79 carbs

If it's broken or just needs tweaked

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bobbed650
Posts: 9
Joined: Wed May 25, 2011 1:53 pm

79 carbs

Postby bobbed650 » Wed Jun 15, 2011 9:47 am

Alright, I came across a 79 CB 650 that I bought for $400 (will put up some pictures later). I bought it from a guy who had it sitting in his garage for 4 years, he had a friend "rebuild" the carbs. So instead of putting a new bowl gasket on #1 Carb they used gasket sealer. Well you all can imagine what happend with that. Yeah the bowl was full of a mixture of gasket sealer old gas gum type material. Prior to tear down I got the bike to run on partial choke but gas was still pouring from carbs 1-3. I tore them down and put rebuild kits in all 4 carbs and a new accelarator pump, and air cut valves. Put everything back together and now it wont start and fuel is still coming from the overflow of the same 3 carbs. After all that my question is. What position should the carbs be in when measuring the float height? It appears that on cosky they have them with the motor side down. Any help is appreciated. Thanks for a great site I have learned a lot just from reading other posts.

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Volker_P
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Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: 79 carbs

Postby Volker_P » Thu Jun 16, 2011 12:54 am

Welcome here! :D

For the PD carbs it is possible to install the floats upside down. Check that out. Below a picture of the floater level adjustment.

However I would suspect that residuals from that gum stuff still prevent the floater valves from closing completely. Inspect them carefully, as well as the needle points.

Another option might be that the previous "experts" have mixed up the floater parts between carbs. E.g. floater cam is quite susceptible to rough surface or slight bending, especially if it is not "run in" with the corresponding float and needle. In this case you probably have sticking floats. One may get them free by knocking carefully with a piece of wood on the corresponding floater bowl. Sometimes this solves the problem permanently, sometimes it has to be repeated and sometimes they just stay stuck and need further care. :roll:
Attachments
CB650_floater_level_piston_[PD5]_carbs.JPG
CB650_floater_level_piston_[PD5]_carbs.JPG (11.25 KiB) Viewed 5004 times
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

bobbed650
Posts: 9
Joined: Wed May 25, 2011 1:53 pm

Re: 79 carbs

Postby bobbed650 » Thu Jun 16, 2011 7:26 am

Thanks, after tinkering lastnight I got 3 of the carbs to quit leaking, but carb number 3 continues to leak. Carb 1 was the carb with the gasket sealer and that's not leaking so I consider that a small victory. I'll go back into Carb #3 and clean it again and check for anything that may be hangin the float or preventing the needle from closing. Thanks for the help.

bobbed650
Posts: 9
Joined: Wed May 25, 2011 1:53 pm

Re: 79 carbs

Postby bobbed650 » Fri Jun 17, 2011 7:56 am

A little more figiting lastnight and still can't get the #3 carb needle to seal. I am thinking of changing the tab on the float to change the float hieght just to see what happens with that. I just put brand new keyster carb kits in all the carbs that included new needles. I currently have all the floats @ as close to 12.5mm as I can get. I suppose I could try floating the float in a container to see if it's not the float that's the problem.

Clutch
Posts: 32
Joined: Mon Jun 14, 2010 9:30 am

Re: 79 carbs

Postby Clutch » Mon Jun 20, 2011 3:23 pm

I had the same problem carbs leaking from the bottom of the bowl cleaned out the carbs & adjusted the floats and problem went away...

bobbed650
Posts: 9
Joined: Wed May 25, 2011 1:53 pm

Re: 79 carbs

Postby bobbed650 » Wed Jun 22, 2011 4:22 pm

I am going to mess with the float hieght and see if that fixes it. When I got the bike the float ht. was at about 15 mm, I moved it 12.5 mm which the manual says it's supposed to be. I am going to try tonight to adjust it till the leaking stops and go from there. It's a little frustrating. We haven't had much of summer here in MN so far this year but I would like to get out and ride before it's officially over. :roll:


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