Topic: 550/650 hybrid or 650 big bore HOW TO

[Soos]

With the stock cb650 liners you can get away with 62mm ID bore.
(However you can use the stock cb650 head gasket up to 61mm.)


I have found that CB900 liners are good enough to work.... but only when going 65mm or bigger, as the cb900 has a 64.5mm bore already.


And the cb760 pistons that are useable, are:(from what I have seen so far)
1.) overbore kits for the 750(the 836, and 812 kits in particular) - they tend to give the cb750 a bump in CR, and the dome is needed for the 650 head.
2.) '77/'78 cb750 pistons with the raised dome




DO NOT try with the '69 through '76 cb750 pistons in conjunction with a 650 head... unless you want to run a turbo.

Every window an opportunity.....




The '79/'80 cb650 head is perfectly aligned for use with cb750 carbs BTW...

According to Soos' info on using 750 high dome pistons with the 650 liners, and the lack of availability of the 750 liners (tried looking but can't find right now) should I just go with the stock SOHC 650 liners?

I'm also planning on lightening and balancing my crankshaft to help out. Also seen some people talking about running stock GSXR connecting rods because they were more light weight. Anyone know if they'll be kosher with the 550/650 Big bore hybrid?

Is there someone besides me using  GSXR 1000 rods?
Mine now have the proper bearings and new bolts installed, but not in a  running yet.
I have LOTS to do before they get running(unfortunately).

The GSXR rods have the same ID where the bearings go, and the shell bearings are the same thickness.
The GSXR crank has the same stock specs and tolerances(nearly) as the CB650 crank.
Center to center of the GSXR rods(bore to bore) are IDENTICAL to the cb650 rods.

IF you can run cb650 rods, then you can run GSXR1000 rods.

BUT **************BE CAREFUL***************
There are only a few years (mine are '06, just checked) that use the proper style of bearings.
I'm still researching rod alternatives.(found some nice options, but some are just flat out pricey!!) The GSXR rods seem to be the only CHEAP(yeah... $300 later for bearings and bolts... cheap.....)
But still under the $1700 tag I got for custom rods, or 1200 for -2mm stroker GSXR rods(I got pistons that would work with that combo though)



If I were loaded I would have a personal shop, and my own website full of tidbits I have learned for others to copy at will......









Ahhh.... but all I get is a kick in the nutz, and a year older.




























l8r

[Soos]

Oh, the pin bore on those GSXR rods is the same as the cb650 as well.




l8r

[Pinhead]

Man, Soos! I'm half-tempted to gather all of your posts on 650 alternative parts and put them in one thread...From what I've read from you so far, there are almost as many parts available for the 650 as there are for the 750! (just by coincidence instead of design)

[kayaker43]

I was just thinking that,.. There's so much good info here but its scattered all over the place.

[Soos]

Man, Soos! I'm half-tempted to gather all of your posts on 650 alternative parts and put them in one thread...From what I've read from you so far, there are almost as many parts available for the 650 as there are for the 750! (just by coincidence instead of design)

If you do, you might want to search over at http://www.hondacb650.com/ as well.
I've posted a few things there.





I've found overbores in :
61mm , 62mm(but impossible to find rings), 65(836 cb750 overbore pistons), and 66mm(easier than 62mm rings, but not un-obtainable)

Paulages is running 64mm 812 cb750 overbore pistons.
And I believe (??Scunny??) has a 65mm bored cb650 as well.




The only PITA about the 650 is not too many people are willing to buy oddball piston set just to look into the option of an overbore.
Heck, most riders never bore out their motors!
I just happen to have enough curiousity, and am willing to risk the $$ for oddball parts(when it's cheap) to check possibilities out.
Pistons, rods, and carbs are about only what I have found little oddball parts that work on a 650.
Others builds (like paulages 550/650 hybrid!) do prod me on though!
Seeing something liek that makes me think what other bikes are close enough to share parts.

I tend to look at specs like bore, pin diameter, carb venturi ID, stroke, DOHC or SOHC(strange the KZ's are DOHC, and have only 2 valves per cyl!)


If you make a compendium, PLEASE post it!
I'm not anywhre the only one tinkering with the 650 motors out there.


and the 750 has short throw rods and stock lengths available, diff. stroke cranks, overbore kits, finned covers, CAMS(god I wish there was SOMEPLACE that didn't want an arm and a leg to make a high profile 650 one!!)

The 650 can use the 550 re-grinds to gain a bit of lift/duration, but you have to convert to a 500/550 tach and tach gear(another aded expense... )





l8r

[mlinder]

I tend to look at specs like bore, pin diameter, carb venturi ID, stroke, DOHC or SOHC(strange the KZ's are DOHC, and have only 2 valves per cyl!)

Not that strange. Most early twin cam bikes were still 2 valve. They didn't do it to get more valves, they got it to change valve geometry, lose the tappets, and have the ability to time intake and exhaust valves differently for increased performance.

[Ecosse]

Not that strange. Most early twin cam bikes were still 2 valve. They didn't do it to get more valves, they got it to change valve geometry, lose the tappets, and have the ability to time intake and exhaust valves differently for increased performance.

good point.

[Soos]

Not that strange. Most early twin cam bikes were still 2 valve. They didn't do it to get more valves, they got it to change valve geometry, lose the tappets, and have the ability to time intake and exhaust valves differently for increased performance.

good point.

Interesting, hadn't thought of that.




l8r

(sorry to hijack the thread paulages)

[manjisann]

First off, Paulages thanks a ton for taking the time to post all of this, and everyone else. I've read this a couple times, but have a few questions. I apologize if I ask questions that have already been covered, but my knowledge of the inner workings of motors is very limited so things that may have already been explained probably went right over my head.

I have a 550 and 650 engine. My current thought is to just take the top end off the 650 engine and put it on the 550 bottom. Here are my questions. Do I need to change crankshafts from the 550 to the 650 if I plan on using the 650 shafts and pistons up? I understand that the 650 has a longer stroke ( am I getting that right?) is this a result of the crankshaft?

I'm doing this mainly to learn and because I can (or at least I think I can  ). I don't have any plans to race this, and I'm really a pretty conservative rider, so wringing the max power out of it isn't my ultimate goal (although I do plan on breaking a ton on it, just so I can say I have.) What I'd like to do is bring the best of both engines into one as efficiently and inexpesivly as possible. I'd like it to make 100 fairly easily with a bit left over, if that makes any sense.

If this info has already been covered, please feel free to just tell me which post to reread. Sorry if I'm cluttering up the thread with my question.

Thanks,

Brandon

[paulages]

First off, Paulages thanks a ton for taking the time to post all of this, and everyone else. I've read this a couple times, but have a few questions. I apologize if I ask questions that have already been covered, but my knowledge of the inner workings of motors is very limited so things that may have already been explained probably went right over my head.

I have a 550 and 650 engine. My current thought is to just take the top end off the 650 engine and put it on the 550 bottom. Here are my questions. Do I need to change crankshafts from the 550 to the 650 if I plan on using the 650 shafts and pistons up? I understand that the 650 has a longer stroke ( am I getting that right?) is this a result of the crankshaft?

I'm doing this mainly to learn and because I can (or at least I think I can  ). I don't have any plans to race this, and I'm really a pretty conservative rider, so wringing the max power out of it isn't my ultimate goal (although I do plan on breaking a ton on it, just so I can say I have.) What I'd like to do is bring the best of both engines into one as efficiently and inexpesivly as possible. I'd like it to make 100 fairly easily with a bit left over, if that makes any sense.

If this info has already been covered, please feel free to just tell me which post to reread. Sorry if I'm cluttering up the thread with my question.

Thanks,

Brandon

hi brandon-

yes, the longer stroke is due to the position of the rod journals in relation to the center axis of the crank journals. in other words, yes: the extra stroke is in the crank. if you want to do this project, make no mistake: it will not be inexpensive unless you cut corners and/or know or are a machinist. that said, if you take your time and do things right you can easily do this. my best advice is you want to do this is to tear both engines down and get a clear idea of what it is exactly that you'll be doing. that plus a good machinist and the help of this forum, and you can have a 550 sleeper that can easily get you to 100MPH.

[B.O.X.N.I.F.E.]

You guys keep going with this. There are those of us out there that are really taking notes. I've already talked to MRieck about doing the work and am in the planning stages of building up a big 550 bike to take out to Bonneville. I'll do a second cross country trip on the 550 before I make any permanent alterations to the frame, but I'll be building up the second motor in the meantime. Trying to do it on a realistic time frame, maybe run in 2011. Anyways, there's guys brainstorming now and you'll see a lot more big 550's because of these threads.

[manjisann]

Paulages, thanks for the clarification with the crankshaft. I realize it won't be cheap like say just swapping the camshafts. I'm going to do it right. In my experience, all cutting corners does is make it more expensive and usually causes more work. I'll have to reread this thread a few more times and take notes, I'm sure I'll have more questions. Thanks again for all the info, without this forum and people like you I wouldn't stand much of a chance of doing cool things like this!

Brandon

[manjisann]

Another question I just thought of. Do I need to upgrade from the cb500 coils to the 650 or even better? I'm going to be running a hondaman box.

Edit- Thought of yet another question. With the basic engine mods, will I need to run a high flowing petcock? I'm going to be fabricating my own tank (or at least giving it a serious try) and I'm trying to figure out what the best petcock will be, so I know what fitting to braze in. Are all modern petcocks the 22mm ones that I'm finding the fittings for?

Thanks again!

Brandon

[paulages]

Another question I just thought of. Do I need to upgrade from the cb500 coils to the 650 or even better? I'm going to be running a hondaman box.

Edit- Thought of yet another question. With the basic engine mods, will I need to run a high flowing petcock? I'm going to be fabricating my own tank (or at least giving it a serious try) and I'm trying to figure out what the best petcock will be, so I know what fitting to braze in. Are all modern petcocks the 22mm ones that I'm finding the fittings for?

Thanks again!

Brandon

brandon-

the HM box won't work with the 650 ignition, as it is a crude electronic ignition. in my opinion, you should modify the crank to accept points-based igintions so you'll have more options- hondman or dyna. the 650 ignition is limited, and the conversion is easy.

if you're fabbing a tank, i'd go for dual petcocks, or if the carbs you decide on only have one inlet, just make sure it's something that will flow well. if your options are open, there are plenty of good products out there.

[manjisann]

if you're fabbing a tank, i'd go for dual petcocks, or if the carbs you decide on only have one inlet, just make sure it's something that will flow well. if your options are open, there are plenty of good products out there.

   haha, hadn't really thought of that. I'm going to be running some 73ish 750 carbs on it, I really hate the 650 carbs, and the old 750 carbs look like they have bottle caps on them   I'll do the 2 petcock idea, so that should fix that. I saw a cool petcock that the base was a banjo bolt so you could swivel it 180 degrees, this allowed the feed line to not kink as bad. I'll have to save up for a couple of them.

the HM box won't work with the 650 ignition, as it is a crude electronic ignition. in my opinion, you should modify the crank to accept points-based igintions so you'll have more options- hondman or dyna. the 650 ignition is limited, and the conversion is easy.

Thats true, I hadn't thought it out that far I guess. Could the 550 ignition be modified to fit on the 650 crank? Sorry, aside from ultra basic tuning I'm not super familiar with the ultra intracacies.

Thanks again for all your help!

Brandon

[mlinder]

The old BMW's had two petcocks, with a crossover inbetween them. Good setup.

[paulages]

if you're fabbing a tank, i'd go for dual petcocks, or if the carbs you decide on only have one inlet, just make sure it's something that will flow well. if your options are open, there are plenty of good products out there.

   haha, hadn't really thought of that. I'm going to be running some 73ish 750 carbs on it, I really hate the 650 carbs, and the old 750 carbs look like they have bottle caps on them   I'll do the 2 petcock idea, so that should fix that. I saw a cool petcock that the base was a banjo bolt so you could swivel it 180 degrees, this allowed the feed line to not kink as bad. I'll have to save up for a couple of them.

the HM box won't work with the 650 ignition, as it is a crude electronic ignition. in my opinion, you should modify the crank to accept points-based igintions so you'll have more options- hondman or dyna. the 650 ignition is limited, and the conversion is easy.

Thats true, I hadn't thought it out that far I guess. Could the 550 ignition be modified to fit on the 650 crank? Sorry, aside from ultra basic tuning I'm not super familiar with the ultra intracacies.

Thanks again for all your help!

Brandon

read back to the first post.. it's all there.

[manjisann]

read back to the first post.. it's all there.

   Sorry, will do

The old BMW's had two petcocks, with a crossover inbetween them. Good setup

Did the carbs that the BMW's used have 2 fuel inlets or just one?

Thanks a ton guys!

Brandon

[mlinder]

Two. The carbs were on either side of the engine case. Boxer engine, and all that.

[paulages]

i posted this on the original build thread, but i'll post here as well..

my friend and machinist Dan Hall passed away tuesday afternoon, and as he was integral to me making this project happen a eulogy here seems appropriate. he competitively raced his nissan 200sx nationally up until 2007 (in his 70's), and was a master machinist and engine builder, with a type of knowledge that has passed away forever. he had been building and racing since the 50's, and knew an incredible amount about the "big bang" that makes engines go fast. he was a great man who lived his life by his terms, something i always strive to achieve.

may he race in peace.

[bwaller]

Sorry to hear that Paul, I know you're proud of the work you two accomplished.

[sinister902]

I just need to bump this up with a question I felt was un-answered in the original thread.....I have read through this 5+ times now because I have a spare 550 engine already half apart. I want to do the 750 liners and big bore pistons with the 650 head.....do I NEED anything 650 besides the head and cam? would I be able to just machine the 550 jugs for 750 liners, drop in some 836cc kit pistons(modified per paul's specs in first post), and toss a 650 head on there? Or are all 650 guts pretty much required to build this beast?

[paulages]

I just need to bump this up with a question I felt was un-answered in the original thread.....I have read through this 5+ times now because I have a spare 550 engine already half apart. I want to do the 750 liners and big bore pistons with the 650 head.....do I NEED anything 650 besides the head and cam? would I be able to just machine the 550 jugs for 750 liners, drop in some 836cc kit pistons(modified per paul's specs in first post), and toss a 650 head on there? Or are all 650 guts pretty much required to build this beast?

you could, though one thing to note is that the 650 crank has a +5mm stroke, which is a really cheap way to gain displacement.

[sinister902]

thank you so much for clearing that up paul, I just want to put together a hot motor for my cafe now that the cosmetics and ergonomics are ironed out, and cannot see myself getting into all that extra machine work and finding a good 650 motor to start with when I have a complete spare 550 that lost compression to fidle with. If I grabbed a 650 head on ebay, 750 liners on ebay, and the 836cc kit that TerryInAustralia found for $110......I could throw the motor together for a VERY reasonable cost over winter.

[Captainkirk]

First off, GREAT THREAD!!!!!!
So much good info here!
Too much to digest in one sitting.
Forgive me if I'm being redundant here, but if you have a relatively quick answer, I would greatly appreciate it.
Taking the CB550 (or 500 motor) AS IT IS...i.e. NOT replacing the cylinders or head, what would you recommend as the best route to gain reliable, quick HP improvement?
The 650 cam is a bolt-in, if I read correctly. Does this require advancing stock cam timing?
What are the largest liners and pistons that will work with the stock 500/550 head without reducing or raising the CR beyond acceptable levels?
Is there a better carb setup (that won't cost a fortune) or a reliable carb mod that provide the right fuel/air mixture for the modded engine?
Which is the best reasonably priced exhaust/what style (4-into-one, I assume?)
Thanks in advance for your help!