Float Tang
Posted: Wed Aug 30, 2023 1:54 pm
A few years ago, I bought a VS 1400. It was neglected and tampered with by others. Although it runs, I suspected that the front cylinder was running lean. Besides "feeling" the exhaust with my hand, after 45 sec from a stone cold start, I shot both cylinders and pipes with a (H Freight) Laser Thermometer. Sure enough, the front cyl was noticeably cold.
Reluctantly, I removed the float from a known and untampered with, factory stock, S83, 36mm carb. I intended to check it with a "Feeler Gauge" and then match it to the front cyl. carb in question, but Feeler Gauges are too big.
I ended up placing a Starrett Depth Gauge, No. 237 (google it), across the top side of the float TANG. (The top is the smooth side and not the side with a 1/32 step). The reading was 1/16, 2/32 or 4/64ths. The Tang was 1/32 off. I adjusted the tang and the bike is now running better. BTW; 1/32 is very close to 1 mm.
The carbs are back together. I'm posting this 3 days later and I've already forgotten... My memory and comprehension is so bad that I invite others to weigh in as to the definitive direction to bend the tang for rich and lean. I've gone over this - so many times > over the years. It all comes down to how fast the gas is to shut off and whether or not the carb is being held upright or upside down. If I recall correctly; With the carb in an upright position and to raise the float (richening), then one would bend the tang down toward the bottom of the bowl and float. That would allow more fuel into the bowl and delay the needle to close. Likewise, if bending the tang toward the float needle then the gas shuts off faster and there is less gas in the bowl (lean). In other words... Bend the tang in the opposite desired float direction. (Isn't this fun? I'm a wrench turner and not an academic. Just something I'd like to see definitively carved in stone and where I can easily find it).
BTW; I've been using RED COAT fuel tank sealer with good results but that is for a different thread. I always need a full quart to cover the baffles in the fuel tank. I'll also note that Armorall and sometimes a heat gun are great for R&R new and old rubber parts.
While searching for info on this topic, I found the following worthwhile info, so I'm passing it on.
Found at: http://www.suzuki2strokes.com/forum/vie ... hp?t=11588 And posted by...
Post by tz375 » Tue Aug 04, 2015 4:05 pm. Re: Adjusting Float Height theory and practice.
I know it sounds too small to be relevant but think of it this way: 10mm of fuel will exert a certain pressure on whatever is at the bottom of it. 20mm of fuel will double the pressure and so on. It's close enough to a linear relationship.
So 1mm change in 20mm is 5% difference in fuel pressure. Air flowing through the carb bore is subject to Mr. Bernouli's wicked little theorem and as it speeds up through the venturi, the pressure differential between the fuel in the bowl and the air in the bore causes fuel to rise up through the main and needle jets.
I would expect that at speed, that 5% change in pressure would result in a 4-5% change in fuel flow. With say a #100 main jet, that's the same as moving to a #105. The effect on slow to mid range will be larger and on top end smaller because of air mixing with fuel.
Reluctantly, I removed the float from a known and untampered with, factory stock, S83, 36mm carb. I intended to check it with a "Feeler Gauge" and then match it to the front cyl. carb in question, but Feeler Gauges are too big.
I ended up placing a Starrett Depth Gauge, No. 237 (google it), across the top side of the float TANG. (The top is the smooth side and not the side with a 1/32 step). The reading was 1/16, 2/32 or 4/64ths. The Tang was 1/32 off. I adjusted the tang and the bike is now running better. BTW; 1/32 is very close to 1 mm.
The carbs are back together. I'm posting this 3 days later and I've already forgotten... My memory and comprehension is so bad that I invite others to weigh in as to the definitive direction to bend the tang for rich and lean. I've gone over this - so many times > over the years. It all comes down to how fast the gas is to shut off and whether or not the carb is being held upright or upside down. If I recall correctly; With the carb in an upright position and to raise the float (richening), then one would bend the tang down toward the bottom of the bowl and float. That would allow more fuel into the bowl and delay the needle to close. Likewise, if bending the tang toward the float needle then the gas shuts off faster and there is less gas in the bowl (lean). In other words... Bend the tang in the opposite desired float direction. (Isn't this fun? I'm a wrench turner and not an academic. Just something I'd like to see definitively carved in stone and where I can easily find it).
BTW; I've been using RED COAT fuel tank sealer with good results but that is for a different thread. I always need a full quart to cover the baffles in the fuel tank. I'll also note that Armorall and sometimes a heat gun are great for R&R new and old rubber parts.
While searching for info on this topic, I found the following worthwhile info, so I'm passing it on.
Found at: http://www.suzuki2strokes.com/forum/vie ... hp?t=11588 And posted by...
Post by tz375 » Tue Aug 04, 2015 4:05 pm. Re: Adjusting Float Height theory and practice.
I know it sounds too small to be relevant but think of it this way: 10mm of fuel will exert a certain pressure on whatever is at the bottom of it. 20mm of fuel will double the pressure and so on. It's close enough to a linear relationship.
So 1mm change in 20mm is 5% difference in fuel pressure. Air flowing through the carb bore is subject to Mr. Bernouli's wicked little theorem and as it speeds up through the venturi, the pressure differential between the fuel in the bowl and the air in the bore causes fuel to rise up through the main and needle jets.
I would expect that at speed, that 5% change in pressure would result in a 4-5% change in fuel flow. With say a #100 main jet, that's the same as moving to a #105. The effect on slow to mid range will be larger and on top end smaller because of air mixing with fuel.