Cb750K7 Electronic ignition units

[Flyingscotsman3]

Hi All,
Recent owner of cb750k7 reg number VAH 182S.
Am planning in the near future to fit electronic ignition, & just wondered if anyone has any recomendations, as in best type, & maybe where to buy from?.
Thanks Kev

[Trigger]

Dyna is about the best but not cheap.

[AshimotoK0]

Back 'in the day' I designed and built a CDI system which retained the points and ran it on my first 400/4 for 20k miles (had one capacitor go short) but apart from that worked great and never adjusted or changed the points after first fit but literally 5 min job to return to standard ignition. Left it on the bike when I sold it. The expensive/hard to get bit at the time was the inverter transformer to convert the 12v to 400 VDC but you can now buy 100W plug in converters for cars for next to nothing, so one day I will update the design using one of those and put one on my CB750. The  one  I made was back in '79/80 so I reckon capacitor technology (the one which discharges 400v into the coil) have come on since then. Used the standard Honda coils BTW with no problems. I stripped down one of the modern car plug-in mains inverters last week and the quality looked surprisingly good (had USB power socket on it too !!)

Cheers ... Ash D

[Johnwebley]

I fitted Boyer to my 500-4 about 1978, !!!!

 still use it,easy to set up,only replaced the box once,about 12yrs ago,


I am happy with the performance and reliability ,

think it cost me about £27 originally
 
may be dearer now

[AshimotoK0]

I fitted Boyer to my 500-4 about 1978, !!!!

 still use it,easy to set up,only replaced the box once,about 12yrs ago,


I am happy with the performance and reliability ,

think it cost me about £27 originally
 
may be dearer now

I have one of those on my  400/4 (it was on it when I bought it)  but it's different than a CDI as it just replaces the points with inductive pickups and switches the coil current with transistors. The capacitor charged to around 400v on a  CDI discharges across the coil and you get a really good spark developed at the plugs. The CDI also takes a lower current at low revs so gives better spark when cranking with the starter motor. Superdreams and CX500's moved to CDI but I think the hi voltage to charge the capacitors is derived from an  alternator winding. The Boyer system has been around a long time though so not knocking it.

Cheers ...AshD

[Lobo]

Gents... I too am beginning to think about replacing the ignitions on my 2 CBs. Whilst I can't find tech data on the Dyna, I note a 'caution' from the Boyer that any voltage drop <9v and it won't play ball. Bike kaput at 8.9v it seems.... This, for me, is a bit too "black & white", as presumably even bump-starting with a flat(ish) battery is never going to work...

I also read that magnetic sensors can be prone to heat, metal mass, rpm fluctuations blah blah .... and consequently upto +/- 7 degs timing inaccuracies. Seems odd... but then an optical pick-up manufacturer (of course) wrote this.

So I'm at a loss what to think... I did have the DSS £100 offering (replaces the points with a magnetic pick-up) - but it's build quality appeared 'cheap & nasty' and after a 2 hr ride the '750 started loosing power (limped home). Can't categorically blame that system, but put back the points etc & have not had a hiccup since.

Anyways... looking for comments on the 9v 'cutoff' & whether (expensive) optical pick-ups are honestly the way to go.

Cheers...

[SteveD CB500K0]

Has anyone considered the Hondaman system?


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[Johnwebley]

hi Lobo, 

   re the Boyer and voltage drop,I have kicked it when the starter is to low,

 not done any tests,

 but its good enough for me

[AshimotoK0]

The beauty of the DC inverter driven CDI is that it takes  lower current, than the standard 'Kettering Ignition'at low RPM and will still charge the capacitors down to around 6v under engine cranking if the inverter is designed carefully.

Cheers ...AshD

[Lobo]

... one thing I'm learning here is that many of these fancy ignition systems replace the coils with higher spec versions... which invariably draw more current. This then has an impact on whether the charging system is upto it (smaller bikes) and long term, the bike's wiring / switches.. eg kill switch & wires down to coil.

Mostly do-able (eg relays I guess)... but worthy of note & a bit of a deterrent bearing in mind all I want is to potter locally versus eek out racing performance. It's seriously coming back to whether I can be bothered due the complication of it all... specifically the road-side maintenance should something go wrong! (remembering that it's an add-on system versus designed into the bike from day #1)

Steve - cheers, the Hondaman sys retains the points... appreciate almost zip current flow / less wearing out... tho' I did fancy getting away from such a 'mechanical' system. BUT... on the plus side you can re-instate the OEM system roadside in about 2 mins. 
Hmmm... possibly tempting in light of 'keeping it simple' & my recent learnings.

[AshimotoK0]

I rest my case for the points triggered CDI. 2 minute job to swap back to standard and superb starting / sparking  characteristics & maintains the standard coils !!

Not sure on Hondaman's I suspect it is a transistor switched coil device. Has a good name to it though.

Cheers .... Ash D

[Flyingscotsman3]

Hi All,
"During the War" er no not quite that far back Lol!, i did fit boyer to me Commando 850 interstate, with no coil swap over, & later to a Gs750 i had, same ran it with standard coils, no probs.
Have heard of the Hondaman system, has anyone got it fitted?.
Stumbled on something called Newtronic ignition somewhere on the web, but as happens annoyingly sometimes, cant find it again grrrr!.
Kev

[MarkCR750]

Hi All,
"During the War" er no not quite that far back Lol!, i did fit boyer to me Commando 850 interstate, with no coil swap over, & later to a Gs750 i had, same ran it with standard coils, no probs.
Have heard of the Hondaman system, has anyone got it fitted?.
Stumbled on something called Newtronic ignition somewhere on the web, but as happens annoyingly sometimes, cant find it again grrrr!.
Kev

is it this one Kev?
http://www.newtronic.co.uk/newtronic/

[Rumpelkrankshaft]

Fitted Newtronic system to the CB550F just after I got it in 1992-never had a moments trouble with it in 23000 miles. Still works down to 10.5 volts. Easy to put back old system if required.

[K2-K6]

I guess what makes it a 50/50 decision is that there is nothing fundamentally wrong with the standard points setup so you're not comparing a significant advance with a crap starting point as some mods will accomplish.

For most people that look after older engines then if you just had a box of components for the points system then they could assemble it all and time it with a fag paper (i appreciate that means something else to USA readers) and get the engine to run quite well.....hence the roadside ease of use case.

The electronic systems all seem to be reliable as well....but if the bike does stop it's just harder to establish which bit is stopping it...it'd be rare for either system to leave you stranded though in my experience.

Magnetic triggers to me have always performed reliably in a number of differning applications, it's more often that the amplification circuitry gives problems and sometimes seem prone to the effects of heat and vibration.

One of the biggest advantages of a better ignition system I believe is the potential to run the jetting leaner.....giving a cleaner burn, less oil contamination (especially at starting) and dryer exhaust pipes....all quite relevant to looking after these old bikes and preserving their condition longer term.