Topic: 1981 CB650 Carb Removal and Rebuild

[TimLoon]

Have been away from riding as too much happening.
Bike has 2300 miles and have been riding it with the choke on a bit and never was able to fully take it off.
Had it serviced by a retired Honda mechanic last winter but still not right. I asked him to pull carbs but he insisted not necessary.
Only rode a few miles this year and it got to the point of not staying running even with choke.
Putting bike away for the winter and want to pull carbs and send off.
Any advice on pulling carbs off this model? I usually have not issue but this one looks crowded.
Would like to send the whole bank intact to someone to go through and rebuild as needed. Is there a go to place for this service.
Anxious to be back on the road in the spring.
Bike is like new otherwise.

[Flyin900]

Download a Honda FSM if available on this site if you don’t have one already for the bike. Hopefully they have one listed on here as I see it is a later CB650.

As far as a carb guy you want someone with real skills and the proper equiptment. I would recommend Mike Nixon I believe he is based in Arizona. He has a website and is an ex Honda and Kawasaki tech guy. I will post a link once I am able to get the information for you.

On this site Hondaman is a well respected go to fellow too, yet I am unsure if he does carbs.

[fizzlebottom]

Mike Nixon's site: https://motorcycleproject.com/

If you are 100% unwilling to do this yourself, prepare to pay several hundred dollars to have them done properly. Mike would be that guy, but you're gonna pay. Don't have your neighborhood bike shop do them because I'd be willing to bet you would end up with aftermarket jets and a headache.

If you are willing to do some work, they are not hard to deal with. Quite easy, actually. The biggest hassle is the carb insulators, which are probably hard as rocks by now.

The FSM on this site does not include the addendum necessary to do this work, unfortunately. You'll have to find a copy with the right info. The 79/80 CB650 came with PD carbs, and yours are VB44A.

Good luck.

[RAFster122s]

The VB carbs, Constant Velocity design, are a real pita to get clean. Ultrasonic cleaning is required, best with commercial quality ultrasonic cleaner. The passages are tough to get clean and all the brass has to come out to do the job.  If pressed in jets they are tougher to remove.
The jets themselves need cleaned with wire or properly sized numbered drill bits (that don't remove any brass).
Soak in CLR can help clean the brass, but still need to scrape the passages with the wire or drill bits.

[Flyin900]

The VB carbs, Constant Velocity design, are a real pita to get clean. Ultrasonic cleaning is required, best with commercial quality ultrasonic cleaner. The passages are tough to get clean and all the brass has to come out to do the job.  If pressed in jets they are tougher to remove.
The jets themselves need cleaned with wire or properly sized numbered drill bits (that don't remove any brass).
Soak in CLR can help clean the brass, but still need to scrape the passages with the wire or drill bits.

+1 to that cleaning need from experience. The accelerator pump circuit is especially tough and an important part of the operation.

[fizzlebottom]

+1 to that cleaning need from experience. The accelerator pump circuit is especially tough and an important part of the operation.

Adding to that, the accelerator pump diaphragm probably needs to be replaced, and they're not usually found in a rebuild kit. If replaced, the stem will need to be shortened to match the original. Most replacements I've found came with ones too long so they can be shortened to fit several models. I typically end up blasting like 1/2 a can of carb cleaner through the accel. pump circuit to make sure its all clean. Test every now and then to see if stuff is squirting through. Haven't had to deal with any that are severely gummed up though, so maybe I've just been lucky.

[TimLoon]

Thank you for the input.
Reviewed Mike's website and will follow his recommendation of doing compression test before reaching out.
At this point, I am well into my 60's and although I have torn lots of carbs down, I am at the stage where I would rather let the experts do what they do best.

[Flyin900]

Tim that is a wise decision IMO. I have rebuilt lots of carbs and yours sound like they have issues likely with the slo jets and the accelerator pump circuit not working correctly. Likely partially gummed up from the choke use needed as you described.
These VB carbs can be difficult to clean properly without the proper tools and most importantly the knowledge. Mike has both, so if you go that route you will be fine.
Nothing worse on carbs that are difficult to remove and install on the bike, than doing it multiple times.

[DaveBarbier]

I do not know if Mike Rieck up in Mass does carb work, but if he does, it would also be top notch like his head porting and top end work (one of the best in the country for these SOHC4’s). He’s a member here so you may want to shoot him a message [mention]MRieck [/mention]

Mike did the head work on my 650/674cc hybrid stage 2+ build and that that thing screams. If he doesn’t do carb work he might know the guy who will.

But Mass may be a good bet because it’s probably not likely you’ll ship your bike out to Arizona, haha.