[jbranson]

In my recent efforts to build a programmable ignition I've come appreciate the simplicity and accuracy of your basic points ignition.

Some things to think about:
At 12,000 rpm the piston is going up and down 200 per second.
The crank rotates once every 5ms (5 thousands of a second).
The crank rotates 72 degrees every .001 of one second.
For timing accurate to 1 degree the points have to fire within a range of .000014us ...or 14 millioneths of one second. That's about the time it takes for a high velocity rifle round to travel one half inch. Or the time it takes a 200mph motogp bike to go 50 thousandths of an inch (just a little more than a spark plug gap).
In a 25 minute race you can expect your points to perform this feat about a quarter of a million times.

I still find it amazing that a reciprocating engine can turn 200 times in one minute....and yet they can do it in one second...closer to 300 times in one second on modern bikes.

Somebody has put a lot of thought into these little engines we thrash around every year.
JohnnyB

 

[texmawby]

johnny,

pick up the new motorcyclist mag this month. they have a full feature on the honda 6 (rc174) that george beale recreated. the numerous factoids of tolerances and different specs that honda came up with in the sixties is mindnumbing.

i especially like the fact that his 50cc racer would put out more horsepower per cc than the motogp bikes running today. i think the figure of it's efficiency magnified to 1000cc equals 320bhp!

i am a honda lover.

aaron lover too!

tex

 

[joe c]

hey john, youd probably really dig that article. tex read me the entire thing on the way back. the crank is soo small and fragile that you can bend it with your hands if youre not careful. and its a 12 piece crank. to hear what the guy did to make the repro makes you wonder how honda was able to go from drawing board to bike in 6 mos. 40 years ago. the rods from the center out are different sizes depending on loading. they made the oil gallerys different sizes and multiple ones to narrow the engine cases by something like 4mm in the end. i mean it seriously amazing the shit they pulled off without the benefit of modern computer systems and cad and cnc. really really cool.

jc

 

[texmawby]

one correction. according to the article they went from drawings to production in two months.

it took two weeks to set up the cnc machine and then it ran for 14 hours using 90 tools just to make the engine cases.

RE-DICK-U-LOUS!

tex

 

[jbranson]

I've read that article somewhere....maybe Vintage Racing mag a while back. All about the guy in England that made the replica?

I'll have to buy a copy and save it.

Hard to find the details but Honda also made a 50cc twin I think...they say the valves look just about like nails.

Stuff like this is kinda why I get pissed at people that bad mouth Japanese bikes, like they are inferior to European stuff. Yeah the Japanese made some bad ones...they also made 10 different bikes for every one European bike that was made. And Honda has a 50 year history of racing. They were screwing with engines back when Ducati was making AM radios....yes Radios.
JohnnyB

 

[FR]

It's kind of ironic that a lot of the people that have a stick up their ass about Japanese bikes happen to ride either HD or BMW, the most anachronistic bikes out there. The HD breed thinks you're being unpatriotic or that the Jap bikes are inferior, and the BMW breed scoffs at the Jap bikes as being copycats (which is true in many cases, but they often did a better job with their "copy" than the original designer) and inferior because they're mass produced.
I must say it took me a while to recognise some of the engineering feats of Honda, mainly because growing up I kind of got brand loyal to Yamaha, so I didn't pay much attention to some of the technical stuff that other brands were putting out.
These days I'm not so brand loyal, although I do take pleasure in beating certain 4 valve Honda singles with my 2 valve Yamaha at the race track...
Can't help it. I must be a caveman.

FR

 

[jbranson]

Yamaha makes a fine bike. I think back in the 70's that Yamaha had to my eyes a better fit and finish than the Hondas did.

Yamaha was I think the first bike I ever saw with socket head screws as OEM equipment.
JohnnyB

 

[FR]

The bike that absolutly knocked me out, that I saw in my waking dreams, that I yearned for in the depth of my soul, was the '68 Yamaha DT1. I wanted that bike as much as any pre-pubescent boy wanted anything. I still think it's one of the prettiest, most balanced designs out there, a quintessential motorcycle.
Later on as a teen, I rode a friends DT2 (I think, the 125cc version) and it sealed my fate with the brand.
There's probably some evidence of brand loyalty starting with the first brand you ride..

FR

 

[Camelhairy]

quote:
I still find it amazing that a reciprocating engine can turn 200 times in one minute....and yet they can do it in one second...closer to 300 times in one second on modern bikes.

Somebody has put a lot of thought into these little engines we thrash around every year.
JohnnyB

JohnnyB,
It's amazing that the valves can work at those speeds but a 2 stroke shouldn't work at all. How does the mixture get from the carb to the exhaust at almost 200 times a second and still have time to burn...it's magic.

FC

 

[jbranson]

Frank...I think a two stroke does it by wildly drawing in about twice as much as necessary and then trying to burn about half of it before it goes out the tail pipe.

Kind of a like a person drinking too much and throwing up....then drinking again
JohnnyB

 

[aaron]

Wait a second... Your not supposed to drink too much, throw up, and then drink again? I knew I was doing it wrong.

Aaron

 

[texmawby]

back in my erie days, when i'd go to keggers at fraternity houses and i'd end up outside ralphing in the bushes......

upon re-entry after getting heckled and laughed at by the "brothas," i'd simply chuckle when stating that now i could go drink more of their free beer.

they never found that too funny.

tex

p.s.- good analogy jb!