Topic: CB650 using a cb550 high performance cam

[Soos]

I was just curious about your exhaust set up.  The 550 firing order is 2-1-3-4.  To get the most even flow out the two exhaust exits, a crossover is required.  The crossover type is said to give the engine better low and mid range power characteristics such as is needed for street machines.  But, they seem to be rare.  I ran with a 4 into 2 and parallel head pipes for years.  It works fine.  If both your exhaust systems are the same, it shouldn't matter which set you chose.  If you feel the flow restriction on one is different from the other, then definitely chose the one you want before fine tuning the carbs.

this a quote by two-tired in this thread http://www.sohc4.us/forums/index.php?topic=20254.15.

The timing for my cb650 is 1-2-4-3....

Would it be possible to use the "hot street/cafe racer" cam from webcam  http://www.webcamshafts.com/for the 550, phase it 180 out of timing to get it to time the valves opening and closing correctly for my 650?
the lift would increase 0.030(inches)
Not too sure how they figure the webcam cam's stats, but the page says the cam i'm eyeing has


HONDA 500 / 550 SOHC 4 CYLINDER (1971-1978) 8v
VALVE LIFT                                        .330
DURATION   IN DEGREES                        290
DURATION@.050 IN DEGREES                265
GRIND NUMBER                                    58b


CB650 cam technical info is as follows:
intake valves:
opens(BTDC) 5deg     @1mm lift
        (BTDC) 58deg.  @0mm lift
closes(ABDC) 35deg.  @1mm lift
        (ABDC) 127deg. @0mm lift

Exhaust valves:
Opens(BBDC) 40deg.    @1mm lift
        (BBDC) 121deg.  @0mm lift
closes(ATDC) 5deg.     @1mm lift
        (ATDC) 65deg.    @0mm lift

Not too sure how that info works out to duration on the cb650's cam.....
well, using http://www.webcamshafts.com/pages/degreeing.html I come up with:
@1mm lift:
10deg. overlap
220 deg. for intake
225 deg. exhaust
@0mm lift:(these numbers seem WAY too wierd to be true)
123deg. overlap
365deg. intake
366 deg. exhaust


I really want a upgrade for my cam to go along with the new pistons i'm going to use, and this is the only other option besides sending the stock cb650's in and having it hardfaced and re-ground.
From my conversation with a Webcam salsewoman, it would be cheaper(hence the shoestring budget) to get the 550 cam than have mine welded and re-ground.

thnks for any help here.

l8r

[Soos]

just noticed the subject line was way off....


Anyone have any ideas on this?



l8r

[crazypj]

It should drop right in and work as intended.
You have to fit the 650 cam 'gear' instead of 550 sprocket which is the only thing I can think of which may be different although I don't think they are. If you time 180 degrees out, it means cyl4 will fire instead of cyl1 as cam runs at half crank speed.
Next time the crank does a 360, cyl 1 will fire. The ignition is crank triggered and not digital so it wont matter, it fires every time the reluctor passes trigger coil, just like a points set up (and has mechanical advancer)
 You do realise you will have to rev it higher though, no more plodding around at 2~3,000rpm

PJ

[Ibsen]

You have to fit the 650 cam 'gear' instead of 550 sprocket which is the only thing I can think of which may be different although I don't think they are.

The 650 have got a HyVo cam chain, so the sprockets are not the same.

[paulages]

...but are interchangeable. you just need to keep the hyvo sprocket to use with the 550 cam.

[crazypj]

Duh, Its what I mean but not what I said , I meant the mountings for sprocket and Hy-vo chain 'gear' are same
PJ

[paulages]

i gotcha pj-- i was just clarifying ibsen's post.

[Soos]

It should drop right in and work as intended.
You have to fit the 650 cam 'gear' instead of 550 sprocket which is the only thing I can think of which may be different although I don't think they are. If 

You do realise you will have to rev it higher though, no more plodding around at 2~3,000rpm

PJ

I actually have purchased a cb550 stock cam to ensure the fit, and it is a drop in, I know the cam gear from the 650 will have to stay, and they do haqppen to swap easily between the 2 cams....

and as to not plodding at 2-3000 rpm....
i'm seeing how far I can take a 650(without just shoving money at this pit)...
I'm figuring that while i'm boring the block to 65mm, i better make sure this beast will be able to breathe to take the best advantage of the pistons.
A little home done head work, and a new cam should really be able to take advantage of the larger piston bores.
Not trying to make a racer... but it may end up that.



l8r

[crazypj]

 
PJ

[Soos]

Ok, I am actually getting work done on my next motor, and I started looking at my cams I have.


First I measured the '81cb650c cam I have out.
Seemed odd... I swore I rembered checking my '79 cam, and it had more lift....

Well, while out in the garage, I pulled my '79 cb650 and '81cb650c cam as well as the ebay special '74 cb550 cam I bought to see the interchangeability.
And started measuring lobes and base circles.

WOW.
Either the '79cb650's cam is WILD, or I got a doozy of a deal on that parts bike.


The measurements I am coming up with are as follows:
550(1974)
1.362 lobe            1.382
1.110 base circle   1.110
0.252 lift               0.272

650(1981c)
1.360                1.380
1.105                1.105
0.255                0.275

650(1979std)
1.390                1.403
1.110                1.110
0.280                0.293



Does anyone know of someplace that shows lift of different stock cams for honda 4's?
I searched, but cannot find anything about the 550's stock lift or the 650's.

My manual shows the "cam lobe height"specs as
intake  : 1.4062-1.4089
exhaust: 1.3903-1.3966

wear limit intake   :1.40
wear limit exhaust :1.39

So did the "C" get de-tuned?

Anyone out there have a cb650 or 550 cam they can measure to compare against?




l8r

[paulages]

Ok, I am actually getting work done on my next motor, and I started looking at my cams I have.


First I measured the '81cb650c cam I have out.
Seemed odd... I swore I rembered checking my '79 cam, and it had more lift....

Well, while out in the garage, I pulled my '79 cb650 and '81cb650c cam as well as the ebay special '74 cb550 cam I bought to see the interchangeability.
And started measuring lobes and base circles.

WOW.
Either the '79cb650's cam is WILD, or I got a doozy of a deal on that parts bike.


The measurements I am coming up with are as follows:
550(1974)
1.362 lobe            1.382
1.110 base circle   1.110
0.252 lift               0.272

650(1981c)
1.360                1.380
1.105                1.105
0.255                0.275

650(1979std)
1.390                1.403
1.110                1.110
0.280                0.393



Does anyone know of someplace that shows lift of different stock cams for honda 4's?
I searched, but cannot find anything about the 550's stock lift or the 650's.

My manual shows the "cam lobe height"specs as
intake  : 1.4062-1.4089
exhaust: 1.3903-1.3966

wear limit intake   :1.40
wear limit exhaust :1.39

So did the "C" get de-tuned?

Anyone out there have a cb650 or 550 cam they can measure to compare against?




l8r

i have both sitting on a shelf at my shop. i'll try to remember to measure them today. those measurements seem to reflect what i remember about the differences between the '79 650 and 550. i wasn't aware that any of the 650's had cams so close to that of the 550, so to me the C cam you have is the mystery.

[Kevin400F]

Are the rocker arm ratios the same between 550 and 650?

[cb650]

There was a "50 hp" cam put in german sold bikes.




               Terry

[Soos]

The '81 cb650c I bought from my neighbor, and he got it from the original owner.
The original owner supposedly bought it new off the showroom floor at a dealership in Salt Lake City(60 miles from where I live).
I DO know there has been someone into the motor, there were a few loose(needed re-torqued?) head bolts, and there were 2 stripped threaded holes holding down the cam covers.(the original inspiration to put a '79 head on the bike) So I guess I cannot guarantee the originality of that cam.(for the '81 cb650c)


I brought the last un-measured ('80 cb650std.) cam home from work, and it measures identical to the '79 cb650std.
Both the '79 and the '80 std cams i'm 99% sure are original to those motors though.
(100% sure on the '79)



Could anyone out there possibly get some measurements off of a 50hp cam??

Are the rocker arm ratios the same between 550 and 650?

I am not really sure, not having a 550 head to compare measurements to.
And I have not measured the rocker arms from a 650 either.
Although if someone comes up with the measurements for a 550 rocker arms, i'd measure a 650 set of rocker arms for comparison.

Who knows, mabey it would be possible to get a added lift with just swapping the arms from one head to another?



l8r

And thnx all!

[CBJoe]

Any update on the cam comparisons??

I have an '80 CB650C engine that i'm tearing down soon and this post has got me interested.

cheers...Joe

[cb650]

On the 650 site someone has some of this info and a pic of the 50 and 63 hp cams.  50 looks terrible.  Think the 650 cams were all the same excet for this.   


                         Terry

[Buber]

If you can see it without loggin on..
http://www.hondacb650.com/viewtopic.php?p=2682
if not, here is what we have there:
650(1981c)
1.360 Lobe 1.380
1.105 Base circle 1.105
0.255 Lift 0.275

650(1979std)
1.390 1.403
1.110 1.110
0.280 0.393


FIND MORE INFO ON STOCK LIFTS 550 AND 650!!!

650 Manual states
Intake lobe :1.4026-1.4089
Exhaust Lobe:1.3903-1.3966
Wear limit intake :1.40
wear limit exhaust :1.39

Here is what I measured at an old 63hp camshaft (probably Z-model) with a slide caliper rule from smallest and largest lobe dimensions:

intake 35.7mm
outlet 35.3mm
base circle 28.25mm