Topic: Crashed my bike. Cb650 engine no spark

[Honda550k]

Hi guys. So I crashed my bike about 2 weeks ago. Was leaning left when I hit a patch of dirt in the road from construction about a month ago. I had a separation in my left shoulder but I have now recovered completely. I've only started to look into working on it again. The bike for a majority of it is still fine. I do have a question. My bike cranks but does not spark. I have a question about the CDI unit from the cb650. How does one test the unit using a multimeter?  I've tried researching this topic here and in the cb650 website with no luck.

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[BomberMann650]

The test is probably "replace with a known working unit".
Check the connections to/from the coils and the plug wires.

[calj737]

First, glad you've come through the tumble mostly unscathed!

The initial diagnostic steps would be to confirm 12v at the key switch, to/from the KILL/RUN switch, then on to the CDI unit. Does your model of bike also have a Clutch Safety Switch? If so, confirm that has not been dislodged (usually wired to the clutch lever) from the tumble.

Are all dash lights functioning too? Neutral especially. Does the Neutral go out when you shift the bike (even not running) into 1st gear?

[Honda550k]

The test is probably "replace with a known working unit".
Check the connections to/from the coils and the plug wires.

I don't have a spare one. I've checked local ads with no luck. I've checked connections and all have continuity.

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[Honda550k]

First, glad you've come through the tumble mostly unscathed!

The initial diagnostic steps would be to confirm 12v at the key switch, to/from the KILL/RUN switch, then on to the CDI unit. Does your model of bike also have a Clutch Safety Switch? If so, confirm that has not been dislodged (usually wired to the clutch lever) from the tumble.

Are all dash lights functioning too? Neutral especially. Does the Neutral go out when you shift the bike (even not running) into 1st gear?

Thanks calj. I was very lucky. I had a friend following me from behind and said the bike flipped and almost landed on me. I've checked that the kill switch is working by continuity. All idiot lights work as they should. I totally looked over the clutch switch. I'll look at that when I get the chance. I left my bike at a buddy's house as the crash happened 30 sec from his place. I've read that the CDI on this bike overheats and melts. I did notice last time I saw my bike, the CDI had black goo on the inside. I forgot how it looked before. I'll update here when I get around to doing this. Ive just been doing some research. Thanks again.

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[eigenvector]

Don't know the year on your bike - but what you're calling a CDI (and what Honda calls a CDI for that matter) probably is really a spark unit and there are two of them.  Your bike doesn't have a true CDI.  I'm only lecturing you because it might make it easier for you to search on a test process.  if you actually have a CDI unit - ignore everything I've said.  You can't test a CDI box, only replace them.

That said - there are tests for spark units and it's not likely the CDI (ahem... Spark Unit) that's bad, more likely the voltage regulator/rectifier or the alternator.  Tons of people who have CB750 DOHC bikes have had to wrestle with this - I did.  Turns out my voltage regulator and alternator were marginal (go figure), and the connectors were corroded.

[Honda550k]

Don't know the year on your bike - but what you're calling a CDI (and what Honda calls a CDI for that matter) probably is really a spark unit and there are two of them.  Your bike doesn't have a true CDI.  I'm only lecturing you because it might make it easier for you to search on a test process.  if you actually have a CDI unit - ignore everything I've said.  You can't test a CDI box, only replace them.

That said - there are tests for spark units and it's not likely the CDI (ahem... Spark Unit) that's bad, more likely the voltage regulator/rectifier or the alternator.  Tons of people who have CB750 DOHC bikes have had to wrestle with this - I did.  Turns out my voltage regulator and alternator were marginal (go figure), and the connectors were corroded.

Thanks for the replay Eigen. I should've mentioned in the original post my bike is a 78 550 with a 79 650 motor and 76 750 carbs. Bit of a Frankenstein bike.

 I found out it wasn't a true CDI during my internet search but rather a spark unit. The 650 motor uses 2 spark units, one for each coils. Now that you got me thinking, there's no spark on any of the cylinders. I'll look into the regulator/rectifier. How would you test that unit? I don't have my bike at my house right now but I have a few spare 550 rectifiers. Do the 650 use the same unit? As for the alternator, correct me if I'm wrong. I thought the only purpose for that was to recharge the battery.

Obligatory pic.

Don't have an after the crash pic though.

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[SOHC4 Cafe Racer Fan]

I have 2 brand new CDI boxes from Rick's Motorsport Electrics.  If you are interested in buying both units, PM me.

[eigenvector]

Looks like they replaced the spark unit with a generic CDI unit
http://www.powersedge.com/oemparts/partsearch/honda  search for 30400-460-662 (your 1979 CB650 A spark unit)

don't know if the 550 unit will work, but if all you're doing is checking for spark - don't see how it would hurt.

The other side of that circuit is the pulse generator on the crankshaft - basically an electromagnet.  Again - I really doubt they're bad, there's not much to go bad on them.

Search around for testing the regulator and alternator - should get plenty of hits for the CB750 DOHC (1979 to 1983'ish) and while I don't promote the site - the CB750C forum has a pretty big collection of tests for the parts on that bike.  I don't recommend becoming a member - but that's my personal opinion only.

[bryanj]

rare for both to go at same time, more likely wiring damage from flip, reg rec would have no effect at all but low battery will

[BomberMann650]

If the ignition works on a flywheel magnet sensor (as hinted to already).  I wonder if the fall farked em up?  My friends suzuki atv has a known defect of that trigger falling off.  Could be a thing, who knows?

[calj737]

550K - Continuity alone won't tell you that you have power. So please confirm with a meter the actual voltage reading at the locations I mentioned  Continuity only confirms the "path" is in tact, not the "level".

[Honda550k]

I have 2 brand new CDI boxes from Rick's Motorsport Electrics.  If you are interested in buying both units, PM me.

I'll keep a tab and I'll let you know if it is the thing I need. Thanks man.

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[Honda550k]

Looks like they replaced the spark unit with a generic CDI unit
http://www.powersedge.com/oemparts/partsearch/honda  search for 30400-460-662 (your 1979 CB650 A spark unit)

don't know if the 550 unit will work, but if all you're doing is checking for spark - don't see how it would hurt.

The other side of that circuit is the pulse generator on the crankshaft - basically an electromagnet.  Again - I really doubt they're bad, there's not much to go bad on them.

Search around for testing the regulator and alternator - should get plenty of hits for the CB750 DOHC (1979 to 1983'ish) and while I don't promote the site - the CB750C forum has a pretty big collection of tests for the parts on that bike.  I don't recommend becoming a member - but that's my personal opinion only.

OK. Thanks Eigen. I'll look around for testing a regulator and alternator. I'll you guys updated once I get the chance to go back to my buddy's place and work on the bike. This day job keeps getting in the way.

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[Honda550k]

rare for both to go at same time, more likely wiring damage from flip, reg rec would have no effect at all but low battery will

Yeah. That's what I thought that both of them wouldn't go at the same time. I only did check the continuity of the wires though as mentioned I should've also looked at the voltage.

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[Honda550k]

If the ignition works on a flywheel magnet sensor (as hinted to already).  I wonder if the fall farked em up?  My friends suzuki atv has a known defect of that trigger falling off.  Could be a thing, who knows?

It's what I thought. But the engine didn't even get touched during the fall amazingly enough.

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[Honda550k]

550K - Continuity alone won't tell you that you have power. So please confirm with a meter the actual voltage reading at the locations I mentioned  Continuity only confirms the "path" is in tact, not the "level".

Thanks calj I'll check for voltage when I do get the chance.

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[DaveBarbier]

The Honda 650 manual is pretty detailed in tests. I'm sure you can find a manual online.

Alternatively, there are two other options that I know of for ignition on the 650. A C5 unit which is expensive but a really nice unit that comes with coils, plug wires, the whole shebang. Also, a PAMCO 750 unit can be adapted to fit in the 650 bosses. Just need a lathe or to move the PAMCO parts off the plate to the 650 plate.


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[SOHC4 Cafe Racer Fan]

I went with the C5 to avoid potential future issues with CDI.  That's why I have the 2 new ones (CDI boxes) available.

[CBGhia]

Also, a PAMCO 750 unit can be adapted to fit in the 650 bosses. Just need a lathe or to move the PAMCO parts off the plate to the 650 plate.

With all of the 650 swaps, we really need to revist with Pamco Pete about making a 650 version. 

Edit:  I sent him a PM asking about it.  Maybe he can help us out and give us an option that doesn't cost $500 bucks (C5).

[PlungerWaffle]

Have you checked to see if the plugs are actually sparking?

[DaveBarbier]

Also, a PAMCO 750 unit can be adapted to fit in the 650 bosses. Just need a lathe or to move the PAMCO parts off the plate to the 650 plate.

With all of the 650 swaps, we really need to revist with Pamco Pete about making a 650 version. 

Edit:  I sent him a PM asking about it.  Maybe he can help us out and give us an option that doesn't cost $500 bucks (C5).

True. Now I actually went with a C5 as well. Just got it in an hour ago . The PAMCO is much cheaper and all Pete would need to do would be to machine a new plate. Still, the 650 is much less popular than the other SOHC4.

[Honda550k]

Update***

So I checked for all the connections responsible for the ignition system. I found that one of the kill switch wires got cut during the accident. I jumped that cable and checked for spark. It's now sparking. All I have to do is repair that wire and pretty much replace the parts that was damaged during the fall.

Regarding the spark unit. I know these things like to go and overheat and melt the black goo. I'm thinking in the near future I may replace these with one from a Chevy cavalier. I've read people doing a replacement with those. It's a GM HEI 4pin part. It fixes the longer start during the colder days and apparently idles a lot smoother. Though my idle before the accident was fine.

I'll update more in here during my process to get back on the road.

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[eigenvector]

Hey, if that Chevy swap out works let us know - I might use it for my CB750 Limited

edit:  although it should be noted that it's hard to get an idle any smoother than what's on an inline 4.