SOHC.co.uk Forums > CB350/400

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

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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

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