Author Topic: 1980 CB650 Custom Refresher (Read 3540 times)

mrfish2 · « **on:** June 14, 2015, 04:18:45 PM »

So I had posted this in the tech forums first, but I think it'll be more fitting over here. Anyway, picked up a 1980 CB650C yesterday with only 6300 miles and very few issues, namely it'll only run with the choke on and has a leaking head gasket. It's in excellent shape, appears to have been garage kept it's entire life, and has zero rust anywhere on it. The plan for now is to get the carbs apart and cleaned, and get rid of the ugly wheelbarrow handlebars in favor for something along the lines of Euro bars. Also, it needs a front tire. I don't think I'll be keeping it long, I need to make a profit on it to have a little extra money when I go back to college in August to finish my last semester before graduating.

I pulled the carbs off of it today (which, suprisingly, was easier than doing so on my 550) and overall they don't look too shabby, just dirty. In pulling them off I discovered the PO's fuel line problems...

Luckily I've got some extra 5.5mm hose laying around so I'm hoping it's the right size. Also, I've been looking at the schematics over on cmsnl.com and found this one of the carb assembly: http://www.cmsnl.com/honda-cb650c-1980-usa_model473/partslist/E++18.html#results
I'm confused though, because my carbs don't have the lines running across the top (#2 in the schematic). Maybe they have the wrong drawing? This is what mine look like from the top. I'm also confused as to the purpose of the two black hoses. They weren't connected to anything when I pulled the carbs off the bike.

One bowls had a bit of old gas varnish in it, another was black on the inside (and smelled a lot like spray carb cleaner), and the other two bowls didn't look so bad.

Like I said, just a little dirty.

The old carb boots are stiff and need to be replaced, so I've gotta find a decent deal on a set of those. They could also use some new gaskets and o-rings all the way around. Emulsion tubes were clean on the outside when I pulled them out, but every single one of their holes were plugged. Nothing is missing from what I can tell, so it shouldn't be too hard to get this bad boy back on the road.

SOHC4 Cafe Racer Fan · « **Reply #1 on:** June 14, 2015, 04:52:55 PM »

Nice find. That bike is in decent condition.

scunny · « **Reply #2 on:** June 15, 2015, 10:56:25 AM »

those 2 hoses are breathers open to the atmosphere.

snowfighter2 · « **Reply #3 on:** June 15, 2015, 12:31:30 PM »

Nice bike! What makes you think the head gasket is leaking? If it leaks oil between the head and the cylinder, then it is most likely the two o-rings just on the outside of cylinders 1 and 4. Might as well call it a head gasket, since you will have to remove the head to replace the o-rings. I have the same issue with my '81.

mrfish2 · « **Reply #4 on:** June 21, 2015, 07:13:23 PM »

Quote from: scunny on June 15, 2015, 10:56:25 AM

those 2 hoses are breathers open to the atmosphere.

Okay, thanks! I finally found a service bullitin that Honda put out later that year in which you could bring the bike in and they fitted the two hoses together to a t-joint and ran a single hose over to the air box.

Quote from: snowfighter2 on June 15, 2015, 12:31:30 PM

Nice bike! What makes you think the head gasket is leaking? If it leaks oil between the head and the cylinder, then it is most likely the two o-rings just on the outside of cylinders 1 and 4. Might as well call it a head gasket, since you will have to remove the head to replace the o-rings. I have the same issue with my '81.

This is what the motor looks like all the way around the front/sides of the jugs. Looks like it's been leaking for quite some time.

I got some bars from another member on here to replace the ugly wheelbarrow style ones and it looks soooo much better with them on. I haven't changed the length of the brake line, throttle cables, or clutch cable, but they seem to be fine for now with the lower bars. I'm waiting to take some pics of it when I can get everything back together.

The carbs cleaned up real nice after a soak in some Gunk Carb Cleaner, as well as all the Keihin brass. The emulsifier tubes were extremely clogged when I pulled them out so that was probably the biggest reason for it only being able to run with the choke on. The new float bowl gaskets and rubber boots got here the other day so I was able to get the carbs back together finally. All I'm missing now is some 5.5 mm fuel line which should get here next weekend. Gonna take the front wheel to get the new tire mounted sometime this week, and also have some OEM style grips coming in the mail that should be here Tuesday. I'll have more pics of stuff put back on by the end of this week.

snowfighter2 · « **Reply #5 on:** June 21, 2015, 09:39:52 PM »

Yep! Your oil leak is identical to mine. It makes for a messy motor if you continue to ride it ( as I do). I just make sure I check my oil level frequently and wash my bike weekly. I am going to tear it apart this fall, I am having to much fun riding right now.

mrfish2 · « **Reply #6 on:** June 22, 2015, 06:03:20 AM »

What irks me is that it looks like somebody squirted some rtv sealant inside the groove between the head and jugs, right where the head gasket it, to try and stem the oil leakage. It's a bloody mess in there, but I'm not really prepared to pull the head off and fix it when I'm so close to being done and getting it back on the road. I need a set of tires for my truck so I gotta sell this bike soon.

mrfish2 · « **Reply #7 on:** July 24, 2015, 04:24:15 PM »

Well after cleaning the carbs, installing the Euro style bars, new front tire, and a new battery I thought I was ready to go. Tried starting it up and it wasn't hardly any better. Ended up taking it to a guy down the road who likes working on carburated bikes to look at. He cleaned the carbs again just to be sure, and did a compression check. It came back at 118, 133, 133, 120. So the numbers were a little low, but not too shabby.

Anyway, he told me he put a mixture of kerosene and Marvel's Mystery Oil in each cylinder to give them a good soak, and came back later to find that his mixture had seeped past 3 out of the 4 cylinder's piston rings. Annnnd there was the answer. Apparantly 3 cylinder's weren't sealing and wouldn't pull vacuum to let the bike run. So after another soak in Marvel's Oil he told me he let the bike idle for a good 10 minutes and eventually the rings started sealing up.

So I went and picked the bike back up from him yesterday and got to ride it good and hard today. Put around 70 miles on it after work until it started bogging down at WOT (even though I still had half a tank of gas) so I think it's running a touch lean. You can see the headers have a hint of blueing too. But now that the bike's running pretty good it's up for sale.