Topic: 1982 CB650 carb issue

[Clinto]

I'm helping a friend with his 1982 cb650. We replaced the head gasket, put everything back together and now there seems to be a fueling issue. The bike started up and idled ok with the choke on but when we gave the bike any throttle it seemed to bog and surge sporadically. We noticed there was also fuel coming out an outlet at the top right of the carb rack just behind the top of carb 4.

http://imgur.com/gallery/J0Xwrao

Does anybody have any ideas on what the issue could be? Is that outlet an overflow outlet? Is it missing a hose? Thanks for any help

[Clinto]

Ok, hoping to get some feedback from someone familiar with the type of carbs on these bikes. The carbs on my 550 aren't PD carbs.

The carbs are no longer overflowing, the bike idles fine and when you slowly roll on the throttle it revs fine but when you give it quick throttle at all it bogs down and dies. Any suggestions? Is it possible this is a timing issue rather than a carb issue? Thanks

[Clinto]

Here's a video. It may look like I'm giving it a similar amount of throttle but I can let it rev or bog down and die depending on how fast I roll on the throttle

[scunny]

I would check the accelerator pump, this will be a diaphragm on the #2 carbie. when you goose the throttle a fine spray should come out of the nozzles in the carb throats. This is to overcome the lean running of the carbs as per the EPA.

[DaveBarbier]

I don’t know the CV carbs that well, but I believe there should be two hoses going to the petcock. One for fuel and one for vacuum. That nipple that’s open is a vacuum line and should have a hose going on it either to the accelerator pump or to the petcock. Post some more clear pictures of the carb rack and petcock. I’m thinking it’s just an issue of not having all the right parts for the carbs installed.

[DaveBarbier]

And yeah, regarding the video: since it has an accelerator pump then running the bike without the tank installed and no vacuum line going to the petcock you won’t have proper fuel flow. What’s your fuel source when the tank is off?

[Clinto]

I would check the accelerator pump, this will be a diaphragm on the #2 carbie. when you goose the throttle a fine spray should come out of the nozzles in the carb throats. This is to overcome the lean running of the carbs as per the EPA.

Thanks for this, I'm unfamiliar with accelerator pumps but I will look into how to inspect them.

I don’t know the CV carbs that well, but I believe there should be two hoses going to the petcock. One for fuel and one for vacuum. That nipple that’s open is a vacuum line and should have a hose going on it either to the accelerator pump or to the petcock. Post some more clear pictures of the carb rack and petcock. I’m thinking it’s just an issue of not having all the right parts for the carbs installed.

I was told the outlet was an overflow tube and should have a line running from it to the ground in the swingarm area? There seems to be a little ring on the side of the carbs that looks like a small overflow fuel line should run through it as seen here in the red circle:


There's nothing on the underside of the tank or the petcock, it looks very simple. here's an overhead of the left side of the carb rack. The hose in the green circle runs to the underside of the outlet where the fuel was coming from (green circle in other picture) and the hose in orange connects the 1&2 carbs and runs over to the 3&4 carbs (orange circle in other picture). The orange line also connect back to the air box via a T connection I believe.

And yeah, regarding the video: since it has an accelerator pump then running the bike without the tank installed and no vacuum line going to the petcock you won’t have proper fuel flow. What’s your fuel source when the tank is off?

I was running it with the tank sitting beside the bike with a longer piece of fuel line. Like I said, I don't see any thing for an additional fuel line to connect to the fuel tank or petcock.



Thanks for the help guys!

[DaveBarbier]

Not an overflow. Far too high up to be one. I’m convinced it’s a vacuum/accelerator pump issue. If I remember, this weekend I can look at my 650 manual and see if there’s a diagram. Unless, of course, someone who is smart comments before me. 

[irish44395]

I would check the accelerator pump, this will be a diaphragm on the #2 carbie. when you goose the throttle a fine spray should come out of the nozzles in the carb throats. This is to overcome the lean running of the carbs as per the EPA.

Thanks for this, I'm unfamiliar with accelerator pumps but I will look into how to inspect them.

I don’t know the CV carbs that well, but I believe there should be two hoses going to the petcock. One for fuel and one for vacuum. That nipple that’s open is a vacuum line and should have a hose going on it either to the accelerator pump or to the petcock. Post some more clear pictures of the carb rack and petcock. I’m thinking it’s just an issue of not having all the right parts for the carbs installed.

I was told the outlet was an overflow tube and should have a line running from it to the ground in the swingarm area? There seems to be a little ring on the side of the carbs that looks like a small overflow fuel line should run through it as seen here in the red circle:


There's nothing on the underside of the tank or the petcock, it looks very simple. here's an overhead of the left side of the carb rack. The hose in the green circle runs to the underside of the outlet where the fuel was coming from (green circle in other picture) and the hose in orange connects the 1&2 carbs and runs over to the 3&4 carbs (orange circle in other picture). The orange line also connect back to the air box via a T connection I believe.

And yeah, regarding the video: since it has an accelerator pump then running the bike without the tank installed and no vacuum line going to the petcock you won’t have proper fuel flow. What’s your fuel source when the tank is off?

I was running it with the tank sitting beside the bike with a longer piece of fuel line. Like I said, I don't see any thing for an additional fuel line to connect to the fuel tank or petcock.



Thanks for the help guys!

the orange circle one is a vacuum that goes to the auto fuel valve the green one is a vent there is also one between 3&4 . I bypassed the auto fuel  valve and my vent hoses just stick up a few inches .I have no problems running except for my top end speed  that I haven't figure out as of yet .
Pete

[DaveBarbier]

These photos might help, might not. I do see that the accelerator pump looks different than in your picture. Could be because this is the ‘81 addendum and you have an ‘82 650 which has the VB44c carbs instead of the VB44a I think. But still, worth a look. Also shows, poorly, the vent and fuel tube routing.

[Clinto]

These photos might help, might not. I do see that the accelerator pump looks different than in your picture. Could be because this is the ‘81 addendum and you have an ‘82 650 which has the VB44c carbs instead of the VB44a I think. But still, worth a look. Also shows, poorly, the vent and fuel tube routing.

Thanks a ton for this. You're right, not the same carbs but good info still. According to this, what I thought was the acceleration pump is the fuel line diaphragm and the accelerator pump is located on the #2 carb as somebody else mentioned. That makes more sense. I feel like the accelerator pump is what needs looked at because all the carbs seem to be getting fuel, just not enough under quick acceleration. It also shows the outlet on the fuel line diaphragm not connecting to anything if I'm reading it correctly. There's no clip or anything at the end of the hose.

Thanks again!