back into my benly project after months away and no spark!

[safetyjon]

hey everyone-
i've been slowly working on this bike for about a year and half now, on and off. it had been sitting for a few months before i was able to find the time to get started on it again, and now i'm finding that there's no spark at the plugs.

i had a buddy come over to help me test a few things and we used some posts on this forum to guide us. we were both a little unsure of exactly how to test at the different points, especially the coil, but we determined that there was something wacky going on between the points, condenser, coil, and likely the wiring that hangs out between them all. the coil had a bit of waxy stuff built up on it, so we were suspect of that. i went ahead and order new points and condenser, and i also found a decent-looking coil on ebay as well. everything arrived and i was pretty juiced to get it installed. really, i thought it may just be the condenser that was faulty since everything else *seemed* to be in order. well, the new bits are in and i'm still not getting spark.

the wiring in the bike is pretty gnarly, and i'm curious about the strange connection in the attached photo. it's the black wire coming from the battery and going to both the headlight nest and the coil, with a weird junction in the middle. maybe it's normal, but it looks a bit odd to me.

if someone could explain to a noob like me exactly how to test the coil for voltage, that'd be a great start!



here's what i've done:

-drained old gas, put in new
-new plugs, properly gapped
-battery full charged
-new points & condenser installed
-points are clean and setup as per the manual
-tested with both the old coil and the new-old coil


thanks!
jon

[Spokes]

The test for the coil is Ohms. IMO 1.5-3 Ohms is a good coil.

The strange connection looks like a hot splice.

What position is the ignition switch at when your trying to start the bike? I hope one click "up" if it's one click down then you will never start the bike!

You will find a green wire connected to the points. Turn the ignition to one click up and check the green points wire for power.

Basd wiring will haunt you every time. I hope my answer helps.

[safetyjon]

thanks for the reply!

both the old coil and the new old coil are testing around 1.5, so they're both ok.

key position is correct, i learned that lesson already

how to check the points wire for power? it is as simple as testing it against a good ground?

[Spokes]

I use my continuity light. Clip the end on a known ground and touch the wire connection with the tip. With the ignition "on" it lights up (or not)

This tool is one of the handiest tools I have. You can buy them at Radio Shack and at most auto parts stores...cheap

[ByTheLake]

Originally Posted by safetyjon

how to check the points wire for power? it is as simple as testing it against a good ground?

I've copied this from an earlier thread - maybe it'll help. You can ignore the piece about the key position - you've already verified that, but I left that topic in for any future readers.

First, be sure to check the fuse, if not already done.

Was the ignition switch in position II or III? If it was only in position I, it will crank but not provide voltage to the ignition. The tests below would be with the switch in position II (no need for headlights for the testing).

So, the harness power is provided to the ignition at the coil with the black wire. Are you getting voltage if you measure from the black wire to ground? (bare aluminum on the engine itself is a good ground source). If so, proceed to the next step. If not, check the connections in the headlight nacelle, since that black wire gets its power source from the key switch.

If you have voltage at the ignition coil's black wire, do you get voltage between the ignition coil's green wire and ground? If so, proceed to the next step. If not, the primary windings in the coil are suspect, but check for torn/frayed wires at the coil housing, too.

Green is a typical color for ground, so the ignition coil's green wire tells us that this eventually gets grounded - which it does, through the points. With the points open (stick a business card or similar insulator between the point contacts) and the key switch in position II, are you getting voltage between the green wire where it mounts to the spring connector and ground? Voltage may read a bit lower, since the condenser is also mounted there and is also grounded, but you should get some voltage. If so, you're in good shape, so verify the point gap setting. If no voltage is here, there's a connection issue where the points wire routes through the engine case.

[safetyjon]

no power to the green points wire. no power at the black wire at the coil. no power at the hot splice where the coil's black wire connects into.

opening up the headlight nacelle, the connections appear to be ok, but it's a mess in there. the harness on this bike is in really bad shape, and i'm thinking it might be best to find a new one rather than trying to wrangle with what's there now.

i remembered last week that i had ordered a wiring harness from Apex Cycle last june, right before i left for the entire summer. by the time i was back home in september, i had completely forgotten that it was ordered so it didn't cross my mind to look for it. i emailed tom at apex last week to ask him about the shipment, and sent a followup a couple of days later...still haven't heard from him.

anyone have reputable source for a harness? ebay seems to have plenty from thailand and used harnesses that look as bad as mine, but i'd rather avoid both of those options if necessary.

[safetyjon]

deciding to not give up so soon, i tore into the rats nest behind the headlight and found that power from the key switch wasn't making its way through the plastic connector to the rear of the bike. see here:


now i've got power at the black wire at the coil, but not at the green wire at the coil. i checked the coil that i received from ebay earlier this week, same story. power on black, not on green. what's the chance that both of these coils are bad?

[safetyjon]

another followup.

after testing the points wire with the points open (as the forum post suggested) there was power! tested the plugs against the block, there was spark! i buttoned her back up real quick and she fired right up!

awesome!

[Larzfromarz]

I don't know if this will help but- I've always found it useful to have a map of what I'm looking at. For electrical stuff it's called a wiring diagram or schematic. Most manuals have one but because we are not used to this particular kind of map it becomes easy to get confused, crossed up or whatever. I've tried to cut out some of the extra stuff in the following diagram. For this discussion we are just trying to get spark so I removed the clutter of other circuits we don't need right now (rectifiers, dynamos, lights etc). Even now the diagram is still a bit cluttered but we can begin to see the circuit that pertains to us. To be more clear I've added a red arrow to indicate the path of the circuit for the ignition. The blue indicates the voltage generated by the coil going to the plugs.
One thing I need to point out-Honda uses a technique called "switched ground". Essentially we can think of the circuit (after the combination switch) as energized but with no place to go until it finds a ground. This is what happens when we apply either the starter button or the horn button. We are suppling a path to ground (not power) to complete the circuit rather than applying power to complete the circuit-
This is one reason ground connection on these bikes are critical.
I'd have to say if there is continuity throughout the circuit then it follows that the electrons have a path to follow. In this case the path to ground is through the condenser and points. If you establish continuity between the points body and the backing plate (indicating the points are grounded) then I'd suspect the condenser is blown. Looking at the bottom half of the second diagram the electrons only have a limited place to go to get to ground. I hope this helps-

[ByTheLake]

Originally Posted by safetyjon

another followup.

after testing the points wire with the points open (as the forum post suggested) there was power! tested the plugs against the block, there was spark! i buttoned her back up real quick and she fired right up!

awesome!

Excellent news. I love stories that end with a motorbike firing right up.