DYNATEC HT Coils - Plug Leads - Plug Caps, opinions on compatible set ?

[400 Cafe Racer]

Hi Guys,

Just in the process of engine rebuild and checking other items before the refit.

The PO has DS Electronic Ignition and the Dynatec Coils fitted with carbon trace HT leads, not copper wire leads (see photo) these are then connected to 5Kohm plug caps. I was interested to check the HT cable resistance seperately.
All plug caps come in at 5Kohms, but the Ht leads measured along the disconnected cables vary, No1 = 12.4Kohm intermittent reading, No2 = 18Kohm solid reading, No3 = 12Kohm solid reading, No4 = 17Kohm solid reading.

I have my misgivings about carbon impregnated cotton plug leads, which can break the carbon chain if the lead is stretched, I'm thinking this could be the reason for the intermittent reading on No1.

Spark Plugs are NGK D8EA

I am interested to hear your views and experiences.

Thanks

Dennis

[K2-K6]

As you note,  there's very divided opinion of carbon type leads. I really like them and have used them widely for many years on cars but not experienced on these bikes directly. 

Also can't see a specific problem used on your bike and it's perhaps been running on them some time.

Agree that the inconsistent #1 lead is quite probably causing you difficulty, can you swap with #4 or replace to test  ?

[400 Cafe Racer]

Thanks K2 - K6,

As you say,opinion seems to be divided. I will probably fit new leads to hopefully even out the resistance readings more.

Do we know what specification of the original leads and caps were please. ?

Would this same combination suit the Dynatec Coils ?

Thanks for your comments.

Dennis

[K2-K6]

Ordinary manual specification is very low resistance leads with 5 ohm plug caps along with non resistance plugs.

"Would this same combination suit the Dynatec Coils ?" That's certainly a more complex question though, with Dynatec seeming happy to use different leads etc to manufacture of motorcycle specification. 

You've also got interaction with the DS switching which I doubt has a parallel technical parity with the points originally installed.

Given the system specification as it stands,  I'd replace the leads with same type and aim for maximum of 15 ohm for each lead, cap and plug line.

[McCabe-Thiele (Ted)]

My Dynatec full system came with carbon leads so that's what I have fitted.

In your situation I would make up a set of copper wired leads as in many ways I'm old school I like the good conection you can see with copper particularly at the ends to coil & plug cap. It's not as if you have a bike radio to consider as regards interference? lol

[K2-K6]

For me the radio suppression aspect of resisted HT systems is the lowest priority. Socially desirable  and often legislated, I can see the need.

Far more interesting from these engine's running strategy is the desirable effect it has within combustion quality.  Honda made a very benign, subtle ignition system that looks so very simple but with almost impeccable attributes for a mechanical system. It's difficult to even match it let alone significantly outperform it I feel.

One of the elements is how the spark event is distributed and lengthened to match what essentially is a moderately slow burning, medium compression ratio combustion chamber. But one that easily reaches 10, 000rpm with no apparent vices.

Deleting the points and condensers looks to compromise that (with the ds system there's no indication of characteristics) I'd assume isn't a match as most aren't.  System like Boyer appear to cover this aspect with multiple firing pulses, which are not claimed for simple systems.

It looks like the use of specific leads on the Dynatec system try to replace the Honda strategy in how the coils interact with the ongoing HT delivery,  for this part I feel that they need to run to spec in components.

[400 Cafe Racer]

Ted,

As a matter of interest do your Dynatec HT leads look the same as mine on the outside. I have no idea if they are the ones that came with the package when it was fitted. ?

K2 - K6,

Is there much hard evidence from the CB400f owners about the combustion efficiency outcomes (power, torque, Air/Fuel analysis readings or carbon deposit colour) on set ups run with or without resistors, or Dynatec   etc. ?

I believe there may be aspects of longer burn time with resistors and the 400 chambers having a swirl.

Interested to see what  the forum may have found. ?

Thanks

Dennis

[K2-K6]

This thread may be of interest http://www.sohc.co.uk/index.php/topic,14609.0.html

[McCabe-Thiele (Ted)]

Hi Dennis,
My leads look like yours definitely a grey colour and quite a thick diameter as well.
Interesting to read the post in the link it reminded me of my old Honda 250 Dream Super Sport you could not cruise at 60 mph in a good headwind without dropping down at least one gear to maintain your speed. Effectively every journey was like a race to keep it on song. My previous Honda a 250 Dream was a far easier bike to live with. Memories eh! Ted

[400 Cafe Racer]

Hi Ted,
Thanks for looking at your leads- do they also have " 7mm HI-TEMP RADIO SUPPRESION CABLE" printed along the leads please ?

Hi K2-K6,
Thanks for that interesting thread, It is nice to think that others have gone to some trouble to diagnose what is happening.
I wasn't sure if the second trace in the first graph was the torque curve ?

I concur fully with your thoughts on the advance characteristics and reason for leanness during low ventui air speed.
( Perhaps fit SU carbs, with the hydraulic damper !!! to richen during acceleration)

In my late teens (about 1962) I specialised on Crypton Oscilloscope tuning, with the additional Exhaust Gas Analyser, working for the large Main Jaguar, Daimler, Rover, Vauxhall, Standard Triumph agency - Attwoods in Stafford. This was an ideal opportunity to dig deep into actually "seeing" electronically what the engines were doing. I count myself as very fortunate to have been in this position at the time and got great satisfaction on tuning and working on E Types, Daimler Darts, Sporty Rovers and Triumphs, road testing on an unrestricted M6 motorway, plus general analytical work for trouble shooting all vehicles.

Coming back to the point I can visualise exactly what you are saying.

Before I stripped the engine to do an inspection, on the previous run I had aquick look at the A/F ratio and it seems that with the Pod air filters and rejetting, that this lean mixture phase may have been overcome.
I will recheck the readings after the rebuild.
It would be relatively easy to delay the max advance to higher RPM by slightly strengthening the springs on the advance unit.

Perhaps someone could modify a DS Electronic Ign base plate to rotate and advance further by using a vacuum diaphragm unit off an old distributor coupled to the vacuum tapping used for the carb balancing. Would need some thought, refinement and planning to simulate what the car distributors did - but not impossible. (Juicy project for someone).

Thanks

Dennis

[McCabe-Thiele (Ted)]

Hi Dennis,

My leads are marked as follows - "8mm High Tension Silicone Jacket 18 Conductive Silicone "
the leads came with the kit.


Cheers Ted

[400 Cafe Racer]

Thanks Ted,

It looks as though the HT leads I have fitted are not the originals with the kit then.

I will do some more research before deciding which way to go with replacements.

Cheers

Dennis

[McCabe-Thiele (Ted)]

Thanks Ted,

It looks as though the HT leads I have fitted are not the originals with the kit then.

I will do some more research before deciding which way to go with replacements.

Cheers

Dennis

Could be they have upgraded over time out of interest what colour are your coils? Mine have a push on rubber connector at the plug ends - no resistor cap.

[400 Cafe Racer]

H Ted,

Pictures attached below. Looked through the invoices from PO and they were purchased in 2016 from 4into1 San Francisco and appear to have done about 5k miles since, with Electronic Ign being added in 2020.

[McCabe-Thiele (Ted)]

H Ted,

Pictures attached below. Looked through the invoices from PO and they were purchased in 2016 from 4into1 San Francisco and appear to have done about 5k miles since, with Electronic Ign being added in 2020.

Mine have Green Bodies purchased in July 2020 as a complete system from I think it was a Yamaha Dealer in the UK.

.Dyna Coil by Macabe Thiele, on Flickr