Anybody know what these are for? CB650


If it don't fit, you're not trying hard enough!
This is on the 81/82 CB650 engine I picked up.

The little tubes that come up from between carbs 1 & 2, and 3 @ 4. I would imagine that they go into the little box or pipe that connects to the crank case vent then to the airbox, but not sure. I paid $70 for these tubes, so they damn well better be useful for something. They're plugged because gas poured out of them before. Have tried running with them unplugged too, makes no difference.


This POS engine won't run either. Dipped and cleaned carbs till they squeaked. Will still piss gas out of all 4 carbs even though the floats and float valves are like new (had apart more than once). Vacuum valve works perfectly too. Still will not start and I've wasted 2 days of my long weekend on it. Has great spark. Tried a few different spots for ignition timing. Valve clearances are set as per the manual. Will get a few fires from here and there, but nothing real great. Backfires out the exhaust and carbs randomly as well. Any ideas anyone?

Re: Anybody know what these are for?

rudy said:
The little tubes that come up from between carbs 1 & 2, and 3 @ 4.

they are just the drain tubes for your carbarator overflow. Try and loosen and then tighten the drain plug screws on the side of each carb bowl and see if that helps the constant flow of gas out of each tube.
Re: Anybody know what these are for?

They look like air vent tubes to me. My Mikuni's have two similar tubes. How did you end up paying $70 for two tubes?
Re: Anybody know what these are for?

If I had to guess, I'd say vent tubes.

Sounds like your float levels are off.

Have you checked your compression?
Re: Anybody know what these are for?

Compression seems decent. Still waiting on an adapter as all I have is 14mm and 18mm for my bikes. Where these tubes connect to the carbs is about 1/4 of the way up the carb throat, so well away from the level gas should be at. From what I see in the fiche's, they are meant to be vertical and pointing up like I have them.

This model has plastic carb floats, not adjustable.

I ended up paying $70 because they aren't available anywhere else for less. At least what I could find. I had to go to the Honda man and bend over and grab my ankles. They aren't given any kind of description either. I asked the clown behind the counter if he knew what they were, I might as well have asked the display of sunglasses instead, as he wasted 20 minutes not finding an answer for me.

I'll likely tear the carbs apart again and re-dip them and clean. Don't know what else to do.

Aren't these the same carbs as what's on pretty much ANY 4 cylinder Honda from that point in time? When everything started going to the CV carbs. Surely they've got to be at least CLOSE to something from a 750.

Looks like you 70$ for some fuel line - OOOps.

Typically you have - fuel line in (sometimes 1 line, sometimes it splits to two), a smaller vent line from each bowl and if you have a diaphram petcock theres a vacuum line from it to the intake. Have you already located those lines?

To get it running you need the Holy Trio : Gas, Good BLUE, properly timed spark & compression. Comp & Blue spark are easy to check. Set the ignition timing with the static method - a 12v light bulb and two wires with aligator clips. This should get you very close (it's all I use).

Fuel - you can pull a drain plug to confirm you have gas that far. After that if it's not starting you can usually see if the plugs are wet or not.

That's about all I got. Are you this far already??
Top Bottom