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Author Topic: '81 CB650C 500 mile report  (Read 853 times)

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Offline fmctm1sw

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'81 CB650C 500 mile report
« on: September 24, 2012, 05:17:56 PM »
Bike starts right up every time and hasn't left me anywhere (save the time I ran it out of gas).  I got an oil leak at the top end.  I initially thought it was the typical oil passage o-ring but it's higher on the head.  I ordered a new valve cover gasket since I can see signs of some kind of sealant around the valve cover.  I also have a leak lower.  Looks to be coming out from the sprocket cover.  I'll take a look when I get my gasket.  I also ordered a new air filter to see if that solves my 70MPH limit bogging issue.  I really like the bike, it's grown on me.



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Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline cb650

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Re: '81 CB650C 500 mile report
« Reply #1 on: September 24, 2012, 05:28:27 PM »
Cam covers and rocker shafts sometimes leak.     Did you try running with the filter cover off?  It sometimes helps the bogging issue.
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18 grand and 18 miles dont make you a biker

Offline BrianScb650c

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Re: '81 CB650C 500 mile report
« Reply #2 on: September 24, 2012, 06:08:23 PM »
I had the same bogging problem when I first got my '81 cb650c. couldn't get it passed 75mph unless I was going downhill for a while, even after changing to a K&N air filter. I later put new NGK iridium plugs, wires, and caps. I now top out the speedometer whenever the need for speed arrives. With these bikes it also helps to keep the bike in each gear until the higher rpms before shifting. Most of the power comes from the top of the power band(7-9k rpms).

Good luck!
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Offline fmctm1sw

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Re: '81 CB650C 500 mile report
« Reply #3 on: September 24, 2012, 06:41:23 PM »
I've had the cover off before, it didn't seem to make any difference.  That was a while back when I was first working on it though so maybe I missed something.  My spark looked pretty good but you never know I guess...
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Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline BrianScb650c

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Re: '81 CB650C 500 mile report
« Reply #4 on: September 24, 2012, 06:48:21 PM »
Quote from: fmctm1sw on September 24, 2012, 06:41:23 PM
I've had the cover off before, it didn't seem to make any difference.  That was a while back when I was first working on it though so maybe I missed something.  My spark looked pretty good but you never know I guess...

Those old cable have a lot of resistance.
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Offline fmctm1sw

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Re: '81 CB650C 500 mile report
« Reply #5 on: September 25, 2012, 05:25:46 PM »
Ok, at least one leak spot verified at the valve cover.  I can see it, tiny little bubbles right at the gasket over cylinder #1.  I still think there may be one under the sprocket cover too, hopefully just the oil pressure switch.  Then I'll get to the rideability issues.  Brian, I've forgotten already, are the coils leads replaceable?
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Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline BrianScb650c

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Re: '81 CB650C 500 mile report
« Reply #6 on: September 25, 2012, 06:18:15 PM »
Yes they are replaceable.  They easily unscrew and then just pull out at the coil. Just remember which goes to which cylinder. Just swap the plastic hardware over to the new wires and push them in and then tighten the screw portion. It will make sense when you look at it.

 You can get high performance cables with NGK plug caps already installed on ebay for about $40 shipped.
These are what I got. Paired with the NGK iridium plugs made my bike run SO much better.
http://www.ebay.com/itm/Honda-CB650-Spark-Plug-Wires-Black-SOHC-CB-650-/390473935403?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item5aea0f6a2b

I'm sure even just replacing the old wires and caps with most any kind new would make a good difference though.
« Last Edit: September 25, 2012, 06:21:08 PM by BrianScb650c »
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