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Author Topic: 550/650 hybrid or 650 big bore HOW TO  (Read 40994 times)

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Offline paulages

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550/650 hybrid or 650 big bore HOW TO
« on: September 09, 2008, 03:00:11 PM »
"HOW TO MAKE A CB550 REALLY FAST", or "CB550/CB650 BIG BORE INSTRUCTIONS"

i've been meaning to condense all the information i gathered during my 718 build into an easy to read how-to, and here it is. please note that all edits will go in this original post, so that any improvements to the article will be in one place. please PM me with corrections or suggestions to try and keep the clutter down.
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   When Honda produced the SOHC cb650, it was immediately following the end of the cb550 production, and it appears that they reused much of the tooling to keep costs down. The resulting improvements I think represented the pinnacle of Honda's SOHC4 design, but unfortunately the bike was at the end of an era and got little accolade. The port design in the head was drastically improved from the earlier fours, with short intake runners, a nice wide flat intake port floor, and less casting mess. The combustion chamber is a hemi design, with nice domed pistons to match. Honda claimed 50 BHP with the cb550, and 62 BHP with the cb650. Dyno reports show numbers more along the lines of 38 BHP and 49 BHP (1979 model) respectively, at the rear wheel. Both engines have untapped potential, but the 650 in particular I feel has more to give than was offered stock. Porting, a nice cam, better carbs, and freer-flowing exhaust alone will go a long way with either engine.

   The following is a list of all parts I found compatible/incompatible between both engines.

TRANSMISSION
---all gears fit both main and countershafts, but the 650 1st gear doesn't mate with the 550 kickstarter gear
---all transmission bearings are interchangeable, though there are some slight differences. the countershaft needle bearing on the 650 has a small oil pump built into the outer race/casing for supplying oil to the bearing.
---primary shafts are interchangeable, but the assemblies on them must be mated with their stock cases, as there is a slight difference in spacing between the bearings in the case.
---parts of the shift assembly/ bearing retainers on the clutch side are interchangeable, though I see no advantage to using one over the other.
---the clutch baskets are interchangeable, but the primary gear that mates with the clutch driven gear must match. if using the 650 primary clutch gear with the 550 clutch cover, some material must be removed from the cover in this area to avoid contact.
---the clutch pressure plate needs to match the cover from the same model, as the pushrod assemblies are different.

ENGINE
---both engines use the same hy-vo primary chain
---both cranks fit either case
---both engines have the same barrel and stud spacing
---the slots for the front cam chain guide are in a different location than the 550. all other 650 cam chain parts work with the 550 case.
---the 650 head is considerably different than the 550. a 650 piston won't even come close to fitting in the 550 head. the 650 head could be used with 550 pistons, though the compression ratio would be very low without appropriate pistons. picture of both pistons, with the 650 on the left:

picture of a 550 combustion chamber top:

same of a 650:

if you look closely, you can see how much cleaner the 650 dome is than the 550. the 550 castings can be unshrouded and look similar.
---the 650 cam will drop into a 550 head with similar results to a mild street performance cam. the 550 cam sprocket must be used, as will the 650 tach, cable, and cam driven gear.
---the exhaust port spacing is the same for both engines
---'79 & '80 cb650 intake ports will mate with SOHC cb550 and cb750 carbs

ELECTRICAL
---the locating pins for the ignition assemblies are 180 degrees apart from each other. The locating pin for the 550 rotor is also smaller than that of the 650. The 650 uses a larger stud to mount the ignition rotor, rather than the smaller bolt the 550 uses:

 The mounting ring for the 650 base plate is smaller in diameter as well, so the stock ignitions must be used, unless appropriate modifications are made.
---the tapered ends of the cranks that accept the alternator rotors are different. due to casting differences, the alternator used must match that models cases as well, unless otherwise modified.

covers
for those of you wanting to dress a 650 to look like a 550:
---both ignition covers are interchangeable, but the 650 is much thicker
---clutch covers interchange, with the appropriate pushrod assembly used
---sump pans interchange; 650 is deeper
---alternator covers do NOT interchange
---rocker covers do NOT interchange without modification


I hope this list will allow anyone really going through the process of building a 550/650 hybrid to pick and choose what to use, but I highly recommend testing these things for yourself if you're really going to get this deep into an engine build.
-------------------------------------------------------------------------------------------------------------

BIG BORE ON A CB650 ENGINE

   I'll start with what's necessary to go big on the 650, then follow up with the necessary modifications to do so on a 550 bottom.

parts list:
cb750 cylinder liners, cb750 pistons (or any other pistons with matching wrist pin diameter) and rings, custom head gasket (cometic.com), and standard gasket and o-rings.

1) Full engine disassembly is necessary. Bag and label everything as if your life depended on it.
2) Remove the cylinder liners. Place the cylinders on the oven at 200 degrees F for 10 minutes or so. Pull them out when hot, and the liners will come right out. with the weight of the cylinders on the bottom of the liners (sitting upright), you can usually tap the top of the cylinders with a rubber mallet, and they fall right off of the liners.
3) The cylinders and top case will both have to be bored out to fit the oversized liners

4) The new liners will have to be machined to the same height and taper at the bottom as the stock ones. when refitting, it will be necessary to flatten the edges of the flange at the top where they overlap, as well as machine around the outer two bolt holes and oil passageways.
 

4) If you are using cb750 pistons, the shoulder will be about 1mm too tall, requiring machining to fit. This will at least allow you to customize your compression ratio and piston geometry. In my case, we started by turning the pistons down .050", and at a 47 degree angle .020" in from the shoulder. This fit on the head, but clearances were a little tight. after a little more work, I ended up with a piston to head (squish) clearance of .027", and a piston to valve clearance of .098" (intake) and .116" (exhaust).
piston before:

pistons after machining:

5) Once fit and clearances are checked and compression ratio determined, the engine should be ready to assemble, following all usual procedures.

USING A 550 BOTTOM
The same can be done on a 550 using the 650 parts from the crank up, but require a little more work. I'll start with the necessary, then explain the "electives" i chose to do as well. Everything above applies, with the following being necessary on top of that:

1) The slots for the front cam chain guide need to be moved forward 16mm:
stock 550 location:

moved slots- lower is the modified location:


2) The alternator rotor I.D. needs to be opened up to fit on the 650 crank. the angle of the taper is 5 degrees. any competent machine shop can do this easily.
3) the locating pin for the ignition rotor is 180 degrees off, so this must be compensated for in some fashion. the easiest thing to do is to simply reverse the coil wires. the 650 crank also has a stud for mounting the rotor, rather than a bolt, and the center of the rotor (stock or dyna) needs to be drilled out larger to fit. The hole o n the crank for the locating pin on the rotor will have to be drilled a little larger as well.
650 on left, 550 on right:

drilled out rotor:


This is all that is absolutely necessary to fit the 650 crank, barrels, head, etc. onto the 550 lower. The following are further improvements I made:

1) The 650 has an oiler for both the primary and cam chains, fed off of the main galley in the bottom case. the adaption is fairly easy, as the 550 already has the mounting point.
650 oiler post:

modified 550 oiler post: note that the mounting point on the right was already there.

oiler installed:

2) the 650 clutch gearing is lower, to produce less strain on the clutch and therefore reduce slippage. I used the 650 clutch basket and then corrected the lower gear ratio at the final drive sprockets. I had to mill a little material out of the 550 clutch cover to clear the 650 primary clutch gear, as it's a little larger.

once everything is mocked up and spun through clearly, the engine is ready for a standard rebuild. don't cut any corners at this point.

---------------------------------------------------------------------------------------------------------

RESULTS
In addition to what i described above, i did the following performance modifications, and came up with the following results.
-64mm pistons, resulting in a displacement of 718cc and 10.6/1 compression ratio
-Stage 2 porting, kibblewhite valve springs, serdi re-cut valve seats by Mike Reick (forum member MReick)
-Megacycle 126-21 cam
-Dyna 2000
-Trans gears lapped in for reduced drag
-520 chain conversion
-early style CB750K carbs with K&N pods
-balanced crank/ piston/ rotor assembly
-mac 4-1 header with 1.5" I.D. glasspacked straight-through baffle

preliminary (untuned) dyno results:

69.7 BHP (182% increase from a stock 550...), and 41# of torque. not bad compared to stock...

---------------------------------------------------------------------------------------------------------
I hope someone else takes this project on. The results are incredible, and i can't describe how much more powerful the engine is. It has all of the low end power and grunt of a CB750, but with the smoothness of a 550. I feel like i can pull out of anything above 30 MPH in any gear i want. Try doing that in 5th gear on a stock 550...

here are some pictures of the engine installed in my 1976 cb550F frame:





EDIT: the engine has a new home as of 9/2009:


also, I have replaced the heavy duty clutch springs with stock items, and have had no slippage, which seems to support the 650 primary ratio as improved over the 550. the same clutch pack slipped a lot in the stock 550 engine.
« Last Edit: September 22, 2009, 11:23:17 PM by paulages »
paul
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Offline paulages

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #1 on: September 09, 2008, 03:09:01 PM »
paul
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Offline Shenanigans

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #2 on: September 09, 2008, 04:58:01 PM »
Great job paulages.

Given any suprises to any 750's yet?  :D
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Offline bwaller

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #3 on: September 09, 2008, 06:24:42 PM »
Agreed, well done Paul, nicely presented and concise.

Offline alltherightpills

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #4 on: September 09, 2008, 06:33:47 PM »
Mods, could we get this put in the FAQ so that it doesn't disappear into oblivion?

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #5 on: September 09, 2008, 07:09:34 PM »
Awesome Paul!!

It's awesome when others share info like this!!(IMO)


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Offline MRieck

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #6 on: September 09, 2008, 07:38:34 PM »
Agreed, well done Paul, nicely presented and concise.
+1 there bro
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Offline jeremy929

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #7 on: September 09, 2008, 07:39:36 PM »
Just out of curiosity, can you bore a 550 out to accept the 650 pistons, and use the 650 head with them?
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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #8 on: September 09, 2008, 07:49:03 PM »
Just out of curiosity, can you bore a 550 out to accept the 650 pistons, and use the 650 head with them?

Ummm.... huh? Isnt that exactly whats shown here?  ??? ???

   This pretty much sums it up.   76' CB592 cafe. 69 750 project, 03 CBR954, 75 750 super sport.

Offline Pinhead

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #9 on: September 09, 2008, 07:56:40 PM »
Subscribed for any further updates. Amazing. :)
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Offline paulages

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #10 on: September 09, 2008, 11:10:53 PM »
thanks guys! just glad i can contribute to the wealth of information on this site. i think i can safely say that i'm probably one of the world's authorities on this subject now.. ::) makes up for all the other #$%* i know nothing about....  ;)

Just out of curiosity, can you bore a 550 out to accept the 650 pistons, and use the 650 head with them?

Ummm.... huh? Isnt that exactly whats shown here?  ??? ???



yes you could, but most of the extra displacement found in the 650 was due to a stroked crank. the piston diameter increase is minimal at 1.3mm, while the stroke was increased 5.2mm. i imagine it would still improve performance a little, but most of it would be in the cam which will drop into the 550 head anyway.
paul
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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #11 on: September 09, 2008, 11:31:55 PM »
Mods, could we get this put in the FAQ so that it doesn't disappear into oblivion?



+1 with posting in FAQ! And I just want to add my thanks for sharing your experience and lessons learned.

I have a glaringly obvious amateur question: can you explain the specific differences between the 550/650 cam cover? I barely know anything about my own 550 still, let alone the under appreciated 650 but it's one of the first things I notice when I see one; someday I will do this upgrade however...mark my words!

Thanks again.
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Offline paulages

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #12 on: September 09, 2008, 11:42:17 PM »
Mods, could we get this put in the FAQ so that it doesn't disappear into oblivion?



+1 with posting in FAQ! And I just want to add my thanks for sharing your experience and lessons learned.

I have a glaringly obvious amateur question: can you explain the specific differences between the 550/650 cam cover? I barely know anything about my own 550 still, let alone the under appreciated 650 but it's one of the first things I notice when I see one; someday I will do this upgrade however...mark my words!

Thanks again.

the bolt pattern is the same, so you'd think they'd fit, but there are a few weak points where the o-ring wouldn't seal. i'd have to look again, but a very crafty person might make a new groove for the o-ring to sit in that would cover all necessary mating surfaces. i've come to like the 650 rocker covers, and realistically they're barely noticeable beneath the tank. the lower engine covers are much nicer on the 550 IMO.
paul
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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #13 on: September 09, 2008, 11:57:08 PM »
Is there really no functional difference between them? I just thought if one wanted to make a 'sleeper' (to the educated eye) 550/650 hybrid they could retain the 550 cover if it was possible. And yeah, I have nothing against the later cover- just different.



I'd like to retain the 550 kicker and go with the 650 guts.   
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Offline kayaker43

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #14 on: September 10, 2008, 07:50:48 AM »
Great info,... please sticky it!!

I like the classic 550 engine look and think the 650 cam cover destroys it. Others have used the 550 cam cover on the 650 head with a little sealer applied. The castings vary and sometimes there is enough overlap in the two shapes to work. Functionally it works, its just a matter of sealing the perimeter. The problem is primarily in the two front outer corners. I think some welding to fill in the square corners on the 650 head could be the  best solution.

Less obvious differences are the cooling fins. The 650 head has larger fins which is good, but they could be re-shaped slightly to look like the 550. The cylinder fins are also larger but less noticable. The cam cover is the biggest visual cue for the older engines.

I would also like to know what it takes to mix clutch parts to make the old cover and release mechanism work with the 650 parts. I'm talking about using a 650 bottom end to start with, and also could a kickstart be added????

Apparently the Dyno covers are just different sizes and won't work but the sprocket covers will.

No one talks about exhaust systems but the 550 headpipes are too small for the 650 ports. That means my old Yoshimura header won't work well, and the options are a cheesy Mac 4/1 for a 650 or a custom header. If you are building a racer, you probably want shorter head pipes than usual anyway.

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #15 on: September 10, 2008, 10:07:33 AM »
I would also like to know what it takes to mix clutch parts to make the old cover and release mechanism work with the 650 parts. I'm talking about using a 650 bottom end to start with, and also could a kickstart be added????

Apparently the Dyno covers are just different sizes and won't work but the sprocket covers will.

No one talks about exhaust systems but the 550 headpipes are too small for the 650 ports. That means my old Yoshimura header won't work well, and the options are a cheesy Mac 4/1 for a 650 or a custom header. If you are building a racer, you probably want shorter head pipes than usual anyway.

i thought i covered the clutch parts interchangeability, but here it is again anyway: all you need is to use the pressure plate from the 550, and the cover works. the ignition side cover fits fine, it's the alternator side that doesn't. the stouter 650 cover is currently protecting my dyna 2000. i'll add that above. i think a competent machinist/ welder could make a kickstarter work on a 650. locating the shaft in exactly the right place might be a little tricky, but if you did that it would just be a matter of fabricating the sleeve it rests in and bracing it in the case.
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Offline kayaker43

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #16 on: September 10, 2008, 11:33:17 AM »
Ok so fitting 550 clutch cover on a 650 bottom end is easy if you plug the kick shaft hole and clearance it for the larger primary gear and use the 550 pressure plate?

I think starting with the 650 bottom end is what most people would do and then dress it in older covers.

I can't seem to get a definitive answer on whether the inner kickstart shaft support hole is in the 650 cases (doubt it) or whether the meat is there and its just not machined?? Also not sure if the kicker gear meshes with the clutch hub gear, if so it won't ever work with the 650 clutch?

The 500 clutch pushes from the other side through a hollow transmission shaft. If you wanted that look, I suspect it could also be made to work as long as the 650 trans shaft is still hollow? The clutch cover may also have to be clearanced for the larger 650 primary gear. Can anyone confirm if the 650 shaft is still hollow? The 500 clutch cover is the best looking IMHO..
« Last Edit: September 10, 2008, 11:35:13 AM by kayaker43 »

Offline paulages

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #17 on: September 10, 2008, 12:07:24 PM »
Quote
Ok so fitting 550 clutch cover on a 650 bottom end is easy if you plug the kick shaft hole and clearance it for the larger primary gear and use the 550 pressure plate?

yes, or you could simply use the whole 550 clutch assembly and primary gear without having to mod the cover.

Quote
I can't seem to get a definitive answer on whether the inner kickstart shaft support hole is in the 650 cases (doubt it) or whether the meat is there and its just not machined?? Also not sure if the kicker gear meshes with the clutch hub gear, if so it won't ever work with the 650 clutch?

here's your definitive answer: the meat is not there on the 650 in regards to the kickstart shaft. also, it doesn't mesh with the clutch- it goes through the case and meshes with the 1st gear on the countershaft. most of the assembly resides inside the case, and must be installed through the sump pan opening. if you could locate the center from the inside, i think it would just be a matter of drilling the hole in the case, making a support sleeve for the outer side, and welding it in with supports. i thought i had pictures somewhere of both, but i can't find them. i think it would be easier to do the cam guide mod to a 550 case, but then you don't get the primary tensioner and oiler without further work.

Quote
The 500 clutch pushes from the other side through a hollow transmission shaft. If you wanted that look, I suspect it could also be made to work as long as the 650 trans shaft is still hollow? The clutch cover may also have to be clearanced for the larger 650 primary gear. Can anyone confirm if the 650 shaft is still hollow? The 500 clutch cover is the best looking IMHO..

i'll have to double check, but i'm pretty sure i remember that the 650 main shaft was different and not hollow like the 500/550. if you're building up from split cases, you could easily swap the mainshaft with a 550 though.
paul
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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #18 on: September 11, 2008, 10:06:47 AM »
i am so dying to do this. but i am also so broke. i'll start with the 650 cam and save money to bring over the rest.  ;D i love my little 550 and would love to suprise a few people. not many lol but some.
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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #19 on: September 18, 2008, 12:37:58 PM »
was just reading lordmoonpie's thread about a deep sump on a 750 and remembered that the 650 has a deeper sump than the 550. honda specs the same amount of oil for both, but the 650 pan definitely took more oil on the 718 engine. good for a wet sump engine.

edited at top to include engine covers interchangeability.
paul
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Offline Ecosse

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #20 on: September 18, 2008, 03:19:28 PM »
Thanks paulages! Is this nugget of info in FAQ yet?
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Offline paulages

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #21 on: September 18, 2008, 03:56:24 PM »
Thanks paulages! Is this nugget of info in FAQ yet?

i asked bob wessner to put it somewhere easily accessible. he said he put it in project shop. if you have a better suggestion, PM him.
paul
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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #22 on: September 19, 2008, 01:20:58 AM »
Ok..we know that the 650 pistons and head will work on the 550 which brings the displacement somewhere around 580 cc if i recall correctly when it was discussed my my thread about the 550 engine as well. What im wondering about is this...could the entire set of top end (cylinders, head, etc)  from a 650 be used on a 550 for those of us that do not have access to the tools to bore out the 550 cylinders?
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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #23 on: September 19, 2008, 12:07:13 PM »
Ok..we know that the 650 pistons and head will work on the 550 which brings the displacement somewhere around 580 cc if i recall correctly when it was discussed my my thread about the 550 engine as well. What im wondering about is this...could the entire set of top end (cylinders, head, etc)  from a 650 be used on a 550 for those of us that do not have access to the tools to bore out the 550 cylinders?

without changing the sleeves, you'd still have to mill the top case for the different cam chain tensioner location. if you're not looking for the extra stroke, you could use the 550 crank, rods, and jugs, with the 650 pistons and head. this would only give you a tiny bump in displacement though as mentioned above.
paul
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1974 CB550 (735cc)
1976 CB550 (590cc) road racer
1973 CB750K3
1972 NORTON Commando Combat
1996 KLX650 R

Offline DarkRider

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Re: 550/650 hybrid or 650 big bore HOW TO
« Reply #24 on: September 19, 2008, 03:02:43 PM »
I went back and looked through that old thread..it would take it up to 570 cc. Now if i did go with the just the 650 pistons and heads in bored 550 jugs would i be able to keep the 550 cam chain? Im guessing this is the reason for using the 550 cam sprocket on the 650 cam correct?
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