Topic: Ignition Part help!!!

[Cam]

I'm so close but so far. So here's the back story.

My bike started running on only 2 cylinders and through some research I learned it was probably the Dyna S ignition the p.o installed. And we all know how expensive those are. Not likely for a college kid who is almost done with his build to swing. So I decided to try to go back to the old points system. The only problem is the Dyna comes with its own (pulser rotor thing I still don't know the exact terminology of this thing because I can't find them anywhere.) and I don't have the stock one. So after searching forever I found one on ebay that claimed it was a 78 but after getting it and comparing it seems to be a 79. The advance that came with it is a little larger and it doesn't sit in my 78 advance right.

So here's my questions. Does anyone have the part I need? I'm willing to purchase immediately. Will the 79 advance and rotor work on my bike if I replace the whole thing? (I don't think it will because the 79 came with a bolt and mine has the bolt coming out of the engine and just slips over it with a nut) but I thought I'd ask. I'm attaching a pictures of the part I need for a 78 cb750k along with two pictures of the parts I have. The 78 has the springs still on it the other is the larger 79 I think. Also pictured is the points plate I purchased because I want to confirm I was sent one that will work on my 78.

Thanks everyone.

[phil71]

Doesn't sound like you've actually tested the dyna. They're fairly simple, and don't easily fail. The 'pulser' you bought is for a factory honda electronic ignition, which your bike doesn't have. You need a spark advancer unit for points, and it appears you have it already. You seem to be in over your head, but I'd do proper testing of the dyna before you swap it out.

[Cam]

You seem to be in over your head

Clearly I'm in the dark about these systems or I wouldn't have posted about it. I posted for clarification and to learn about it. Thanks

[phil71]

Compare what you have with this pic. It looks as though you're missing the actual points cam. Again, I recommend really checking out that dyna.
Could just be something dumb.

[Cam]

Yes that's what I figured. I'm missing the points cam. (I didn't know what it was actually called.) The other advance was one I purchased on ebay and I only bought it for the points cam not knowing it was for an electronic ignition as you stated.

So my options are to find the points cam I need and go back to stock or diagnose the dyna. I just don't really know how to go about figuring out the dyna. If anyone can point me to a previous write up on diagnosing ignition issues I'd be happy to read it and go through the motions. I just can't seem to find anything about it, and as stated before I'm still learning these systems.

[phil71]

the thing to do would be first to have a look at the soldered areas with a magnifying glass. make sure there's no cracks around the solder points, or heavy oxidation.
THen, if you'd just have switched the blue and yellow wires around, you would see if the spark problem moves with it. If it does, the dyna is probably bad. if the same 2 wires are still not sparking, then you have a bad coil or plug cap etc..

[Xnavylfr]

http://www.hondachopper.com/garage/dyna_s_installation/dyna_s_installation.pdf

Try this short T/S for the DYNA before you throw it out, if it shows that it is GOOD ,then try this.  Swap the blue and yellow wires from the DYNA to the coils and also swap 1/4 plug wires to #2/3 cylinders and 2/3 wires to #1/4 plugs. If the problem changes to the other two cylinders, it is a good chance you have a coil going out.


Xnavylfr(CHUCK)

[scottly]

Doesn't sound like you've actually tested the dyna. They're fairly simple, and don't easily fail.

They fail quite often; every spring for the last 3 years the reports start coming in. The symptoms are usually dropping 2 cylinders as the bike gets hotter, while running OK when cold. The units involved appear to have been manufactured 5 or 6 years ago. Dyna has since redesigned the modules, but it's too soon to tell if the issue has been corrected. Most of the failed ignitions were outside the warranty period of one year, so there was no support from Dyna.   

[phil71]

ok, so a bad run? I have had 10 year old dynas that were still fine.  Either way, no point on jumping to the conclusion with zero testing.

[scottly]

Yeah, evidently a bad run. I've heard of 30+ year old Dynas that still work fine. The bad run has given all electronic ignitions a black eye...

[Cam]

Alright so let's assume I ended up with a rough production of a Dyna. Where can I find a points cam that I'm missing?

[Xnavylfr]

Will a points CAM from ANY CB750 work?? Or the complete advancer and cam??


Xnavylfr(CHUCK)

[Cam]

I have the stock advancer I think I'm just missing the cam because the Dyna comes with its own cam. As far as years I'm really not certain. I showed my advancer above in the pictures. Mine is the shorter one with the springs still attached.

[seanbarney41]

any cb750 points cam from ko to k8, fo to f3 will work fine

[phil71]

they're littering ebay, and cheap. But you'll be buying the whole advancer .. doesn't look like too many people pull the points cam off.
While you're waiting for fed-ex, test the dyna.