R&D platform

[heli_madken]

Start over with a new reply, press CTRL+V and you will see your text magically re-appear

[bobcat]

Well, the short piece I just wrote vanished ! No "server error" this time.
I guess the subject Gods don't want me to write this! BUT I WILL if it takes
the rest of the month !

Now that we're way off topic.....

[bobcat]

Start over with a new reply, press CTRL+V and you will see your text magically re-appear

Text Magic ! That's what I need !

[herdygerdy]

If I am posting a long-ish post, I will typically open the Notepad application (or your favourite text editor of choice) and do all my draft and preparation in there. The below assumes you're on a Windows machine...)
Once you are happy with what you have written in Notepad, then:
1. Save it somewhere but leave the file open.
2. Ctrl, A to select/highlight ALL the text
3. Ctrl, C to copy all the text in your Notepad document to the clipboard
4. Switch to your internet browser, access the forum and open the Reply box
5. Ctrl, V to PASTE the contents of the clipboard into the Reply box
6. Select 'Preview' so you see how it will look on the forum - may need a tweak here and there to 'look' right.
7. Hit 'Submit' and you're done!
Once you've done it a few times, it becomes quick and reliable. Maybe do a run-through a few times to get the hang of it...
Hope this helps Bob, looking fwd to your next submission.

[bobcat]

Tony, I just wrote a response for you, hit submit, ....INTERNAL SERVER ERROR !!!!



Maybe my computer ?

Yeah, I look forward to my next submission (on topic) too!


Yawn...I think I just discovered part of the problem. Poor lighting and
the "end" button is directly above the "backspace" button on my keypad.

Unless I look very closely while uni-digit typing.....
back to bed.

[Syscrush]

Maybe my computer ?

I very much doubt that it could be your computer.

Others have suggested composing your posts in an editor on your computer - even better is Google Docs - which auto-saves every keystroke. It's almost impossible for you to lose your data that way.

[bobcat]

Thanks Phil, but I've never used any of that stuff before. I need to learn it
and practice a little.

Meanwhile I'll try to pick up where I left off a little later this afternoon, keep
it in short segments and maybe the server bug will leave me alone. I might try
what Heli suggested and give that a shot. Sounds simple enough.

[Syscrush]

Thanks Phil, but I've never used any of that stuff before. I need to learn it
and practice a little.

It is a feature-rich word processor that works in your browser, and it's available for free. Here's a tutorial for beginners. If you can use this forum, you can use Google Docs:

https://youtu.be/z9i_h-WMQ68

[bobcat]

...So the questions are what are the optimum LC numbers and how is that determined ?
How did Honda arrive at the numbers that were used ? (my evaluation).

When the CBX was first introduced, the focus was on peak HP and top speed In the power
race, to be king of the hill and it was briefly. Then the HP limits were introduced in 1980
and Honda had to dial it back to comply. When Honda decided to make the CBX a "sport
touring bike" they needed to improve the low and mid range power more suited for that
category of rider and probably to pull the extra weight. This was accomplished by advancing
the IN. cam, increasing valve overlap. They were going in the right direction but were likely
limited by emissions rules, fuel mileage considerations and smooth (tame) idle.

The optimum LC numbers are lower yet. ....continued...

I'll try to pick up where I left off;

So the goal in max. cyl. filling would be to open the IN. valve(s) as soon and far as possible
just before the piston reaches tdc. of the EX. stroke. The exiting EX. gasses velocity as the
EX. valve closes begins to pull the IN. fuel/air charge into the cyl. so that when the piston
begins the IN. stroke downward, the cyl. filling is maximized. The momentum of the fresh
charge continues well after the piston reaches BDC and begins upward on the compression
stroke. Even though the piston is moving upward the IN. valve needs to remain open long
enough to take full advantage the incoming charge momentum.

The limiting factor of how far to advance the IN. cam is the closing of the IN. valve. The sooner
it is opened, the sooner it is closed. Close the IN. valve too soon and you shut the door on the
still flowing charge momentum. This is where opening and closing becomes a balancing act.
....break time !

[bobcat]

Well, that last big, long sentence was a confusing mess.
I won't even try to go back and edit it.

Well, I decided to edit (re write) that mess.
Hopefully that was more understandable.


BTW heli, A+C+V worked to perfection ! Magic !

[bobcat]

...Similarly there's the question of the ideal timing of closing and opening
the EX. valve(s). Close the valve too late (retarded EX. cam) and too much of
the incoming IN. charge is lost out the EX. and IN. flow momentum is diminished.

Close it too soon and the scavenging effect on the IN. flow is diminished. Then
there's the consideration of when to open the EX. valve. At what point does the
downward force on the piston from combustion begin to diminish enough to open
the EX. valve and begin releasing the still expanding combustion gasses.
Once again, a balancing act. This phase, beginning the EX. stroke (bbdc)
would offer the most flexibility timing wise.

Without a dyno and lots of patience, wear and tear on the motor and $ (unless
dyno time is free), it's a guessing game. This is where the previously mentioned
"lobe center chart" comes in handy....

[bobcat]

...The "lobe center chart" was given to me by a rival tuner in Legends car racing.
We were talking at the track (TMS) and got on the subject of cam timing and jetting.
He had attended all the motorcycle schools all the way through the most advanced
classes on engine building for racing and he built and tuned for a number of car owners
there at the track. I was hired by LSW racing, unofficial title of their "engine department"
and was responsible for 5 or 6 cars and customer's jobs brought in.

He gave me this chart and I glanced at it, 2 pages of a bunch of numbers resembling the
CBX valve shim chart. I really didn't have a clue what I was looking at and I was happy
with the numbers I was using already (my cars were beating his) so I just set it aside with
my other notes and thanked him. I finally picked it up some time later and tried to figure
out what to do with it, how to use it as he had given me no explanation of it. I guess he
thought I already knew.

It consists of a cross reference of Stroke dived by 2 (=stroke radius) along the left side of the
page and rod length (center to center) across the top. When you cross reference these numbers
it shows a number for the "starting LC number" for that motor configuration.
I thought OK I'm getting somewhere understanding this. Barely

[bobcat]

A little more story and then I can get to the nuts and bolts of this.
Long before I began working on Legends car motors (Yamaha FJ and XJR 1200)
I was tuning for a guy racing a GSXR750 in 750 and open superbike categories.
I was on the phone ordering some stg. 2 cams from Yoshimura, speaking with
Don Sakakura. He was asking what all was done to the motor so far and what cam
timing numbers I was using (stock cams). I told him 104 IN. and 106 EX. which
I thought were good all around numbers. The bike was very competitive but just
needed a little more power. Without explanation he suggested I try 103-105 instead.
Coming from Yosh. R&D I didn't ask why, I just did it. That change, advancing the IN.
one degree and retarding the EX. one degree (more overlap) transformed that bike
into a first and second gear wheelie monster. Next race out he (Jeff Harder) destroyed
the field in both classes and was accused of running an 1100 motor in the 750 chassis.

I thought I had been given the Holy Grail of timing specs and used them again on other
race motors for customers, different bikes, Hondas and Yamahas (4 valve/cyl.) with the
same results. Later I will get to why it seemed universal, but a faulty assumption.

When I was given the LC chart and started to understand how to interpret it, the learning
curve got steep and my enthusiasm for learning became intense....out of the chair time break...

[NobleHops]

Great reading, Bob. Thanks for taking the time.

[bobcat]

Thanks Nils, my pleasure. I'll try to get going again shortly.
The best is yet to come as I'm trying to lay this all out in hopefully understandable
detail so I show how this (cam timing) should and can be a routine service item like
valve, cam chain or ignition timing adjustment. Your interest is appreciated !