What i want to know is degrees, and what is the optimum some people have found. I have been going back and forth from 25 all the way up to 55 BTDC. I only have an SAE dial caliper right now....but better yet a timing light rigged up on it. works like a charm. lets hear your thoughts.
18 to 21 degrees BTDC if you want to go fast & last.
I use timing light with marks i made on case & flywheel .
Fast bat out
How did you come up with this mister man? Is this because of the temps it reaches?
I appreciate the word.
Thought I would let people know that I have now ridden my metra about 30 miles and this kit is a beast!
I would now like to ASK another question, HAS ANYONE EVER ATTEMPTED A TIMING ADVANCEMENT? Can anyone tell me why there is no such thing on these little motors? I mean these are some very high rpm motors and lets say i set the timing to 21 BTDC and then rev it up. With the speed of the traveling piston(lets say 8000 RPM) that 21 degrees BTDC drastically retards to possibly 10-15 degrees BTDC. WOuld a timing advancement not be useful....HOW COME? ANYONE?
What makes this motor invincible to rpm timing alteration. IT DOESNT>>>>>Should we do something about this?!?<<<<<FOLLOW ME!
!!!BaCoN!!!
People have installed cdi with a programable black box that alters the timing. Fixed timing does go well with 2 strokes because as heat builds in the 2 stroke at higher RPMS more advance would push it into destruction in some situations
Just wanted to point out a couple of things:
setting the metra at 2mm or .078" =about 44 degrees BTDC.....ooooo...I feal a wiki article comin on.
So i did what our friend powerchair recommended and set it at 21 degrees BTDC. I havent measured it yet because its late and i am extremely giddy because i think powerchair is right about the timing. Huge, HUGE improvement.
Now i have been told several times 2-4mmBTDC. If you look at the first figure, setting the timing to 4mm would mean about 90 degrees BTDC. That is insanely way to advanced, and i would expect to see a burnt piston...exhaust port.....melted head, cylinder, wallet.
WHY is it that people are telling this crap info?
BaCoN
If 4mm is 90 degrees BTDC, then wouldn't 40mm(the stroke length, roughly) be 900 deg BTDC?
Less bacon more math? isn't 4mm/40mm out of 180 degrees 18 degrees?
What i've always been told is that you can go up to about 21 to 23 deg BTDC but you're pretty much guaranteed to blow something up at that point. 18 is a safer maximum, and 11 to 15 is fairly normal.
first of all you can never have to much BACON!
And you bret are freakin spot on my friend. I appologize.
I am so damn used to working on 4 stroke engines its hurting and warping my mind. I forgot one small variable with my timing light......it is a 4 stroke timing light.
With that being said...im going to bed.
BaCoN
Fixed timing set ups need 18 to 21 degrees BTDC if you want to go fast & last.
A CDI set up 23 to 27 deg MAX BTDC at 2000 RPM,s .
But the CDI needs to retards to 15 to 19 deg,s at 6,000 to 8,000 rpm,s depending on setup port timing / pipe compression / carb / reeds or no reeds / EX back presser /weather spark plug heat rang / etc.
I think two of the big point’s that need to be looked in to or timing and compression or as my dad wood say hot and hotter.
#1
Timing the stock timing is at like 23 to 26 deg BTDC.
It kind of works like this The carb is a flame thrower .
The more time you give the flame it the hotter things get like cylinder piston & head .
We have no vacuum advance to adjust timing with or BIG flame throwers giving less flame/heat timing at WOT but some have CDI.
So in part we need to set or timing for WOT .
Timing needs be more retarded for more top end over 6500 RPM's and more advanced for more low end power .
And the higher the performance of the motor over stock.
The more retarded from stock you want your timing !
So by reducing flame burn time in the combustion chamber we reduce BTU / heat transfer to cylinder piston & head.
Thar or three ways to do this.
The biggest is spark timing try like 18deg’s BTDC.
Next wood be a Ex system with to much back presser.
last exhaust port timing give it more timing up it 5 or 10 deg’s.
And the port is dumping more flame / heat in to the Ex system.
The exhaust chamber loves it hot up to 800 deg's f Max 4" down from flang on out side of header pipe.
As RPM’s go UP and UP it gets hotter and hotter
As it gets hotter presser goes up .
More heat and presser make the shock waves move faster moving the power band up in RPM’s at the same time = more power.
#2
The higher the compression makes all hotter .
Higher compression makes things burn faster to (so you need a colder spark plug ).
Giving faster heat /BTU transfer to cylinder piston & head.
Compression you don’t need HI Compression with a well tuned EX system ports and carb.
A good EX system will supercharge/raise compression by over stuffing the combustion chamber.
10 or even 9 to 1 shod be fine.
Fast Bat out
hey powerchair,
I appreciate the extra words! Your help is forever greatful.
I have set my timing down to 18 BTDC, and put a #8 plug in it, and temps have gone down and power has gone up.
Im not challenging you to a pissing contest but, in your thread you say we need more retarded timing up top and more advancement down low.....is this possibly backwards thinking?
With constant tuning on my little supercharged 4 banger vw, i noticed and also have been told, retarded timing gives real power down low. and then when advancing the timing you kinda loose some bottom end and then gain up top. same goes for valve timing, which i had a varible cam pulley with -/+ 8 degrees. But then again this is a 4stroke. only been tinkering with 2 strokes my whole life, and really got into them in the past 3 months. I am about to throw all 4 stroke logic out the window.
what you think?
Is this principle not the same for 2 strokes?
thanks powerchair!
!!!BACON!!!
(BACON Im not challenging you to a pissing contest but, in your thread you say we need more retarded timing up top and more advancement down low…..is this possibly backwards thinking?)
Crazy Wayne No Not on 2 stroke,s things tend to burn faster at higher RPM,s.
and the exhaust works like a pols jet eng .
As you a test it works .
You can be fast and last or melt down /seize and be slow.
Fast bat out.
Man...this thread is awesome. I was out blasting my 80 Metra yesterday after I finally got it all sealed up - no air leaks, solid exhaust mount, carb setup....and it rides great, but I know it has more.
I haven't messed with the timing but it sounds like 18 BTDC is going to be a good start. It does well on the low end, but I feel as if it's not hitting hard enough up top.
Where can I get a good timing light? I've heard that it's not hard to make one?
I will wiki this later this weak i need to get my not,s together first.
Fast bat out
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