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@garncarz avatar
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Molto Verboso
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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Molto Verboso
@garncarz avatar
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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UTC quote
Does it matter which direction the electrode is pointed?
@gravelrash2004 avatar
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Addicted
P Series / Li / LML / Motobi
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Addicted
@gravelrash2004 avatar
P Series / Li / LML / Motobi
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UTC quote
into the combustion chamber for maximum boom.....

otherwise nope, just wind it in and tighten it up
OP
@garncarz avatar
UTC

Molto Verboso
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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Molto Verboso
@garncarz avatar
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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UTC quote
I'm looking at the burn pattern in the head and thinking the electrode is currently 180 degrees out of position.
Forum member supplied image with no explanatory text
@birdsnest avatar
UTC

Not So Moderator
VNB VSC VMA VSX - o9c vbc vmb
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Not So Moderator
@birdsnest avatar
VNB VSC VMA VSX - o9c vbc vmb
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UTC quote
What does the head of the piston look like?
OP
@garncarz avatar
UTC

Molto Verboso
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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Molto Verboso
@garncarz avatar
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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UTC quote
Solid uniform carbon.
UTC

Molto Verboso
1958 Allstate 177VMC, 1962 Allstate, Yamaha Vino 70cc
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Location: Philadelphia
 
Molto Verboso
1958 Allstate 177VMC, 1962 Allstate, Yamaha Vino 70cc
Joined: UTC
Posts: 1923
Location: Philadelphia
UTC quote
garncarz wrote:
I'm looking at the burn pattern in the head and thinking the electrode is currently 180 degrees out of position.
I've never heard of a plug being out of position in that way in my life. Too long or short sure but never that the electrode was facing a right or wrong way. Never even thought about it. Interesting. Like you, I'm now wondering if that's a thing
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@garncarz avatar
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Molto Verboso
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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Molto Verboso
@garncarz avatar
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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@garncarz avatar
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Molto Verboso
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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Molto Verboso
@garncarz avatar
1964 Allstate Cruisaire, 2022 Husqvarna Vitpilen 401, 1972 Suzuki T500J
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UTC quote
Maybe it's all academic, especially with a 5 hp engine, but if the electrode gap was facing inboard of the head, it would see the fuel-air mix faster and if nothing else would facilitate easier starting. Currently the gap on mine is in the shadow of the ground electrode as evidenced by the heavy carbon up the middle of the head. No?
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@greasy125 avatar
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Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
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@greasy125 avatar
Weird 80's Vespas & Cool Vintage Lambrettas
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UTC quote
I really wouldn't worry about it to be honest. unless it's a high compression and high performance build it won't make a gnats ass of a difference.

flame front travel in regards to indexing is only going to come into play when you got something hot-shit cooking. on a stocker? nah.
@kshansen avatar
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Molto Verboso
GTV300 (wife's)
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Molto Verboso
@kshansen avatar
GTV300 (wife's)
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UTC quote
greasy125 wrote:
I really wouldn't worry about it to be honest. unless it's a high compression and high performance build it won't make a gnats ass of a difference.

flame front travel in regards to indexing is only going to come into play when you got something hot-shit cooking. on a stocker? nah.
Agree! Somethings that can be important if it's a race car where the difference of a couple tenths of a second can make a major difference in race just are meaning less on a engine for daily use.

I recall somewhere, think it was a Harley forum, where someone was claiming you needed to use spark plug wires if the same length or else the timing would be off from the front to rear cylinders. Like the spark running through the wire at 186,282 miles per second is going to be noticed from a difference of 2 or 3 inches of wire!
@xantufrog avatar
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Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
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Moderibbit
@xantufrog avatar
1980 P200E - "Old Rusty", 1976 ET3 Primavera
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UTC quote
kshansen wrote:
I recall somewhere, think it was a Harley forum, where someone was claiming you needed to use spark plug wires if the same length or else the timing would be off from the front to rear cylinders. Like the spark running through the wire at 186,282 miles per second is going to be noticed from a difference of 2 or 3 inches of wire!
LOL. People are full of so much shit sometimes. Does it technically take more time for an impulse to travel 2 more inches? Yes. But someone thinks the tolerances on their HD are way more (too) precise than they are
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Ossessionato
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Ossessionato
@gickspeed avatar
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UTC quote
Ask yourself . . "will indexing this sparkplug get me home?"

in theory, probably matters if you are doing some kind of timed test. would you even notice on a 5 Hp engine? probably not. i'm not even sure i would even notice on a 25 Hp engine.
@pullmyfinger avatar
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Hooked
Some Vespa, some Yamaha, some Suzuki, some Kawasaki...
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Hooked
@pullmyfinger avatar
Some Vespa, some Yamaha, some Suzuki, some Kawasaki...
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UTC quote
On a head with centralized plug you index open end toward the boost port, where the fresh charge is coming from. On these offset heads it's all wonky, but I'd say that you want the open end to face the squish band since that's where the fresh charge is being pushed from. It also makes sense that you don't want the spark facing a corner of the combustion zone. Stance on indexing depends on which side of 80/20 you stand, which in the case of race engine building is that it takes 80% work to get that last 20% which makes all the difference.
@mod_eric_the_skin avatar
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Hooked
'59 VBA, '05 Stella 177, '80 P125X
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Location: Athens GA
 
Hooked
@mod_eric_the_skin avatar
'59 VBA, '05 Stella 177, '80 P125X
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UTC quote
xantufrog wrote:
LOL. People are full of so much shit sometimes. Does it technically take more time for an impulse to travel 2 more inches? Yes. But someone thinks the tolerances on their HD are way more (too) precise than they are
As stupid an idea that this sounds like (to me anyway, and at least one other forum member), apparently people do give a shit- at least in the high performance world:
,
https://www.moroso.com/pub/media/wysiwyg/PDFs/NASA_Speed_News.pdf
@xantufrog avatar
UTC

Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
 
Moderibbit
@xantufrog avatar
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: UTC
Posts: 8892
Location: Atlanta, GA
UTC quote
Mod Eric The Skin wrote:
As stupid an idea that this sounds like (to me anyway, and at least one other forum member), apparently people do give a shit- at least in the high performance world:
,
https://www.moroso.com/pub/media/wysiwyg/PDFs/NASA_Speed_News.pdf
Just to clarify, I wasn't reacting to the sparkplug indexing idea with that comment. I was reacting to the idea that modern Harley Davidsons won't run right if one spark plug wire is 2 inches longer than the other
UTC

Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
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Location: Siam
 
Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: UTC
Posts: 2537
Location: Siam
UTC quote
Sometimes I release a bit of air from my tires into a special test unit to measure the oxygen content in my tubes to make sure I'm getting maximum performance and optimal gas mileage. I remember reading that in one of my Piaggio service manuals.
@oopsclunkthud avatar
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Banned
3:5
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Location: San Francisco
 
Banned
@oopsclunkthud avatar
3:5
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UTC quote
I have some surface gap sparkplugs to play with on a custom head, but this would come into play only after:
* central squish
* squish gap optimized
* central plug
* toroidal combustion chamber shape
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Hooked
Joined: UTC
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Hooked
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UTC quote
Tested it back in the day with my race bike. Zero difference on a small frame with the angled plug. Not worth the time.

Compression ratio was 13.5:1 which is way higher than any off the shelf kit for reference.
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