Topic: 1981 CB650 (mild resto, potential cafe)

[Scotty.]

Hey everyone!

I just picked up a new to me 1981 CB650 last week friday (9-16-16).

The guy I bought it from said that he thought a float was sticking as the bike would bog down and shut off then start to dump fuel from one of the carbs.  When I went to look at it he started it up and it did just that.

I got it cheap due to the fact he was not a mechanic and didn't want to tackle rebuilding the carbs.  I take it home expecting to need to rebuild the carbs and take care of a few other things.

Well the short of it is I have not been able to replicate the issue, so if a float was in fact getting stuck it hasn't been doing it since.

I still plan to do a mild rebuild of the carbs.  Basically new gaskets and a good heavy cleaning.  I understand the carbs on the 81 have pressed in jets, I'm not against pressing them out and putting new ones in but I'm not sure it will need it really.

It needs new tires so that's on the list.

Also needs front turn signals and the rear signals don't come on or blink when the switch is flipped so I'll need to figure that out.

Upon further inspection today I have come to the conclusion the bike was dropped on the left side at some point as the handle bars are ever so slightly bent, the clutch lever has a slight downward bend to it, and the shifter was pushed in a little.

The day I brought it home.

[Scotty.]

Full disclosure: this thread is going to be more for me to keep track of a timeline of when things get done. I've also been known to in the past forget to update my build threads, but this being my first bike and my first project bike I will probably be a little more excited to keep up with it here. 

I'm not a huge fan of that seat but for now it will stay. As I'm more concerned about getting it running right and reliably and going down the road.

Today I decided to give it a good soak in simple green and then a light power wash.  The engine was covered in oil so I'd like to know where it is coming from to start replacing gaskets.

After the power wash I let it dry out a bit and decided to take it for another quick run down the street and back.  Well I guess it doesn't like being wet at all because it wouldn't start unless hooked up to a charger/jump box and it wouldn't idle, as well as running pretty rough once moving. 

I'm guessing it was a combination of things but probably one of the ignition coils was too wet and not happy about it.  Another thing on the list, go over wiring and look for/remedy corrosion and exposed wires.

After it dried out more it would fire right up under its own power.

I'm getting a bit of hesitation around 3k rpm, not sure if it is carb related or not but it does have K&N filters on it. the ones that feed 2 carbs each.  And from my understanding these carbs hate anything but the factory airbox.  If I can't get the stumble sorted out I'll need to find an airbox on ebay or otherwise and put it on to rule that out.

For now the list is growing but should be doable, and not all of it is dire at this moment.

Here it is in the shop for the night after the power wash.

[SOHC4 Cafe Racer Fan]

I'm more concerned about getting it running right and reliably and going down the road.

Excellent priorities.  Download a copy of the service manual here on the forum.  Print it out and put it in a binder for handy reference in the garage.  Perform the 3,000 mile service.

Sitting gas turns into a varnish like substance that can clog and stick.  Running the bike can sometimes free up sticking parts (floats), but not always.  It sounds like the bike is due for a carb complete rebuild.  Order a rebuild kit, preferably OEM. 

Purchase a multi-meter and check out your electrical wiring harness.  You should also clean each connector of corrosion. 

Drain your old oil, replace your filter and examine the oil for particulate matter or water.

A leak down test would be good to check the compression on your cylinders AFTER you have run the bike for a while.  If you have decent compression and no leaks from the main gaskets count yourself lucky.  You may need to refresh the base, head, oil pan or side gaskets.  If you have poor compression, you may need to lap the valves and rehone the cylinders.

Service your brakes -- new brake fluid.

Rebuild your forks if they have not been rebuilt.  30-plus year old fork oil and springs could likely use a refresh. 

[rb550four]

Welcome. Always excited to see a 650 on the board.
   What cb750 cafe racer fan said is spot on.
     Your new machine looks so much better without that giant seat. That's always the first thing off around here , the second thing is the book rack...but some guys really like them.
      The 650 has been cursed with ridiculous handlebars, I always change them out first so I can get an positive feel of what the finished product will look and feel like....keeps the blood flowing throughout the project.
     The 650 is just a nice machine, handles very nicely, takes 2 up easily ,and is snotty enough that you won't be crying for more power all the time.
     Good luck with this , lots of 650 guys here to help if you have Q s .

[Scotty.]

Hey, thanks for the welcomes and the suggestions.  My boss actually had two 650's about 10-15 years ago and had a Clymer's manual for it! I've been a mechanic and car painter for about 10 years and now work in a fabrication shop so I'm not new to the old vehicle refresh haha.

Anyway, I just got tags for it today, put on new tires yesterday, bought a chain guard and put that on as well.  I have turn signals for the front in the mail somewhere and also have oil/filter, spark plugs, and a new bulb for the headlight.  I'll start riding it with the temp tag on it and get my list of everything together as more stuff pops up. 

For now I think I'll just collect parts, etc. until the winter and tear it down then.  Probably rebuild carbs, forks, engine gasket kit, adjust/lap valves and new seals, new brake line, new tapered tree bearing set and go over the entire wiring harness and fix it up (not afraid of wiring haha)

I plan to clean up the look of the bike, not sure what style it would fall under but I'll say probably more brat style.  I want to get lower bars, smaller gauges, maybe a shallower headlamp, and then rework the rear of the frame and rear fender/lights.  Plans are to make my own straight seat so I can carry a passenger on occasion.

Probably wont be able to wait until the winter to start making changes, we will see how long I can last! haha

I'll get some decent pictures up soon as the weather clears up more.

[pmanning]

About that fuel leak...  My son bought an '81 CB650 that had been sitting a long, long time.  It also had an intermittent fuel leak that when present would pour gas from the carbs.  We replaced the needle valves with no improvement.  Finally replaced the o-rings on the "T" tubes between carbs 1 & 2 and 3 & 4.  That took care of the leak.

[Scotty.]

I plan to replace all of that when I tear it apart, it's been fine so far.

Today I took the bike out for a ride for the first time.  It rode and ran really well.  I was able to confirm the speedometer is off though.  It reads 40 when the actual speed is 50. It was jumping around before, so I lubed the cable.  That at least made the cable steady, but I still need to figure out the reading too slow issue.  Possibly clean the speedo unit itself or wait until I get it through inspection and put a new speedo on.