Float Tang

[Springer Fla]

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.

[hillsy v2]

Fuel flow / mixture is primarily governed by jet sizes and mixture screws. Fuel height plays a part but is not as critical (unless there is no fuel for the jets to draw from). You always check float height with the carbs inverted. And you need to "angle" them so the float doesn't compress the spring in the float valve. Then when you are done you should check the fuel height against the float bowl.

Changing the float height does not change fuel pressure - the pressure is always the same as it is governed by the fuel pump when the float valve stops the fuel flow (usually between 2-5psi).

And changing the fuel level in the bowls is not a substitute for changing jet sizes (EG: if your main jet is too small no amount of fuel height change will rectify this).

[Springer Fla]

Thanks Hillsy, Well written and informative.

I started the thread to help others with a subject that I’ve struggled with over decades and further info will now have a “home” here on the IA Board. I work with floats and tangs so infrequently, that I forget.

The Clymer manual is insufficient for me and calls for approx 9mm float ht. on the front carb. The only way that I get 9mm is to push the needle completely into the needle seat, which would shut fuel off. Sadly lacking and that is all I’ll say about it. My bike runs and the carb is working.

I will say that I watched a tech on Youtube. I think it was posted by “How2wrench.” He was using a Harley carb. Harley has simplified things – for back yard mechanics, to where the float is flat and runs parallel to the casting. HD factory recommends shimming and using an Angle Gauge set at (20° - for that carb) so that the carb is inverted and the tang is just touching the needle. In my line of work, shimming or C-clamping is always better than manhandling parts. (I don’t know much about HD. I’ve always rode British or Jap bikes).

Although, I change front ends, seats and body work, I’ve always kept my motors stock, so jetting isn’t an issue (unless they are damaged or worn) which I’ve had experience with.

My VS 1400 sits a lot, which is an issue in itself as I’ve experimented with different front ends, while leaving the 36° neck – stock. So far, it can’t be done and it's the same as for making a bigger battery box to fit between the stock exhaust. My Avatar is S50’s with a stock 33° rake and at 6” over they handled perfect.

I’ve got more 2 carbs issues. #1 is the bike seems to have a hard time getting fuel up to the frt cyl. (after it sits for a week or more). I know about the relay between the Start switch, fuel pump and clutch. Right now, I simply pull a wire at the clutch > press Start> and with my auxiliary tank and fuel lines, I can watch the fuel run > until full or the pump shuts off. I don’t want to bypass the relay and I may install a switch to the 2 wires at the clutch. I’ll read other posts and get into that later. Right now, the bike runs and the carbs need a better sync.

#2 Most urgent… I see on Ebay, Membrane Carb Vaccuum Piston. I’d like to just buy the membrane at $12 and not $80 which includes the piston (and no needle). Has anybody changed out a membrane before? There is a plastic piece at the bottom of it but if it breaks – then it is Big Bucks. Right now, I’ve got a dab of Supper Glue on some suspect wear but I’d like to change the part if I can cheaply do it.

[hillsy v2]

I’ve got more 2 carbs issues. #1 is the bike seems to have a hard time getting fuel up to the frt cyl. (after it sits for a week or more). I know about the relay between the Start switch, fuel pump and clutch. Right now, I simply pull a wire at the clutch > press Start> and with my auxiliary tank and fuel lines, I can watch the fuel run > until full or the pump shuts off. I don’t want to bypass the relay and I may install a switch to the 2 wires at the clutch. I’ll read other posts and get into that later. Right now, the bike runs and the carbs need a better sync.

#2 Most urgent… I see on Ebay, Membrane Carb Vaccuum Piston. I’d like to just buy the membrane at $12 and not $80 which includes the piston (and no needle). Has anybody changed out a membrane before? There is a plastic piece at the bottom of it but if it breaks – then it is Big Bucks. Right now, I’ve got a dab of Supper Glue on some suspect wear but I’d like to change the part if I can cheaply do it.

There is no problem with bypassing the fuel pump relay - do a search on here as many people have done it. Pretty sure you can just wire it in directly from the kill switch wire - but really any switchable power source will do.

As far as the slide diaphragms are concerned they have a locating tang on the outer lip and this needs to be correctly aligned with the under side of the slide (it's contoured specifically for airflow).



Unless you have done this before it's probably best to pay the extra and get the entire slide with diaphragm. Get it wrong and your carb will run like crap.

[Herb]

There used to be a company that sold just the diaphram for a number of different bikes. I posted a link to it's website a long time ago. Not sure if they are still in business.

I have found that patching the holes with red RTV works the best. Clean the diaphram with alchol and just a thin skim coating on each side of the hole works well. Both of my carbs have multiple patches on them and I have never (yet) had to repatch an older one.

Using super glue isn't so good because it dries really hard and stiff, the movement of the diaphram will cause it to break around the glue. If you will notice the majority of the holes will be in a crease.

[Herb]

Here is a site with some diaphrams but I am not sure which will fit on the 1400. I remember the other site wanted a measurement of the inside and outside diameter and cautioned about carbs that have the vacuum hole in the diaphram edge or a locator tab on the edge of the diaphram. I will keep looking for the other site.

https://www.nichecycle.com/ncs/categori ... lides.html

[hillsy v2]

You can get the diaphragms easy enough (https://www.ebay.com.au/sch/i.html?_fro ... =0&_sop=15) but the problem is swapping them out and getting them back in the right spot.

[Springer Fla]

Thanks Herb and Hillsy, This thread is going to be a good source of info for others. The IA Board will be the place to be. At least - until I get my bike sorted out. (I was on the old board in the late 1990's but dropped out for awhile.) I consider this bike to be a junker, for rainy days and salt air. I have better bikes.

Hillsy, your photo is excellent. I was inquiring about R&R the white ring, under the diaphragm. I imagine that it is a compression fit and if it breaks... then it's done. I don't see replacement rings offered with the online diaphragms. Again, you've supplied good info. I'm sure that you are saying to align the diaphragm vent hole to the two holes in the piston. My ignorant mind would have missed that > until I was actually doing the job & even then?? Thanks

For alignment, I'd paint the piston with some layout dye / magic marker, etc and square it with my Starrett, to the center of the two holes. Is there any other way?

[Herb]

One of the articles I read gave advice on aligning the slide properly and it was pretty much what you are saying. The article also said that their diaphrams don't need the plastic ring because they fit tight enough to not slip. They said to just cut the plastic ring off with a pair of dikes.