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ET: Engine (Twin) Running Weak on Part Throttle


Bill Thomas

Well Known and Active Website User
VOC Member
So will a higher float level, Only effect slow running John ?,
I would have thought it would have an effect a bit higher up, As I have said, The Mk2 Amal, The Pilot screwed in a bit, Can make a weak slide feel much better on my Bike, I hand cut too much cutaway, On my slides, But a tweak on the pilot made almost perfect, Till I got round to taking a Nat's off the bottom of the slide,
Cheers Bill.
 

Sakura

Well Known and Active Website User
VOC Member
I don't get this? Surely the float level is influenced by the amount (volume) of fuel in the float chamber, not the sg of the liquid? Isn't the top level constrained by the needle seat?
Thank you, I get it now. The float sits higher on the liquid the denser the liquid and vice versa. Every day is a schooldays.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Probably too late to find the Specific Gravity of earlier petrol now but it would be interesting to know the difference in S.G. between then and what we use now.
 

timetraveller

Well Known and Active Website User
VOC Member
Sakura, remember Archimedes running down the road shouting Eureka. Try floating in fresh water and then the Dead Sea. You will find a difference in your floatation height. Same with a carb float and different density fuels :)
 

mercurycrest

Well Known and Active Website User
VOC Member
So will a higher float level, Only effect slow running John ?,
I would have thought it would have an effect a bit higher up, As I have said, The Mk2 Amal, The Pilot screwed in a bit, Can make a weak slide feel much better on my Bike, I hand cut too much cutaway, On my slides, But a tweak on the pilot made almost perfect, Till I got round to taking a Nat's off the bottom of the slide,
Cheers Bill.
I'm just saying the difference will be next to nothing. Take a remote float, fill it with petrol, measure it then repeat with paint thinner. Water is 8.325 lbs per US gallon, Gasoline is 5.95 lbs per US gal. Divide 5.95/8.325= 0.715. Acetone is 0.792 so, the difference is almost negligible, your float level won't change very much at all, unless, of course you set it with a micrometer.
;)
 

vibrac

Well Known and Active Website User
VOC Member
(The carbs were refurbed by Martin Bratby who made the slides, the cutaway measures somewhere between 3.1/2 and 4.)
Why not do the obvious and try 3.1/2 slides? With the engine running and riding down the road, the specific gravity of different petrols isn't going to be any kind of issue at all.
I wondered that but perhaps he cant because the carb has been Bratburied the slides are a special size
 

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