New owner of 1980 Honda CB650, have questions.

Hey guys.

Recently I bought a 1980 Honda CB650. It ran pretty good for awhile. I had it for maybe a month, and as soon as I got my bike license I took it for a ride across town. That's when it started acting up.

It used to start up very easily, but one day it got very hard to start. We'd have to fiddle with the choke and the throttle to get it to start. And it would hesitate a lot if you jumped the throttle until it warmed up considerably. It always cutted out some when you was on the throttle going down the road, but it much more severe this time. When I got close to my destinatino, the idle was starting to fluctuate quite a bit. It died on me a couple times and other times it was ideling way to fast. I had to constantly adjust the idle screw in order to make it to where I was going.

Upon arriving I found that some of the bowls were overflowing and leaking onto the motor. I thought I only seen 1 or maybe 2 bowls do it, but later on my dad claimed he saw all 4 doing it at one point or another...

We took the carbs out and took the bowls off. The floats looked fine. The rubber tips on the needles looked fine. The seats for the needles looked fine. The floats were in the ballpark range (12.5mm or 0.5") from the carb body like the haynes manual said.

Something we did notice however is that the passenger side choke butterflys were hard to move, like they were binding up. The driver side moved smoothly. The choke cam wasn't moving them either.

On instinct and/or luck, we tried loosening the screws that hold the plates onto the shaft and that loosened up the whole thing and allowed the choke cam to operate them. We tightened them back down and rechecked.

Something else we found was that on the # 4 carb (far right/passenger) there was a brass tube missing from the bottom inside of the bowl. All the other carbs had them, but #4 was missing the left one on the bottom if I remember correctly...

A previous owner had apparently had the #1 carb bowl taken off, because we found a cut up o-ring used as the gasket. We didn't have anything handy so we reused it along with some RTV.

We through it back on the bike and started it up. It started a lot easier this time, about like I would expect. However it is still leaking lots of fuel from the bowls overflow tube. And yes the bowl drains are tightly closed. The seems to run better but it's still a little iffy. We didn't take it for a ride so I'm not sure if it would still cut out a lot or not...

My dad tried putting his hand over the carb air intake (we left the air filter box off) and he was able to completely cover the #1 carb air intake without a noticeable difference in the way the engine ran. Also there was some backfiring occurring through the carbs. Just some.

So what do you guys think the problem is? Supposedly the previous owner had the carbs worked on by a guy that knew what he was doing. We're not so sure he knew anything by looking at the #1 o-ring used as a gasket, lol.

My dad's got some experience with bike carbs, I have almost none. But we do have common sense.

I'm not sure we could find a guy in our town that knows how to work on this thing...

I don't know if you have checked or not but when i took apart my carbs I had a constant flow from one of the bowls with eveything closed off. I found that my overflow tub had a crack completely down it. You can seal it with gas resistant epoxy and marine water seal on top. If you do happen to have that problem. As for the gasket being cut up. I do know why people do that it is hard to get a replacement gasket. If you remove the one that is on there the only way to get it back on is to cut it into sections. They sell a Gas resistant sealant at any auto store. They say that is better to use than rtv sealant. Just some words that might help from someone that has been there with his own and found that was the reason. Hope you get it fixed. Good Luck.

Steve

It sounds to me, as far as the losing power, that you have partially clogged jets. I would clean them all out(disassembled). Some people swear by seafoam for cleaning out jets while you ride. I use it a couple times a year but i dont know if it really works cause i clean my carbs every spring, but my bike never gets too dirty.

as for the leaking bowls, that is tricky. i would start by cleaning out the valve seats. if there is even a spec of rust in there, it could be enough to cause overflow. if that doesnt work replace your needle valves, they are pretty cheap, less than $5 at most.

and you can get new float bowl gaskets on ebay usually or various other internet sources. try crc2onlinecatalog.com. i got needle valves there for a cm400.