New to me 1981 CB650C. Now what?

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F16Viper68

New to me 1981 CB650C. Now what?

Postby F16Viper68 » Wed Oct 05, 2011 8:55 pm

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I recently picked up this basket case. I was told it hasn't run in a four to five years but it was running like a champ when the previous owner stopped riding it due to a charging issue. From what I've been reading this is a very common occurance on this model. :lol: I'll work on that later.

I'm wondering where do I start? The gas tank is a mess inside and out. I think it was internally sealed and the sealer is coming off and of course there's rust under the flaking sealer. I've been reading a lot of that subject and will try to clean it up with POR-15.

How do I hand crank this motor to make sure the pistons aren't frozen?

I'm open to advice on the steps necessary to getting this bike running again.

Dave...

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Volker_P
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Re: New to me 1981 CB650C. Now what?

Postby Volker_P » Thu Oct 06, 2011 1:22 am

Welcome here, Dave! :D

Looks not too bad, maybe just needs a bit cleaning.

Good idea to start with the tank, a clean tank is a prerequisite to avoid annoying carb issues.

For charging, start with cleaning all charging related contacts and plugs and measure rotor resistance between sliprings. Should be 4-10Ohms.

For turning the engine, remove the right side crankshaft cover. There you can turn the engine with a 24mm socket. If it should be stuck, don't use force as this may smash the grooves in the pistons for the rings. Instead try soaking with oil or open the engine. If you see oil or obvious oil residuals at the sides of the engine at the head gasket level, consider this engine probably having the typical oil leak and you may like to remove the head anyway before any cranking efforts. I'd also imagine that the valve stem seals are hard and leaky after that time. Check out if you see oil or wet soot on the valve stems after removal of exhaust and carbs.

As you already have the right side engine cover off, remove the complete advancer mechanism for cleaning and lubrication. Especially if you found brown dust in that cover. Pulser gap should be in the order of 0.4-0.6mm.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

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Ouch
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Re: New to me 1981 CB650C. Now what?

Postby Ouch » Thu Oct 06, 2011 7:07 am

Welcome!!!!!!!
if you find the pistons are stuck...go to AutoZone and buy PB BLASTER and spray that in them...let them soak for a few hours and that will do the trick ......POR-15 is a great tank cleaner and sealer and ather way to clean the tank out cheap is "THE WORKS" toilet clear that can be purchased at walmart....pour a couple of bottles in there and alternate bewteen letting sit and moving it around....pour it out and flush it with a mixture of bakingsoda and water ( base for the acid) coat it or fill it with gas to avoid flash rusting! Congrats on the bike and best of luck

F16Viper68

Re: New to me 1981 CB650C. Now what?

Postby F16Viper68 » Thu Oct 06, 2011 1:56 pm

Volker_P wrote:Welcome here, Dave! :D

Looks not too bad, maybe just needs a bit cleaning.

Good idea to start with the tank, a clean tank is a prerequisite to avoid annoying carb issues.

For charging, start with cleaning all charging related contacts and plugs and measure rotor resistance between sliprings. Should be 4-10Ohms.

For turning the engine, remove the right side crankshaft cover. There you can turn the engine with a 24mm socket. If it should be stuck, don't use force as this may smash the grooves in the pistons for the rings. Instead try soaking with oil or open the engine. If you see oil or obvious oil residuals at the sides of the engine at the head gasket level, consider this engine probably having the typical oil leak and you may like to remove the head anyway before any cranking efforts. I'd also imagine that the valve stem seals are hard and leaky after that time. Check out if you see oil or wet soot on the valve stems after removal of exhaust and carbs.

As you already have the right side engine cover off, remove the complete advancer mechanism for cleaning and lubrication. Especially if you found brown dust in that cover. Pulser gap should be in the order of 0.4-0.6mm.


Yeah this little guy is going to need a lot of cleaning but you're right, it will look a lot better once I get it cleaned up and the tank/side panels painted.

First priority is to get it running. I need to see if it's even worth putting money into the cosmetics. Although I did just commit to buying a bunch of stuff someone parting out a bike on this forum. :)

Last night I pulled the plugs (running rich but dry) and the pistons looked ok. Same deal with the valve covers. Really clean. Which makes sense since the bike does only have 9k miles on it.

I pulled the right side crank cover and was easily able to hand crank the motor over. It has compression but no binding or scary noises. You're right there was brown dust inside the cover. Thanks for explaining that mystery. I'll look in the service manual to see how clean/lubricate/adjust the advancer. Whatever that is. :lol: Learning, learning, learn. My V-Strom is a whole different animal.

I'm going to pull the carb rack and was wondering should I rebuild them or simply clean them out with carb cleaner? If I do go the rebuild kit route, should I remove/replace the accelerator pumps at the same time?

Thanks for all the advice. I'm learning a lot for reading everyone's posts.

Dave...

F16Viper68

Re: New to me 1981 CB650C. Now what?

Postby F16Viper68 » Thu Oct 06, 2011 2:10 pm

Ouch wrote:Welcome!!!!!!!
if you find the pistons are stuck...go to AutoZone and buy PB BLASTER and spray that in them...let them soak for a few hours and that will do the trick ......POR-15 is a great tank cleaner and sealer and ather way to clean the tank out cheap is "THE WORKS" toilet clear that can be purchased at walmart....pour a couple of bottles in there and alternate bewteen letting sit and moving it around....pour it out and flush it with a mixture of bakingsoda and water ( base for the acid) coat it or fill it with gas to avoid flash rusting! Congrats on the bike and best of luck


I was reading about the "THE WORKS" yesterday and was thinking about trying that prior to POR-15. There's some sort of film/paint/sealer that's flaking off insides of the tank. I think it was sealed by someone a long time ago and the sealer is coming loose. Problem is under the sealer is a layer of rust. I'm not sure if I can fix this tank without sending it to a professional. We'll see I guess.

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Dave...

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Volker_P
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Re: New to me 1981 CB650C. Now what?

Postby Volker_P » Fri Oct 07, 2011 1:04 am

With a only 9k engine (I feared something like that from the dirt pattern...) still turning smoothly and having compression, this bike is certainly worth to be reanimated.
You may do a coarse compression test by turning the engine with the 24mm socket forward (as you already did) and feel for four equal compressions during two turns. Nevertheless a bike standing that long may have sticky rings that get free again after the first time getting really hot.

For that tank, I'd try to get a replacement. Guess getting all rust out in this case means the remaining thing is a sieve. :lol:

For the carbs, have a look inside and decide if you need parts. However if you have to separate them, better replace the small O-rings of the conneting tubes. Moreover have a look at the T-vents between the two outer carbs for cracks. This is quite typical and may cause trouble. They are still available but really expensive and a cheap workaround seem to be T-vents for aquarium air equipment.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

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Ouch
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Re: New to me 1981 CB650C. Now what?

Postby Ouch » Fri Oct 07, 2011 8:17 am

Dave...did the bike sit out side during its years down. (Mine did and the carbs were nasty!!!!) If you do have to go the path of tearing the carbs down...document document document! Meaning take notes and lots of pics, lots of questions gets asked about putting it back together because (including my self) someone tore it down and didn't pay attention....special note...keep all parts per carbs DO NOT INNER MIX PARTS PER CARB!! Simple green and (just learned this one) pinesol works great for cleaning carbs. If you can make a cheap soda blaster, works wonders also ( http://forums.sohc4.net/index.php?topic=61848.66 or http://www.aircooledtech.com/tools-on-t ... a_blaster/ )!

Best of luck!

F16Viper68

Re: New to me 1981 CB650C. Now what?

Postby F16Viper68 » Mon Oct 10, 2011 10:35 pm

Ouch wrote:Dave...did the bike sit out side during its years down. (Mine did and the carbs were nasty!!!!) If you do have to go the path of tearing the carbs down...document document document! Meaning take notes and lots of pics, lots of questions gets asked about putting it back together because (including my self) someone tore it down and didn't pay attention....special note...keep all parts per carbs DO NOT INNER MIX PARTS PER CARB!! Simple green and (just learned this one) pinesol works great for cleaning carbs. If you can make a cheap soda blaster, works wonders also ( http://forums.sohc4.net/index.php?topic=61848.66 or http://www.aircooledtech.com/tools-on-t ... a_blaster/ )!

Best of luck!


It spent a lot of time outside but I don't think it was recently (past 10 years). I was able to remove the float bowls, clean out the jets, and reassemble. After fighting a bad start relay (cleaned/repaired) and building a temp gas tank, I was able to get the bike running for the first time since 2003. It won't stay running unless fully choked. Probably missed something when I was cleaning the jets. I'll be buying rebuild kits and an accelerator pump soon.

Thanks for the links to the soda blasters. I'll surely be building one in the near future.

Dave...

F16Viper68

Re: New to me 1981 CB650C. Now what?

Postby F16Viper68 » Sun Dec 04, 2011 3:11 pm

Ok, some progress has been made.

Carb's have been cleaned and rebuilt.

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The charging issue was traced to shorted wiring behind the primary cover. I removed three inches of frayed/charred wiring. Everything checks good now. Can't believe the R/R or Stator wasn't fried.

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I've rebuilt the forks and cleaned up the front end.

Before:

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During:

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After:

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I'm in the process of rebuilding the brake calipers but I've had to stop so and order new pistons due to this.

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Dave...

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Volker_P
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Re: New to me 1981 CB650C. Now what?

Postby Volker_P » Mon Dec 05, 2011 6:33 am

Good work and great progress! :D
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

F16Viper68

Re: New to me 1981 CB650C. Now what?

Postby F16Viper68 » Sat Dec 10, 2011 9:42 pm

Well my new brake pistons from David Silver's (UK) arrived while I was away on business. So today I started disassembling, cleaning, and painting the calipers. I hope to have both sets primed before I get on a plane tomorrow evening.

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Dave...

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Volker_P
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Re: New to me 1981 CB650C. Now what?

Postby Volker_P » Sun Dec 11, 2011 7:09 am

As you have them out could you please measure diameter and height of the brake pistons? I wonder if they are the same like for the 1980 Custom (my European model has also double disk).
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

F16Viper68

Re: New to me 1981 CB650C. Now what?

Postby F16Viper68 » Sun Dec 11, 2011 11:05 am

Volker_P wrote:As you have them out could you please measure diameter and height of the brake pistons? I wonder if they are the same like for the 1980 Custom (my European model has also double disk).


It's a square. :)

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cb650
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Re: New to me 1981 CB650C. Now what?

Postby cb650 » Sun Dec 11, 2011 5:16 pm

In your tag here you should put a link to the thread in the sohc4 site. Many more replies and info there.
Did you clean the tank out?!?!?!?!

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Volker_P
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Re: New to me 1981 CB650C. Now what?

Postby Volker_P » Mon Dec 12, 2011 6:39 am

Thanks a lot, that's great! :D
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum


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