them from mounting where they should, thus causing them to hang down towards the engine.
- Bend a small length of the rod into a U. The top of the U goes into the mounting bracket, the bottom half loops through both coils. This holds the coils up, preventing them from bouncing on the engine. There's enough tension on the front of the mount to stop any horizontal movement and this bracket stops any vertical movement.
- Put the cotter pin through the rod so it doesn't slide out.
- Connect your ignition wires.

Does this make any sense? I'm Google impaired right now, but there is another guy who has pics that illustrate what I say.

It's really not any harder than what else you're suggesting with resistor mods.

Corey

 

hi all

now im in the same boat as every one else it seems i need a coil.for my 80 mod 650 max what is the best cheapest coil ?

thanks john

 

The free one your Uncle Joe has laying on a back shelf in his shop!
Had to pull your leg mate, that one was too good to pass up.
Seriously, you've a few options. Dyna is a good coil and I've had no trouble with my Accels. I am not aware of the price of the Dynas but I paid $125 USD for the Accels some 13 years ago, not sure what it would run this day in age.

 

I know Hap's website has information on installation here: Maximum Maxim X

I plan on doing this too, once winter truly sets in and I can't ride anymore.

 

Actually, I may be able to hold off for a while. I tested my coil resistance today and the wires 1&4 produced 12.16 and wires 2&3 produced 12.29.

I'll still upgrade sometime in the future, but at least I cna put it off for a while.

 

That's the one!

Good instructions, but I do think that he's making it slightly harder than it needs to be. I didn't use the brake line to hold the coils apart and I don't see any horizontal force that would make them smack together. I also didn't need the extra bends in the rod. I just made a perfect U and it keeps the coils raised and happy. I couldn't find stainless steel rod, but Home Depot had brass in stock and I think it will be fine.

Corey

 

I've seen his bike. (Nice ride, btw... pretty color). He is a real source of information when it comes to the Maxim X and I have relied on him many times. He's supposed to be re-doing the page; maybe he'll take that part out. I figure if he says it needs to be there, he's been doing this a lot longer than me, so eventually when I change mine, I'll do it like he did his.

I tested my coils first, which were within spec at 3.2ohms. I've been trying to track down a hard start problem. Then on to the plugs. I tested all of them first, found one at 32.0kohms, and one at 18.2kohm. Well outside operating specs. I went and bought 4 new ones, and so far, the bike is still running. I also received my CarbTune II today and colortune plug. Yay! I posted a bunch of pics on my blogsite. Check it out.

My Blog!

 

>I tested my coils first, which were within spec at 3.2ohms.
That doesn't mean anything, the HV winding can be bad with a shorted winding or short to ground or the case can be cracked, which is pretty common. You need to test the output voltage on a scope or at least use a spark tester to see if it makes a decent spark that's strong enough to fire a plug.
In my experience hard starting is caused by a weak spark due to bad coils and a lean mixture if it's cold out. With the colortune you can check the mixture at idle but most people forget about the starting jets that can be clogged and you can't really check them except to see if they make the mixture richer and the hole in the jet is completely open like it should be.

 

Dang it! I just started grasping the concept of the multimeter and now you're telling me I need a scope or another kind of spark tester? Yikes!

Sounds like you really know what you're talking about. You've had trouble with hard starting too? If so, I'd like to hear what you did to rectify it.
I know a few of the spark plug caps were bad; having a resistance of 32.0 is a good indicator that spark wasn't getting through, right? I haven't yet tried it this morning, but that's going to be one of the first things I do. I'm excited and scared at the same time. I hadn't thought about the starter jets... seafoam has been run through this bike for the past 2 weeks, added some with every gas fill up (just about).

I'll look into other spark testers. Thanks for the info!

 

MadMaxim, the reason you can't count on your multimeter to do a complete diagnosis of the High Voltage side of the ignition system is the multimeter uses voltages 1/10,000th or so of what is generated for the spark.

You can think of the high voltage side of the ignition like a water hose. In your garden hose your goal is to get water in one end and out the other. Things that can prevent getting the water to the other end are:

1) restrictions (kinks)
2) leaks

Imagine testing your garden hose with just a trickle of water. There may not be enough pressure to have any noticible amount of water lost to leaks. Also, the kinks in the hose may not be severe enough to noticibly prevent the water from flowing.

Now imagine turning the spigot on full blast. The kinks reduce the water flowing through the hose and the leaks let water out all over the place, reducing the pressure.

At the end of the day, the only way to know if your hose is in good shape is to look at the outlet when the water is on full pressure.

This is what ArizonaSteve is telling you how to do with the ignition system.

It is not unusal for the high voltage side of ignition systems to have "leaks". The insulators in the system can degrade. They will hold the 2 volts from your meter in fine but will drain that 25,000 volt spark right away, leaving just a trickle or nothing for your spark plug.

SIDE NOTE:
Dad used to check the high voltage side of his car ignition systems by looking at the engine running in the dark. Many of the leaks glow like little blue lights. An internal problem with a coil cannot usually be seen this way, but a great way to check out the wires and plug caps.

 

Yep, you can still check the ignition system in the dark.
I cured any hard starting problems by putting on Accel coils. A lot of owners report not being able to start if the battery is slightly weak but I get a good spark and can start just fine even with a weak battery as long as it's got enough power to turn the starter.

 

Elp u lot out a little.

1st , a resistor does indeed reduce the current THEN the effect of that drops the voltage. mr Ohms law , look it up , there are free little progamms out there to play with.

2nd,the main reason it might not be healthy to use a 1.5 ohm coil instead of a 3 ohm coil is only due to the TCI transistors that switch the current on AND off might not be able to handle the extra current when lowering the resistance using 1.5 ohm coils , BUT if the TCI transistors could handle it the spark will shurly be increased in strength compared side by side.

In other words the yama TCI design factor.

Lower resistance = more current AND a higher voltage as when the field [12v coil side] collapses with a few extra volts on it the few extra are transfered to the secondary coil [HV] by the turns ratio of them.

Quoted differences of eg:12,000 ohms =12k ohms , from 12.5k or even 13k is a negaligable difference and effect at those resistances and voltages [40k volts] , in other words , a bee's dick difference.

Differences at low volts [12v] with resistance ie 2 ohm compared to 10 ohm depending on whats doin what can be dramatik.

hope that elps a little.

 

Play here http://www.csgnetwork.com/ohmslaw.html

 

Once again: Bosch Car Coils from any Car that has electronic ignition .
That would be about '76, But Go for '80 onwards (just for insurance) Almost FREE at a wreckers (these are almost indestructible things) they have 3 ohm primaries making them exactly compatible with Yama units but with a 45,000 volt output. .
In truth they are largish ugly things.. but.. they will do their job better than most any others you can buy... for Lots less $$

 

Chacal far from me to outsmart you when it comes to XJ's but on yamaha service manual for XJ700 N/NC it states the coils should be 2.7ohm + or - 10% at 68F/ 20C it is on page 6-28 of the above mentioned manual. So that being said 3 ohm sounds within spec for the mini dynatek coils plus there are several guys here using them and even saying that some anomalies like erratic idle and hard to start ae all gone now.

 

Holy thread revival Batman!