1983 CB650 Won't start

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jason
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1983 CB650 Won't start

Postby jason » Sat Feb 28, 2015 2:25 am

Hello everyone,

I'm new here. After I rebuilt the petcock and carbs a year ago it started up but I could tell the carbs were out of sync and there was a throttle issue. Now that I'm working on it again the petcock is leaking again and it won't start. Probably a vacuum problem somewhere. I also have oil coming out of, what I believe is, the 1st carb float bowl drain.
Also, do any of you know the screw size to the vacuum plug screw on the intake boots/carburetor insulator? I need to get vacuum line adapters to do a homemade carb sync after I can get fired up.
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Folsoml
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Re: 1983 CB650 Won't start

Postby Folsoml » Sat Feb 28, 2015 12:59 pm

If oil is coming out of there, we have a serious problem. There should only be fuel in that are. First, tap on the float bowl with a screwdriver handle or something similar. Often this will get the needle to seat and resolve the problem. If this does not fix it, try removing the float bowl screw and making sure the tip is in good condition. While it is out, run a pipe cleaner or something similar through hole the screw came from. Sometimes there can be a small bit of crud that is keeping the screw from sealing up good. If this does not fix your problem, you will need to remove the carbs to inspect the float, float needle, and needle seat to make sure there is no problem there.
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jason
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Re: 1983 CB650 Won't start

Postby jason » Sat Feb 28, 2015 5:08 pm

Thanks for the reply. What does it mean if oil is coming out of the float bowl? After several attempts yesterday I think I flooded the carbs. I tried again today and got the bike started but I had to twist the throttle all the way for it to idle, for less than a minute, until it ran out of gas. I cleaned the petcock (it leaks on 'off' and 'res' but not on 'on') and connected a longer hose to it to get the gas tank out of the way. I loosened the 1st carb float bowl screw and gas came out. I have an auto zone fuel filter between the petcock and carbs. Now, I can't seem to get fuel to the carbs.

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Folsoml
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Re: 1983 CB650 Won't start

Postby Folsoml » Sat Feb 28, 2015 6:57 pm

jason wrote:What does it mean if oil is coming out of the float bowl?


I cannot even imagine how oil COULD be coming from there--short of the fuel tank being filled with oil.

It sounds like the slow jets in your carbs are plugged. Has it been a year since the bike has been running? With regards to your fuel problem, make sure you do not have a point in your fuel line where it is lower than where the fuel goes into the carb (similar to a plumbing trap).
Have a problem with your CB650? Have a technical question? Click here!


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jason
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Re: 1983 CB650 Won't start

Postby jason » Sat Feb 28, 2015 7:14 pm

It hasn't been running for a year +

jason
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Re: 1983 CB650 Won't start

Postby jason » Sat Feb 28, 2015 8:05 pm

I drained the float bowls and green snot colored gas came out. Do you think all the gaskets and rubber parts in the carbs are messed up? I raised the gas tank high to give it a straight shot to the carbs but gas wouldn't remain in the in-line filter. Maybe the petcock is messed up.

cb650
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Re: 1983 CB650 Won't start

Postby cb650 » Sun Mar 01, 2015 12:15 am

The petcock on the DOHC4 had the auto shut off in it and wont flow without vacuum.
Did you clean the tank out?!?!?!?!

jason
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Re: 1983 CB650 Won't start

Postby jason » Sun Mar 01, 2015 12:56 am

You mean it has to be connected to the vacuum line on Carburetor #2's intake boots to flow?

I don't know the petcock is leaking when it's on "off" and "res". I replaced the o-ring that connects with the fuel tank. It's missing the long cylindrical filter that goes in the tank but everything else seems to be in good shape. It's been difficult finding images of the stock petcock for this bike.

cb650
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Re: 1983 CB650 Won't start

Postby cb650 » Sun Mar 01, 2015 10:56 am

Yes it has to be connected to vacum. If it is all still there.
Did you clean the tank out?!?!?!?!

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Volker_P
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Re: 1983 CB650 Won't start

Postby Volker_P » Tue Mar 03, 2015 2:32 am

jason wrote:I drained the float bowls and green snot colored gas came out.
This does not sound like something one likes to have in his carbs.

jason wrote:Do you think all the gaskets and rubber parts in the carbs are messed up?
If it was all right one year ago, it is probably just filled with some residuals. So I would assume a good cleaning is necessary, but no complete rebuild. As already mentioned, it is probably the idle jets that cause the trouble you have.

I recommend to drain the floater bowls if you do not run the bike for more than a few weeks. These drain screws make some sense. :wink:
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

jason
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Joined: Wed May 16, 2012 5:38 pm

Re: 1983 CB650 Won't start

Postby jason » Tue Mar 03, 2015 7:19 pm

Thanks for the replies. I read somewhere else that the vacuum line on the 2nd carburetor could be plugged with a screw. In fact, when I bought it that was the case but now gas is not going to the carbs that way.

I forgot what kind of cleaner I used on the carbs in the past. What do you guys use?

Also, I took a dremel to one of the brass screws (pilot jet? - I don't remember what is was) because it didn't have a notch for a flat head or philips so I could unscrew it...I probably should have messed with it. Any idea what that could have been? Doing that probably created issues. I was planning on putting pod filters on so I think that is also why I messed with those jets but ultimately decided stock airbox/filter would be smarter for now.

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Folsoml
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Re: 1983 CB650 Won't start

Postby Folsoml » Wed Mar 04, 2015 6:02 am

Pictures would help. Check the link in my signature.

With regards to cleaning, check out this carb cleaning manual. The carbs are not exactly like yours, but they are close enough for cleaning.
Have a problem with your CB650? Have a technical question? Click here!


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