1979 Honda CB650

If it's broken or just needs tweaked

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GeorgeSweety
Posts: 155
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Location: UK.

Re: 1979 Honda CB650

Postby GeorgeSweety » Mon Oct 02, 2017 1:50 am

Hi jaffy, did you remove, clean and lubricate the auto advancer behind the pulse generator plate, on the right side of the engine? The symptoms you describe sound like the bob weights may have stuck slightly open during your maiden voyage due to lack of maintenance. This is (should be :roll: ) an easy fix that costs nothing other than time. Scribe a line on your engine case and pulser plate before you remove it and realign the scribed line when you put the pulser plate back on to preserve your ignition timing. Remove your auto advancer, photograph it if needs be to help you rebuild it, the outer part with the bob weights will need to be removed from the inner shaft, this "WILL" be tight but it has to come off, lubrication here is vital to smooth operation. Take some really fine emery paper (I use 1200 grit) and lightly remove any rust from surfaces that move, lubricate sparingly with high melting point grease, assemble then check everything moves really freely. Replace on engine, hopefully start engine. :)

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Folsoml
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Location: North Florida

Re: 1979 Honda CB650

Postby Folsoml » Mon Oct 02, 2017 5:23 am

Check your pulse generator. Take a multimeter with you on your next ride (I would not go far :D ) and check it when it is hot as well. Often the pulse generator will go bad and short out only when it is hot. Then, when it cools down a little, it will go back to working again.
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jaffyrider
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Joined: Mon Feb 27, 2017 5:10 pm

Re: 1979 Honda CB650

Postby jaffyrider » Tue Oct 03, 2017 8:22 pm

Hello Folsoml and GeorgeSweety, and thank you both.

I'll certainly direct my attention to that side of the engine, since it looks like both of you honed in on that area. If either, or both, of these parts (the pulse generator and/or the auto advancer) are faulty or dirty would that affect both of the issues I am having? Both issues being the stalling out after riding for a bit, and the lack of engine response when I blip the throttle quickly when the bike is warming up. Or is the "blip issue" a totally separate thing?

Thanks again for the help. Looking forward to taking off the engine case on that side. That's one part of the bike I haven't really gotten to, and now this gives me a good reason to go for it.

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GeorgeSweety
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Location: UK.

Re: 1979 Honda CB650

Postby GeorgeSweety » Wed Oct 04, 2017 2:07 am

Hi Jaffy, I can only speak from experience as I'm not a mechanic, I had the same throttle blip problem with my bike and it was caused by the auto advance being dry and rusty. I'm presuming at the moment, that yours has not been looked at since before your bike was stored for numerous years, if ever! The symptoms you described sounded like your advancer had stuck in a certain position while under load, causing your ignition timing to be slightly out.
Folsoml's suggestion sounds equally logical but I have never come across a problem like that myself. It could be that Folsoml's solution may work, or mine, or a combination of both or neither :roll:
We have to start somewhere with the information we have and we have both opted for a solution that costs nothing but time to check. :D Please keep us updated as others reading this with a similar problem may find this useful.

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Folsoml
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Re: 1979 Honda CB650

Postby Folsoml » Wed Oct 04, 2017 5:30 am

GeorgeSweety wrote:Folsoml's suggestion sounds equally logical but I have never come across a problem like that myself.


I do have first hand experience with this, although it was on a 1982 CB750C. The pulsers are the same.
Have a problem with your CB650? Have a technical question? Click here!


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jaffyrider
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Joined: Mon Feb 27, 2017 5:10 pm

Re: 1979 Honda CB650

Postby jaffyrider » Wed Oct 04, 2017 8:05 am

You got it. I may have some time this weekend to check it out. I'll be sure to share the results!


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