Amal carbs and spark plugs issues and concerns

arcpoint said:
Ok, took off the right carb bowl and the hollow float is full of gas. Def the issue. Curiously, the base of the tickle plunger rod that flares out is jagged. Not sure if an issue or just sloppy manufacturing because it doesn't matter.
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Should I replace the old hollow plastic floats with stay up floats or will that cause a problem in the old Amals?
 
No the new stay up floats will be fine but you have to set the float levels right, I am still running the old floats in my Amals and have never had any problems with them, but I don't use E10 fuel.
 
ashman said:
No the new stay up floats will be fine but you have to set the float levels right, I am still running the old floats in my Amals and have never had any problems with them, but I don't use E10 fuel.
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So it's the ethenol that kills the floats, not a surprise. And you're able to get ethenol free gas down under? I may keep on using the old floats or try the Perma floats. You're right, once apart they are pretty simple. And your YouTube story is 🤣🤣🤣🤣
 
arcpoint said:
So it's the ethenol that kills the floats, not a surprise. And you're able to get ethenol free gas down under? I may keep on using the old floats or try the Perma floats. You're right, once apart they are pretty simple. And your YouTube story is 🤣🤣🤣🤣
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It's more likely being 50 years old that kills the plastic floats!

Since the carbs are very old you may also have the brass float needles. They were obsolete a very long time ago. If you want to keep going with those carbs, you need two of RKC/561 if it's a 750 or RKC/602 if an 850. You also need two of 622/055S (float bowl) and two of 622/155 Float bowl drain plug. And, possibly two of 928/603 if a 750 or 928/6035 if it's an 850. And finally two if 622/122-106 Needle Jet.

Once you have all that installed, you'll still have non-Premier carbs made of Zinc alloy but they will be the best they can be. You will have spent over $200+shipping. That's about half of the cost of a set of new Premiers.
 
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I read somewhere that 106 needle jets are now made 1065 although marked 106 , perhaps to compensate for the ethanol now in the fuel. So i measured a new one , 1065 . I fitted new plastic floats and after problems with flooding went back to brass with no problems , but i dont leave fuel in the carbs when laid up.
 
I too have always removed the chokes, but there is a (small) price to pay:
The bike starts fine, but will run rough, and occasionally stall for the first few 100 meters,
But I can live with that. If it would run fine from the start, that would mean it is set up too rich.

Recently I read about someone using water to check the float level on a test set-up .
(can't find the post..)
Fuel is lighter than water, so the float will 'sink' deeper in the fuel.
Meaning: The fuel level in the bowl will be about 2 mm higher.
Using water to set the float to the 'correct' height, will result in a rich condition if you don't allow for the difference in density with fuel.
 
ludwig said:
I too have always removed the chokes, but there is a (small) price to pay:
The bike starts fine, but will run rough, and occasionally stall for the first few 100 meters,
But I can live with that. If it would run fine from the start, that would mean it is set up too rich.

Recently I read about someone using water to check the float level on a test set-up .
(can't find the post..)
Fuel is lighter than water, so the float will 'sink' deeper in the fuel.
Meaning: The fuel level in the bowl will be about 2 mm higher.
Using water to set the float to the 'correct' height, will result in a rich condition if you don't allow for the difference in density with fuel.
Click to expand...
Usually best to not knock it if you haven't tried it! Technically you're right - practically, you're wrong. The volume is so small that they measure the same.
 
ludwig said:
I sure did. Have you ?
( measured the difference, I mean..)
The volume doesn't matter. It is about the fluid level.
Ever heard of Archimedes' law ?
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Yes, I measured with gas, alcohol, and water. Water is the easiest to work with, alcohol second and gas last. Yes, my physics training is 50 years old but not forgotten.

The fluid level was well within tolerance for all three. The volume of the float and the displacement of the liquid absolutely matters - that's how a float works!
 
So we have different load lines marks on all our cargo ships , regarding if we are : summer, winter ,tropical , north atlantic , tropical fresh water , and fresh water , just because of Archimed , and better to respect them if you want sail without big problem with harbour authorities !
 
If you tickle by pushing the tickler rapidly rather than holding it down it can punch a hole in the float. I suspect that's what happened to yours, if I'm following the thread correctly.
 
norton twins the fuels have changed now being made has planet based fuels, so you all need to change your spark plugs to the muliti electroids ones, all information on this is at www.greensparkplugs.co.uk. like I now use the new champion N9bcy has the same heat range as the old N5c has I am running with a single carburettor set up, instead of the twin carb set up that was on the bike from new, for a twin carburettor set up, use champion N7bcy has the same heat range as the old N4 these are 3 point elctroids and give better shelding againast ethernol fuels this is what modern petrol cars have fitted hope this may help
 
Float levels in twin carbs need to be the same in both carbs. Other than that ,when you set the needle height, that adjusts the mixture. Main jets are not very important as long as they are a bit rich - so fuel height in the bowls is not critical for those. If you are carburetted rich on the needles, performance suffers. If you are lean on the needles, you should know it by the way the motor misses when you ride the bike. I usually lower the needles until the motor misses, then raise them one notch.
With Mikunis, float height is often measured from the gasket face. I don't know about Amals. With Japanese bikes, the manual often says how to set the float height.
 
marshg246 said:
.. The volume of the float and the displacement of the liquid absolutely matters - that's how a float works!
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Exactly.
The float is pushed up by the fluid till the needle shuts off the flow.
The upward pressure on the float is equal to the weight of the displaced volume of liquid.
Fuel is considerably lighter than water : 0.72 to 1.
To create the same amount of lift (and shut off the flow), more fuel than water has to go into the bowl.
If you use water to set the fluid level 5mm below the top of the bowl, then the fuel ( not the float) will inevitably rise above the water mark . About 2.5mm IIRC, and set the fuel level well above the recommended limit of 4mm.
 
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