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Ouch!

Submitted by graham_cooper1 on Fri, 09/06/2023
Forums
Commando

This is the result of using a Boyer digital ignition with a kickstart Commando which backfired around 1/3 of the time. When it runs it’s great.  I’ve checked the timing marks with a TDC gauge and degree wheel, strobed the timing, got a battery low volt indicator and still it backfires. I’ve tried retarding the ignition by 5 degrees and still it backfires. I’m going back to a Boyer analogue ignition, Mk4 with the low voltage mod. If anyone wants a pristine Micro Power setup (electronic box, micro coil) which I’m sure will be fine with electric start, and the idle is good, and the current consumption is low, then let me know!

 

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Submitted by david_comeau on Sat, 10/06/2023

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If your unit is a micro power, what is the possible source of backfire? Is this on kick start only or during running?

Does this kick back happen with tested 12.8 +/- AT THE BOX? not just battery?

The spark scatter for the analog boyer is well known now that I discovered and published it 20 years ago. It is also well documented the spark scatter is advance AND retarded. Though only advance causes start kickback.

I had also tested the micro digital back then also...

Thanks

Submitted by graham_cooper1 on Sun, 11/06/2023

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Only when kick starting. I believe the unit continues to use the speed-dependent magnetic ignition signal, and I know that the signal is modified for stable idle speed, evident from the dip in the advance curve at around 700rpm. I guess that the analogue signal is digitised and then modified as a function of rpm. My suspicion is that the large variation of signal time interval at kick start speed sometimes causes excessive advance - ouch! Anyway, let’s see how the Mk 4 performs.

Submitted by steve_adkins on Sun, 11/06/2023

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Morning Graham,

Tri-Spark is fit and forget.

I did this on my Mk2A years ago and slung the legacy Boyer into e-waste. I am not associated with Tri-Spark and do have Boyer powerboxes, (not ignition's), fitted to several bikes and these work well.

Regards Steve.

 

Submitted by david_comeau on Mon, 12/06/2023

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This makes me ponder a possible cause for kick back on kicking.

How does the analog start trigger from the magnets potentially change from, start trigger, to antistall advance trigger?

If the magnets were too strong ? falsely make the computer select(calculate)  an advanced(earlier) antistall trigger? Responding as a stalling (advanced) trigger rather than normal delayed starting (nominal) trigger.

The combination of digital and analog components(concepts)  can become confusing to folks lacking a very intense education....

Having studied these systems decades ago, only further studying to the heart of the beast will reveal and give up its secrets or defect for failure to work correctly.

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Submitted by michael_coare on Mon, 12/06/2023

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...you've got a foot like that, kick-starting a Commando wearing sandals! ;-)

Submitted by graham_cooper1 on Mon, 12/06/2023

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The news so far is that the mk 4 Boyer appears to have resolved the problem but I’ll reserve judgement for a while. Bike started first kick this morning after fitting (I’d kicked it over a few times to get some mixture in the cylinders). It then started first kick while hot with a little throttle, and with timing still retarded from installation. I then advanced the timing to the correct setting but haven’t started it since. My wife sat on the bike with rubber mat underneath the centre stand were insufficient to prevent the bike travelling backwards scary fast at around 3000rpm while I was trying to strobe the ignition so I resorted to photo!

 

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Submitted by graham_cooper1 on Wed, 14/06/2023

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No more back firing confirmed from riding the bike yesterday with the Boyer mk 4 fitted, what a relief :-)

 



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