Topic: 650 cam into a 550

[paulages]

I was reading older posts regarding the 650 cam and came across a post that claimed the cb cam was only different from the 550 offering about .03 more lift, and no dration. 
Does anyone have any new info on this as I would like to not see this one slowly die like the other threads

according to the lobe measurements i made, that seems about right.

[squirley]

Paulages, on a previous post you mentioned that it appeared that the 650 cam had more duration, was this just a visual guess? Is there no added duration?

[JZEROE]

Well I'll be watching this thread VERY carefully...

In the meantime, though, what aftermarket cams are there? I haven't seen any at all...

[paulages]

Paulages, on a previous post you mentioned that it appeared that the 650 cam had more duration, was this just a visual guess? Is there no added duration?

yes, this is just a guess. not sure if there's any way of determining this with out measuring off of an assembled engine. i'd be surprised if those specs weren't out there somewhere already though.

[kayaker43]

This thread has some measurements

http://www.hondacb650.com/viewtopic.php?p=2682

There's a typo but I think it looks like an extra .028 and .021 lift which isn't huge, but at least we probably don't have to worry about piston clearance?

If it has some more duration that's a bonus. Apprently there's a 50HP 650 cam for Germany that's real weak.

My search turned up another thread and some guy has a 650 cam in his race bike,.. just says its awsome?? When my ebay cam shows up I'll report back. I don't have time or tools with me now to degree it in and give specs, but will give an impression of how it feels  I'm just changing the cam and nothing else on a stock motor with Hooker header and pods, so this should be revealing.

[kayaker43]

Hey Paulages, How about sharing some of that hard earned knowledge about other interchangability issues. You don't have to write a book, just a quick summary? What about things like dyno covers, clutches and clutch covers. and sprocket covers. I know the cam cover sort of works. Any chance of fitting a kickstart to the 650?

It would be nice to dress up a 650 motor in 550 covers. Maybe start another thread so searches will find the info easier?

[kayaker43]

As far as cam choices, the only one still around is webcam, but they regrind which I don't care for as much. Not sure if they weld up the lobes or grind the base circle. Otherwise hunt ebay for an old Yoshimura, Action fours, and I think Poweroll made one.

[kayaker43]

OK I found specs for Yosh cams.

Street special part# YH500-121-00

IN opens 20 BTDC, closes 50 ABDC  .278 lift
EX opens 50 BBDC, closes 20 ATDC  .307 lift


TT Special race cam  #YH600-122-00

IN opens 27 BTDC, closes 57 ABDC  .324 lift
EX opens 56 BBDC, closes 27 ATDC  . 336 lift


From another post, the lift on stock cams is:

CB650    IN .280 
            EX .293

CB550    IN .252
            EX .272

It looks like the 650 isn't too far the Yosh street cam as far as lift, not sure about timing?

[FunJimmy]

If the CB650 cam has higher lift without added duration, the ramps would be quite a bit faster.
More duration with the higher lift would be a likely senario.

Just a thought.

[kayaker43]

I think .030 or so more lift would have a miniscule effect on ramp angle, but more duration would add to it. No matter what, lift is good, but its the timing that matters. The most important timing event as far as "feel" is intake closing. Closing later moves power up the rev range because it gives more time to fill at high revs.

You can advance or retard the cam timing to move the power up and down the RPM range within reason. Even though you shifted all the other open/close events. they have less impact than intake closing.

Others have commented that you can easily see the bigger lobes on the 650 cam so I'm hoping for a noticable difference in feel?

I'm also wondering if the 650 valve springs wouldn't be better? They have to deal with heavier valves and a little hotter cam, so they must be heavier.

[paulages]

Hey Paulages, How about sharing some of that hard earned knowledge about other interchangability issues. You don't have to write a book, just a quick summary? What about things like dyno covers, clutches and clutch covers. and sprocket covers. I know the cam cover sort of works. Any chance of fitting a kickstart to the 650?

It would be nice to dress up a 650 motor in 550 covers. Maybe start another thread so searches will find the info easier?

the ignition covers are interchangeable. the stators and covers are not. the transmissions are, though there are differences in the needle and cage bearings on the end of the shafts. these must be mated with the appropriate cases. the clutch baskets are interchangeable, given the primary clutch gear is changed with it, though this will change the final drive ratio. the valve covers are not, at least without welding in some more material. a kickstarter cannot be added to the 650 without boring a hole and welding in a support post for the shaft. the 650 clutch cover could be used on the 550 (resulting in an lighter lever), as long as the 650 clutch pressure plate is used with it. 650 cylinders will plop right onto 550 cases, but the slot for the cam slipper must be mover forward 16mm. crank journals and bores use the same bearing selection parameters, which means that the 650 crank can be used on the 550 cases, as long as the appropriate clearances are checked and bearings selected. and as we know, the cam blanks are interchangeable.

most of this is already in the thread i started about my 718cc build. the actual build thread will contain more technical specifics.

[kayaker43]

Thanks Paulages, great info.

The cam cover interchange thing is like the 650 cam needing clearance in some 550 heads and not others. Apparently the castings just vary? The one I checked did have enough overlap between the mating surfaces to work, but a few corners were marginal. Its purely a sealing problem and a little bit of welding solves it. The 650 head and cylinder also have bigger cooling fins that can be trimmed to look like the old motors if you're building a "sleeper"

The primary drive ratio has changed from 500 to 550 to 650, each time spinning the clutch and trans faster to decrease the torque the components see. Changing the earlier motors over to the latest primary ratio would be a good thing for racing. Nice to know the 550 clutch cover fits too, that means the 500 cover would work if the 650 has a hollow transmission shaft to use the pushrod and actuator mechanism on the left side. I believe the sprocket covers interchange for all? Too bad about the stator covers, I'll have to see what can be done there?

I have a 6 speed Yosh CR trans so can't use the kickstart anyway. Back then a lot of the Honda trans parts interchanged, I wonder if the CB400F six speed is what the yosh kit is based on?

There really is enough info for a book, just wonder if there would be enough demand to write one?

[kayaker43]

Can you post a link to your 718 build? I've seen it a while back but can't hit the right search term to find it now? Also I bookmarked some very old threads that turn up dead now. I wonder if the archive gets purged or if was some info lost?

[paulages]

Can you post a link to your 718 build? I've seen it a while back but can't hit the right search term to find it now? Also I bookmarked some very old threads that turn up dead now. I wonder if the archive gets purged or if was some info lost?

a lot of the old links just need you to change the "us" in the address to ".net". here's the 718cc thread:
http://forums.sohc4.net/index.php?topic=13519.0

nothing you can do about the stator cover-- they actually changed the castings in that area, as the diameter of the 650 stator is a bit smaller. as much as i prefer the look of the 550 to the 650 i wouldn't touch the fins, as the extra cooling capacity will be helpful especially in an overbore.
 
you have it backwards on the clutch gear ratio with the 550/650. the reduced the ratio at the clutch on the 650 to reduce clutch slip. i forget the ratios, but i figured them out at one point and posted them either in that thread or another specifically about gear ratios. i believe the 550 mainshaft is still hollow with a brass bushing inside, but the 650 is not. billy has his 400F trans apart right now-- just for #$%*s and giggles i'll compare the two.

concerning the "book"... my 650/550 engine combo "how to" thread will be pretty comprehensive. maybe i'll add in as much of this info as possible so it will at least all be in one place.

[paulages]

doh! forgot one. the points or dyna ignitions can be used on a 650 provided you drill out the hole on the center of the advance mechanism or magnetic rotor to fit over the larger stud on the 650 crank. then the wiring must be reversed somewhere in the coil circuit as the 650 fires 180deg. out from the 550. i very nervously did this the the rotor on my dyna 2000. you also have to open up the hole a little bit on the crank for the locating pin as well.

[kayaker43]

Bummer, I cleared out all my dead links already

Let us know how that 400F trans looks. When I got the Yosh close ratio transmission, some of the gears were in OEM honda parts bags. I jotted down the numbers somewhwre and assumed they just cobbled it together with gears from other models. The 6 speed would obviously need a different shft drum so I assumed that was from a 400F? When i get back to Michigan again, I'll look closely at mu trans parts to see if we can't create a close ratio box from Honda parts??

Whatever the terminology, the newer primary gearing spins the clutch faster than it used to (a lower ratio meaning closer to crank speed), thus reducing the torque load it has to see for a given HP. Same principal as snowmobile brakes, one itty bitty disc spinning real fast. Some vintage dirt bikes even had a tiny clutch right on the crank and ATK used a tiny disc on the countershaft to get this same effect. The final drive ratios probably changed too unless the extra HP was able to pull the old gearing?

[paulages]

here's the link to the thread i started regarding 550/650 trans ratios.
http://forums.sohc4.net/index.php?topic=14672.0
i'm going with the 650 trans, but 550 1st gear. the 650 gears are actually all farther apart than the 550, but the 650 trans i had was in much better condition. the 5th gear ends in a lower ratio too, which could pull me a higher top speed depending on whether or not the engine can make power all the way through 5th. i'd love to figure out what the oem #s are on that yoshi kit. i'd pull the engine back out to get that kit fit in....

[kayaker43]

I spend winters in Florida till May and all my parts are in Michigan so I can't help with anything till then. I will start a thread on it when I can. I just know you can build a CR trans with parts from other Hondas. I ran the Yosh 5 speed kit and that's the one I have some part numbers for.

I also have the 6 speed kit but never used it. Someone installed it in a motor but put one shift fork on backwards and it didn't shift so I bought the whole motor. It also came with Yosh ported head, super rods, tt100 cam, not a bad deal for $200!!

The CR trans isn't good for street use. first gear was so high it was like taking off in third so it was brutal on the clutch. My powerband was from 8500-11,000 and the CR trans made it sound like a 125 motocrosser.

Your big bore motor will more likely be a torque monster so it will pull a wider spread of gears.

[hymodyne]

Found this recent thread on cam switches in a 550 head...

very helpful.

hym

[kayaker43]

Well I got my ebay 650 cam but its got a couple of lobes with some wear on them. I'm not going to drop it in my low miles motor. I was hoping for some instant gratification. I have another good cam but I'll have to wait a month or so till I get back home and try it again. At least the seller gave me a refund.

Visibly it appears to have some nice fat lobes with good duration that would be gentle on the valves. I've seen aftermarket cams with wicked pointy lobes that need crazy valve springs.

Too many people focus on lift and say its not enough change to be worth it but these engines responded well to more duration. At this point I'm still believing it will be a good cheap and reliable boost for the 500/550??

I just can't believe this hasn't been tried and well documented already 

[MRieck]

 In corresponding with hymodyne I guessed the 650 cam would have about .020 more lift than the 550 cam. Kayaker's #'s say I was close. I also guessed about 10 degrees more duration at least on the intake.

[kayaker43]

The big question is still unanswered after all these years,.. what does a 650 cam do for a 550? I would have thought this to be common knowledge after about 1984!!  Its got to be helpful and considering the availability of cheap 650 cams, it should be a no brainer upgrade for anyone rebuilding a 550??

Also within the limits of valve/piston clearance, how much more improvement can we see from adjusting the cam timing?

[hymodyne]

I know I would have to replace the cam sprocket from a 650 with the one from a 500/550K, but would it be necessary to oval out the sprocket mounting holes so the sprocket could be adjusted?

hym

[FunJimmy]

Sounds like a task for Mythbusters!

[kayaker43]

I hear you just bolt on the 550 sprocket and go? The only other complication is the tach drive will be off but this may be as easy as swapping the plastic drive gears???