Rich or lean - air:fuel ratios

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Hi hobot.
That is a mighty fine looking M3 Fastback in that photo.
I have searched 'Phil Yates' in the top right corner seearchbox and he is from Mittagong which is only 635 metres elevation so probably is running 'low' altitude settings.
Ta anyway.
 
Yes seems similar to Florida fairly near to coasts. Sent photo giving ride to grinning 80 yr nieghbor woman in the sidecar. Anywho maybe you missed this gizmo for attitude compensation on carbs.

Rich or lean - air:fuel ratios


More Power
Improved Fuel Efficiency
Easy Precision Jet Changes
Adjusts For Altitude and Temperature
Works on Snowmobiles, Motorcycles, ATV’s & other vehicles

The Thunder PowerJet fits any size or brand carburetor. It is exactly what you need to achieve maximum performance with your engine. The TPJ improves performance by precise fuel metering with needle valve adjustment. Fuel distribution is improved by adding fuel through two sources instead of just one. This means more horsepower at any temperature or altitude. The TPJ gives you a range of over 10 to 12 jet sizes with precision external adjustment.

I got most my insights on Lake Gravity Fed Injectors from aircraft users and immune to attitude/pressure skewing of mixture ratios as not venturi based just mass air flow. Thanks for the break.
 
Hi hobot.
Yes, I did see the external jetting around the time I thought about UFO.
I am not intending any extended high altitude rides (lack of mountains really) but was only querying AMAL's advice.
BTW, would you like a throttle pump for an AMAL? I am thinking some unsettling thoughts on this subject since you mentioned air tanks. More to follow.
Ta.
PS: look what I got today! WOOHOO... New conrod nuts are still in transit. BOOHOO.
 
hobot said:
Anywho maybe you missed this gizmo for attitude compensation on carbs.

https://thunderproducts.com/wp-content/ ... Jet_02.jpg
Click to expand...

I thought those Thunderjets were for all those lean running (carbed) moderns,
which are jetted terribly lean to meet emissions standards.

Previous discussion here has C'dos running quite rich by comparison ?

Adding more fuel isn't going to help much of anything ??
And, can we ask, have you actually tried them Steve....
 
The actual adjustments which you can make to the Amal MK1 are very limited
they only offer two 4 stroke needle options for the MK1 and needle jets .105 / 106 / 107 main jets in increments of 10 so adjustments are very limited

Mikuni /Dellorto / kehien all have massive ranges of needles and jet tubes / main jets with small increments

You can actually buy Dellorto tuning software if you have a laptop Barometer and thermometer load your base line settings and it calculates the set up changes based on the atmospheric pressure and temp
ideal for track use but you would have to carry your own weather station for mountain riding

This is one of the reasons manufacturers developed fuel injection and knock sensors , they can send a vehicle to any part of the world and it self adjusts AFR as required
 
Hi Frankie17.
Re your : "...The actual adjustments which you can make to the Amal MK1 are very limited they only offer two 4 stroke needle options for the MK1 and needle jets .105 / 106 / 107 main jets in increments of 10 so adjustments are very limited..."

We also have throttle slide cutaway variants and (depending who you talk to) float bowl fuel height.
You are correct that there is no closed loop self adjustment inbuild to AMALs - (and the tuning notes need an update/review).
Ta.
 
Frankie17 said:
Mikuni /Dellorto / kehien all have massive ranges of needles and jet tubes / main jets with small increments
Click to expand...

Some folks might comment that all those possible combinations of jets and needles and fine adjustments in Miks, Dellortos, etc can be more a curse than useful. Its all very well to have a huge box of bits that will only jet a 50cc for running above 35,000 ft (!),
at least the basic set of Amals will have you somewhere near the ballpark with only a few basic settings and changes.

And as you say, jetting it so accurately that you'd need to change the jets if a cloud came over, or you went up a hill, can be less than useful too.

Remember that the basic Amal carb settings will operate it from a cool night at sea level to a hot day at some altitude. (or vice versa)
Without changing anything. Thats quite a good range for common use.
 
Has anybody taken into account the barometric pressure at sea level on the day when changing needles and or jets?
The reason I ask is that I had my race bike on the dyno yesterday and was surprised why I had a 10rwhp difference than a previous session some months ago.
We were running high 60's at the start of the session, and within a hour or so of the start, there was a severe storm brewing in the area and the atmospheric pressure was dropping rapidly, we did a pull on the dyno only to find I only had high 50's rwhp, thought I had trashed the engine!!!

Anyway as the storm passed, we were back to the high 60's.

A change to longer , thinner needles also solved an issue of being too rich in the initial part of fuel ratio curve.

Damn the climate change!!!!
Regards Mike
 
Your comment on barometric pressure at any level will affect the jetting to a small extent since the barometer can move between the morning and the afternoon as much as 3 inches in some countries, just the same as if you jet it at sea level then try to run the same engine at 4,000 feet.
At the South African GP the atmosphere was so thin that with the old 500 GP V4 two strokes they came down 100 on the main jet, which just goes to show how much it can affect an engine.
 
hobot said:
Phil Yates still pesters me with what he rides in OZ

Rich or lean - air:fuel ratios

Rich or lean - air:fuel ratios

  • http://i184.photobucket.com/albums/x93/hoboter/Norton%20Commando%20items/PhilYatesride1_zpskbtpntkd.jpeg
Rich or lean - air:fuel ratios
Click to expand...

Steve, did he ever build the hot rod engine he talked (so much) about?
 
Ugh, someone asks - how can adding more fuel with an extra jet/needle and even float bowl help hi attitude, duh, the carb main jet/needle has to be reduced 20-25% so its the only fuel feeder at highest altitude so the 2nd added one can fill in towards sea level. No one I head of so far tied the ThunderJet on Commandos so who knows if worth while or not in our crude clunkers.

Phil has collected-coordinated a dozen or so capable builder specialist-shops, from frames to pipes and finishes plus several spaces mostly already cluttered by cycles of all types/ages to restore and customize and maybe sell for some return. The Red BMW was mainly to show some new pipes they made installed. In general one on one we get along fine with cycles as common denominators but in this pubic arena fur flys so easy and long. if Peel proves out mostly as good as I hope likely will finish off alienating me to the sloppy handling slow poke cutie pie Commando crowd too.
 
dennisgb said:
If you get one of these it will make your tuning life so much easier.

They sell a sniffer that goes in the pipe to make it portable too.

http://www.ebay.com/itm/370520832034?_t ... EBIDX%3AIT
Click to expand...

Thanks dennisgb.
That is exactly what I use - along with a thermocouple connected to an Exhaust Gas Temperature gauge at the handlebars.
The 'sniffer' up the pipe is not so good on what is essentially a single cylinder because of the 1 in 4 pulse of gas to piston stroke (I found it better to insert the O2 sensor and thermocouple into a 'tuning' header nearer the valve).
Ta.
 
hobot said:
Ugh, someone asks - how can adding more fuel with an extra jet/needle and even float bowl help hi attitude, duh, the carb main jet/needle has to be reduced 20-25% so its the only fuel feeder at highest altitude so the 2nd added one can fill in towards sea level. No one I head of so far tied the ThunderJet on Commandos so who knows if worth while or not in our crude clunkers.
Click to expand...

Sounds like a whole mess of trouble, for want of a little jet changing ?
And for something that we don't even know will work....
 
I use two 34mm Mk2 Amals with No 6 Mikuni needles with methanol. If I was running petrol, I'd still run a bit rich on the main jets, and adjust the needle to the leanest right across the range from 1/4 to 3/4 throttle until I just stopped getting a miss. For high altitude, I'd lift the needles one notch if they tended to lean off enough to get a miss during gear changes. With conventional Amal needles, it must be almost impossible to get the mixture right from 1/4 to 3/4 throttle ? What I am talking about is really good acceleration up through the gears with no missing or bogging down as you wind the throttle on. I think running slightly rich on the mains is essential in any situation.
That attachment in Steve's photo is similar to the power jet which was fitted to two strokes in the 70s - it richens the mixture at very high gas flows. With two strokes you can achieve similar by recessing the top of the needle jet and metering lower, so at full throttle the motor actually runs on the main jet when the tip of the needle is in the recess. In other words the tip of the needle must always be trapped in case you get a hung throttle.
 
acotrel said:
I use two 34mm Mk2 Amals with No 6 Mikuni needles with methanol. If I was running petrol, I'd still run a bit rich on the main jets, and adjust the needle to the leanest right across the range from 1/4 to 3/4 throttle until I just stopped getting a miss. For high altitude, I'd lift the needles one notch if they tended to lean off enough to get a miss during gear changes. With conventional Amal needles, it must be almost impossible to get the mixture right from 1/4 to 3/4 throttle ? What I am talking about is really good acceleration up through the gears with no missing or bogging down as you wind the throttle on. I think running slightly rich on the mains is essential in any situation.
That attachment in Steve's photo is similar to the power jet which was fitted to two strokes in the 70s - it richens the mixture at very high gas flows. With two strokes you can achieve similar by recessing the top of the needle jet and metering lower, so at full throttle the motor actually runs on the main jet when the tip of the needle is in the recess. In other words the tip of the needle must always be trapped in case you get a hung throttle.
Click to expand...

If you start changing the float level, you introduce another variable. It would probably drive you insane.
 
I only know what I read in the papers and the additional jet been sold a long time and expanded on as applying directly to air pressure partial oxygen pressure density compensation, so thot ok to point out in case someone that does know something and desire-need to try it and see. I looked into them for Peel to suck in anti-detonation fluids but decides anything heavier than methanol best not impinge on alu blands a few dozen 1000 rpms. Still interesting that Amal attitude advice and fundamental carb throttle stage flow physics conflict yet works good enough at times. My heart dropped when they paved Piles Peak to challenge Peel but still leaves racing it down hill which scares the shit out of me but Peel just craves it.
 
I would have thought that an increase in altitude would reduce air pressure and need leaner jetting, however perhaps the air is colder and the jetting should be richer ?
 
acotrel said:
I would have thought that an increase in altitude would reduce air pressure and need leaner jetting, however perhaps the air is colder and the jetting should be richer ?
Click to expand...

The theory has less air molecules available at higher altitude (relative to sea level) but jets allow the same volume of fuel through therefore too rich. Small jets/larger cutaway/airscrew wound out to match fuel to available air at higher altitudes is the consensus correction.
A solution: IF, as AMAL suggest, lowering float level creates a leaner mixture across the slide opening range surely inserting (say) 5mm or 10mm or 15mm spacers between bowl and body would be a simpler correction.
Ta.
 
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