The Honda CB650 Motorcycle

Restoration Project

The CB650 Stripdowns

Like I said before, I have two CB650s:

My 1981 (left) and 1980 (right) CB650s - The 81 is without it's seat and gas tank

My 1981 (left) and 1980 (right) CB650s - The 81 is without it's seat and gas tank

80 CB650:
I bought this one for parts but it was actually in better shape than my 81. It also has a bit less mileage. I even rode it on an almost daily basis in the summer of 2004.

1980 CB650 as it looked in 2004

1980 CB650 as it looked in 2004

81 CB650 Custom:
Had it for a while and rode it on a daily basis from 1995 to 2001 rain or shine from late March to mid October. I live about 45 km from my place of work, mostly highway. Then it sat for 3 years and as I mention below, it was completely dismantled in 2004.

1981 CB650 as it looked in 1995 - nice!

1981 CB650 as it looked in 1995 - nice!

1981 CB650 as it looked in 2004 - VERY used!

1981 CB650 as it looked in 2004 - VERY used!

Starting the Restoration

I actually started working on this project in 2004 but only got back to it this summer (2009). In October 2004, I completely stripped the 1981 down to the frame. I left all the parts on a big shelf in my detached garage and basically did nothing with it for 4 years.

The 1981 CB650 Custom in pieces

The 1981 CB650 Custom in pieces

This summer (2009), I brought the 1980 in my other garage and started stripping down the engine while it’s in the frame.

Part of the 1980 top end removed

Part of the 1980 top end removed

This is the way I intend to go about it.
I will be using the 1981 frame for the rebuilt. I will be rebuilding the 1980 engine and fitting that in the frame. I will also be using the 1980 carburetor (i don’t like the vacuum operated 1981 carb). I’m using the 1981 gas tank because the inside has been treated for rust, although the other one is not too bad. I only have two side cover emblems, so I’m keeping those. I need to buy 2 new tires with white letters. I’m keeping the best two of the other four tires for the one I’m selling. The 1980 electrical system will go on the restored machine. Need new mufflers so that will go on the restored bike. The front dual disc brake system goes on the rebuild but I need new brake pads, SS braided lines, one disc rotor and a master cylinder.

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  1. me puedes vender el cigueñal…?? claro si esta en buen estado todavia…!!

  2. I just got an 1981 cb650 custom and i having a hell of a time with the vacum carbs . Does the older ones work ok on this model . I think im going to have to do a top end rebuild too as the oil leaks like a bitch ,was it an easy enough gob to do .


    • The older carbs should work ok. It’s the same engine. In my case the diaphragm on the vacuum carb no longer works so I had to bypass it or change the diaphragm. This part prevents the fuel from flowing when the engine is shut off. If it doesn’t work, then the engine won’t start. Either way, these motorcycles are finicky no matter what carbs you have. You need to adjust the carbs properly and let the engine warm up. You have to play around with the choke a lot. Once you get use to it, it’s not a big problem.
      These bikes also tend to leak oil but it’s fairly easy to do the top end rebuild if you have a good manual like the Clymer.

  3. Will carbs from a 1979 cb650 work on a 1981 cb650?

    • Yes it should. The engines from the CB650 1979 to 1982 are the same. Just make sure that you have the right boots for the carbs you’ll be installing. The engine side will fit but the carb side will be different.

  4. I just bought A 1982 CB 650 with 16000 miles all original and complete excfpt sode cover CB650 emblems are missing. Would you have them? Also do you have any idea of value of this bike?

    • I need the ones I have but you might want to look on ebay or your local salvage yards for emblems. In my area (Ottawa, Canada), 79 to 82 CB650s in good shape would go for around $1200.

  5. Do you know if the 80’s gas tank fits the 81 650c?

    • They’re the same except for the fuel petcock. The opening size is different, but if you take the fuel tank along with the proper fuel petcock, than it will fit because the rest of the tank is exactly the same and it will fit on the 81 bike.

  6. hi i too have an 80 and 81 and am working on the same stuff. the carbs wont swap over unless you change the head and air box as well. as far as the tank the petcock is different because of the vacume on the 81 and the threads for the petcock is different too. the 81 petcock requires a vacume to flow fuel even when in the on posistion.

    • That’s interesting. I’ve been trying to run the 81 petcock and tank with the 80 carbs. Everything fits, but I’m having a hard time adjusting the carbs. Now I’m thinking it might be because of the needed vacuum you mention.

  7. Hey, enjoying your page. I too have a 1980 cb650 that I got about 9 years ago. It was driven into a lake and sat at the bottom for two nights. Back then It ran but wouldn’t hold a charge. I had lofty goals of turning it into a chopper, now im leaning more towards the café racer style. However, back then I took the engine out of the frame and it has sat ever since. Now im looking to do a complete rebuild of the engine all around. Was wondering if you had any good web sites and or books that would aid in this process. Thanks!

  8. Shot in the dark here. Wondering if you might have a passenger grab bar laying around from one of the 650s you would be willing to sell.

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