Topic: '72 CB 750 - "Kinetic Aline"

[sangyo soichiro]

Thanks for all the interest guys.   

Quit effin around and pick your toys up off the deck!!  They sure did take a bunch off.  How much does it weigh now? And the stock one?

I have a really accurate scale, but the crank was too heavy for it, so I couldn't get a measurement.  But I'm very curious myself as to the weight difference.  I'll try to get a measurement one way or another....

[wannabridin]

wow, 14,000 rpm redline...  makes it nearly worth it to get the crank lightened!!  i'm stickin with 4th over pistons from Z1, but i don't think a lightened crank would be worth it really.  balanced, yes, but lightened that much?

either way, VERY nice piece of work there, i'm uber jealous of how your project is coming along!  i haven't touched my bike in over a week... 

how far up in the rev range do you think you'll be making (useable) power?

[sangyo soichiro]

The paperwork that came with the crank states, "Balanced for sustained operation to 14,000 RPM."  So I probably shouldn't state anything beyond that.  But I just thought it'd be cool to word it the way I did originally.  

The crank is lightened and balanced to withstand the forces at 14,000 RPM, but I'm not sure about the rest of the engine.  That's what all the heavy duty stuff is for, like rods, studs, valve springs, cam chain, etc., but who really knows?  I'm not going to push my engine too far to find out.  But I'll be sure to tell everyone about the "14,000 redline."  

Lightening the crank cost me about $300 give or take, including the shipping.  I think it was worth it myself.  The only thing that I really skimped out on was a valve job.  Instead, I decided to polish everything up myself, but in a few years when it's due for a good cleaning, I'll likely send it Mike Rieck's way and have it done properly.

I have no idea how far up the rev range I'll be making usable power.  I know by the seat-of-the-pants method, the stock bike gets so far and starts to peter out.  I'm not sure how much farther up the rev range this one will put out.  There's just too many things that are changing for me to guess.  You got me curious about the answer to that one myself though.  I suppose we could sneak a peak at someone's dyno graph that has a similar setup....

[MCRider]

Wannabriden and Soichiro: The cam is pretty much the dictator of the power curve. I'd bet the 41a peaks around 9,000 for hp, maybe before, and with your parts can pull higher but the power peak will have been reached. and you'll feel a slow down in the rate of increase, and finally a decline altogether.  A dyno run will point it out. The tach on dynos is much better. Torque usually peaks 5500 to 6000 for most engines regardless, and is a nice place to ride.

On a WOT accel run, the tach will be slow, lagging by about 500+ rpms. So if you grab the next gear at an indicated 9000 you likely will already be higher. And if you are power shifting the revs between shifts will go on up, that's where the heavy duty parts come into play, so when you drop the clutch (an instant later) at the next gear, you'll be right at the power peak.

Every bike and instrument is different so you need experience with the set up to know where your peaks are. Your tach may be reading 8000 but your really at 9000 and need to shift. And the stock tach is not up to it. But your butt is and you can average the two.

[sangyo soichiro]

Thanks for the info MCRider.  It makes sense that the cam is the dominant component determining where the peaks are at.  Also good to know about the tach lag.  I love it when you guys that have been around these bikes since the '70s share your knowledge.

[wannabridin]

you could play around with it at home using a dwell meter to see just how accurate things are.  take it up to an indicated 2500 rpm in idle and see where the tach reads.  it could be the tach just being slow to get there, or it could be the needle was placed wrong and you're just off a couple hundo RPM's or more...  either way, great info MC!!!

[MCRider]

Its not so much that its inaccurate at a steady speed.  That's probably pretty good. So if you want to see how high it will rev you can probably do that OK, just bring your revs up a little slower than under a drag race condition and you'll get a pretty good reading probably. And pay attention with your butt as to where the peak is.

But with the lighter crank, faster revving engine, the slight lag of a stock tach gets worse. So its a lag getting there, and under fast shifting it will be off.

Of course the tach was never intended to be revved past 9,000 so you have to be suspicious of higher readings.

I'm thinking a digital instrument of some kind would be the most accurate.

And I may be way off, others may have better experience.

[sangyo soichiro]

Guess what I just bought...

along with

and



 

Got them from Dynoman Performance.

[wannabridin]

you would!!!  no HM (HondaMan) box?

[sangyo soichiro]

It was a toss up for me.  But in the end I decided to go with the thing that has been around longer. 

[sangyo soichiro]

Actually, I was originally going to stick with the stock points.  And I had my eye on the Cycle X kick-only system.  But I went for the maximum performance mod instead.  I'd still like that Cycle X kick-only system, but I have to make sure it's compatible with the Dyna 2000 now.   

[MCRider]

Actually, I was originally going to stick with the stock points.  And I had my eye on the Cycle X kick-only system.  But I went for the maximum performance mod instead.  I'd still like that Cycle X kick-only system, but I have to make sure it's compatible with the Dyna 2000 now.   

I think its kick only in that it removes the electric start hardware. That starts with the smaller rotor. With the smaller rotor, no ES clutch. and no ES clutch you might as well pull the rest of it.

As far as generating power, it makes what the bike needs to run ignition and lighting plus some. I think. OCICBW

I'm thinking of it for my distant 75F cafe racer.

[jaguar]

great build.
interested to hear more about that clutch basket and to know what you find out about the Cycle X stuff

[Doctor_D]

Guess what I just bought...

Jeez... we're building virtually the same bike. At least it'll be easy to compare notes.

[wannabridin]

id be interested in hearing more about the cyclex kick only system as well.  pretty neat!

[sangyo soichiro]

Guess what I just bought...

Jeez... we're building virtually the same bike. At least it'll be easy to compare notes.

Yeah... and you may recognize these.  I just ordered them.   

Thanks for the tip!   

[MCRider]

Those are the same ears I'm using except...

I had mine chromed.   

[sangyo soichiro]

The Cycle X system I'm interested in is this one:


You can read about it on CyX's webpage:
http://www.cyclexchange.net/Elec%20System%20Comp%20Page.htm

It allows for a battery-less system - which is the attraction for me.


All I have to do is make sure it is compatible with the Dyna 2000.  That is, I need to know if the Dyna 2000 needs power before the engine is actually running, or if it can do its thing with no initial voltage applied to it.  Because, a battery-less system will only provide power to the Dyna 2000 when the engine is turning.  Maybe the rotation from the kick starter would be enough to get the entire CyX+Dyna system going.  That's what I got to find out.

Of course, if any of you know the answer, let me know!   

[sangyo soichiro]

Those are the same ears I'm using except...

I had mine chromed.   

I'm having mine diamond plated.   

[Doctor_D]

Maybe the rotation from the kick starter would be enough to get the entire CycleX+Dyna system going.  That's what I got to find out.

Of course, if any of you know the answer, let me know!   

Because it's a permanent magnet system, unlike the Honda one, it will generate current with a flat battery or no battery at all.  However, you would likely want to incorporate a capacitor into the charging system to really make batteryless operation painless.  There's one manufactured by BHC (63 vdc, 4,700 uF) that I used on a total loss race bike a few years back with good results.

The good news is that they're common and cheap: http://www.newark.com/panasonic/ecos1ja472ca/capacitor-4700uf-63v-capacitor/dp/01M7489 Or you could spend more to buy a "kit", http://www.summitracing.com/parts/ALM-151308

[sangyo soichiro]

Maybe the rotation from the kick starter would be enough to get the entire CycleX+Dyna system going.  That's what I got to find out.

Of course, if any of you know the answer, let me know!  

Because it's a permanent magnet system, unlike the Honda one, it will generate current with a flat battery or no battery at all.  However, you would likely want to incorporate a capacitor into the charging system to really make batteryless operation painless.  There's one manufactured by BHC (63 vdc, 4,700 uF) that I used on a total loss race bike a few years back with good results.

The good news is that they're common and cheap: http://www.newark.com/panasonic/ecos1ja472ca/capacitor-4700uf-63v-capacitor/dp/01M7489 Or you could spend more to buy a "kit", http://www.summitracing.com/parts/ALM-151308

Thanks for the tip, David.

Yeah, that system would be nice to have in the event of the zombie apocalypse.  I've seen the movie where they couldn't get the engine started in time...  

[jaguar]

dyna 2000, lightened motor, and cafe plans......me too....lol
but o got the TTR400 headlight mounts.

[SKTP]

Yeah... and you may recognize these.  I just ordered them.   

Thanks for the tip!   

where are those from? I am looking for clean fork ears

[CBJoe]

Yeah... and you may recognize these.  I just ordered them.   

Thanks for the tip!   

where are those from? I am looking for clean fork ears

Pretty sure these are the ones from Mikes XS....Not sure if they're available somewhere else.
 
http://www.mikesxs.net/products-77.html#products

Joe

[sangyo soichiro]

Yes, I ordered mine from Mikes XS.  I got that link from Doctor_D in his build thread.