Topic: Pros & Cons of the CB650 engine

[bill440cars]

         I kinda looked around and didn't find anything on this subject, even though I thought I had seen
something on it. For near future reference, I'd like to know the good and bad features of this engine.
I know where there is one but, I don't know if it would be worth the effort. I would appreciate any input on this subject and I value your opinions. If I do go with it, I'll be putting it in a CB550 frame.
 
                                               Later on,  Bill

[GroovieGhoulie]

Upsides:

Will fit a 550 frame with no mods
More CCs probably mean more power (I've never checked it).

Downsides:

No kickstarter, or even the provision for a kickstarter.
I hear the EPA carbs are a pain with all kinds of pumps and vacuum things and other nonsense.

If you don't llike tuning your carbs and are ok with electric start only, then you should be good to go.

[bill440cars]

Hey Groovie,
             I was thinking that it would fit the 550 frame. I didn't know about the kick starter but, (while
I'd like to have a kick starter) my 80' CB750K doesn't have one either. Will other carbs work, I read all
the time that 750 carbs will work on a 550? I don't remember if this engine has carbs or not. I'm not
sure if I'll go after this or not. Might just be asking for problems. I've got plenty of time to sort this out
so I wanted to run this by you guys for some input.  Than you,  Bill

[GroovieGhoulie]

I'm no 650 expert (being a 400 owner and all), but I'm not sure if 550 carbs would work.  750 carbs on a 550 flow too much fuel and air and unless the motor is highly tuned and modifed, it ain't gonna run right, and when it does it'll be on the top end running flat out.  It'll still suck around town.

I like engines that I can work on and the non-adjustability of the 650 carbs is a issue to me as is no kickstarter.  I want the redundancy and the look.  Pushing a button is ho-hum, but jumping up and lighting that sucker with your foot, now that's cool.  YMMV.

If you just want to bolt it on and ride, I'm sure it'll be fine. 

Now and interesting concept would be 650 crank, pistons and cylinder on a 550 case.  Then you get the kickstarter.  I'll bet you could jet the 550 carbs up to feed the 650.  Maybe.

[cb650]

Things I've gathered but not done to the 650.  It will fit in a 550 frame.  The 79/80 650 carbs wll fit on a 550. FYI the 81/82 carbs head where diff.
No kick starter sucks but factory electronic ignition is cool.  A lot of complants with the charging but I have never had a prob. 



                      Terry

[Vatch]

Should fit on the 550 frame.  The 650 (actually 627 or something) is a modified 550.  Carbs on '79 are not overly complicated.  Some people have suggested the 650 engine did not last as long as the 550 or 750 due to the enlarging of the 550, but I've never seen any real data on that. 

[Ted Nomura]

         I kinda looked around and didn't find anything on this subject, even though I thought I had seen
something on it. For near future reference, I'd like to know the good and bad features of this engine.
I know where there is one but, I don't know if it would be worth the effort. I would appreciate any input on this subject and I value your opinions. If I do go with it, I'll be putting it in a CB550 frame.
 
                                               Later on,  Bill

I heard that CB650 engine is not as reliable as the CB550 but that's motorcycle magazine test riders talking.

[eldar]

I think the 650 died mainly because the sohc was phased out for dohc. Probably nothing more than that.

[TRPLE]

I've read a lot about interchangeability between these engines.  Somewhere else in this forum is a thread about someone who is going to make a 672cc out of a 550.  When I read an article about that, it basically called for using the 550 cases, 650 head and cylinders, and then capping it with a 550 cam cover for better aestetics.  I certainly would imagine that if the 650 is based on the 550 that it has the same bore spacing.  If it does, the carbs ought to be easily swappable.  Those Kehin CV's are just junk if you don't leave them stock.  A buddy had them on a CB450 and we fought them forever.

I can't say that I've done any of this, of course, but there is at least one resource out there that discusses it.

 - Matt

[byidesign]

If you are interested in tuning the cv style carbs get the
   Haynes motorcycle carburettor and fuel injection techbook.
   it is a good investment {covers ALL carburetion} and there is
    a lot of fine tuning you can do easily to the cv's, after reading the book,
    My 82 cb650sc has a little over 140,000 miles, still runs great..
      {moter refreshed only once]   follow "hondamans" advise
     and change oil and filter often.

[Ted Nomura]

If you are interested in tuning the cv style carbs get the
   Haynes motorcycle carburettor and fuel injection techbook.
   it is a good investment {covers ALL carburetion} and there is
    a lot of fine tuning you can do easily to the cv's, after reading the book,
    My 82 cb650sc has a little over 140,000 miles, still runs great..
      {moter refreshed only once]   follow "hondamans" advise
     and change oil and filter often.

Wow, 140,000 miles, even my Honda PC800 don't have that much and it's now ready for an overhaul.

[Vatch]

I think the 650 died mainly because the sohc was phased out for dohc. Probably nothing more than that.

Yeah, that's my understanding.  The 650 may be the ultimate rat bike as it was put together with other parts and technologies in the factory.  Not much novel engineering going on there, just the last of the breed.  Not that it's a bad thing.

[rob]

Isn't the engine in most 650's just a bored 550?  They advertise it as a 650, but the actual displacement is a less (perhaps 627?).  Can anyone comment on it?

Rob

[scunny]

650 is a 550 bored and stroked with larger valves etc etc, as for reliability I'm pulling apart an engine with 75,000 k's and there doesn't seem to be much wear so far.

[scunny]

sorry, forgot to add that both my engines have 626cc stamped on the jugs

[cb650]

They are all junk but you can send them to me.
Only one time in all my travels on a 650 has one stranded me.  A spring in the tranny broke and it wouldnt shift.  Runnin but stuck in 2nd gear. Took $1 to fix it.  Damn junk anyway!!!


                       Terry

[nickjtc]

Still reading through old posts........

So here's a question. Why would a person want to take a 650 motor and put it in a 500/550 frame? Or a 750 motor, for that matter? Just curious.

[scunny]

nickjtc... some people just like to mess around with things.
and as an update on my 79 motor, it's lying in a million pieces and the only other part that looks suspect is some wear on the primary chain tensioner, I will probably fit new chains and bearings since it's apart anyway

[Pinhead]

The 627cc motor in the 650 was the "last" of the SOHC4's and has the best of them all. It has a true hemispherical combustion chamber with slightly domed pistons. The camshafts are basically the same, though the 650 has a tad more lift and slightly more duration. If you put a really hot cam for the 550 into a 650, you won't be as "extreme" though you've got the extra cc's to make up for it. The electronic ignition is great, I haven't had any trouble with mine thus far. The charging system can be a pain, though if yours works and you go through the connections to eliminate corrosion you shouldn't have any trouble.

About putting a 650 motor into a 550... I'm not sure about the balancing of the frame, etc. but there are more aftermarket parts specifically for the 550, so that could be the advantage of the 550 frame with the 650 motor. Also, it kind of makes it more of a "sleeper" if your race buddy doesn't really know what he's looking at. "I can whop a puny 550..."

I've got a '79 650 and I replaced the mains, went from 90's to 102.5's. Removed the stock aribox cover, and will be slightly drilling out the exhaust. After just the jet change and cover removal, all I can say is, "WOW!" It'll lift up the front tire in 1st and 2nd. I've never ridden a 550, but I don't think many of them are doing wheelies...

[scunny]

Pinhead, I read your other post regarding the ability to save on front tyre wear after the jet change, I might have to try that when assembling my bike.

[Pinhead]

Most people recommend going with 98 mains. I got 102.5's because I couldn't find the 98's (didn't look very long, though). Before I took off the air filter cover it was running rich. Sputtered at 1/4 throttle and the exhaust stunk of gasoline. Wouldn't run over 6k down the highway. After removing the cover, I was amazed. I may be running a tad rich (haven't done a WOT plug chop because I'd have been running 100mph) but I'm definately impressed.

[prsman23@hotmail.c]

I've got a '79 650 and I replaced the mains, went from 90's to 102.5's. Removed the stock aribox cover, and will be slightly drilling out the exhaust. After just the jet change and cover removal, all I can say is, "WOW!" It'll lift up the front tire in 1st and 2nd. I've never ridden a 550, but I don't think many of them are doing wheelies...

I've got to agree I had a 650 (buying it back this week hopefully!), completely stock and I got the front up, my 500 would take a lot more coaxing...

[eldar]

While i dont care for the 500/550, I would liek to get my hands on the the last 2 years of the 650. I like its styling a bit better than the 79.

[prsman23@hotmail.c]

Yeah the one i"m getting back is an 80. I dig it alot for some reason, not as much as my 750, but it's such a quiet easy going bike. I used it alot for errands and cruising the backroads, just a nice little bike in my opinion.

[Vatch]

Damnit.  Now I need to get my front wheel off the ground.