Rich or lean - air:fuel ratios

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worntorn said:
If you reread the thread you will see there are a number of us who live and ride in high places. 80 percent of the Province I live in is covered in mountain ranges. You also have a response from a Colorado dweller, that state is pretty much all high elevation.

Glen
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Hi worntorn.
Not discounting the contributions of everyone to date but supplementing the collective knowledge by data-mining the accessnorton database for additional reinforcement prior to advising AMAL for correction.
 
They will probably reply that the Mt Lofty ranges are only 727 metres at the highest point. (wiki)(thats slightly less than 2400 ft).
So you can safely tune for it at sea level...

Amal only need to look in their manuals of old to see that they recommeneded dropping the needle a notch or 2 for altitude,
as well as changing the main jet for a size or 2 lower if a more permanent use was higher up...
 
Two notches on the needle is usually a big change, especially if you are using petrol. I would have thought dropping the needles one notch would be sufficient, and in any case most riders would not notice if the bike becomes slightly sluggish if it is rich on the needles due to altitude. The only time I have changed jetting when racing, has due to a big drop in air temperature. Of course we don't usually experience the altitude effect. I would have thought that most bikes would be carburetted rich enough on the mains that neither air temp nor altitude changes would matter.
 
acotrel said:
Two notches on the needle is usually a big change, especially if you are using petrol. .
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Some of the mountain passes in the Himalayas are ~18,000 ft, so 2 notches might be necessary. !!

Some of these Enfield tours in India etc go over some of them,
and they report that you can definitely feel the lack of air.
And thats just the rider, let alone the bike...

http://scribol.com/environment/the-view ... on-earth/3

If you hunt around there are proud owners with their steeds photoed up there.
Rather them than me, brrrrrrrrrr. !?
 
If two needle notches higher were necessary to stop the cough at sea level, the bike would be really sluggish to ride at very high altitude if the lowering changes were not made to compensate . It is a really big change even with methanol fuel. Of course a bit depends on the needle taper.
 
Air density at 18,000 ft is approx half of sea level.
So it would be odd if big changes weren't needed ?

No idea otherwise what those comments translate to in english, but methanol fuel is a strange comparison anyway,
which only you seem to subscribe to. Do they race at those altitudes ?
 
i once rode my triumph between tempe, arizona and mexican hay lake-- 1300 to 10,000 feet, on the stock 30 mm concentrics. i didn't bother with the mains because i stayed off the throttle up there. i lowered the needles on the mogollon rim at about 6000 feet, and raised them again going down.

at 10,000 feet my 650 carbureted clean but wouldn't go over 45 mph, and the more or less open exhaust just went ffffftt-ffffftt-ffffftt-ffffftt-ffffftt.
 
Rohan, Methanol fuel makes jetting changes about half as sensitive as changes made when using petrol. If you'd ever used it, you might have some idea what lowering the Amal needles on a commando by two notches does with a petrol fuelled motor. If the needles are too high by even one notch on my methanol-fuelled bike under normal circumstance it makes a very big difference to performance. Lowering them two notches to compensate for high altitude would be absurd. As for your statement that the air density is halved at an altitude at which you can ride a motorcycle .... were you talking about air pressure ?
 
Absurd or not, its what AMAL recommended of old for riding at very high altitudes.
Remember, engine power is only approx about half at 18,000 ft.
Amal also offer a (limited) range of other needles/needle jets.

If anyone else here rides methanol, let alone on the road, they are yet to speak.
It works good in little miniature aero engines.
Not that I've even heard of one getting up that high....
 
From a post that (again) seems to have suddenly disappeared,
Aco is talking METHANOL in race bikes, and needless is talking ETHANOL in Brazil.
Talk about confusion, this forum is going downhill..... ?
 
Rohan said:
From a post that (again) seems to have suddenly disappeared,
Aco is talking METHANOL in race bikes, and needless is talking ETHANOL in Brazil.
Talk about confusion, this forum is going downhill..... ?
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Opting in - I too am curious re my post disappearing - opting out.
Ta.
 
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