The International CBX Owners Association

Ideally I would have a video or at least pictures and diagrams to post along
with the descriptions but for now explanations will have to do.
The side thrust cam holders to be drilled are between cyl. 5 and 6, holders
no. 7 and 15
The drill bit should be no larger than the width of the cam flange.
The idea of doing this procedure remotely on the R&D platform motor would allow
the use of a drill press and easy clean up. All that would be needed is the right side
cam halves and the side thrust cam holders to do the job.
One issue I haven't resolved yet is how to "lock" or hold the crankshaft at exactly TDC
while positioning the cams. On the 4cyl motors it is easy. When 1and 4 are at TDC,
I use a BDC piston stop on 2 or 3 to lock the crank in position but with the CBX when 1 and 6 are
at TDC the other pistons are at 120 degrees of crank rotation instead of 180 so the BDC
piston stop idea won't work in accurately locking the crank in position. Using a TDC piston
stop to locate exact TDC doesn't hold the crank in a locked position needed for accuracy.
Using the TDC mark on the right end of the crank doesn't account for the few degrees of
piston "dwell" at TDC and the crank needs to be locked or held in position in the center of
the dwell.
However, this close of detail is splitting hairs because if the piston is at TDC anywhere in
the dwell range you are still very close to exact and not likely to notice the difference.
The goal is getting the cam timing as close to the desired settings as possible, short of
obsession, and make it easy to adjust at service intervals.

"It should be fun, not a dreaded chore" ...said the psychologist to the mechanic.

Short of locking the crank in position at TDC 1 and 6, I came up with an easy to attach
degree wheel that mounts on the end of the crank. It consists of a 6 point 17mm socket
that the wheel attaches to that is dilled and tapped every 120 degrees through the
flats in the hex for three 6mm set screws that clamp on to the hex end of the crank.

I gave the original to Jebbysan (anyone remember Jebby?) with the intention of making
a new improved version that I haven't got to yet. It worked quite well. At least you would
be able to see with some accuracy if the crank/piston is at TDC when the cams are set.
Still, the goal is to avoid having to use a degree wheel or dial indicator to adjust the cams
and there's too much room for error using the marks on the end of the crank.
What to do...?

I was going through some articles my machinist friend sent me last night
and came across one about cam LSA (lobe separation angles) and how it
determines valve overlap and the effects that different amounts of overlap
have on power delivery. The article said basically what I've been trying to
explain in the cam timing part of this thread, only in automotive terminology.
Just substitute LSA for LC numbers.

While reading I was reminded of a couple of things, observations I had planned
to "circle back" to. The first is the beauty of the DOHC design. You can change
the amount of valve overlap and therefore the power characteristics without
having to go to the expense of buying different grind cams. With single cam design
you have to change the cam to change valve overlap which can get quite expensive
in order to find what works best for you. Then if you throw in lift and duration changes,
cost can be prohibitive unless you know exactly how a certain grind combination will
work.

With the DOHC design you can experiment with different LC or LSA numbers, find what
meets your needs best and then work on lift and duration. You might find that the stock
grind cams work just fine when the LC/LSA numbers alone are changed. Such is the case
with the CBX motor most of the time.

The other observation I was (will) go into is the difference between 2 and 4 valve motors,
what LC/LSA numbers work best....

Clarification edits 10-21-22 entry ; cap/holder, dowel, bit/tool.

Before moving on, I found a diagram that illustrates some of the terminology
I've been using. I imagine something similar has been posted somewhere on
the forum before but I'll throw this in. I hope it doesn't do more to confuse than
explain.
What is shown is an example of a SOHC configuration, both IN and EX lobes on
the same shaft. If you can picture the IN lobes on one shaft and EX lobes on
another shaft you (obviously) have the DOHC setup. Everything else in the diagram
remains the same but the overlap portion looks quite different.
Lobe center numbers and LSA nos. are the same thing but the lobe center (line)
and separation angle (difference between lobe centers) are different things (terms).
One thing not shown here is the "acceleration ramp"(AR) which is where the lobe
profile outline meets the base circle outline, where IN or EX opens, closes.
Mike Nixon does a good job explaining ARs and their function in one of his tech
articles. motorcycleproject.com

The line drawn through the center of the shaft and tip/nose of the lobe illustrates
the LC (lobe center). Later I'll go into symmetrical and dual profile lobes and why
the difference and also why the center of the lobe and the center of the duration
are sometimes different.
Hopefully this will clarify what all the terms used represent :

In the diagram above, the cam lobe shown is an example of a symmetrical lobe
where the opening half is identical closing half either side of the LC line.
Symmetrical lobes are used on all shim/bucket type cyl. heads where the camshaft
center is directly above the valve stem center(line).
When the camshaft center is moved away from the valve center line, as in rocker arm
type heads, the shape of the lobe becomes asymmetrical. The rocker arm acts as a
lever between the cam and valve and the leverage point, where the cam contacts the
arm (pad) determines the shape or profile of the lobe, flat on one side, curved on the
other. The location of the pad between the rocker arm shaft (pivot) and the tappet
(where the rocker contacts the valve tip) is referred to as the leverage angle*. The closer
the pad is to the valve the closer to symmetrical the lobe profile becomes. The closer the
pad is to the pivot shaft the more pronounced the flat side of the lobe becomes.
It's hard (for me) to picture how a dual profile cam lobe with a flat side and a curved side
acting upon a rocker arm mimics the action of a symmetrical lobe acting upon a shim/bucket
arrangement but it does. *I also have a hard time picturing how this would be illustrated in
a diagram. I sometimes wonder if my chemistry teacher is responsible for my inability to
cognitively grasp certain ideas due to having us students handle mercury in the palms of our
hands to demonstrate viscosity. (nervous sys. damage ?)

Many years ago I was talking with Dave Rash (founder of D&D Exh. Sys.) when
he was developing CB750F/1025 motors for Daytona. We were on the subject of
cams and valve train stuff and he mentioned trying out dual profile cams on the
shim/bucket arrangement. If he tried it I think I know why I never heard anything
else about it. Visualize shims exiting the cam cover and valves imbedded in piston
domes etc.

Thanks for keeping at this, Bob.

I don't think there's any reason to doubt that your brain works just fine, regardless of what materials you've handled!

I'm gonna give this all a careful re-read - there's some stuff in there that I struggle to get my head around, too.

Syscrush wrote: ↑

Fri Feb 03, 2023 1:57 pm

Thanks for keeping at this, Bob.

I don't think there's any reason to doubt that your brain works just fine, regardless of what materials you've handled!

I'm gonna give this all a careful re-read - there's some stuff in there that I struggle to get my head around, too.

Hey Phil, I guess it's about time I acknowledged your generous words.
I hope you're not struggling with something I tried to explain but rather the same things
I have a hard time with. Otherwise I've failed with my attempt to explain.

I've been reading some posts in other threads and it seems that the subjects will shift
from what started as exhaust to carbs and vise versa with heads and ports in between.
Rather than post something in one thread only to find the same subject matter in a
different category/thread I would like to try to pull all three subjects together here
so the readers aren't having to jump back and forth to discuss the same subjects.
I think it's called bundling but it might help to get a grasp on how each affects the
other and how one, lets say poorly functioning exhaust can screw up what might be
accomplished in the carb and port areas. A great exh. sys. won't do much good if the
carbs and/or ports aren't functioning well. The subject of ports largely includes cam
timing, valves and seats. More after a break from this torture chair.....

BTW - something I've been thinking about a lot lately is variable valve timing. I don't see it as something that I will try to undertake, but I'm curious what your thoughts are on this. I could be wrong, but I don't think that a set of custom cam phasers would be the most radical work that's been done on a CBX.

Maybe something like the "dumb" purely mechanical system that's on the GSXR1000 would have benefits for the CBX - or maybe it's all more trouble than it's worth...

....Sorry, that was a long chair break...

Yes , it has crossed my mind about variable valve timing but it would
take a lot of precision machine work and there's the consideration of
how to make it fit into the limited space of the cam chain well without
some serious modification to the head. The Oldham joints and cam half
system further complicates the idea as well as the dual cam chain system.

In that video the Suzuki system appears to only retard the cam timing. It
doesn't change the duration or lift but it makes sense to retard the timing
at high rpm to build cylinder pressure which increases top end HP then return
to advanced cam timing at lower rpm to bring up low/midrange power/acceleration.
I've read several articles about different systems but so far Honda's variable system
is the only one that varies lift as well as duration. I believe it was Kia (automotive)
that developed a system that increased duration without changing the cam lobe
profile by just delaying the dwell time of the cam at high rpm.

Something I didn't learn about until I had built/tuned a handful of the Yamaha 5 valve
motors is that the center of the 3 IN cam lobes is advanced from the other 2 lobes.
It seems like a clever way of increasing the duration without long duration lobe profiles.
To me it brought to mind the question of which lobe(s) would you take the timing readings
from ? It would be rather complicated but it only made sense to take the valve opening
readings from the center lobe and the closing readings from one of the other 2 lobes.

Any way you look at it, it would be very challenging and expensive to try to incorporate
a variable cam timing system of any kind in the CBX motor. This brings me back to the
fact the CBX suffers from lack of low end/midrange power due not only to the relatively
small displacement cylinders but the high cam timing numbers for peak HP (that the CBX
doesn't need). This is why I use the lower numbers the LC chart calls for (103-105) to increase
the low end/midrange power. The motor seems to wind up more quickly so you don't even
notice much, if any loss of top end power. Besides, changing the cam timing is is a hell of a lot
cheaper (costs nothing but time) than trying to develop a variable system or trying out different
grind cams. (should be 50cents adjusted for inflation).

I haven't been working on or riding my bike this year (or last year) at all due to outside issues, but have finally caught up and began to service it for startup.
While searching the forum for something unrelated, I stumbled upon this thread and spent most of the afternoon reading.....and re-reading through the posts. I must say Bob, that you sure are a good story teller and I thoroughly enjoyed reading this thread.....hopefully with more to come.
Cheers, Forrest

Thanks Forrest ! Sorry for the really late reply but I hope to write more as soon as I
can get out of this hospital.

BTW, the "stories" are non fiction. Thanks for reading !

I was wondering if you had an illness Bob, hope you get well soon!

Well, still stuck in the hospital (med./phys. therapy) and can't walk so no work getting
done on the project. This is getting very old. Just got the computer going and it's good
to escape boredom of this place with no cable tv and some hard to tolerate staff.
I still can't walk but at least no amputations. It took a long time to get this way and
I guess it will take a long time to undo the damage. You guys are more "family" than
my own family but I've got a grandson that has some promise and mechanical interest
so I'll have some help with the project when/I can escape this place.