CB550 Re-build to the max
- Thread starter Bodacious
- Start date
And why do you think that the Rods are the first parts on the critical path? With everything else stock, superlight rods will not make much of a difference. Rods are forged and then machined unless you buy a set of Carillo rods or find someone to machine a set of Titanium rods - those would be cool.
To make more power start by thinking about the motor as a series of connected and interdependent systems that have to work together. If you used a software package you would probably start with defining a target HP and RPM and test against that to be sure it made sense. Then you would look at the gas flow in and out of the head to see how that stacks up against the targets.
Based on that data you could then look at valve and port sizes to meet the targets and examine possible alternative sized valves or valve weights. Then you would see what cams are available that would generate the sort of lift curve that would support your flow requirements and the actual flows of your ported head.
If you want higher engine revs, you would already have worked out what revs you would need and how thin the rings would need to be to sustain those revs and once you design teh lighter pistons to work with those thinner rings, you could calculate the big end and rod forces compared to stock and decide if you need to change the stock rods.
That's what I do.
Or you read everything around and see what anyone did in the day when they actually raced these fool things. You could check for example for Ontario Moto Tech and Kaz Yoshima and his CB400. You could also find old Yoshimura catalogs and see what Pops did back in the day. Or hang out on SOHC 4's net and see what guys are getting up to on that motor.
When they came out, I liked the 500 but I remember being very disappointed when I took a mate's CB500 for a blast. Nice bike with some potential but not a rocket ship.
I hear that a CB650 motor is a good transplant into a 500/550 chassis. Let us know what you decide to do. I'll be interested to see what you can do with it.
To make more power start by thinking about the motor as a series of connected and interdependent systems that have to work together. If you used a software package you would probably start with defining a target HP and RPM and test against that to be sure it made sense. Then you would look at the gas flow in and out of the head to see how that stacks up against the targets.
Based on that data you could then look at valve and port sizes to meet the targets and examine possible alternative sized valves or valve weights. Then you would see what cams are available that would generate the sort of lift curve that would support your flow requirements and the actual flows of your ported head.
If you want higher engine revs, you would already have worked out what revs you would need and how thin the rings would need to be to sustain those revs and once you design teh lighter pistons to work with those thinner rings, you could calculate the big end and rod forces compared to stock and decide if you need to change the stock rods.
That's what I do.
Or you read everything around and see what anyone did in the day when they actually raced these fool things. You could check for example for Ontario Moto Tech and Kaz Yoshima and his CB400. You could also find old Yoshimura catalogs and see what Pops did back in the day. Or hang out on SOHC 4's net and see what guys are getting up to on that motor.
When they came out, I liked the 500 but I remember being very disappointed when I took a mate's CB500 for a blast. Nice bike with some potential but not a rocket ship.
I hear that a CB650 motor is a good transplant into a 500/550 chassis. Let us know what you decide to do. I'll be interested to see what you can do with it.
Thanks for the input! I can assure you that the connecting rods are just the tip of the iceberg. I am an engineering student currently and I have picked this motor and a 350 to blueprint and re build as a project. I am basically going to re engineer everything i can on it and turn it into 4 cylinders of pure power. Well I'm going to try anyways.
I havent looked into the cam yet, but I am looking for a crank right now and machining some new valves, Eventually I want to machine a whole new set of heads for it, with matching pistons. I am going to redesign the intake and am looking at using 4 carbs vs 2. I'm regearing and looking to reduce rotating mass there. And a few other odds and ends.
We are basically just trying to get raw speed overall. I plane on taking it to Bonneville in a few years. Right now I'm just crowd sourcing some ideas and looking for anything that already been done past the point of improvement.
But yes my first project is pistons, connecting rods, and valves. The Motor came with some pistons I'm not sure are stock. They are very light, much lighter than the ones out of the 350
I havent looked into the cam yet, but I am looking for a crank right now and machining some new valves, Eventually I want to machine a whole new set of heads for it, with matching pistons. I am going to redesign the intake and am looking at using 4 carbs vs 2. I'm regearing and looking to reduce rotating mass there. And a few other odds and ends.
We are basically just trying to get raw speed overall. I plane on taking it to Bonneville in a few years. Right now I'm just crowd sourcing some ideas and looking for anything that already been done past the point of improvement.
But yes my first project is pistons, connecting rods, and valves. The Motor came with some pistons I'm not sure are stock. They are very light, much lighter than the ones out of the 350
you seem confused, the first thing you need to do is educate yourself 
what can be done with these motors has already been done and it is written in stone so to speak
i commend you on your desire to build an engine from scratch but i would suggest you learn to tune a stock one to it's peak first
what can be done with these motors has already been done and it is written in stone so to speak
i commend you on your desire to build an engine from scratch but i would suggest you learn to tune a stock one to it's peak first
I hear you, and I know you're right, but i say again this is a school project the whole purpose of which is to learn limitations and possibilities from an engineering standpoint. But I see no point in doing this if I can't experiment and learn for myself. No i probably wont have anything truly original with the 550 but I can try. No one is going to talk me out of doing it my way if you now what I mean. 8)
that is from factory balancing and there lies the rub unless you have the facilities and know how to dynamically balance a crankshaft you are better off just staying close to stock in the crank shaft area
why not focus on what really matters and that is the volumetric efficiency ?
do you even know how to degree a camshaft ? have you ever set the timing on any engine ?
no engine builder was successful without either being a supertuner and I mean an exceptional tuner or being partnerned up with one..
if you can't tune then trying to build all kinds of trick parts is MEANINGLESS because if you can't tune you won't be able to use them
why not focus on what really matters and that is the volumetric efficiency ?
do you even know how to degree a camshaft ? have you ever set the timing on any engine ?
no engine builder was successful without either being a supertuner and I mean an exceptional tuner or being partnerned up with one..
if you can't tune then trying to build all kinds of trick parts is MEANINGLESS because if you can't tune you won't be able to use them
ex119x
Been Around the Block
Bodacious said:
You seem to be operating under some misconceptions here. The CB550 comes stock with 4 carbs. Why are you looking for a crank? It appears to have one. Whay would you be comparing 550 pistons to 350 pistons? Compare the 550 pistons to the ones pictured in the manual. You do have one, don't you? Stock connecting rods are not the limiting factor in that motor until you are well past redline. Why would you machine valves? There are any number of reputable suppliers that can sell you whatever valve you want in whatever material you want. Here is a hint for you- the limitation on that motor is all in the head.It needs to have serious port work done to it. Back when it was a current model and we were road racing one, the difference between a stock head and one ported by Jerry Branch was amazing in both appearance and performance. You mentioned that you were going to make your heads? The CB550 has only one cylinder head. If you mean you are planning on machining your combustion chambers that is a horse of a different color. I would suggest as a first step you research the engine and what tuners have done in the past and make a plan for what you are going to do. I'll give you another free hint: Leave the bottom end alone. All the HP is in the cylinders, pistons, valve train and head. And you will only be able to get so much out of a 2 valve head. Valve float and valve area will limit your RPM long before your crank or rods.
Yeah I am picking up on that. I had seen 2 separate 2 carb configurations on 2 diff 550's that I looked at a while back so I guess I assumed that the rest had been a 4 carb mod. My friend and I are workin on this motor and he know all the ins and outs of tuning it, whereas I know more about the physics behind it so we are trying to kinda tag team it with his hands on learnings and my theoretical knowledge. I realize I have a long long way to go, which is why I have allotted 2 years for the build, still in the info gathering stage. I am doing the head for a school project though and just going to purchase a stock head off ebay or something like that. I realize that I'm not going to get a lot out of the bottom end besides maybe rpms, which is what we are shooting for, so I just thought that perhaps the 650 crank was a slight upgrade, being newer and all. As far as the connecting rods and valves I am aware that I can purchase them just about anywhere and of a variety of materials, however that takes away from the "I built this" factor as well as costing me more money. I was comparing the 350 pistons with the 550 pistons from the sole standpoint of wow there is a noticable difference in weight, I wonder what the difference in composition is so I could make some pistons for my 350 out of the same material, again saving myself somewhere to the tune of $150 and addint to the "I built this" factor. Now on the flip side I do see that Dynoman makes a bore in piston set for around $600, of varying bore sizes. This would definitely be an upgrade from stock but again thats more than I want to spend if I'm not making it myself. I have done some research and found some material to fab some Titanium valves and good god that shit aint cheap! But on the flip side I drew up some blue prints last night (just for the 350) and found that simply switching to a 5mm conversion and using titanium instead of stock, my new valves would weight 16.4 grams after grinding, where the stock ones weigh 46 grams (exhaust valves). I dont care what kind of experience you have with these things, this is a performance boost in and of itself, even with stock springs.
SO, now I am trying to come up with a little more cost effective materials for the valves and connecting rods. I will update later after I meet with the materials strengths and data supervisor here and get some ideas. I will also post my drawings and mod'ed designs tonight if anyone is interested in seeing what I am trying to make here.
SO, now I am trying to come up with a little more cost effective materials for the valves and connecting rods. I will update later after I meet with the materials strengths and data supervisor here and get some ideas. I will also post my drawings and mod'ed designs tonight if anyone is interested in seeing what I am trying to make here.
Anytime somebody re-invents the wheel it can be interesting. I'm to see what you come up with.
Forget Ti valves in a SOHC head. Side thrusts cause them to seize in the guides.
Now I'm confused. Are we talking 350 4 or twin or a 500/550 or all of the above?
By all means red everything there is to red and then start with the basics. For the motor you have, what are the max safe RPMS based on mean piston speed. A 350 twin has a long stroke crank - for its size and the 550 isn't a high rev machine either. If you want revs, you start with a short stroke crank and then you work out what bore size works with that stroke to get the engine size you want. With say 1.5:1 bore:stroke on a 500, that means you have to use 4 valves and all of a sudden you realize that Honda and Yamaha et al already did that.
If this was 1970, when I was an engineering student and designed a 4 cylinder 16 valve DOHC 500 street bike in a chrome moly frame, it would make sense. In 3014 - not so much.
So then you ask yourself what the objective is. Is it to develop a given motor to see what works and what doesn't within some reasonable cost boundaries, or is it to jump ahead to try a combination of parts that you don't know if they work?
Let's say you were to define the project along the lines of: To develop a 1970 era motorcycle engine to maximize power within reasonable cost constraints. That way you develop a series of improvements to test on a dyno that can be published. That will not get you through a PhD thesis review but for an undergrad project it might work.
The best place for design ideas is the SAE.
Now I'm confused. Are we talking 350 4 or twin or a 500/550 or all of the above?
By all means red everything there is to red and then start with the basics. For the motor you have, what are the max safe RPMS based on mean piston speed. A 350 twin has a long stroke crank - for its size and the 550 isn't a high rev machine either. If you want revs, you start with a short stroke crank and then you work out what bore size works with that stroke to get the engine size you want. With say 1.5:1 bore:stroke on a 500, that means you have to use 4 valves and all of a sudden you realize that Honda and Yamaha et al already did that.
If this was 1970, when I was an engineering student and designed a 4 cylinder 16 valve DOHC 500 street bike in a chrome moly frame, it would make sense. In 3014 - not so much.
So then you ask yourself what the objective is. Is it to develop a given motor to see what works and what doesn't within some reasonable cost boundaries, or is it to jump ahead to try a combination of parts that you don't know if they work?
Let's say you were to define the project along the lines of: To develop a 1970 era motorcycle engine to maximize power within reasonable cost constraints. That way you develop a series of improvements to test on a dyno that can be published. That will not get you through a PhD thesis review but for an undergrad project it might work.
The best place for design ideas is the SAE.
Damn man I'm here for some help and conversation, if you're going to be a fuckin dick every time I make a statement then forget I asked you. If I'm gunna spend that much money on Ti stock, its going to be on something that will really count. I can still shave mass going to something other than stock, I was just remarking that Ti round stock was expensive considering how much waste there will be. I thought these forums were supposed to help people not be all snobby every time someone says something. "Oh if you're complaining about Ti stock now just quit then BLEEEHHHHHH" Way to show support for your fellow oldschool enthusiast.xb33bsa said:
Bodacious said:
i fully support your enthusiasm but you are ignorant and are seemingly ignoring the facts
we have already told you where you need to focus
if you want to build something build a flow bench and learn how to use it,maximize a multiple cylinder head for efficiency,and equality across the board
that would be impressive and show signs of intelligence