1979 Honda CB650

If it's broken or just needs tweaked

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jaffyrider
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1979 Honda CB650

Postby jaffyrider » Tue Feb 28, 2017 8:50 pm

Hello everybody,

I'm glad to be part of this forum, so allow me to give a bit of a background.

I've just purchased my first bike and it's a 1979 Honda CB650. I got it off Craigslist and before that the seller got it from a storage facility. The seller seemed to think it had been sitting for over 10 years but he wasn't entirely sure. The tires held air when he pumped them up and the engine turned over, and it had keys and the original manual and tool set.

I realize this is a lot of work, but I'm going to use this opportunity as a learning experience. I've put in a new battery and all of the lights and blinkers seem to work but not the horn. I've taken the gas tank off and I plan on cleaning that with some vinegar. I also have some new oil, an oil filter, air filter, and spark plugs that I will install shortly before I try to sincerely start the thing up.

However, the biggest issue is cleaning the carbs and that is hopefully where I can get some guidance from the people here. I've ordered the Clymers manual which has a section on carb maintenance. Also, I printed part of the Honda CB650 manual dealing with the carbs from the following website; http://cosky0.tripod.com/, but the picture quality isn't the best from the manual. I've watched a few YouTube videos, stocked up on compressed air and carb cleaner, and I think I have the time and patience. But, before I take the carbs off and attempt this for the first time, I'm wondering if anyone on here has some other resources or advice they could offer me that may help with this project?

Any advice at all would be appreciated. Thanks in advance.

cb650
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Re: 1979 Honda CB650

Postby cb650 » Wed Mar 01, 2017 6:36 am

Do you plan on separating the carbs? Should be to change the O rings. Not a easy task for a beginner.
Did you clean the tank out?!?!?!?!

jaffyrider
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Re: 1979 Honda CB650

Postby jaffyrider » Wed Mar 01, 2017 10:30 am

Hello,

No I wasn't planning on separating the carbs. I'm guessing you would suggest that so I can change those o-rings you mentioned? Any other benefit to separating the carbs?

Thanks

cb650
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Re: 1979 Honda CB650

Postby cb650 » Wed Mar 01, 2017 3:43 pm

you can soak them in stronger cleaner as then you dont have to worry about damaging the o rings.
Did you clean the tank out?!?!?!?!

madmax
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Re: 1979 Honda CB650

Postby madmax » Mon Mar 06, 2017 2:51 am

Full rebuild - I followed these instructions, worked perfectly. 650 parts hard to find so don't break/lose anything. Was first time I ever did anything like this, wasn't as hard as I thought it would be.

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

Re: 1979 Honda CB650

Postby jaffyrider » Mon Mar 06, 2017 3:22 pm

Hello,

Great, thanks everybody.

Madmax - you followed the instructions to the link I posted (cosky tripod) or you followed the Clymer's manual?

I've started cleaning the carbs and it's going pretty well. As you all may know, the slow jets are pressed into place so they don't come out. What's the best way to clean them. Just shoot carb cleaner in there and then follow that with some compressed air? Excuse my ignorance, but where do the slow jets go; i.e. where am I shooting carb cleaner and blowing compressed air?

Also, I'm cleaning the tank so I took the petcock off. Is there a gas filter in the tank somewhere, or should there be? There's nothing on the petcock except the valve part and a plastic straw. However, I've seen a couple blown-out diagrams where a filter is shown.

Thanks for the help.

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Folsoml
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Re: 1979 Honda CB650

Postby Folsoml » Tue Mar 07, 2017 12:23 pm

jaffyrider wrote:
Also, I'm cleaning the tank so I took the petcock off. Is there a gas filter in the tank somewhere, or should there be? There's nothing on the petcock except the valve part and a plastic straw. However, I've seen a couple blown-out diagrams where a filter is shown.



The filter usually stays in the bunghole when you remove the petcock. It's not easy to get out. I'll usually find a bolt that just barely screws into it and use that to pull it out.
Have a problem with your CB650? Have a technical question? Click here!


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jaffyrider
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Re: 1979 Honda CB650

Postby jaffyrider » Thu Mar 09, 2017 10:08 pm

Great. Thanks again.

I've read in a couple places that it's a good idea to "bench synch" the carbs after cleaning them. Am I supposed to do this with these carbs from a 1979 Honda CB650?

Thanks

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tario
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Re: 1979 Honda CB650

Postby tario » Fri Mar 10, 2017 1:49 pm

If you bench sync them you have to get vacuum gauges and properly sync them afterwards. I'd just leave them alone at this point. They might be adjusted for any less than perfect gaskets and seals. If you rebuilt the top end with new gaskets/rings and everything was working perfectly I'd say a bench sync would be a good option. When the bike is ready to ride I would look into a vacuum sync just to help the bike run better. I usually do all the free stuff first though.

The pressed in jets can be pulled out. I'd toss a good 5-10 wraps of electrical tape on your plier jaws then try to pull them out without crushing them. (A few light scratches on the outside won't ruin them) Then you can soak them in ALL THE CHEMICALS. Any dirt in your jets will cause constant and immediate problems with the fuel mixture. Cleaning everything else mostly stops you from clogging your jets as quickly.
1979 cb650
1980 cb650

jaffyrider
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Re: 1979 Honda CB650

Postby jaffyrider » Wed Mar 15, 2017 4:49 pm

Hello again everyone,

So over the weekend I thoroughly cleaned the gas tank and the carbs. I didn't separate the carbs from each other, but I cleaned out each one individually. Then I put the tank (with new in-line filter) and the carbs back on the bike. I changed the oil, put in a new air filter, and changed the plugs and was finally ready to try to fire her up for the first time.

So I made sure the bike was in neutral, put the switch to "run", and hit the red start button.....and nothing happened. By nothing happened I mean I hit the start button, and I didn't hear anything and the engine wasn't turning over (no noise at all).

The main fuse looks in good shape, the bike was in neutral, and the battery was fully charged.

Any advice/tips on where to start on tracking this problem down? Could it be the start button, solenoid, starter motor, bad wiring, etc, ...how do I tell?

Thanks again

jaffyrider
Posts: 13
Joined: Mon Feb 27, 2017 5:10 pm

Re: 1979 Honda CB650

Postby jaffyrider » Wed Mar 15, 2017 4:51 pm

Also thanks Folsom and Tario, I was able to pull out those slow jets and found that filter in the gas tank.

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Folsoml
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Re: 1979 Honda CB650

Postby Folsoml » Thu Mar 16, 2017 8:36 am

Did your bike have power when you turned the key switch? If so, did you also try pulling in the clutch? If the answer is yes to both questions, try jumping across the two bolts on the starter solenoid (touch a screwdriver or something to both bolts at the same time). It will spark, so don't surprised. If the starter turns when you do this, your problem may be a bad solenoid.

Have you gone through your entire wiring harness and cleaned every contact? This is something it probably needs anyway. Unplug every plug and make sure the connections are good and clean. Often you will find broken wires or other issues while you are doing this.
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 » Thu Mar 16, 2017 4:59 pm

Yes, my bike has power when I turn the key. The blinkers, rear light, and the headlight work, and the lights on console light up including the green neutral light. No, I did not pull in the clutch lever when I tried starting the engine. I feel kinda silly that I didn't try that now, but it had been a long day. That's what you mean by "pulling in the clutch" right? Am I supposed to do that when I start the bike?

Okay, I will try jumping the solenoid as described. And I have not gone over the entire wiring harness, but you're right that is something that should probably be done anyways.

Once again, thanks for the help.

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Folsoml
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Re: 1979 Honda CB650

Postby Folsoml » Thu Mar 16, 2017 5:44 pm

jaffyrider wrote:No, I did not pull in the clutch lever when I tried starting the engine. I feel kinda silly that I didn't try that now, but it had been a long day. That's what you mean by "pulling in the clutch" right? Am I supposed to do that when I start the bike?



Yes, that's what I meant. It should start without doing it when the bike is in neutral, but there may be a problem with the neutral switch. I've had bikes that did that.
Have a problem with your CB650? Have a technical question? Click here!


My Current Bikes: 2005 HD FLHTCUI Electra Glide Ultra Classic, 2007 Yamaha Vino,

jaffyrider
Posts: 13
Joined: Mon Feb 27, 2017 5:10 pm

Re: 1979 Honda CB650

Postby jaffyrider » Sun Oct 01, 2017 6:35 pm

Hello everybody,

It's been awhile since I last posted. Sorry for falling off the radar, but I've been busy dealing with the logistical nightmare of getting this old (and untitled) bike registered and insured in a very picky and stringent state (Massachusetts). Anyways, it's all legal. Hurray! So to celebrate I took it out today for a nice little ride because I know we're not going to be getting very many more warm, sunny days up here in the Northeast. And well.....the bike broke down.

So here are the symptoms. The bike starts up and can idle at around 1200 rpm. However, I've noticed in the driveway that when I "blip" the throttle hard, the engine doesn't respond too well. That is, the RPM's don't shoot up accordingly. The engine seems to hesitate and sputter when the throttle is turned wide open very quickly. But, when I turn the throttle gradually, the RPM's will go up gradually. So it's kind of like I can sneak up on it, and increase the throttle gradually, but if I do it too quickly it will want to die out. So I had noticed this in the driveway, but figured I'd take it for a ride anyways. It was going great for about 15 miles, but then it just lost power and stalled and I coasted to a stop. It felt like I ran out of gas. I waited a bit, turned it back on and tried to get home, but it stalled again. It did this once more before I was able to ride it home without stalling out; but it was a rough ride. It felt like I was on the brink of losing power most of the time. Now it's able to idle in the driveway, but again it doesn't like it when the throttle is turned real fast.

So, I have cleaned the carbs out thoroughly once. Also, when I was getting some new tires put on it, I had the guys there take a look at the carbs and they also said they were cleaned out pretty well, but they put in some new float needles in because I guess the old ones weren't seating correctly. I also put in a new accelerator pump because the old one was all rigid. Now, my first inclination to this problem is that it's the carbs; like some of the jets are still gummed up. But they've been cleaned! Once by me, and another time by a real, bona fide, shop mechanic.

So, is it something simple (hopefully) like a vacuum leak, or a dirty fuel line? Or do you think I have to pull the carbs again? Or is it something internal in the engine. Maybe, after it heats up I'm losing compression, because something is expanding more than it should be? Is it two problems (the unresponsive throttle blip problem and the stalling and losing power problem).

I appreciate any advice/suggestions. Just a novice bike rider/backyard mechanic here who fell in love with a beat up '79 Honda CB650. She looks real nice, but so far the ride has been anything but smooth.


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