Topic: CB500K2 Cutting Out - Coil Wiring Issues?

[mrmunsell]

Hi All,

I just bought a CB500K2 last Friday in relatively good running condition.  While it runs pretty good overall, it does have some issues which I have been trying to sort out.

One problem symptom first cropped yesterday morning while I was out riding.

Symptom: Cruising with steady throttle position, bike seems to be running great with no obvious signs of problems... and then power suddenly cuts out.  Sometimes it cuts back in on its own shortly afterwards (fractional second to a few seconds).  Sometimes it takes minutes or tens of minutes.  When the problem is occurring, it still runs.  But it is rough and lacking power (can only slowly accelerate and maintain lower speeds, etc).  And it requires throttle assist to idle.  Then all the sudden for no apparent reason, the symptom subsides and the bike runs great again.

Due to the way the symptom was abruptly cutting in and out, I was suspecting some type of electrical / ignition issue.  I got a chance to look into this tonight.  When I pulled the tank to check out the coils, I was disappointed to find the wiring situation in the attached images.  The first image shows how it looked after I took a twist tie off one of the wire bundles to investigate further... when I removed the tie, one of the wire ends just fell out of its crimp connector.  The second just shows the wiring after unbundling it.  I stuck that one wire back in place to keep track of what went where, but another wire had started falling out of the ignition coil as well.  I am not fond of these particular type of crimp connectors for auto / moto use anyway, but it looks like they didn't even use the proper crimp tool for them.  So I suspect I could easily pull out any of these wires out of the blue crimp connectors if I tried.

So, I think I may have found the cause of this particular symptom.  The wiring to the other coil still looks stock... although it was also re-crimped where it mates to the main harness as well.

I have the shop manual.  From what I can tell so far, it looks like the factory wiring already had connectors (bullet, etc) at these same locations in the main harness, correct?  So the changes someone made here were: replaced the original main harness connectors for the coils, replaced the connectors on the right coil harness, and made a new left coil harness (using the same crimp connectors plus some non-OE wiring).  I suspect just re-crimping these with the proper crimp might improve or resolve the symptoms... but I would rather fix it right and revert all this back to original.  Anyone know of a good source for the OE style bullet and spade connectors with the hoods?  Or any other suggestions on how to better repair this?

Also, while I am here - how can I tell if these are OEM coils (vs cheap aftermarket, etc)?  I went ahead and measured the primary impedance even though the issue probably wasn't the coils after all.  2.5 Ohm on one coil.  2.6 on the other.

Thanks!

[DaveBarbier]

Yes, ugly wiring. Fix that.

The coils look OEM, but to be sure they should say TEC on them and made in Japan. Cycleterminal.com and vintageconnections.com are where most here get their bullet terminals. They also sell spade terminals. If you don't have the crimp tool, buy it. It's not expensive and makes for a perfect OEM style crimp.


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[mrmunsell]

Thank you both for that information.

Cycleterminal.com is closed until around August 13th, but vintageconnections.com has everything I need to fix the wiring.  I'll get all that ordered today.

The coils are obsolete per a Honda dealer I usually buy parts from for my newer Honda.  Still searching, but I haven't found any sources for stock or NOS coils.  Aftermarket coils are pretty easy to come by though.

Are the 'reproduction' coils that 4into1.com sells any good?  They are 4.6 Ohm.  The reviews on the site are all positive.

http://4into1.com/honda-ignition-coil-30501-300-003-cb350f-cb400f-cb500-cb550-cb750/

Any better options out there for stock spec coils?

[Duke McDukiedook]

Dynatek makes 5 ohm coils that should fit your bill and allow you to change out spark plug wires. Most aftermarket coils have fixed plug wires.

[mrmunsell]

Duke McDukiedook: Thanks for that coil suggestion.  Reading up on those now.


Meanwhile, some updates:

I removed the existing coils and they have no apparent make or model markings that I could find.  Just some stickers that say '12 V' (black print on metallic background).  So these would seem to be aftermarket replacements.

As I went to place the order for the wiring parts, I realized that vintageconvections.com does not currently offer any 3.5mm multi-barrel connectors (per the shop manual, I believe I needed a double barrel connector for the main harness coil ignition connections).  They had a listing for a triple barrel connector that could have worked, but there is a note indicating it is no longer available.  So, still looking for other sources of those before I do something that strays from stock.  For example, upsize to the larger 4mm connectors.  Or use a single 3.5mm barrel connectors at the main harness and then do something on the coil harness side to split the ignition wire to the two coils.  Found more sources for the 3.5mm single barrel connectors, but not any multi barrel variations.

[CycleRanger]

Check this out for connectors.
http://4into1.com/search.php?search_query=bullet

[mrmunsell]

Thank you.  I was actually there earlier looking for various other parts, but didn't think to check their site for the bullet connectors.

I also found the double bullet connectors at the link below, but will probably order from 4into1 now since I think I likely going to be ordering some other stuff from them anyway.

http://www.easternbeaver.com/Main/Elec__Products/Connectors/Bullet_Connectors/bullet_connectors.html#3.5

[Deltarider]

The wiring doesn't look reliable but, who knows, maybe it has worked. So don't forget this easy check: see if there's any (intermittent) arcing between HTleads and/or plugcaps and the engine (ground). What resistance do you read in the sparkplugcaps? Your coils do not have the right resistance unless your bike has a ballast resistor somewhere in the + line to the coils or has some special (other than conventional) ignition. Please inform us a bit more on the rest of your ignition like: breakerpoints? Pitted? Leaky condensers that show arcing?

[mrmunsell]

Thanks Deltarider.

There are no ballast resistors inline.  Aside from that ignition wiring in my images and an aftermarket fuse that was spliced in place of the original main fuse (just a bare splice with tape), the rest of the wiring appears to be stock and unmolested.

The ignition is still the stock design.  The points / condensers are cheap aftermarket, but in good condition and recently adjusted.  They have relatively few miles on them since replacement (by PO).

Three of the plug caps are 5 KOhms +/- 250 Ohms.  One is a bit outside that range at 4.58 KOhms.

The HT leads are in good condition and have a thick (rubber?) outer sleeve running over most of the length of the wire.  I had not noticed any arcing when it was last running, although I didn't specifically check for that either.

[Deltarider]

Thanks for you reply. By what you describe caps and HT leads seem good. Most probably your presumption is right (about on and off contact in the wiring). For a conventional ignition, the coil primary resistance is too low however. It will result in pitting of the breakerpoints. Ideally the primary resistance is between 4,5 and 5 Ω. Just to complete you may have a look at your breakerpoints in action and compare it with this vid. Sometimes it'is not until they're warm that they start showing arcing like in this vid.

In this video left condensor (1+4) shows arcing and is bad, right condensor (2+3) (minor sparking) is good.

[mrmunsell]

That is very helpful information.  I will check the points in action once I get it back together.  Thanks!

[mrmunsell]

The new connectors came in last week and I finished fixing all the known questionable electrical connections over the weekend.  A previous owner had also replaced the stock fuse with an aftermarket inline fuse... but in that case it was just a splice wrapped in electrical tape (no crimp connector, no solder, etc).  I took care of that as well and cleaned all the connections in that area with electrical cleaner while I was there.  Most were not that bad... but the bottom wires on the three molded connectors had a little bit of corrosion (which cleaned up well with electronic cleaner).

I also put on new Dynatek 5 Ohm coils / Dynatek plug wires / NGK 5 KOhm caps / NGK plugs.

It will be another day or so before I can take it out for a ride to see if this has any impact on the cut out symptom... I am waiting on some carb parts from Honda (had a carb overflow issue I am also trying to resolve - carbs are off the bike right now).

[mrmunsell]

I got my motorcycle back on the road today.  The cut out symptom is resolved.  I made several changes since it was last running (carb work, new exhaust), but I am pretty confident that resolving those wiring issues is what resolved this particular symptom.

Also, I think those 3 Ohms coils were taxing my charging system.  After getting it running with the new coils today, the regulator output was over 15 Volts at 3000 RPM.  I have an Oregon regulator which had been installed and adjusted (to 14.4 V) by a local shop.  I dialed the setting back to get the output back down to 14.4 V and all seems well again in that regard.

[CycleRanger]

Terrific! Now you can gear up and hit the road. 
It's only 102° during the day now.....

[mrmunsell]

I was measuring at the regulator, not at the battery.  Although I just went out and measured at both points (engine running at 3000 RPM).  The measurement was similar at the black wire from the regulator and at the battery (less than a tenth of a volt difference).