Topic: Plug wires/caps/coils

[Cincycaddy]

So I've searched through the threads and haven't really come across a complete answer.  Appears that the coils on my honda are OEM or as close to oem as I can tell, the plug wires are pretty dry rotted and they appear to be the OEM style.  Bike has about 30k miles on it.

Anyway, as I posted in another thread I bumped up, I was looking for just wires at first.  Then come to my realization they are all one piece, coils wires and the caps are seperate. 

Bike is a going to be an occassional cruiser, to school and back etc.  Running points now, stock motor to the best of my knowledge.  Read that the aftermarket coils, i.e. Dyna are 3 ohh, which tend to be  a burden on the points. Don't plan on going with electronic ignition or even modifying her, just want it running.

Question then comes to should I just go with the OEM Honda Coils, wires and caps? Pricey, yes,($230) but I guess as it I see it sometimes it is what it was designed for.   Others noted the 900 coils with modification, then if I go with those, what wires/caps are needed?

I think I've already answered my own question, in that I guess I'll just go OEM, but was maybe hoping for a list of model numbers parts for the alternative.

Thanks again,

Chris.

[eldar]

The 900 coils and those suggested by ben are used on the 750.
You can go to wwwpartsnmore.com and get oem style coils for like $30 each. you just need some ngk plug caps about $4 each. So about $76 with free shipping. Others will have places they get stuff from but I have gotten things from them that have been very good and fairly cheap. they are in canada so shipping will be about 1 week or so. Something to check out. Again this is for the 750 and I dont know what bike you have. but I think the coils on the 500/550 and 750 are the same but I am not sure.

[hcritz]

Cincy...I'm in the same boat...The wires on mine are 29 years old and don't like to get wet!
Have a couple of ideas to try and will get back with you...Will test the GM one tonight...see if they will function and fit...
The 900 coils that Eldar mentions sound like a good alternative too!

[Cincycaddy]

Ok, sorry, it is a CB750K5.  Always forget that.  My problem is I'm anxious to ride, and have found that even though this bike is in good shape, that little things here and there are needing attention.  Amazing what some people are able to engineer to get something to work.

I saw those coils on their site, partsnmore that is, I guess I will give those  a try. $30 just seems to good to be true, lol.

Chris.

[hcritz]

Hey Chris.
Does it run ok now?
Mine runs perfectly as long as they are dry...a good washing and it is difficult to crank and misses until things dry out.
I'm planning on a restoration this winter...but would like to ride this summer too and you can't always predict a rain shower!
I'm not sure what kind of primary voltage the GM coils run...will test with 12 v and see what kind of spark they generate...
also if there is room under the tank for them...would be easy to pick up a set of 4 cyl. wires to make them work if they will fit.

[Cincycaddy]

The bike seems to run fine, the problem is one of the wires for the inner two cylinders has really fallen apart.  All other wires are in pretty poor shape to.  I really cannot judge if she is running really well or not as this is my first bike ever.  She runs rough when cold, but if I run her around the block a few times , or roughly 2 miles she seems to do ok, but this seems to be a problem with these anyway, at least from reading on here.   Guess the plugs wires have really taken a beating as I have been pulling them on /off quite a bit in efforts of pulling the plugs in/out to roughly adjust the carbs.

Chris.

[eldar]

dont know about the gm coils. auto coils usually provide more spark. it is the ohm rating that might hurt things. 900 coils andsuch are 3 ohm which can wear out points faster in some cases. if those gm coils are 1 ohm, then that will most certainly do it. I wont say to not do it cause it may work awesome just eat more points and condensers.

[Cincycaddy]

Ok--2 clicks from purchasing the coils and caps on partsnmore.com They seem to be out of stock on the right angle ones, can I order the straight ones and be ok, essentially running the straingt plug caps on all 4 cylinders. 

Secondly I thought about just ordering 2 of the straight ones and then reusing my right angle ones, but a quick check with a DMM and they seem to be 10k ohm plug caps.

Chris.

[eldar]

standard caps are 5K ohm so 10 would indicate they are not very good.

I would think straight would work fine but as duster said somewhere else (i think) you might get them from honda so maybe check with them before ordering the caps.

[Cincycaddy]

Thanks guys, I ordered the $30 coils from partsnmore along with 4 straight plug caps. I'll have to check at Honda when I go to pick up my oil filter bolt later this week.  Figure the straight ones will hold me over hopefully untill I can source 90 degree ones.

Chris.

[TwoTired]

Probably don't care about this post anymore.  But, I spent all that time typing...

The stock coils will be the most straightforward to replace.  IF you can still get them from Honda.  Shouldn't take more than 30 minutes to install.

You will likely need to fabricate some kind of mount or adapter to mount others to the frame.  Not difficult, but extra time and thought required.

Dyna used to make 5 ohm coils for these bikes.  Might need to call them to get the current number to order.  You'll have to purchase wires, too, of course.

3 ohm coils will work with points.  But, the increased current will shorten their life some, and require more frequent attention to maintain correct timing.  The spark plugs should last longer, though.

Plug caps are available in both 5K and 10K ohm resistance.  Seems the Cb550s normally had 10K and Cb750 had 5K from the factory.  Which strikes me as odd since they both used the same ignition coil.  I imagine either is fine to use as long as they are all the same.  Just don't use Resistor plugs along with the resistor caps.

Cheers,

[Cincycaddy]

I'm using champions now, can't remember what the model number is off hand,but they cross reference to the cb750k  are these resistor plugs?

[eldar]

hard to say. as long as there is no R, it should be ok. thats how it is for ngk anyways.

[TwoTired]

I'm using champions now, can't remember what the model number is off hand,but they cross reference to the cb750k  are these resistor plugs?

If there is an R in the plug number, then yes.  If you want to run these plugs, get plug caps with no resistance.  Most of us don't like the Champions in these motors and prefer NGKs, for various reasons.  I find their longevity rather poor.

For those have issues in wet weather, note that any cracks in the HT leads will cause issues.  But, if you have no cracks and are still having wet issues check your points cover gasket.  I wrestle with wet issue a couple years until I figured out the points were getting wet.  I made a gasket out of neoprene from the hardware store and that cured all the wet run issues I had.  I even put the garden hose spray on the motor and it still ran without a miss, stock coils, too.

Cheers,

[Cincycaddy]

Well this may explain why she has been running not as well as expected-

Original plugs when I got her were D8EA's in the inner two cylinders (2 and 3) and Champion RA8HC in the outer two (1 and 2)

Pulled all 4 and am now running brand new RA8HC's in all cylinders.

Is the D8EA's what I should be looking for? Again the bike is a CB750K5.

[Bob Wessner]

Is the D8EA's what I should be looking for?

Yes, if that it what the manual for the K5 calls for. The "R" in the Champion plug ID indicates these are resistor plugs. If you have otherwise stock ignition (coils, plug caps, etc.) the plug caps are resistor caps. You shouldn't run resistor plugs as well, this weakens the spark.

[Cincycaddy]

Thanks all, got 10 new NGK plugs, new coils/wires and plug caps a coming, I'll keep ya'll posted.

Chris.

[Cincycaddy]

In my desire to find something to work on on my bike, I wired up a relay directly to the battery, fused at 15 amps to power the coils, 86 to ground, 85 to kill switch, 87 out to coils 30 fused 12 volt constant.  Anyway, is this an effective mod? Seems like it would be worth the 10 minutes or so it took to do, if anything I guess it can't hurt, and I figure from looking at the schematics, that hot wire to the coils goes through a couple of connections before actually hitting the coils, so the more direct route has to be better.

Chris.