Topic: I got a new toy. CB650 '81. Now what......

[robsbots]

Hey all.

I've been looking for years, but I have finally found a chopper project, in my price range with the look I want. It was a Honda CB650 1981. It's now a hard tail with springer front end and some well chewed wiring.
I have been told the carbs had been cleaned and rebuilt. It had some pod filters which didn't really fit and had various bits of rubber and duck tape to make them work. Well. I had the bike running poorly with the filters as supplied on the day or purchase. At some point we had the bike running with no filters whilst playing with the "custom" chock cable, and got a back fire though carb 2. The bike has not run since.
I think I have a fueling issue with the carbs.  I have the Keihin carbs and have a rebuild kit on order or them.

When checking over the wiring I noticed some black sticky grot on one of the spark units. I removed it to clean it off and it turns out the black gunk is potting compound from the spark unit it's self. The other unit seems to be fine. Any ideas what has happened here. I don't think this is standard break down over time. I assume this is because the unit was getting hot. Can this be caused by A) poor timing, B) poor wiring, C) Spark unit dying, D) Something else.
I notice on a few posts here people have said replacement units are available (Non factory).

I'd like this bike to be a daily rider. So, where do I go from here ? Should I be looking to repair what I have on the ignition side, or should I replace the ignition with some "New Modern Kit" with hall effect sensors and digital black boxes etc. I love the rolling chassis and could replace the engine with something more modern, but I love the look of the lump too and would rather make it work. Also, are there any kits for wiring harnesses with correct colour coding. Think I'll be starting from scratch with the wiring.

When I grow up and earn some forum points I'll post a picture and you guys can see the "Raging Goat". (NOT Greatest Of All Time. Just a description of the ride from the previous owner  )

Any input greatly appreciated.

Thanks guys.

[newday777]

The melting pot compound is a common thing in the 80s ignition spark units, I think I remember reading on one of the goldwing forums that you can fill it in with epoxy.

David Silver Spares says they can special order the spark units.....not cheap though!
https://www.davidsilverspares.com/parts/by-part-number/part_30400426154/

[fizzlebottom]

Those original spark units do exactly what you described. They eventually leak right on out and cease functioning. Just replace and move on. Aftermarket units are just fine for this. The only way to diagnose one of these parts as bad is to swap in a known good part. Yours is known to be bad, so I'd just get a new pair and call it a day.

[robsbots]

Thanks for the replies.

As previously stated, I'd like this bike to be a daily ride. I would like to make it bomb proof and I suspect there are better systems nowadays to ignite fuel in a cylinder. If i replace the "iffy" looking spark generator, that's almost half the price of the bike. (Id like to replace both and start from a known good position but at $400 a pop that's quite an investment).  Is there a better place to invest my money and bring the system more up to date and more easily maintained in the future. These parts are getting difficult to find now, so is there a better direction ?

I've just been reading though Hondamans post on his transistor ignition and it looks good but only works with point systems. Could I go backwards and install points on the lump ? I assume previous models would have had points.

As for replacing the potting compound as newday77 mentioned. That's not an issue. I could get the proper potting compound and replace it, but I suspect the fault isn't in the compound, but that the spark unit is running way too hot and as such is stuffed or will be soon.  I just don't like these little metal boxes with unknown magic inside them and no real way of testing them.

So in essence, should I replace like for like as fizzlebottom mentioned or is there something better out there ?

Thanks guys

[RAFster122s]

Caferacer ? modified a plate for the dyna to fit the 650 and changed the ignition system to be dyna based eliminate the offending expensive parts.

[fizzlebottom]

Thanks for the replies.

Id like to replace both and start from a known good position but at $400 a pop that's quite an investment

Get them from Rick's Motorsports.

$400 is bananas. Get them both for just over half the price of one. Yes, $130 each is still a hefty price but that's just the platform you bought into.

There aren't really any other aftermarket solutions that would be more friendly to your wallet, or more reliable for everyday use. The move from points to transistorized ignition took out a huge pain point for a lot of people, especially now since proper condensors and points sets are getting harder and harder to find.

[scottly]

Should I be looking to repair what I have on the ignition side,

If I were you, I would do some more research into what is really going on. Are you getting spark on all 4 cylinders? If yes, is it happening at the right time? The pulse generators have a certain polarity, and if the leads are reversed, you will have spark, but at the wrong time. If you have spark on one pair of plugs but not the other, check the resistance of the pulse generator.

[robsbots]

Been feeling rough for a day or two (Man flu  ) so haven't achieved a lot since my last post but this is what I have so far.

I believe the plugs are connected to the correct terminal on the correct coils, and I think the spark generators are also connected correctly. At least the coil end.
I seem to be getting a reasonable spark at each plug, and I've checked compression on each cylinder. (Not fantastic, but well within spec according to the manual).
I assume, if the plugs are connected to the wrong coil or terminal on the coil, this would mean my timing would be 180 or +/-90 degs out depending on which terminals was incorrect ?

As I was investigating the wiring a couple of crimp connectors pulled off their wires so I'll go though and check all connections and work out what is original, whats been added, and make sure all connections are clean, well secured and correct.
Once I get my carb  kits and rebuild the carbs, that should cover compression and air/fuel mix. Got some new plugs to put in and I'll grab some new leads and caps, just to give everything the best chance. Then I'm left with timing and spark.

I'll hit Dynatech and see what they offer.  Hopefully my current spark units have enough sparks left in them to at least get the bike running. Then I can assess my position and choose my next move. New spark units, or a new ignition system.

Thanks very much for your help guys. I'll post an update when I get a bit further.

[fizzlebottom]

Dynatek doesn't list any directly compatible units for the SOHC CB650, but Webike does list a Dynatek-S setup as compatible for the CB650. The price for the full conversion looks like a whopping $650 vs the ignition plate & pickups alone at $300. Realistically, you will not reap any benefits from this conversion if the only thing(s) you currently have to replace are spark units. I'd consider it if I needed to replace everything in the ignition chain, but not before that. I also do not know what else might need to be modified to make this work.

https://japan.webike.net/products/1099727.html

https://japan.webike.net/products/24903912.html

[scottly]

I assume, if the plugs are connected to the wrong coil or terminal on the coil, this would mean my timing would be 180 or +/-90 degs out depending on which terminals was incorrect ?

If the spark plugs are connected to the wrong coil, the timing would indeed be 180* off, but the pulse generators are something different: if the polarity is incorrect, the timing will be off, but less than 180*. I don't recall how much, or if it's retarded or advanced.
Each pair of pulser wires has a band around one of the wires, which connects to a matching wire in the stock harness. Normally, the stock plugs prevent any mix-up, but when things have been modified it's easy to make a mistake. You might try testing with a timing strobe to see if the timing is at least in the ball park.

[robsbots]

OK. I'm moving forward a bit.
I was reading a thread on here about the spark units. Somebody cleaned out the potting and took some measurements and started to back engineer the unit. Anyway, both of my units buzz out at similar values across various ranges including Resistance, capacitance, and diode junctions. (Haven't figured out the internals yet, but I think there is a varister in there I think) I think the units may be ok and the fault is with the wiring, I can't see much more inside as the potting compound has changed from a soft consistency to a glass like finish with some numbers printed on it. I would love to get under there and see whats going on. I'll go though the wiring on the bike and check that's up to scratch then try again with nice clean carbs and if It fails to fire I'll grab some new spark units.  Then I can chip away at one of the old ones to see whats inside.

[Stev-o]

I have the Keihin carbs and have a rebuild kit on order or them.

What kits did you order?  Aftermarket kits have been known to cause tuning issues, been there.  Check what existing brass parts you have and if there are Keihin, clean and reuse them, if not source genuine jets.  Aftermarket gaskets should be fine to use.

[robsbots]

It's quite a new kit in there. As far as I know it hasn't run reliably on the parts that where in it, but I'm just going to use the bare minimum from my kits. Float bowl gasket, o-rings here and there. That sort of thing. The needle jet looks to be a different size in my kit so I've gone with the jets and needles that where in there. I have a range of main jets to tune the carbs if I need to, but other than that I'll stick with with what was there for now. If I get any problems I can swap parts out if needed, or get the real thing.