R&D platform


CBX1000FAN
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Re: R&D platform

Post by CBX1000FAN »

Looks good!!

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bobcat
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Re: R&D platform

Post by bobcat »

BTW, where this thread shows up as recent posts (next to featured photo),
I have no idea where the "amp;" part came from or what it means. It's just
always been there and I don't know how to correct it.
Bob
82 CBX, 81 CBX, CB1100F, 79/82 CB900F (avatar)

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Syscrush
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Re: R&D platform

Post by Syscrush »

I just found my way here from the CBX Racing thread, looking forward to giving it a careful read.
bobcat wrote:
Wed Nov 03, 2021 2:58 pm
BTW, where this thread shows up as recent posts (next to featured photo),
I have no idea where the "amp;" part came from or what it means. It's just
always been there and I don't know how to correct it.
The "amp;" is a way of "escaping" or encoding an ampersand in a URL. Something other than an ampersand has to be substituted in, because the ampersand itself has a specific meaning (it's used to separate parameters sent to the server as part of the URL).

There's nothing for you to fix. If your topic subject is being displayed with "amp;" in place of the ampersand, that's an issue with the forum software.
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

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Re: R&D platform

Post by Syscrush »

bobcat wrote:
Wed Nov 03, 2021 12:14 am
In short, I couldn't find an exhaust system I liked so I decided to just design and have built
one to fit my vision of what would go with my overall project/build.
More later if these hastily taken, somewhat out of proportion pics will post. The foundation of the
rest of the system :
I've been coming back to this thread to stare at that collector at least once a week for months now.

It's a thing of beauty.
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

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bobcat
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Re: R&D platform

Post by bobcat »

Thanks Phil. I'll try to get some better pics of it along with a few other items I've collected
for the project. The header tube configuration is as important or more than the collector
for the desired function of the system. The problem with this system (and project) is the cost.
Just the collector cost more to build than most people are willing to pay for a complete system.
Oh well, it's only $$$ !
Bob
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Re: R&D platform

Post by bobcat »

Back to the original topic of remote cam timing on the R&D platform.
There is a way to do it that covers all variables such as surfaced heads
and cyl. blocks, gasket thickness, cam chain stretch, etc. The only variable
left is dowel pin location of the side thrust cam cap and that is minute.
I learned this from building Legends car motors (FJ1200 Yamaha) and working
on my vintage Acura (timing belt) and it occurred to me that the same could
be applied to the CBX and DOHC four. More on this later...
Bob
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Re: R&D platform

Post by bobcat »

....I had wanted to do a video of the procedure (also suggested in a pm) before
going into this further but it won't happen soon so until then I will just describe
the process, what is required and how I arrived at the lobe center numbers I use.

Cam timing is the foundation of performance tuning, not "diminishing return" as
commented on in another thread. Changing the timing is easier to do than rebuilding
the carbs and costs nothing but a little time but requires some special tools and
understanding what to do with them and an understanding why the changes are beneficial.
It is the single biggest improvement you can do for power where you want it short of a
big bore kit.
With this procedure you will not have to repeat the set up again in order to restore your
original settings. To be continued...
Bob
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Re: R&D platform

Post by Syscrush »

Thanks for your work and for sharing your results. Looking forward to learning more.
Phil in Toronto
A cool guy deserves a cool bike, a dork needs a cool bike...
Pics of Perry, my '79.

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Re: R&D platform

Post by bobcat »

Syscrush wrote:
Wed Jul 20, 2022 11:13 am
Thanks for your work and for sharing your results. Looking forward to learning more.
Thanks Phil. I'm working on the next step in presentation, where to begin besides the vague
outline I've written already. Most likely it will be how I came up with the LC numbers I use.
Collecting my thoughts first. :-)
.
Bob
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Re: R&D platform

Post by bobcat »

After reading through this 8+ year old thread I found several things I want to
address. Some of these are overlapping a bit and I'm in considerable physical
pain. Concentration is difficult so I may wander a little.

First of all there seems to be a focus on peak horsepower. The cam timing changes
alone produce no more HP but it changes the power delivery in the rpm band. Coming
from a road race background, my focus is on acceleration rather than top speed and
the power to maintain it. Unless you are running at a track like Daytona with long straits
or ride suicidal on the streets at top speed a lot, acceleration through the mid range
(seat of the pants feel) is a preferable experience for most.
That brings up the power changes through the models Z, A,B and C and the cam timing
changes that are the primary differences in power delivery. I must take a break.... :-|
Bob
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Re: R&D platform

Post by bobcat »

....Disclaimer (?)

I'm sure much of what I'm writing has been covered in one way or another on this
site and I may write some things that sound like plagiarism without a credit to the
author but it isn't intentional. I had a lot of teachers and it would very difficult to
research all the proper footnotes so I'll procced with the subject. Some (many?) of
you know the content and descriptions already but in the interest of topic unity I'll
risk being repetitive.*

I am not claiming to be an ultimate authority on the subject, just my conclusions
and opinions backed up by previous experiences at the track and on the street,
a little dirt too ! :-)

Exhale.., Break.....

Next: stock OEM lobe center numbers and cam chain stretch....
Bob
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Re: R&D platform

Post by bobcat »

...Lobe center numbers: Remember, as you advance the in. cam the number falls.
107.5 advanced 1 degree=106.5. the opposite is true if you retard it 1 degree.*
If you advance the exh. cam the number climbs. 107.5=108.5, retard it1 degree
=106.5 and so on.

Off the showroom floor the 79Z lobe LCs are both 107.5 (in. and exh.). The high
numbers (cams rolled away from each other) builds cyl. pressure, helps peak HP no.s
but moves the power delivery higher up in the rpm range.
When the HP limit for 1000cc bikes was imposed, 100 max., 80 A models had the exh. cam
advanced to 112 deg., all but killing the valve overlap^ phase (closing the exh. valve at TDC
on the exh. stroke) but keeping the peak HP under 100. The in. cam remained at 107.5.
I haven't had an in. cam to measure but I believe the lift was reduced also. Seat of the pants
feel (to me) the 80 models felt anemic power wise, all through the power band.

^Will discuss later.

Next, the 81 and 82C....break time....
Bob
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Re: R&D platform

Post by daves79x »

Yes, the lift on the '80 intake cam was reduced slightly also. FWIW, most guys notice no 'seat of the pants' difference between a '79 and an '80. The only place it shows is the dragstrip (11.50s vs 11.70s).

Dave

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Re: R&D platform

Post by bobcat »

daves79x wrote:
Thu Jul 28, 2022 7:35 am
Yes, the lift on the '80 intake cam was reduced slightly also. FWIW, most guys notice no 'seat of the pants' difference between a '79 and an '80. The only place it shows is the dragstrip (11.50s vs 11.70s).

Dave
I noticed and so did a couple of friends that bought them back when they were fairly new.
They bought them because, besides fascination, they heard the CBX was really fast and they
were disappointed.

Thanks for verifying what I thought about the in. cams
Bob
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Re: R&D platform

Post by Rick Pope »

Call me an under-educated nerd, but this is fascinating stuff. Back in the day, (1977) I had a CB750 motor built by a local guy, Greg Cope. He spent a lot of time fiddling with the cam timing. I still have that bike, and it pulls hard from 5,500 rpm up to over 10k. In fact, it will power wheeie with my fat butt in the saddle.

Mr. Cope went on to join his old rivals in drag racing, Vance and Hines. Last I heard, he was a crew chief for them.
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