8 stroking

MikeG · Jun 29, 2023

on a cylinder thats 8 stroking what would the plug look like? Also, what would cause an 8 stoke condition on an engine thats been running perfectly fine? Been running down the usual suspects but found nothing so far.

KiwiShane · Jun 29, 2023

MikeG said:
on a cylinder thats 8 stroking what would the plug look like? Also, what would cause an 8 stoke condition on an engine thats been running perfectly fine? Been running down the usual suspects but found nothing so far.

If she's been recently running sweet ... my guess would be either a air induction restriction (blocked air intake circuit or oiled up air filters ?) or electrical issue ? (Plug breaking down) causing excessive over richness symptoms ... my 2 cents
[Edit] Running "Perfectly fine"..or..."progressively worse"

ntst8 · Jun 29, 2023

When does it 8 stroke.
I recently had the issue on one cylinder and only on a warm engine - after sitting with the petrol taps on. Turned out to be a poorly seating float needle flooding one carb, wasn't an issue on a cold engine as the taps were off.

Matt Spencer · Jun 29, 2023

Air Balance toob on manifolds ?? Yer gettit with l o n g intake manifolds , on idle .

SO , If Its Only on Idle , look between carbs'n'ead . and seating of these . Soap Bubbles ? Leak Tec . ?

acotrel · Jun 29, 2023

8 stroking is usually due to too rich - too lean creates a cough. If there is black smoke coming out of the exhaust - that means too rich. When the white smoke escapes elsewhere - that means your electrics are stuffed.
If the black smoke escapes from only one pipe, it might mean one carb is flooding.

concours · Jun 30, 2023

If the air passage has clogged, it will be overly rich as described.

kommando · Jun 30, 2023

Main jet coming loose and sitting in float chamber is another potential cause.

MikeG · Jun 30, 2023

No black smoke. Issue is there throuout throttle range. It's gotten worse. Last time out I would get a hesitation on rapid throttle opening then a bang from the left pipe. My guess is not enough spark to fire the charge, dumps raw fuel into pipe and when it does fire the fuel in the pipe goes too. The plug on that side looks good, almost a bit lean. Opposite of 8 stroking cause. Took carb apart (brand new premier last year) nothing amiss. Compression check and a look at valve adjustment next. Coil is a single unit with 2 leads, Powerarc ignition from Old Britts.

Schwany · Jun 30, 2023

Bad ground or electrical short messing with the ignition. Is that a guess or a test. lol

Is "8 stroking" an Access Norton or Euro symptom descriptor? I've never heard it before.

concours · Jun 30, 2023

Schwany said:
Bad ground or electrical short messing with the ignition. Is that a guess or a test. lol

Is "8 stroking" an Access Norton or Euro symptom descriptor? I've never heard it before.

It's an age-old way to describe misfiring, in an even cadence, every OTHER combustion event.

Also see "four stroking" as used to describe a very rich 2-stroke engine, usually at light/moderate load

MikeG · Jun 30, 2023

What is 8-stroking? What does it sound like?

Hello, I'm doing a bit of carb tuning and I am curious as to what is meant by the term "8-stroking." What does this sound like? Why is it called 8-stroking? I am assuming it is some pattern of irregular exhaust impulses, but I'm not really sure. Is there a way I can recre...

www.britbike.com

kommando · Jun 30, 2023

If you want to hear what 8 stroking sounds like then put on the choke or remove the main jets. The carbs without main jets will run as normal up to 3/4 throttle and 8 stroke progressively worse until full throttle.

MikeG · Jun 30, 2023

Still baffled as to why, if that cylinder is not firing all the time, its not blacker than it is.

Schwany · Jun 30, 2023

concours said:
It's an age-old way to describe misfiring, in an even cadence, every OTHER combustion event.

Also see "four stroking" as used to describe a very rich 2-stroke engine, usually at light/moderate load

Interesting. I've never heard it used in 72.5 years. Running too rich I've heard, and experienced.

acotrel · Jun 30, 2023

If you get hesitation on throttle-opening - sounds like too lean, but might be too rich. Too rich usually means sluggish - too lean usually creates a miss when you ride the bike. With experience, you know immediately. I usually lean-pff the jetting intil I get a cough , then raise the needles one notch. The taper on the needles is important. If you have slow taper needles, it should be possible to make the motor hesitate if you wind the throttle on too fast, but your bike will be quicker that way.

acotrel · Jun 30, 2023

Schwany said:
Interesting. I've never heard it used in 72.5 years. Running too rich I've heard, and experienced.

To me 8-stroking means too rich - hesitation usually means too lean. The taper on the needles is there to compensate for less vacuum in the inlet port - less vacuum means less fuel gets sucked, so more jet opening is required. But if you get 8-stroking, you would be miles too rich. There is probably something in the float needle holding it open.
Check the tank breather.

concours · Jun 30, 2023

Schwany said:
Still baffled as to why, if that cylinder is not firing all the time, its not blacker than it is.

You gutta WRING IT'S NECK!

Blow the carbon outta the old bitch!!

KiwiShane · Jun 30, 2023

concours said:
You gutta WRING IT'S NECK!

Blow the carbon outta the old bitch!!

I'd take the air filter off ...and wring its neck

Schwany · Jun 30, 2023

acotrel said:
To me 8-stroking means too rich - hesitation usually means too lean. The taper on the needles is there to compensate for less vacuum in the inlet port - less vacuum means less fuel gets sucked, so more jet opening is required. But if you get 8-stroking, you would be miles too rich. There is probably something in the float needle holding it open.
Check the tank breather.

I actually get carburetor tuning. I've just never heard the 8 stroking term. Now I be more edumecated.

htown16 · Jun 30, 2023

If your bike has chokes ie enrichers, put them down when it's well warmed up. That's what too rich sounds like.

8 stroking

MikeG

Mikeg

KiwiShane

ntst8

Matt Spencer

acotrel

concours

kommando

MikeG

Mikeg

Attachments

Schwany

concours

MikeG

Mikeg

What is 8-stroking? What does it sound like?

kommando

MikeG

Mikeg

Schwany

acotrel

acotrel

concours

KiwiShane

Schwany

htown16

Similar threads