CB650 Ignition

If it's broken or just needs tweaked

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Pinhead
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CB650 Ignition

Postby Pinhead » Mon Jul 14, 2008 6:08 pm

As I've found through my rigorous search on the interweb, we don't actually have CDI ignition on our bikes. We simply have a transistorized Kettering system.

In other words, we have transistors/pulse triggers that replaced the points.

Describing CDI Ignition:
http://www.jetav8r.com/Vision/Ignition/CDI.html
With the Kettering Induction ignition design, the coils are powered all the time at 12 volts and are commanded to collapse to spark by the ignition module. Here, the ignition module disconnects the primary winding coil ground. The coil secondary winding collapses to spark at about 30,000 volts. In the CDI design, the coils are not powered. They receive a short high (250 volt) pulse from the ignition module and then amplify that (100:1) to a much larger voltage spike (about 40,000 volts) . Since the potential output of a CDI coil can be over 40,000 volts you have stickers all over your engine bay reminding you that: This can KILL you!!


THIS IS WHAT WE HAVE:
Image

AFAIK, we have the same ignition as the CBX's; I've found a lot of information HERE.

From the CBX article with regards to the Spark Units:
TPI’s spark units have easily recognizable failure modes. A common one is when an attempt is made to start the bike after it has sat awhile and the battery is low. During starting, battery voltage normally dips when the starter is used but with less to start with, the battery’s voltage drops too low for the spark unit to operate, and the engine will not start due to loss of spark. Meantime, the transistor is overheating, and will soon permanently fail. This is such a known failure mode that Honda later added time-out circuits to their TPI systems, as did also other manufacturers. Another possible route to failure is the unthinking substitution of ignition coils having too low a primary resistance. Such coils will burn out the spark units. You have no doubt heard of this. High performance ignition coils have higher potential voltage output because they have larger primary to secondary winding turn ratios. There are two ways to build a coil with a larger turn ratio - either leave the primary the same and increase the secondary turns, or leave the secondary the same and decrease the primary turns. The latter method was once very popular. However, it results in a coil having lower than stock primary resistance. While not big deal on a points bike, whose points will merely arc a bit more, the transistors in a TPI system will not endure the increased current flow through the coil for very long, and the spark units will fail. We’ll address this issue again in Part 3. One thing you do not have to worry about with spark units is failures due to loss of ground. Their metal boxes do not physically ground, but rather, the spark units get their grounds through the green wire feeding back into the wire harness. And here are a few tips. When the ignition system is acting up, but it is mostly when the engine is warm, don’t suspect the spark units. The pulsers are likely the problem. When the ignition performs badly whether hot or cold, then the spark units become more suspect.


So it's actually not the higher voltage of an overcharging alternator that generally melts the sparkers, it's the low voltage of a bad battery after sitting for a while that causes the damage.

I'll keep updating this post/topic as I find more interesting information. ;)
Last edited by Pinhead on Tue Jul 15, 2008 7:49 pm, edited 1 time in total.

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Volker_P
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Re: CB650 Ignition

Postby Volker_P » Tue Jul 15, 2008 2:59 am

Pinhead wrote:So it's actually not the higher voltage of an overcharging alternator that generally melts the sparkers, it's the low voltage of a bad battery after sitting for a while that causes the damage.

I'll keep updating this post/topic as I find more interesting information. ;)

Interesting. I found the melting of my ignitors insulation stuff corresponding with an about 1V enhanced charging voltage resulting from an additional resistance in the ignition lock switch. Or rather in the switch which I used instead at this time. :roll:
I think I once saw a scheme of the ignitors interior somewhere, possibly Cosky's manual. I'll try to find and post it to complete confusion. :lol:
-just found it: it is the above scheme there.
As the ignitors are part of a very early version of CDI-like ignition, I can imagine that there may be differences to a "typical" CDI layout.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

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Chris
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Re: CB650 Ignition

Postby Chris » Tue Jul 15, 2008 5:12 pm

I just recently won a paper version of the factory service manual on ebay. Last night I was inserting the pages into some of those plastic envelope type page protectors and noticed that the manual describes the ignition as exactly that, 'Transistorized'. Also, there may be some pages there that aren't included in Cosky's manual. I'll get back to ya'll on that in the proper thread. If I don't, please send me a PM to remind me as I have alot going on right now.
1980 CB650c

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5.4L to Freedom
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Re: CB650 Ignition

Postby 5.4L to Freedom » Wed Jul 16, 2008 8:29 am

Newbie here, can somebody post a picture of what all this stuff looks like outside the wiring diagram... been having lots of issues lately, maybe one of the things mentioned above is at fault?

I need to know where to look to start testing! How to test idk yet? But i've got a multimeter and a bunch of time so we'll figure it out :)
Dr. SOHC650... former rider I got sick of fixin my CB so I bought a Harley and fix everyone elses...

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DVMPiper
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Re: CB650 Ignition

Postby DVMPiper » Wed Oct 01, 2008 9:28 am

I have a '82 CB650 that has some funky points. Cylinders 1/4 are intermittent firing and when I psuh tha points around, it will get them going. What I need to know from those with experience, is do I need to verify the gap, how best to test them, and how to adjust them properly. The manual I have doesn't make it clear enough. Bike runs great if all 4 are firing. Everything else in the circuit checks out.

Doc
Bryan Robinson, DVM

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Volker_P
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Re: CB650 Ignition

Postby Volker_P » Thu Oct 02, 2008 1:12 am

Welcome here! :D
I am a bit irritated as you talk about points and gaps. The CB650 had electronic ignition with pickup coils from the beginning on. So I can't imagine what you really mean when you write "when I push the points around ... ".
A proven procedure to get happy is to exchange 1-4 vs. 2-3 ignition circuit components until you know which one causes the trouble by shifting the problem from 1-4 to 2-3.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

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DVMPiper
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Re: CB650 Ignition

Postby DVMPiper » Thu Oct 02, 2008 9:57 am

Okay, sorry for the wrong use of terms. :shock: :? But, when I checked the gap of one versus the other, there was one, likely the 1/4 cylinder pickup, that was wider than the other. When I repositioned it to match the narrower one, I was able to get 1/4 to fire. The following day, I started with the same non-firing problem and when I took the cover off and pushed the 1/4 pickup closer, the rotor actualy brushed the pickup briefly and I got all cylinders firing. So, is it a distance issue or a dirty pickup issue? Maybe the pickup is bad. If it is dirt and grime, what works best to clean and keep it clean? If it is distance, what should they be set at?

Also, is it safe to swap the wiring of one pickup to the other at the coils? Or where do I switch them if the coils isn't the place? I tried swapping the coils and CDIs with no improvement.

Thanks,
Doc
Bryan Robinson, DVM

gdongarra
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Re: CB650 Ignition

Postby gdongarra » Thu Oct 02, 2008 2:31 pm

Guys,
I was an Electronics Tech in the Coast Guard and all that made complete sense to me...
Depending how the voltage dividers set transistor bias, a lower source voltage could actually cause the transistors or the diodes to be "on" and conducting current when they should not be....

Good find pinhead...

George

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arcangel
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Re: CB650 Ignition

Postby arcangel » Sun Oct 05, 2008 6:01 pm

The pulser clearance should be 0.012 - 0.016 in or (0.3-0.4 mm)
Don't forget to use some lock tite or finger nail polish to
coat screws to keep them from changing from vibrations during riding.
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Volker_P
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Re: CB650 Ignition

Postby Volker_P » Tue Oct 07, 2008 2:14 am

The distance can be adjusted as close as possible however avoiding mechanical contact. There is no need to have a certain gap like for mechanical points to have time to load the coils or so.
Dirt (except metallic files) should have no impact on the magnetic signal between the pulser and the crankshaft. But dirt or oil with filings might have an impact on the cabling especially if the insulation is brittle. Remember these are very weak signals.
A short inside pickup coil windings may also weaken the signal and cause problems like yours but first check the cabling between pickup coils and spark units/ ignitors. The pickups can be tested separately, their resistance should be 530 Ohms ± 50 Ohms at 20°C between both blue (for 1-4) and both yellow cables (for 2-3), respectively.
http://cosky1.tripod.com/id1.html provides some help, however the scheme is wrong as it shows only one spark unit that acts for both circuits while we all have two independent units, one for each circuit. BTW, cosky0 contains the rest of the manual. :wink:
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

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arcangel
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Re: CB650 Ignition

Postby arcangel » Wed Oct 08, 2008 6:14 pm

I got the Specs on the gap from the clymer manual however Volker is right about the spacing close is better than to far as long as it is not so closeit hits.
I don't know if the voltage it makes would be to hi if it were to close but probley not but to faraway it would definitely not make the same current needed basicly it is a small generator and the coils boost the voltage or amps.
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