Hello from a new member. 1979 Cb650 with a couple of issues.

If it's broken or just needs tweaked

Moderators: Volker_P, tidd650

Barneycanoe
Posts: 6
Joined: Wed Jul 18, 2018 11:27 am
Location: Toronto, ON

Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Barneycanoe » Fri Jul 20, 2018 1:48 pm

Hello all, I have a 1979 CB650 which, not coincidentally, was my first bike as a skinny 20-year-old. This particular bike I purchased in 2011, fixed up a few things, painted the tank, and sold to a young couple. It had about 9000 miles on it. A friend had made me a new leather seat for it.

Browsing Kijiji one day, I did a double-take when I recognized that old bike and the seat, now being sold for parts. I went and took a look and it was in sorry shape. Had been left outside by the looks of it for the past seven years. Apart from four broken turn signals it seemed complete and nothing was bent where it shouldn't have been. It had no ownership or keys. Got it for $360.00 Imagine my surprise when I obtained the used vehicle information package and found it was still registered in my name!

I've always worked on my own bikes. This site has been a huge help in assisting me with the peculiarities of the 650s.

So far I've
-Replaced the ignition
-Replaced front master cylinder and caliper
-replaced both tires
-replaced sprockets and chain
-replaced the turn signals
-new fork oil
-oil change and filter
-cleaned the tank
-cleaned the carbs (without pulling the slow jets) They were not in terrible shape
-disassembled the speedo and tach to straighten the needles during which I broke the tach needle :(
-vacuum-synched the carbs
-adjusted the valves
-checked the timing
-checked the coils and that all plugs are getting a park
-adjusted the floats (only 1, actually)

So here are my issues:

Minor- two-wire aftermarket rear turn signals are turning on with ignition. Everything wired correctly so not sure how this is happening. Only the three-wire fronts are supposed to be running lights.

Major- Cylinders number three and four are not heating up the pipes. Plugs on one and two are textbook tan. Three is a bit better than four's plug which has a bit of black easily wiped-off carbon but doesn't really look used. This was the carb than needed the float adjusted as it was filling too high. I also have a stumbling around 6,500-7000k rpm now and it won't rev higher. Somewhere along the way I had it revving strongly to 8,000 so I'm not sure where I went backwards. I do have a new air filter on order but the old, probably original one doesn't look terrible.

Three's pipe gets hotter than four but not as hot as 1 and 2. Occasionally there has been a bit of white smoke out of the right side muffler.

11,000 miles seems a bit newish for ring problems. At this point all I can think of is to re-check the valves but I did them very carefully with my wife checking things as I went along.

Any suggestions would be welcomed.
Dave, Toronto, Canada

Barneycanoe
Posts: 6
Joined: Wed Jul 18, 2018 11:27 am
Location: Toronto, ON

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Barneycanoe » Fri Jul 20, 2018 1:51 pm

ps, I am getting some popping from the right hand pipe on deceleration

Dave

User avatar
Volker_P
Posts: 5330
Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Volker_P » Thu Jul 26, 2018 3:09 am

Welcome here! :D

Interesting reunion story.

To your problems:

The plug cables from left coil go to cylinders 1+4, from right coil to 2+3. You would not be the first one who mixes them up :wink:
Also try to swap plugs just to be sure.
1+2 are closest to the fuel inlet of the carbs, 3 is a bit further and it is the longest path to 4. So consider a fuel issue, too.

If you did that:
Barneycanoe wrote:...
-vacuum-synched the carbs
...

before you fixed other carb and engine related stuff and you had to adjust a lot your carbs might be heavily out of sync now. :roll:
Check if all four sliders open simultaneously from completely closed to the same, small gap when you turn in the idle adjustment knob.
Probably you need to take the carbs out again to do so, so check out for other possible issues before.

Good luck!
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

Barneycanoe
Posts: 6
Joined: Wed Jul 18, 2018 11:27 am
Location: Toronto, ON

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Barneycanoe » Thu Jul 26, 2018 9:54 am

Thank you. Plug wires are on the proper coils. Here are a couple of pics of my plugs taken yesterday.
20180725_173458.jpg
20180725_173458.jpg (144.43 KiB) Viewed 844 times
20180725_173451.jpg
20180725_173451.jpg (136.97 KiB) Viewed 844 times


I did not take the carbs apart when I cleaned. I hear what you are saying about the distance of the carbs from the fuel hose, and three seems a bit hotter than four. But all carb bowls fill up with no issues. Thing is, after first carb clean I had the bike up to 8k rpm with no bogging so I am trying to figure out what I could have done that has caused this.

AF screws were originally 4 1/4 turns out. I have them at about 3 turns out now.

Dave

User avatar
Folsoml
Posts: 1631
Joined: Sat Apr 07, 2012 9:02 pm
Location: North Florida

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Folsoml » Thu Jul 26, 2018 12:03 pm

You say you cleaned the carbs, but did not take them apart? It's tough to get them really clean while they are still together. There are a lot of internal passages that can get plugged. Also, if the fuel tank has not been thoroughly cleaned, there may have been debris in the tank that came out and is now in the carb bank somewhere.
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,

Barneycanoe
Posts: 6
Joined: Wed Jul 18, 2018 11:27 am
Location: Toronto, ON

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Barneycanoe » Thu Jul 26, 2018 12:55 pm

I did thoroughly clean the fuel tank, fuel strainer still intact and clean.

Dave

cb650
Posts: 2949
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
Contact:

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby cb650 » Thu Jul 26, 2018 1:27 pm

most likely both jets and emulsion tubes need cleaned in all the carbs.
Did you clean the tank out?!?!?!?!

Barneycanoe
Posts: 6
Joined: Wed Jul 18, 2018 11:27 am
Location: Toronto, ON

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Barneycanoe » Thu Jul 26, 2018 3:41 pm

Going to pull the slow jets and have a look. The carbs were actually not as bad as I thought they would be when I got into them (twice now).

User avatar
Volker_P
Posts: 5330
Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Volker_P » Fri Jul 27, 2018 1:17 am

Thanks for the helpful pictures.
Your plugs look good. 3+4 seem to have fired a bit, too, but never got hot. I would expect 3+4 look wet and black if they had fuel but no ignition or compression. Therefore my guess is a fuel/carb issue here.
Forget about the idle jets and passages for now, they should play no role for riding rpm's.
At least not directly. :roll:
But as I already mentioned: if you tried a vacuum sync with a clogged idle system you probably had to adjust a lot and now slider positions might be poor.
And that could impact riding rpm's, too!

For now I would try the following first:
Open the petcock and then the release screw at the bottom of carb #1. Use a jar to catch the fuel and watch for while.
Then close #1 and repeat for #4 and compare the fuel flow. If you can notice a difference, #2 and #3 are interesting, too.
I understand that #4 floater bowl has fuel but it is also a question of refill.
And -as you said- headers #3 and #4 are not just cold. Maybe 3+4 quit after a short time or fire only occasionally after some time. This would match the look of your 3+4 plugs.

From your above list:
-adjusted the floats (only 1, actually)

You remember which one?
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

Barneycanoe
Posts: 6
Joined: Wed Jul 18, 2018 11:27 am
Location: Toronto, ON

Re: Hello from a new member. 1979 Cb650 with a couple of issues.

Postby Barneycanoe » Fri Jul 27, 2018 10:04 am

SUCCESS! It was not the pilot jets, they were fine. It was a blocked vent line between carbs three and four. Wow! Like new bike now. Guess I'll have to redo the carb sync and still have to figure out the air fuel screws. Idles really high on choke, too.

Thanks for all your suggestions I had a feeling it would come down to the carbs.

Dave


Return to “Technical Discussion”

Who is online

Users browsing this forum: Bing [Bot], Google [Bot] and 30 guests