The International CBX Owners Association

NobleHops wrote: Sun Aug 28, 2022 2:18 am Great reading, Bob. Thanks for taking the time.

What Nils said!

Syscrush wrote: Mon Aug 29, 2022 2:34 pm

NobleHops wrote: Sun Aug 28, 2022 2:18 am Great reading, Bob. Thanks for taking the time.

What Nils said!

I guess that means I need to get back to it !

Will do as soon as I can regain my focus. Chair=pain= -clarity.
However, your interest keeps my mind off of it, keeps me going !

I would post a picture of the LC chart but I've written all over it with
notes, measurements and highlighted boxes that it's very hard to read.
Besides I'm not sure where I put it. I'll try to find one similar to post.

When I was still working on race bikes I used the same LC numbers on various
bikes including an FJ1100 endurance bike and later an FJ1200 street bike. We
(riders and I) were amazed at how well the FJs responded. The FJs had horrible
stock cam timing specs making the changes that much more noticeable.

When I went to work on legends cars it was a no brainer to go straight to the same
LC numbers as on the bikes. Other car owner/drivers couldn't figure out why our cars
would pull away from them off the corners. It was entertaining to watch them rejetting,
using different air filters, changing gearing etc. and winding their motors up
until they hit the rev limiter at 10.2k rpm. while our cars rarely needed over 9.5k rpm.

However there were some motors that I tried those same no.s on that fell on their faces
like the 5 valve Yamaha Genesis motors and most all 2 valve/cyl. motors. According to
the chart those no.s should have worked. I'll try to get back to these variations later
but it sent me farther into how to use and interpret the chart. I'll go more in depth
about the research after a break .....

Thank you Bobcat, very interesting and the small bites (unfortunately necessitated by your discomfort) make a complex topic quite 'digestible' for us luddites. Please keep at it when you can (and email sent)

herdygerdy wrote: Tue Aug 30, 2022 3:46 pm Thank you Bobcat, very interesting and the small bites (unfortunately necessitated by your discomfort) make a complex topic quite 'digestible' for us luddites. Please keep at it when you can (and email sent)

Hey Tony, from one luddite to another, thanks for reading !
I'm trying to do what I can (Dr.s no help).

Email ? It must be held up in customs, it hasn't got here yet.

I'll try to gather some steam here shortly...

I thought I'd better look up "luddite" before possibly hurling an insult.

Hi Bob, that's weird it was sent a couple of days ago.

I've also sent you a Private Message on this forum. Hope you got that one!

herdygerdy wrote: Tue Aug 30, 2022 8:43 pm Hi Bob, that's weird it was sent a couple of days ago.

I've also sent you a Private Message on this forum. Hope you got that one!

Found the PM just now. I'll get back with you soon.
Thanks !

...I should clarify something from the last (on topic) paragraph time wise.
I was discovering that the magical LC numbers didn't necessarily work on all motors
long before I was given the LC chart. Once I got the chart and began to understand it
is when I found out that those no.s should have worked which further confused me.

However I knew that they did work on a great deal of motors and the chart told me why.
It was that all of these motors shared the same stroke radius/rod length relationship
(ratios ?), shared the same box number(104) on the chart and they were all 4valve/cyl.
The CBX just happens to be one of them and responds to the LC no.s the same as the
other motors !

So when it came time to do jonesbear's 82 it wasn't a "let's try these no.s and see if they
work" type endeavor, especially given jones' skepticism. I was armed with the LC chart.
It was his idea to try to use the 79 cams, IN., in particular. I hadn't really thought about
the cam swap before but I was absolutely sure about the no.s

He called me every day for a week describing how much better, stronger it felt than before.
I was happy he was happy ! This was a bone stock motor other than the cams and timing
and some minor low end jetting changes and it had about 24k gentle miles on it.

This isn't the end yet, there's much more about the chart,(104), it's use and what I propose to
do to make cam timing a routine service check/adjustment.....

(104) is the starting point, but why ?.....

Well, I was going to try to continue last night but I couldn't concentrate well enough
but I did go back and edit (add) some things a couple of entries back.

Meanwhile I found the LC chart stuck in my CBX fsm right where I thought it was !
I'll try to get my wife to make some copies to send to Phil (Syscrush) who generously
offered to try to clean it up so it can be posted.

For now, a few pics : Kinda fuzzy, cheap camera.

Sorry for the delay but it's been a rough few days.

I hope this jumping back and forth through time from when I first got those LC
numbers from Yoshimura and when I got the LC chart hasn't been too confusing.
Sometimes it's hard to separate the two.

When I built my CB900F (about 28 yrs. ago) a machinist friend donated some mild
Andrews cams to the project. He said they were for a 750 but they had more lift
than 900F cams, less lift than 1100F cams and more duration than both. They suited
my project motor perfectly but came with no timing specs.

Since the 900 was a 4 valve/cyl. Honda I decided to try the 103-105 LCs since it had
worked on so many others. I was disappointed that it just didn't have the power I had
expected above 6k rpms. On top of that it would "ping" at lower rpm briefly under a
load, more than half throttle. At first I thought it had to be jetting but nothing I did would
change it. One time when I had the carbs off, I got a flashlight and looked into the IN.
ports and found something puzzling. The backside of the valves and ports just above the
seat inserts were coloring like EX. ports would.

What is going on here ??? After a lot of speculation (and a couple of beers) I came to the
conclusion that the EX. valves weren't closing soon enough and some of the gasses were
getting blown back into the IN. ports just as the IN. valves were opening. I rationalized
that the EX. gasses were heating the IN. charge and causing the "pinging" crackling noise
although that turned out not to be the case.
The logical solution ; advance the EX. cam timing, closing it sooner.

Break time but I'll be right back.....

....This story is leading somewhere....

Rather than set up the degree wheel, dial indicator, etc. I decided to just
guesstimate about 2 degrees advance by loosening the EX. sprocket bolts
and bumping the cam forward. I had looked at enough cam/sprockets to
guess about 2 deg. I wouldn't do this on a customer's bike but I felt like
exploring on my bike.

The first ride was a surprising WOW ! The top end power was back almost as
I had expected and the IN. ports quit coloring like EX. !

However this opened up a lot more questions about cam timing. I decided to
find out what the stock specs for the CB900F were. Surprise ; 102.5 IN. and
107.5 EX' which is very close to what I wound up with. I left the timing where
I had it but I still felt like the motor had more power to be found. As it turned
out the rest was in the jetting, the needle profile. It wanted a far richer needle
but that's another whole story.

Much later when I was given the LC chart, I looked up the 900F starting LC number
and curiously it was105. I remembered something that the guy said about the "split
lobe center" method and like most all other info, no explanation. I'm not sure how I
arrived at the idea of adding 103 and 105 and diving by 2 =104 but I guessed that must
be it, "split lobe center". I'm still to this day not sure if it is but I learned something
about using the chart. Stock CB900F ideal starting point is 105. 102.5 +107.5 = 210
divide by 2 = 105, start. point ! Now I'm getting somewhere with how this chart works
BUT...what is "Ideal" about the starting point number ? I could only assume that it was a no.
arrived at by the engineers and much dyno research and beyond my capabilities to grasp.
Thus the saying "the more you learn, the more questions there are"... something like that.
Why the staggered numbers from the Ideal starting point ? .....

I come seeking the magic numbers, your Sageness.
"But, my child, there are no magic numbers"

Great story and a perfect illustration.

Thanks Phil, but that's not the end ......

I'm on the edge of my seat, waiting for the next installment.

Rick Pope wrote: Thu Sep 08, 2022 6:59 am I'm on the edge of my seat, waiting for the next installment.

Me too, literally ! This chair is killing me.
Relax Rick, the movie comes out soon !

I've always been given information with no explanations, the "whys" behind
the "whats and how tos" so I thought I would try to explain some of the "behind
the scenes" rather than just throw a bunch of numbers out and expect the reader
to make all the connections. In the process it takes on somewhat of a story form
so I hope it doesn't get too tedious and lengthy.

I can only imagine all the stories stored in the minds of the teachers, information
sources that never get told....