Topic: '72 CB 750 - "Kinetic Aline"

[sangyo soichiro]

The engine update starts here.

After 5 years of having the engine in pieces, the putting it all back together update starts here.


When I was putting this machine together I was not a member of this forum.  So I never had a build thread.  But I'll eventually upgrade the engine and such and I'll document it in this thread. 


I will also list all the things I've done so far - but give me a while to do that.   

Anyway, right now I have some pictures but no place to put them.  So here's my "post-build" thread.

Thanks for stopping by.   




[You can view larger versions of the photos if you right-click and open in a new window.]

[Flying Tattooed Monkeys]

Me likey!!!

[Toxic]

That's got to be the smallest tail lights ever. Looks great.

[sangyo soichiro]

Thanks guys.   

That's got to be the smallest tail lights ever. Looks great.

Thank you.
Yeah... it's pretty small.  It's actually a running light I got at a Meijer's store.  It only has two LEDs.  And since it's a running light (either on or off, no dimmer setting like a real tail light) I had to put a 470 Ohm resister in between the running light wire and the LED.  Why 470 Ohm one may ask... well, I chose that size resistor through the highly scientific process of... using the only resistor I had.     But it works really well.  It's fairly bright when the headlights are on, and it's brighter when I apply the brakes.  I've had a couple cops follow me and neither has pulled me over, so that's a good sign.  But I'm always conscious that cars may not see me from behind (although my license plate also glows pretty bright in their headlights).  Anyway, I always ride with my head on a swivel and a mind for safety.

[Zaipai]

Sweet ride, you have to be proud of that bike!

[sangyo soichiro]

Sweet ride, you have to be proud of that bike!

Thank you very much.  I do feel somewhat proud unique when I ride where I live because I have never seen another cafe racer in my area.  But after seeing what the guys on this forum do with their bikes, I feel a little less proud.  There are still a lot of things I want to do to improve performance, functionality, and looks.  There are a lot of machines in this forum that inspire me to want to achieve greater things. 

Hopefully soon I will make the time to start Phase II.   

[sangyo soichiro]

Update: Phase II - engine modifications

Someone in this forum (I forget who) said that most cafe racers are more cafe and less racer.  That line struck a chord with me.

So I started Phase II - souping up the engine.  I'll go into more detail when the times are appropriate, but my general goal is to increase performance via finesse (and maybe a little brute force  ).  I want to maximize the horsepower at the crank, and maximize the transfer of that horsepower to the rear wheel.  I want to ultimately focus on increasing the acceleration of the bike.  Oh yeah, and I don't want to break the bank, so I'm going to try to keep the cost down, but it'll probably still be upwards of two grand (some things I don't want to skimp on).

The goals in general are to:
A. Rebuild my leaky engine,
B. Learn about engines and performance,
C. Make the bike quicker (a lot quicker...  ),
D. Minimize the cost by doing as much as I can myself,
E. Reduce the overall weight of the bike.

The tentative 'Phase III' will concentrate on goal E.  But that'll probably be next winter's project.   

Here are a few pictures.  Some parts are starting to trickle in, so I'll update and go into specifics at a later date.   

[Zaipai]

Can't wait to see how things work out. I have to rebuild my motor next winter, so will be nice to see what you run into.

.: Scott :.

[sangyo soichiro]

Can't wait to see how things work out. I have to rebuild my motor next winter, so will be nice to see what you run into.

.: Scott :.

Thank you Zaipai.

I'm a little behind on my descriptions here, but I should have more photos come Monday.  I have actually been documenting everything with video.  But I've learned that I'm certainly no Gregory Peck.

I was taking apart my K4 spare engine and was going to use that one until I found out the lower case was cracked from what looks like a broken chain.  So I pulled the K2 out of the bike and now I have two engines completely apart in my basement.

Anyway, a quick list of some of the parts I have in hand now:
Webcam 41a hardweld cam (from Dynoman)
Cycle X rods
Ti retainers (APE, but bought through Cycle X)
HD valve & clutch springs (Cycle X)
HD studs (Dynoman)
Tsubaki cam chain (Dynoman)
cam sprocket (Dynoman)

I ported the head and polished up the stock valves.  This weekend's project is to prep the crank to ship out to Big Jay at APE for lightening and balancing.  The only last big engine purchase will be pistons and boring.  I've been talking to HavocTurbo about that.

I haven't put much thought into an ignition, I was going to stick with the points and stock coils for now.

I also want to tweak the "innards" of the engine and transmission to lighten it and reduce the moment of inertia of the rotating parts.  For a lot of that work, I'll need access to a machine shop.  I used to be a journeyman tool and die maker, so the machining will be easy for me, but I don't have the easiest access to a machine shop nowadays.

I'll probably get some alloy rims before riding season starts (they're lighter, and can spin up faster), but I want to put some serious thought into that before I spend the money because Phase III will perhaps involve a modern front end, and it'd be a money loser to buy a rim to only use for one season.  So I have to consider that some more.

[Zaipai]

Sounds like its going to be a killer motor when its complete.

.: Scott :.

[traveler]

Very nice little racer you have there.

Thanks for taking the time to share with us.....it is appreaciated, and it is fun to relax and read/see what others are doing with these truly outstanding little machines.

How is the performance?  Runs pretty hard?  Did you change the gearing at all? (sorry, I haven't taken the time to really sit back and read all the posts as of yet).

Keep the rubber down and ride safe,

~Joe

[traveler]

Acceleration?  How about a custom rear sprocket about 2-4 teeth larger?

http://www.sprocketspecialists.com/Products.aspx

Custom alloy rear sprocket...might lose a tad bit of speed on the top end, but acceleration will be much better!

~Joe

[sangyo soichiro]

Scott,
I hope so.  But I guess it depends on if I can get some decent time in a machine shop.

Of course, my big plans for this weekend were foiled by a sore back that lasted the entire weekend.      


Joe,
Thanks for the compliment.  I'm still working on the engine, so I won't know how it runs until later this spring.  I'm already really anxious to see what difference there will be.  I won't change the gearing, but in the future I may play with sprocket sizes.  I did plan on doing some work on the gears, but I'll wait to explain it and go into more detail later.   

As far as increasing the acceleration, my thoughts are basically two-fold: reduce the mass of the bike, and reduce the moment of inertia of all rotating parts (as is possible - some parts cannot really be reduced).  Some items are easy, like simply replacing the old rims with lighter ones.  Other items, like internal engine parts, I'll need to get into a machine shop.  Lowering the mass increases the acceleration (via F = m*a), and removing mass from rotating parts not only reduces the overall mass of the bike, but also gives the added benefit of a lower moment of inertia (and allows those parts to spin up faster).  I'll go into more details and the math later, when I can make more time to do a decent job of explaining it.

The nice thing about those general principles is that they are relatively inexpensive to implement.

Add to that the porting, cam, high-performance pistons, and many of the other the usual suspects to increase performance, and I'm hoping to see some good improvements in acceleration (and maybe top end...).


Of course, the main goal for me is to learn about all this stuff.  And the best way to learn is to jump in head first.   

[wannabridin]

bump for more updates!

[sangyo soichiro]

Thanks for the interest!

I'm still waiting on my crank from APE.  It's been about two months since I sent it (March 8th).  I did, however, get a set of 29mm CR carbs from Dynoman.  Once I get the crank back, I'll get the bearings and should be ready to roll.


A few other things to do, but that's about where it stands.

So far:
Cycle X rods
Ti retainers
HD valve springs
HD clutch springs
lightened clutch basket
APE lightened crank (and polished before I sent it out)
Wiseco 836 10.5:1 pistons
polished stock valves
ported head (done myself - many, many hours)
Sun brand alloy rims
HD cylinder studs
polished transmission
undercut transmission
resurfaced head
new cam chain (Tsubaki)
adjustable cam sprocket
Webcam 41a grind hardweld cam (0.360 lift, 280 duration)
29mm CR carbs (with extra jets for tuning)
new intake boots
(why do I feel like I'm forgetting something...)


Things to do:
Sort of want to drill the brake rotor,
mount the new rims (and all the rest that goes into that...),
new tires (I'll swap the current wheels to my K4 and replace those old ones),
lighten the valve rockers a bit (and do so evenly among all the rockers),
order bearings and rear shocks,
order oil seals,
lighten and polish a few other things here and there,
(still feels like I'm forgetting something...).

Anyway...

Seriously considering getting the Cycle X battery-less kick-only electrical system...



I know, I know...
worthless without pictures!  I'll get some pictures soon.   

[MCRider]

subscribe (if I'm not already)

We'll have to have a pi--ing match over who's got the longer goodies list!

         

[sangyo soichiro]

subscribe (if I'm not already)

We'll have to have a pi--ing match over who's got the longer goodies list!

         

Well you'd win hands down in the longest build thread competition.   

Thanks for the interest!

[wannabridin]

you mentioned a $2K engine budget....  methinks you've gone a slight bit over??      damn fine list of goodies there though, i'm most jealous!!

[sangyo soichiro]

you mentioned a $2K engine budget....  methinks you've gone a slight bit over??      damn fine list of goodies there though, i'm most jealous!!

Did I say that...   

I'm afraid to add it up. 

I started to make a list right now, but it got to the point where I was guessing too much at what I paid for certain things.  Maybe I'll make an accurate list later. 

But I look at it more as money towards an education in engine souper-upping.   

[MCRider]

subscribe (if I'm not already)

We'll have to have a pi--ing match over who's got the longer goodies list!

         

Well you'd win hands down in the longest build thread competition.   

Thanks for the interest!

Yeah really, don't rub it in. I'm embarrased how long mine is taking. You'll be done before me!

[wannabridin]

Yeah really, don't rub it in. I'm embarrased how long mine is taking. You'll be done before me!

well if you wern't such a perfectionist MC, we'd all be drooling over your ride on the road by now!!  well maybe not quite as big of a drool puddle as we'll have at your current rate, but a puddle nonetheless!!

[wannabridin]

updates!!!   

[sangyo soichiro]

updates!!!  

Okay.  
I'll try to get pictures this weekend.  

A new development has occurred in this last week though...  I went with a friend to get some CX 500 parts for his bike this last weekend and the seller had an old CB 750 (minus the engine and other stuff) in his shed.  He said he'd like to get rid of it for a fair price.  Bam!  I may have myself a dual front disc brake!    Me and my friend plan to get it this next Wednesday.

Otherwise, I'm still waiting on my crank.

[wannabridin]

don't you hate it when new projects/parts bikes get in the way of your budget!  i've had to scrap my june/july completion time as it's taken me over a month just to get the carbs done, damn dirty girlfriend and other interests!!

[traveler]

updates!!!  

Okay.  
I'll try to get pictures this weekend.  

A new development has occurred in this last week though...  I went with a friend to get some CX 500 parts for his bike this last weekend and the seller had an old CB 750 (minus the engine and other stuff) in his shed.  He said he'd like to get rid of it for a fair price.  Bam!  I may have myself a dual front disc brake!    Me and my friend plan to get it this next Wednesday.

Otherwise, I'm still waiting on my crank.

Does the 750 have a clean title?

~Joe