Topic: CB550 can be bored to 672cc!

[volz1fsu]

I am very glad to announce that the 550 engine can be taken to 672cc just by boring.  First you have to obtain 750 sleeves and do some machinework to them as well as the cylinder block and case to fit them.  Once they are in there, boring can be done to fit 836 pistons for a 750 big bore.  Also the stock internal oil lines can still be run without interference.  Compression ratio with that engine combination would yield 10.9:1, on the high side but still should be streetable.  I would definitely recommend an oil cooler to help with the higher temperatures.  You could machine a little of the tops of the pistons to drop that compression ratio down.  I can't wait to build that engine but first I am just going to get my 591cc engine built and work on the 672 in the mean time.  I will provide pictures and more details on all the machine work when I get it done. Better watch out you 750 guys!

[n9viw]

Awesome news! Imagine a bike that weighs 2/3rds as much as the 750, yet has power approaching it! Still not a match for a well-tuned modern sportbike, but to get that kind of power out of a vintage metric is impressive. You'll have to keep us up to date about its performance, any problems or issues that crop up like hot spots, reduced plug life, etc.
What kind of intake/exhaust and ignition are you planning to run with this micro-beast? Doing any other changes to reduce downstream damage, i.e. better primary chain, harder shift forks/dogs, beefing frame strength, etc? Will you be changing the cam or doing any head work? Enquiring minds want to know!

[volz1fsu]

What kind of intake/exhaust and ignition are you planning to run with this micro-beast? Doing any other changes to reduce downstream damage, i.e. better primary chain, harder shift forks/dogs, beefing frame strength, etc? Will you be changing the cam or doing any head work? Enquiring minds want to know!

I will be going with the Dyna ignition from www.oldbikebarn.com.  It is rather pricey but worth it.  I don't know what series ignition it is but supposedly it takes samples from every 50 rpm and adjusts accordingly.  I am also porting and polishing the head and I am looking at different cam possibilities.  Megacycle looks to be the way I will go. I will just run my own exhaust that I modified (4-2), It is stock with the exception of my own hand built baffles. 
The things I am somewhat worried about are the things that n9viw mentioned.  Hopefully the transmission can take the power as well as the Primary chain since I don't know of any performance modifications or replacements for these.  I can't imagine the frame flexing, I think it is strong enough in stock form however  I may add some strength to it when I decide to have it powdercoated as a preventative measure.  I want to keep the weight of the thing to a minimum, the lighter it is the faster it is.
Right now I know it is physically possible.  Later I will find out if it will last on the road.

[oldbiker]

I think you would be very unwise to machine anything off the top of the piston. If you make the piston crown thinner you can run into danger of the piston crown melting. If you want to go down this route, it would be better to reduce compression ratio by using a slightly thicker head or base gasket.

[volz1fsu]

If you want to go down this route, it would be better to reduce compression ratio by using a slightly thicker head or base gasket.

Also an unwise idea since changing the distance the cam is from the crank will offset the cam timing.  That could be a very bad idea unless a custom grind cam could be made to correct for the timing.  It would be better to machine the pistons tops, mind you that taking off a little will make a lot of difference.  Ceramic coating the crowns after this has been done will prevent burning through.  There is more matterial there than one would think.  The pistons have to be cut for the valve pockets anyway and that would will most definitely cause a thinner area in the piston than what I am proposing.  I wouldn't even bother with it though since 10.9:1 would be fine as is.  I am just making a suggestion to those who would rather not run that ratio.

[MRieck]

If you want to go down this route, it would be better to reduce compression ratio by using a slightly thicker head or base gasket.

Also an unwise idea since changing the distance the cam is from the crank will offset the cam timing.  That could be a very bad idea unless a custom grind cam could be made to correct for the timing.  It would be better to machine the pistons tops, mind you that taking off a little will make a lot of difference.  Ceramic coating the crowns after this has been done will prevent burning through.  There is more matterial there than one would think.  The pistons have to be cut for the valve pockets anyway and that would will most definitely cause a thinner area in the piston than what I am proposing.  I wouldn't even bother with it though since 10.9:1 would be fine as is.  I am just making a suggestion to those who would rather not run that ratio.

You can correct changes in distant with an adjustable cam sprocket (available from Falicon).

[Sam Green Racing]

Mike, Did you get the PM. ?

[volz1fsu]

If you want to go down this route, it would be better to reduce compression ratio by using a slightly thicker head or base gasket.

Also an unwise idea since changing the distance the cam is from the crank will offset the cam timing.  That could be a very bad idea unless a custom grind cam could be made to correct for the timing.  It would be better to machine the pistons tops, mind you that taking off a little will make a lot of difference.  Ceramic coating the crowns after this has been done will prevent burning through.  There is more matterial there than one would think.  The pistons have to be cut for the valve pockets anyway and that would will most definitely cause a thinner area in the piston than what I am proposing.  I wouldn't even bother with it though since 10.9:1 would be fine as is.  I am just making a suggestion to those who would rather not run that ratio.

You can correct changes in distant with an adjustable cam sprocket (available from Falicon).

Great to know, problem solved.

[csendker]

I will be going with the Dyna ignition from www.oldbikebarn.com. 

There's been a bit of discussion about the quality, or lack thereof, from OBB. Personally, I bought a new clutch cable from them with no problem, but I may be the exception.

http://www.sohc4.us/forums/index.php?topic=7235.msg65605#msg65605

[bryanj]

Sounds interesting but i think you will have to change the primary chain every 10,000 or less

[cb(r)]

very good and interesting thread.  I am curious to hear how all this work pans out.  good luck with the "BIG BOAR"  it should be an animal when it is done!

[cbjunkie]

volz - check this link before you buy from OBB - Dyna for 120...

http://www.z1enterprises.com/

[eldar]

This would be better than useing a "1400cc" 750 with a charger on it. Although the 550 is not 2/3rds the weight of a 750, it is 4/5ths.

[volz1fsu]

volz - check this link before you buy from OBB - Dyna for 120...

http://www.z1enterprises.com/

Thanks for the link cbjunkie!  I still have many websites, like this one, to find for parts and such.  I wish there was some links page or something to handle all these specialty sites.

Even though it is only 4/5 the weight, 100 lbs. is still a world of difference for a cycle with about the same power if not more.

[Teach]

volz - check this link before you buy from OBB - Dyna for 120...

http://www.z1enterprises.com/

I wish there was some links page or something to handle all these specialty sites.

Here ya go!
http://www.sohc4.us/forums/index.php?topic=743.0

[cbjunkie]

beat me to it teach! 

volz - ya, z-1 is where i got mine from - i'm gonna stick with my stock coils for now, but when i found the thing for 120 i had to get it.

good luck!
cbj...

[volz1fsu]

volz - check this link before you buy from OBB - Dyna for 120...

http://www.z1enterprises.com/

I wish there was some links page or something to handle all these specialty sites.

Here ya go!
http://www.sohc4.us/forums/index.php?topic=743.0

NOW I'M IN HEAVEN!!!

[Teach]

volz - check this link before you buy from OBB - Dyna for 120...

http://www.z1enterprises.com/

I wish there was some links page or something to handle all these specialty sites.

Here ya go!
http://www.sohc4.us/forums/index.php?topic=743.0

NOW I'M IN HEAVEN!!!

[Rob Lloyd]

I am also porting and polishing the head and I am looking at different cam possibilities.  Megacycle looks to be the way I will go.

Why not try the 650 head? It fits right on the 550 engine - you can even use the same cams. If you want to keep it "550" looking, you can use the 550 rocker box. The 650 head already has bigger ports, valves, and combustion chamber than the 550 head. Might be a better match than a heavily ported 550 head. You'd need a 650 exhaust, though.

-Rob

[bill440cars]

      volz1fsu -- Sounds like quite a beast. I, along with others will be anxiously waiting for details and pics
   I too am wondering about the stress on the primary chain and the trans.  Keep us posted,  Bill

[volz1fsu]

I had no idea that the 650 head would fit on the 550 or that it had bigger valves and ports. Where have I been?  That may be the route I go, but I hate to get a different exhaust system.  The extra power may get the better of me though,.... oh who am I kidding, it always does.

I still am wondering about the primary chain.  I have been thinking a lot about modifying the engine to have a primary chain tensioner. Do the 750s have those, I thought I seen some part like that in a diagram.  I wonder if I could even go the the extreme and have gear to gear contact.  The only downfall to that would be a loss in power to turn the extra weight, and I an almost certain that it is not even possible.  It is fun to dream though.    The stock primary chain will probably last me a very long time anyway and I would be glad to replace it after several years.  The idea of changing it after 10,000 miles, like was suggested, is fine with me.  I only put on 1500 miles last year and I could go a good 6-7 years at that rate.   I think that sometimes people underestimate the strength of steel though.  I have seen it hold together under some very stressful situations.  Then again if there is one flaw in the material, it will come apart.  The tensioner is the best idea because the chain will stretch and that is why it needs to be replaced; at least with a tensioner I can tighten up the slack and postpone an engine teardown.

[n9viw]

   Rob, wasn't it your own site that said the 650 bits must be used from tip to toe in order to work properly (650 jugs with 650 crank, pistons, rods, head, etc) due to some difference in the mills? I recall thinking about going the 650 route, but not liking the idea of switching over to a Hy-Vo cam chain (I've not had luck with them in the past).
   Also, if you plunk down a 650 head on a 550 block, you'll run into the same issue some 750 owners have when they bore to 836 and put a 750 F head on, thinking they'll benefit from the F's larger valves- the F has a larger valve chamber, and domed pistons to match, but nobody makes 836 F pistons. The combination of K style flat-top pistons with the F domed-chamber head effectively REDUCES the compression due to extra volume. I'd rather have a head that was flow-matched to the engine than one that just happened to have some of the things I wish it had, but also has some of the things I don't want.
   Volz, the 750 does have a primary tensioner, but it does take up a lot of space. I don't know of any way you could fit it, or any other tensioner, in that tight 550 case, without having to do some really 'creative' milling on the cases.

[TwoTired]

Has any thought been given to the balance of the engine?
Bigger pistons mean more piston weight, doesn't it?  Isn't the the 550 crank counter balanced for the stock 550 piston weight?  Seems to me that if you don't add the proper weight to the crank counter balances, you will have to significantly lower the red line, at least, so all the moving bits actually stay inside the engine cases.

[Rob Lloyd]

   Rob, wasn't it your own site that said the 650 bits must be used from tip to toe in order to work properly (650 jugs with 650 crank, pistons, rods, head, etc) due to some difference in the mills? I recall thinking about going the 650 route, but not liking the idea of switching over to a Hy-Vo cam chain (I've not had luck with them in the past).
   Also, if you plunk down a 650 head on a 550 block, you'll run into the same issue some 750 owners have when they bore to 836 and put a 750 F head on, thinking they'll benefit from the F's larger valves- the F has a larger valve chamber, and domed pistons to match, but nobody makes 836 F pistons. The combination of K style flat-top pistons with the F domed-chamber head effectively REDUCES the compression due to extra volume. I'd rather have a head that was flow-matched to the engine than one that just happened to have some of the things I wish it had, but also has some of the things I don't want.
   Volz, the 750 does have a primary tensioner, but it does take up a lot of space. I don't know of any way you could fit it, or any other tensioner, in that tight 550 case, without having to do some really 'creative' milling on the cases.

If you want to use the 650 crank, then yess you have to use the 650 jugs, cylinder, pistons, and head - or go severly custom with all of the above. But, the 650 head by itself will bolt onto the 550 cylinder. And, yes, the CR will be lower due to the bigger combustion chamber. It has been done before...

And, Lloyd is right. Changing the piston weight significantly will affect the balance of the engine. The counter weights on the crank are weighted to balance the piston/rod assembly. If you can lighten the pistons back down to stock weight (or at least close) then it shouldn't be an issue. Or, you can take the entire reciprocating assembly and have them re-balanced by adding weight to the crank. But, that's expensive. Doing nothing will put higher loads on the main bearings and COULD result in premature wear...

[volz1fsu]

And, Lloyd is right. Changing the piston weight significantly will affect the balance of the engine. The counter weights on the crank are weighted to balance the piston/rod assembly. If you can lighten the pistons back down to stock weight (or at least close) then it shouldn't be an issue. Or, you can take the entire reciprocating assembly and have them re-balanced by adding weight to the crank. But, that's expensive. Doing nothing will put higher loads on the main bearings and COULD result in premature wear...

Actually you are both wrong,... it happens to me too.
In these four cylinder engines, two pistons and rods are positioned 180 degrees on the crank from the other two piston and rod assemblies.  This cancels there weight out when running.  When I took a maching class we learned all this and it even holds true on some 6 and 8 cylinder in-line engines which are designed like that to make balancing of the crank easier and it will also make a smoother running engine.
We balanced all kinds of crankshafts as a requirement to pass the class and the v-configuration engines had to have the piston rod assembly weighed very accurately and the proper counter weights of the exact weight were added in place of the piston/rods on the journals.  Every four cylinder was balanced without counter weights  because that is just how it works.  The only thing to be aware of is that each piston/rod assembly is weight matched to each other exactly.  I took a spare crank from a 550 in and put it on the machine.  It was perfectly balanced without counter weights.  I will probably do the same to the crank I am going to run with this combo.  I wouldn't want to throw in a bum crank and think the thing came apart for other reasons.
Adding weight to a crank is expensive but when you have to add Mallory metal to it because adding steel isn't enough, it puts a whole new meaning to expensive.

[bill440cars]

    I can understand swapping heads. What I don't understand is using the crank, cylinder and head of the 650 in the 550 case? Would it be possible to use a 650 engine with a different primary chain set-up?
Just a thought. Later on, Bill

[Rob Lloyd]

    I can understand swapping heads. What I don't understand is using the crank, cylinder and head of the 650 in the 550 case? Would it be possible to use a 650 engine with a different primary chain set-up?
Just a thought. Later on, Bill

Yes, you can use a 650 engine in a 550, but I don't understand your question about the primary chain. Why would you need to change it?

[bill440cars]

Rob,
     I should have said "cam chain". n9viw said he hadn't had much luck in the past with the "Hy-Vo
 cam chain. Rob, you'll have to pardon my ignorance but, what is meant by"Hy-Vo" chain? I only
 mentioned the chain because he seemed to have a problem with it. Myself, I haven't had alot of
 experience with the Honda fours. I've had some experience with others in the past but, I'm always
 willing to listen and learn from others. Anyway, couldn't the 650 be a performer with modifications,
 just like the others? Waiting to hear.     Bill

[Rob Lloyd]

Rob,
     I should have said "cam chain". n9viw said he hadn't had much luck in the past with the "Hy-Vo
 cam chain. Rob, you'll have to pardon my ignorance but, what is meant by"Hy-Vo" chain? I only
 mentioned the chain because he seemed to have a problem with it. Myself, I haven't had alot of
 experience with the Honda fours. I've had some experience with others in the past but, I'm always
 willing to listen and learn from others. Anyway, couldn't the 650 be a performer with modifications,
 just like the others? Waiting to hear.     Bill

Hy-Vo is a brand name for a style of chain. Commonly called "silent chain". It's more common now in cars. It should be stronger and more efficient than the rolelr chain that was stock on the 500/550. But things don't always work as they should, right?

Yes, the 650 could be a performer. I don't see why the 750 sleeve trick wouldn't work just as well on the 650 as it does on the 550. What would and 836 piston kit take a 650 out to anyway? Something like 720cc, right?

[bill440cars]

Rob,
     I should have said "cam chain". n9viw said he hadn't had much luck in the past with the "Hy-Vo
 cam chain. Rob, you'll have to pardon my ignorance but, what is meant by"Hy-Vo" chain? I only
 mentioned the chain because he seemed to have a problem with it. Myself, I haven't had alot of
 experience with the Honda fours. I've had some experience with others in the past but, I'm always
 willing to listen and learn from others. Anyway, couldn't the 650 be a performer with modifications,
 just like the others? Waiting to hear.     Bill

Hy-Vo is a brand name for a style of chain. Commonly called "silent chain". It's more common now in cars. It should be stronger and more efficient than the rolelr chain that was stock on the 500/550. But things don't always work as they should, right?

Yes, the 650 could be a performer. I don't see why the 750 sleeve trick wouldn't work just as well on the 650 as it does on the 550. What would and 836 piston kit take a 650 out to anyway? Something like 720cc, right?

      Rob,
          Sounds like a person could end up with a real "Sleeper" that could blow away the competition
  when awakened!! Would be interesting to see how it would perform. Later on, Bill

[Terry in Australia]

"Vroom, Vroom, KA-BOOM!" I reckon a 672CC 550 would be so fragile it'd make a Ducati look like a Mack truck, ha ha!

[n9viw]

How about this setup:
550 rocker cover
Megacycles 126-00 mild 550 cam
650 head
550 block with
750 cylinders and
836 pistons

Is such a mishmash conglomeration possible? Or even desired?

[cb650]

I want to get over the mega site and check the cam specs out compared to a stock 650 cam.




                   Terry