CB200 carb issues

[Sesman]

yes, Ted.That’s correct. The primary resistance is not paramount and the difference in coil resistance being suggested is of no great importance…..in this instance anyway.

[Johnwebley]

Ventured into the garage

Checked the  caps,

All read about 5.3k

Coil secondary 17k

Started and warmed up nicely

Then it started raining

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[K2-K6]

Point of reference,  will it rev to the red line in neutral ?

Once warmed that is 

[Johnwebley]

Point of reference,  will it rev to the red line in neutral ?

Once warmed that is 

Mmmmmm


Not sure I want to try

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[K2-K6]

It's far less load than pulling us around under torque loading, it won't hurt it in any way.

[Sesman]

Yep, at least that would indicate a load related issue. Eg spark break down under load…..or fuel….or something…

[Sesman]

Hi, John. One thing I forgot to mention about the coil….dwell time. Are you sure the advance mech is functioning correctly? As the engine revs up there is less time for the coil to reach its steady state current. If the dwell time is such that the coil time constant doesn’t permit the DC steady state current to be established the HT side will falter. It’s just that at around 6k rpm I’m guessing you are approaching full torque and if the timing unit is not working properly neither will your ignition. For example, if the motor starts to hold back and die at 6k, but come back as the revs fall, it’s a good clue as to the problem. I’d strobe the ignition? Apologies if that’s already been mentioned

[Sesman]

Back on topic, was the misfire, holding back problem solved?

  not quite died yet,its been cold,so I have left it until it warms up.

BUT,thinking  ,at 6,000 rpm itis generating 100 sparks per second,using the 4.7ohm coil ,

 is that enough to make the coil refresh??
infact,at the red line of 9K,it should be having 150  bangs a second,.

I know it was hopeless  with a wide contact gap,reducing it to 12thou  certainly improved  the general running,but not increased  how high it revs.

does anyone know the spec of the original coil?

no details on either  DSS or  CMSNL,Wemoto  give 4.7 for one,and 4.2 for another.


 HELP

John.

Very basically, at 6k the engine is firing at say 100times per second. For a typical coil time constant of say 4ms, the coil could reach steady state DC magnetism say 250 times per second, so you can see there is significant time for the coil to “charge” as some folk like to describe it. However, the ability of the coil to achieve ‘steady state’ will be determined to some extent by the timing advancer. Without advance the rpm might well outstrip the time constant/dwell time and hence the ignition break down. I’m convinced it’s an ignition system issue. Though I could be wrong, I normally am. I’m very suspicious of that 6k figure as it definitely resonates with ignition advance, coil and points.

[Sesman]

Apologies 125 times per second, not 250 as the coil needs to discharge too…..

[Sesman]

Just stumbled  across this looking for typical coil time constants - explains it far better than I do.

https://www.denso-technic.com/bg/everything-you-need-to-know-about-ignition-coil-charge-up.

[K2-K6]

Certainly an interesting discussion (we should do this as topic I feel as it brings interesting views to consider) that's as opposed to trouble shooting thread.

Hopefully to constructively add something;- the ignition advance doesn't change dwell or compensate for it's shift. Dwell change is because a mechanical system with rotor, although constant geometry, will pass the trigger point faster and faster with increasing revs, and so shorten in time frame the effect of that gemoetry. This has to be accommodated in coil performance if the ignition is to function at both low and high rpm.
It's something that true electronic triggering and accompanying switching eliminates via constant dwell TIME through full rpm range, if designed correctly.

Ignition advance shift is solely to take care of fuel burn characteristics, this is relatively constant and wouldn’t complete at the correct point in power stroke as rpm increaesd (a diesel is like this, and limited generally in max rpm because of it) to get the fuel to reach peak combustion at high rpm at correct position in stroke there's need to start the fire earlier and earlier, hence ignition advance to make sure the burn constant is fulfilled even though the piston is travelling faster.

[Johnwebley]

Gentleman, thank you for your input,
This is typical of this forum, lots of intelligent discussion and help,
Great fun reading it,

Ok,the weather has improved, so I shall get the 200 out for a run,

Might even see if it will rev past 6k with no load,

Might get the 500 out, that does rev past 9k,but it has Boyer ignition

Thanks guys,

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[K2-K6]

I do think that Boyer is a really clever system John, and didn't grasp the theory/ strategy of design until looking at diesel injection system (very similar in running retard control rather than advance) in how it works, signalled by correctly checking ultimate timing at full "advance" position to correctly set the baseline.

[Johnwebley]

I do think that Boyer is a really clever system John, and didn't grasp the theory/ strategy of design until looking at diesel injection system (very similar in running retard control rather than advance) in how it works, signalled by correctly checking ultimate timing at full "advance" position to correctly set the baseline.

  I first used Boyer  in around 74,on a BSA A65 powered  sidecar racer,

  then about 78,I got  a set for the 500,

[Sesman]

Get the 500 out JW. You know it makes sense.