Topic: 1979 CB650.... She's ALIVE!!

[Chad]

So I've been looking for a pre-'78 CB750 or CB550 on CL for months and then I came across a deal for 2 '79 CB650's (both with good motors) for $300. One frame is a started bobber project. The other is stock.

At first I was kind of hesitant, because it seems like these bikes are looked at as the runt of the CB family, but the more I thought about, the more I liked it so I went ahead and bought them. Plus, I never really liked the idea of chopping an earlier CB550/750......but these bikes I can chop all I want with no feelings of remorse. 

According to the PO, the main motor was rebuilt within the last year and the other motor needs new rings, but it's a good motor. We'll see about all that. 

Here they are the day I got 'em home:

[Chad]

So here's my first question on this project...

When I got the bike, all of the electronics were off, so my first priority was to get it all hooked up and see what worked. I got it all hooked up last night except for one connector. Here is a pic of it from the wiring diagram:



The female connector is missing just leaving 4 wires. As you can see from the diagram, there are 2 blues and 2 yellows. My question is, how do I know which yellow/blue cable goes to the other yellow/blue cable on the male connector? Does it matter?

[onepieceatatime]

your pictures did not show up, so we are not sure what connector/wires you are talking about.

[Chad]

Ah. Well pics would help. Thanks for letting me know. I tried uploading them to my Google account, but that doesn't seem to work right. They should be there now.

Anyways.. all electrical has been hooked up and works great minus that one plug. After getting that plug sorted, my plan is to put the carbs back on (they've been cleaned, set the floats, etc.), change the oil, put in some gas and try any start her up.

So, anyone have any ideas on the electrical issue?

[pangloss]

It sure does matter..!!
I've just rewired my 650 motor .  Hopefully the cable coming from the engine ie the "sender will still have little white or blue tabs on the yellow cables and a white tab on one of the blue cables.

Go to cb650.com 

 http://www.myhonda650.com/images/cb650wiring.jpg

This is a great little Coloured diagram of the electrics

J

[Chad]

Thanks for the reply pangloss. Thankfully, the white tabs were still there so I got it hooked up. Don't know how I didn't notice those before. 

I'm almost ready to try and fire her up. I had some trouble getting the carbs on last night after cleaning them because the rubber boots were hard as a rock. I ended up boiling them in water for 10-20 mins. and the carbs slipped right on the bike. That was definitely the easiest attempt at putting carbs back on that I've ever had. I may start doing that every time now.



Made a gas tank for the test fire:

[Chad]

Good news and bad news:

The bad news first. I caught my bike on fire inside of my garage. ... Oh and, the bike was covered in gas.

And the good news. I tried starting it, and it fired right up. Sounds great!

Here's the story:

I went to town to pick up the last few things I needed for the bike. I was getting anxious and wanted to start it up today. Got the battery charged, hooked up my plastic bottle gas tank and....... the bowl overflows starting pissing gas. There was also gas coming out of the air intakes. I immediately unhooked the gas tank (or bottle I should say) and got ready to pull the carbs off. Then.. a little thought popped in my head that there was gas in the bike and I could try and start it. I got excited and totally forgot about all the gas that had just poured all over the bike. Tried to start it, and it started right up. Then.... FIRE. I ran and grabbed a hose and got the fire out before it did any damage.

I have some questions about setting the float height correctly, but I'm sure it's already been asked here before so I'll look around the site first. Love this place!

[pangloss]

I have found from experience that when a fuel/carburetor related conflagration is unexpectantly presented , a couple of flagons of fresh beer is a marvelous extinguisher when lightly shaken

[pangloss]

I have found from experience that when a fuel/carburetor related conflagration is unexpectantly presented , a couple of flagons of fresh beer is a marvelous extinguisher when lightly shaken

[Chad]

Ok. So after the fire, I went through the carbs again, put them back on, and tried starting again. Then, I got a backfire coming out of the carb intake. Any ideas on what would cause this? Here's a video of it happening. Thanks

<a href="http://www.youtube.com/v/P9gFKCYF-Mg?version=3&amp;amp;hl=en_US&amp;amp;rel=0" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">http://www.youtube.com/v/P9gFKCYF-Mg?version=3&amp;amp;hl=en_US&amp;amp;rel=0</a>

[Chad]

Anybody have any ideas on this? (bump)

[iron_worker]

The only thing I can think is the valves are adjusted too tight and it's spitting back through the intake valve and thus the carb. That or your timing is waaayyyy out somehow and it's firing on your intake stroke.

OR I guess your intakes could be hung up partially open. Guides are gummed up or something.

IW

[cb650]

Is it the "rebuilt" motor your starting?  Could be the cam timing is off.

[Chad]

The only thing I can think is the valves are adjusted too tight and it's spitting back through the intake valve and thus the carb. That or your timing is waaayyyy out somehow and it's firing on your intake stroke.

Adjusted the valves and timing today. The timing was way off. The pulser plate was turned about 25% to the left. (The window that you look through to see the timing marks was all the way to the left.) Whats weird is there were some marks that the PO made that it was lined up to so he must of done this on purpose. Is there some reason to have it like this?

Is it the "rebuilt" motor your starting?

Yes.

So, here's where I am now. I have set the valves, timing, and gone through the carbs yet again. Tried to fire it up and it did try, but couldn't get it to really do much. Also, still backfire out of the carbs. Here's another video. Any more ideas on what this could be?

And another question.... If you listen in the video, you can here the flasher relay continuously clicking. I don't have any rear turn signals for the bike. Would not having them hooked up cause electrical issues in the rest of the bike?

<a href="http://www.youtube.com/v/f3mhiShQ8g8?version=3&amp;amp;hl=en_US&amp;amp;rel=0" target="_blank" rel="noopener noreferrer" class="bbc_link bbc_flash_disabled new_win">http://www.youtube.com/v/f3mhiShQ8g8?version=3&amp;amp;hl=en_US&amp;amp;rel=0</a>

[scunny]

flasher relay shouldn't impact on starting.
have you staticly timed the ignition, it's a while since I've done it but you watch the lobe of the advance come equal with the wee magnet on the pulsar, and check your timing marks.
I will throw a wild one out here tho, can you turn yor advance mechanism to the advanced position , let it go and it snaps(not a violent snap) back into position.

[Chad]

flasher relay shouldn't impact on starting.
have you staticly timed the ignition, it's a while since I've done it but you watch the lobe of the advance come equal with the wee magnet on the pulsar, and check your timing marks.
I will throw a wild one out here tho, can you turn yor advance mechanism to the advanced position , let it go and it snaps(not a violent snap) back into position.

I did statically time the ignition (according to the manual). The advance mechanism does snap back if I turn it.

[scunny]

bugger, shall have to rack the brain a bit more then.
lets do small steps.ignition timing is ok, then the cam timing must be out. edit will go back to vid now it's working.

[scunny]

it's not a regular backfire thru the carb. just unburnt charge being ignited. do you have the air box and put that on, it might need to have some restriction before the carbs. my 650 hates an open passage to the carbs.
just something to try

[iron_worker]

Not having the air box shouldn't keep it from starting although it may run a bit rough when it does.

Did you do any head work when you rebuilt the engine? Guides? Lap the valve seats?

I would also keep looking at timing. Is it possible you have the 1-4 and 2-3 coil backwards somehow? Points wires mixed up? Coil wires mixed up?

IW

[23tbucket]

Backfiring back through the intake is almost always due to a lean fuel/air mixture. It definitely can be an ignition problem, valves, camshaft wear/timing, etc., but from my thirty plus years of engine repairs and troubleshooting it is usually a carb or fuel supply issue. I'd look at your carbs firstly.....

Hope this helps; Clifford

[Chad]

Figured it out!

So a few posts back, I asked about the wires coming from the pulser. (the 2 yellow and two blue). The previous owner had chopped the connector off so there was just bare wire. The wiring harness showed that there were white stripes on one of the blue wires and one of the yellow wires, the problem was, the blue wires had been cut too short and the white stripe was gone. There was a piece of white tape on one of them so I assumed, that must be the one that had the white stripe.... nope. Switched the two blue wires and she fired right up. Starts immediately every time and idles great.

Next question... the bike isn't rideable. Needs a lot. Tires, lights, new tank, chain, etc.

Is there anyway for me to make sure the engine is in good running condition without taking it out on the road and actually driving it? Before I strip in down the the frame and start on cosmetics, I want to be sure that all of the engine work is done and when i get it back together it will be ready to ride.

By the way, thank you guys for all the help. I'm new to working on bikes and it would be impossible for me to learn as much as I have with out the help of the people on this forum.

[cb650]

Compression and oil pressure check but nothing beats taking it out.   Might drop the pan and see what it looks like inside.  Plan on a some leaks.  Number and severity of leaks depends on the previous put together.