Author Topic: CB650C Recommission  (Read 4355 times)

Offline Clunker

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Re: CB650C Recommission
« Reply #15 on: July 20, 2017, 09:12:17 PM »
Well I got back on the bucket and pulled the carbs off again, I had managed to dislodge the diaphragm on the accelerator pump. When I removed the float bowl on no.2 carb I noticed a snot like substance in the bowl so I gave it a wipe out. Then I removed the other bowls and found the same crap in them as well.
The PO told me when I bought the bike that he had put clean fuel in the tank, he didn't mention that he hadn't drained the old fuel out first though. I emptied the tank into a bucket...............I have never seen fuel look as bad as that before! In the bottom of the bucket was a load of what looked like black silt with green snot mixed in, with a layer of really dirty petrol floating on top.
I had some clean but old petrol in the shed so I poured a couple of pints in the tank and gave it a right good swilling around then emptied it out, still dirty so I did it again and I think I got most of it out.
I put fresh fuel in and put the tank back on the bike, tried to start her up but the choke lever won't move, not even a bit ??? Took the tank back off and operated the choke pulley by finger tip underneath the carbs, it moved very freely, thought I'd pinched the cable somewhere but couldn't see anything obvious. With the carbs in place on the bike you can't actually see the choke pulley where the cable locates so I traced along the cable with my fingertip, it wasn't connected to the pulley but was trapped inside the airbox rubber.
When I refitted the carbs it must have slipped out of the pulley and hung loose until it got in the way of me connecting up the airbox rubbers ::)
I freed the cable and put it back on the pulley then tried to start her up again, choke worked fine, bike started but something didn't sound right, 1+4 headers were cold and 2+3 were hot.
This is the part where I love having two of the same bikes (or very similar) at the same time.
I borrowed the left coil from my Nighthawk and put it on the Custom, still the same, no spark on 1+4 so I moved on to the spark igniters, swapped both of them just to save splitting them, sparks on all 4 plugs  ;D.
I put the plugs in, tank on, fired her up, all headers getting warm, let her run till she no longer needed choke. Switched her off then started her again, did this a couple more times just to check for any problems.
I forgot to mention that when I rebuilt the carbs I replaced the slide and needle in number 4 carb as the original slide had some deep scratching and the needle was distorted, probably due to the resin bodge on the carb body. The replacement slide and needle came from some CB650Z carbs but were exactly the same as far as I could tell.
Due to the PO's rather fanciful stories about he "did this" and "checked that" :-\ my next steps are going to be to free off the clutch while changing the oil and filter which he said he had done, check the valves like he said he had done....then balance the carbs and adjust the mixtures with my glass spark plug. So that is how she stands at the moment. I didn't take any pics of the above stuff as I just pulled up a bucket and started fiddling and one thing just led to another. :)
Usually sat on a bucket polishing my nuts.

Offline mike the bike

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Re: CB650C Recommission
« Reply #16 on: July 20, 2017, 09:39:36 PM »
Good bit of fault-finding going on there, glad it all works.  How do you get on with the glass spark plug?
Where's that 10mm socket got to?

Offline Clunker

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Re: CB650C Recommission
« Reply #17 on: July 20, 2017, 10:09:10 PM »
To be honest Mike, I've never used one on a Honda before but they helped set up my kwaks a treat, made them purr like kittens on tickover and roar like lions on the road. Have you used one? anything I should look out for?
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Offline mike the bike

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Re: CB650C Recommission
« Reply #18 on: July 21, 2017, 08:31:31 AM »
Never used one.  I like the theory of them; adjusting the mixture to the right colour for most efficient burn, just like a gas boiler.   Some things are more trouble than they are worth, I wondered what they're like to use.
Where's that 10mm socket got to?

Offline hairygit

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Re: CB650C Recommission
« Reply #19 on: July 21, 2017, 08:55:03 AM »
I've used them many years ago on cars with SU or Zenith Stromberg CV type carbs and they were okay, but not much use on fixed jet carbs other than to adjust the idle mixture. Mine was a "Colourtune" made by Gunson, but proved pointless on most bike carbs, as to sort the mixture above idle meant dismantling to adjust needle height or jet sizes.

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Offline Clunker

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Re: CB650C Recommission
« Reply #20 on: July 21, 2017, 01:02:13 PM »
I will let you know how it works out with these carbs. When I used it on the kwaks I balanced the carbs first then used the Colortune then balanced the carbs again. Both bikes ticked over superbly and went like excrement off a digging implement. Both bikes were carb strip jobs that had been stood for years.
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Offline mike the bike

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Re: CB650C Recommission
« Reply #21 on: July 21, 2017, 01:37:59 PM »
I would have thought the colourtune would be useful for setting the air mixture screw because the existing advice is a bit hit and miss.   Not something I play around with,  if the bike starts and runs ok then I don't adjust anything but I wouldn't mind checking.
Where's that 10mm socket got to?

Offline Clunker

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Re: CB650C Recommission
« Reply #22 on: July 21, 2017, 02:19:55 PM »
It was after I first balanced the kwak carbs, then tried adjusting the mixture screws according to the Books and plug condition, with less than satisfactory results that I invested in the Colortune. With the Colortune I could actually see how different the settings for each cylinder were, even though they were adjusted as much as possible to proper specs. I set out at plug 1 with the tank off and a motorcycle cover over myself and the bike, engine running of course, screwed in the mixture screw all the way then backed it out until the "bunsen blue flame" appeared then carried on going until I lost it, then backed it in again until "bunsen blue" again. Did this for each plug, also opened the throttle about a quarter on each cylinder to observe colour change in the chamber, got each mixture screw set so that the response was as close as I could get with each cylinder. I figured that if each mixture screw was set as closely as possible to the rest then that wasn't going to be a bad thing and balancing the carbs again afterwards was going to be as close as I could possibly get by myself without expensive equipment. Anyway, it sure did improve throttle response and performance. I'll just have to try it with the CB carbs, it's not gonna cost me anything to give it a go as I've already got the gear. Watch this space! ;)
« Last Edit: July 21, 2017, 02:40:22 PM by Clunker »
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Offline Clunker

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Re: CB650C Recommission
« Reply #23 on: July 22, 2017, 08:51:16 PM »
Today I freed off the clutch plates, lubricated the extremely stiff clutch cable, changed the oil and filter. While the clutch cover was off I got the polishing tackle out, 400 + 800 + 1200 grit wet & dry, fine wire wool, toothbrushes, tube of Solvol and bucket of warm soapy water. The clutch cover now matches the rest of the casings, just need to do the black circle with Humbrol Satin black. Rain stopped play! >:(  Clutch works great though! 8)
« Last Edit: July 22, 2017, 08:54:05 PM by Clunker »
Usually sat on a bucket polishing my nuts.

Offline Clunker

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Re: CB650C Recommission
« Reply #24 on: July 26, 2017, 09:34:52 AM »
Yesterday I set the valves, PO told me he had set them. He must have used a shovel for feeler gauges cos they all had way too big settings. :o
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Offline Clunker

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Re: CB650C Recommission
« Reply #25 on: July 31, 2017, 09:18:02 PM »
I won't be posting anymore updates to this thread as CB650's seem to be a non subject on this site. Regards Clunker, signing off.
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Offline Nurse Julie

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Re: CB650C Recommission
« Reply #26 on: July 31, 2017, 09:21:40 PM »
Nooooo, don't go away. I'm sure its only because no one else on here owns one (I think) It is a SOHC so still an important bike on here. I have read all your posts but know diddly squat about them so can never comment.
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Offline mike the bike

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Re: CB650C Recommission
« Reply #27 on: July 31, 2017, 09:37:52 PM »
Keep 'em coming Clunker,  we like our success stories on here and the photos.  And when you're scratching your head we all chip in with advice it becomes a team effort.

One word of advice though: upgrade the the bucket to a mechanics stool so you can scoot it around with your feet.
Where's that 10mm socket got to?

 

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