Needing Air

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Triton Thrasher said:
It's the jet that meters fuel to the cold start system in Mk 2 and Mk 1.5 Concentrics.

Believe it or not.
Click to expand...
Oh, I believe it now! I've just never seen either. Do you have pictures of those circuits/jets/etc?
Ta.
 
Test ride today 230km. Country and city.
New condition: Popping through exhausts when throttle backed off. Resolved by reducing ignition timing to 30° BTDC.
Just for extra fun: Acceleration from 55kph to WOT in 4th gear with throttle snapped open. Smooth through all transitions (flat top spray nozzles fitted instead of stepped). Hope that helps.
Ta.
 
needing said:
Smooth through all transitions (flat top spray nozzles fitted instead of stepped).
Click to expand...

And this differs HOW ? from the stock stepped spray tube version ??
Pardon me for seeming cynical, but going from a smooth transition to a smooth transition doesn't seem like a step in any difection ?

We guess too your peashooters weren't equipped with the somewhat restrictive mutes ?
 
84ok said:
no way he's muting
Click to expand...
Nope. Page 5 shows my muffler build-up.
I currently have 90° s/steel bends fitted to the outlet (see page 4) to reduce sound levels at my ears on the highway but don't believe they restrict flow. In fact, they may provide a Bernoulli effect that dyno runs can't emulate. Aaargh, now I need a wind-tunnel.
Ta.
 
Dyno runs today with flat top spray nozzles replacing the stepped type.
Low end richness is cured but needle at parallel is now rich.
The plan: replace 106 needle jets with 105s.
Next dyno run on Friday.
Ta.
Note: returning the ignition timing to 30° from 32°BTDC lost the 2HP previously gained.
 
needing said:
Low end richness is cured
Click to expand...

The 1st graph doesn't really go down low enough to say for sure it has a 'low end richness ??
Where it begins, it isn't much different to what the 2nd graph shows ?

needing said:
In fact, they may provide a Bernoulli effect that dyno runs can't emulate. Aaargh, now I need a wind-tunnel.
Click to expand...

Its doubtfull if a Bernoulli effect can work (much) on a high-pressure stream of exhaust gas ??
The high pressure would completely overwhelm the Bernoulli effect...
 
Rohan said:
Its doubtfull if a Bernoulli effect can work (much) on a high-pressure stream of exhaust gas ??
The high pressure would completely overwhelm the Bernoulli effect...
Click to expand...

High pressure exhaust pipes? Whatever next!

The Bernoulli effect of connections into exhausts is used to evacuate crankcases in competition cars.
 
The dyno plots provided above are a graphical record of what I also observe from the onboard A:F ratio gauge connected to an oxygen sensor screwed into my bike LH header pipe. How could the dyno provide accurate A:F data unless connected into the same fitting?
To clarify (based on objective test data rather than shrill hyperbole): stepped spray nozzles, perhaps introduced for 850s, create a low end rich condition in my bike that is cured by using the flat top type. QED!
The thermocouple and connected Exhaust Gas Temperature gauge confirms my A:F tuning data while on the road. Temperature in the header went to 780°C when A:F ratio was in the 14+s:1 for varying throttle openings.
Ta.
 
needing said:
The dyno plots provided above are a graphical record of what I also observe from the onboard A:F ratio gauge connected to an oxygen sensor screwed into my bike LH header pipe.
Click to expand...

But the 5th Aug dyno plot doesn't show the low rpm A/F ratio ?
So how do you know where it is ??
 
Triton Thrasher said:
High pressure exhaust pipes? Whatever next!
The Bernoulli effect of connections into exhausts is used to evacuate crankcases in competition cars.
Click to expand...

So you agree with me then...

Exhaust gases at high pressure have a LOT of energy, witness them driving a turbo etc.
Some farm machinery has rotary aircleaners driven off the Bernoulli effect of a pipe with exhaust gases flowing over it.
Lotta energy there.

Different though to bernoulli acting ON the pressure in the exhaust system.
Really basic physics, low pressure won't have much effect on high pressures.
'shrill hyperbole' doesn't come into it.
 
Thinking out loud re: my AMAL Mk1.
The slide needle diameter at the parallel is 2.5mm or 0.098”.
My currently fitted needle jet is 0.105”
Therefore, the annular clearance between the slide needle parallel and needle jet is only 0.0035” i.e. 3 and ½ thou.

The air and fuel flow at slide opening of 6.5mm will pull the needle toward the manifold resulting in wear of the needle against the needle jet.
From your experience, needle and needle jet life expectancy is ??
Ta.
 
needing said:
Thinking out loud re: my AMAL Mk1.
The slide needle diameter at the parallel is 2.5mm or 0.098”.
My currently fitted needle jet is 0.105”
Therefore, the annular clearance between the slide needle parallel and needle jet is only 0.0035” i.e. 3 and ½ thou.

The air and fuel flow at slide opening of 6.5mm will pull the needle toward the manifold resulting in wear of the needle against the needle jet.
From your experience, needle and needle jet life expectancy is ??
Ta.
Click to expand...

It's the jet that wears fast.
 
WZ507 said:
Less than 10,000 mi.
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Thanks for replying WZ507 (& Triton Thrasher).
That's annual commuting milage (=16,000km) for some or a decade(s) of riding for others.
By consensus (n=2), I've put 'Replace slide needle and jet at 16,000km max.' onto my routine maintenance schedule. My A:FR gauge readings will better determine actual usage/distance until they go 'off' for more accurate scheduling.
Ta.
 
needing said:
WZ507 said:
Less than 10,000 mi.
Click to expand...
Thanks for replying WZ507 (& Triton Thrasher).
That's annual commuting milage (=16,000km) for some or a decade(s) of riding for others.
By consensus (n=2), I've put 'Replace slide needle and jet at 16,000km max.' onto my routine maintenance schedule. My A:FR gauge readings will better determine actual usage/distance until they go 'off' for more accurate scheduling.
Ta.
Click to expand...
I have put 3520 miles on my clock within a month of summer riding.(July through August) I will easily put +5000 miles on my bike per year. I should do more. :oops: Bruce Chessell recommended to me that after 5000 to 7000 miles on his re-sleeved Amals to put in new needles and needle jets... To keep things running sweet.
Cheers,
Thomas
CNN
 
Hi CNN.
5000 miles seems awfully low for any comsumable.
More thinking out loud:
A throttle slide has 3 to 4 thou clearance from the throttle body from new and is subject to near 0 to 20 inHg pulses per stroke cycle. Therefore, rigidly fixing the slide needle in the slide to provide equal needle jet annular clearance is impracticable by design. Oh well...
Ta.
 
needing said:
Hi CNN.
5000 miles seems awfully low for any comsumable.
More thinking out loud:
A throttle slide has 3 to 4 thou clearance from the throttle body from new and is subject to near 0 to 20 inHg pulses per stroke cycle. Therefore, rigidly fixing the slide needle in the slide to provide equal needle jet annular clearance is impracticable by design. Oh well...
Ta.
Click to expand...

needing
I tend to agree with you. While I was at the Norton Rally I had some issues with my bike and spoke to Bruce (who was there) about the mark 1's and I took apart the carbs 3 times, looking for a problem that they did not have....(Turned out it was a Coil going south). Anyway the carbs, needles jets and whole assembly worked as intended.
problem was I was chasing the wrong tail. Live and learn.
Keep on Riding
Cheers,
Thomas
CNN
 
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