TR2/3/3A SU Carb Float Question

[hit_n_miss]

I went to start the Triumph this morning and noticed fuel squirting out the overflow line at the top of the float chamber of the front carb. I removed and disassembled the float chamber. When I shake the float it sloshes and there are three tiny weep spots along the seam between the upper and lower halves of the float.

I think with the float too "heavy" it can't lift enough to shutoff the fuel, hence the observed overflow line fuel squirting. Is this a correct assessment?

I think the best repair is to just replace the float. However, I have an event this Thursday where I want to drive the Triumph and I wouldn't have a replacement float in time.

I'm thinking of drilling a tiny hole in the top of the float to drain it and then use JB Quick to seal that hole and the weeping seam. Is there a terrible downside to this plan that I'm overlooking? Thanks!

 

[Brinkerhoff]

Accurate diagnosis and give the JB a try !

 

[GTP1960]

To bad TRF doesn't stock SU-H6 floats.(I don't think).
TRF is only about 50 miles from Pitt, aren't they?

 

[hit_n_miss]

TRF is 48.4 miles door-to-door. And sadly they don't stock the floats.

 

[Marvin Gruber]

Will work fine so long as the weep holes are not under the needle arms.

 

[Don Elliott]

I seem to remember that the FOT guys (Friends of Triumph) - they race TRs - announced that someone was selling a plastic fuel resistant replacement float for SU carbs. The story I heard was that the solder used I the original floats gets eaten through by the ethanol in "modern" gasolines and this permits them to fill up and sink.

Try Ted Schumacker or Joe Alexander or Curto for more recent details.

 

[hit_n_miss]

Moss offers two different floats; the "original" in brass and a replacement in Nitrophyl. The Nitrophyl is a closed cell foam. Has anyone had any experience with the Nitrophyl floats?

 

[Brinkerhoff]

The brass floats last a long time and I think failure is more random than not. I've got the originals still in my 54 XK and 48 TC ( same brass float as the TR). Give the new kind a try.

 

[Marvin Gruber]

Brass floats have been known to last a long time but I have box of bad ones. I keep saying I will take a day to fix several of them.

marv

 

[Don Elliott]

I still have both original brass - soldered floats in my 1958 TR3A for 57 years - but when I saw one in a flea market, I bought it and carry it as a spare - JUST-IN-CASE !

 

[TFB]

Brass floats have been known to last a long time but I have box of bad ones. I keep saying I will take a day to fix several of them.

marv

If you get a brass reproduction float,and I have no experience with the reproductions offered for SUbut I have come across brass repros much heavier than OEM so I would carefully weigh the float.A heavy float requires a lower float lever setting and results in a sloppier control of float level,so use your JB or Marine-tex sparingly.
I buy Nitrophyl floats form a guy who pioneered their use in vintage motorcycles to replace cork and he offers no guaranty the floats will last forever due to the ever changing digestive properties of todays blends,but he offers free replacement for any swollen floats.

Tom

 

[dklawson]

I have not worked with brass SU floats but I have worked with them on other carbs. I would not blame ethanol for the failures. What I have typically seen is almost like stress cracks that were probably introduced when the brass sheet was drawn into the float shape. I have drilled those floats and used a heat gun to dry the gasoline out. A thin film of solder over the cracks and the small drill hole generally works to restore operation.

The JB Weld will also work. It is part of a common modification process to use later VW Solex floats in earlier Solex carbs.

 

[hit_n_miss]

I have not worked with brass SU floats but I have worked with them on other carbs. I would not blame ethanol for the failures. What I have typically seen is almost like stress cracks that were probably introduced when the brass sheet was drawn into the float shape.

Doug, that sounds like what I observed. The weeping occurred at the diameter transition where the upper half of the float was enlarged to fit over the lower half. They were not visible cracks, but allowed the gas to weep out.

 

[TR3driver]

TRF has the float listed as available in their database. Did anyone actually have them check stock on part number SUWZX1303 ? I've heard before that their telephone operators can't always find parts given just a description; but I know I bought a spare float from them some years back.

 

[GTP1960]

TRF has the float listed as available in their database. Did anyone actually have them check stock on part number SUWZX1303 ? I've heard before that their telephone operators can't always find parts given just a description; but I know I bought a spare float from them some years back.

Randall,

just curious, how'd you find that part # at TRF?
Nothing came up on there data base search ( by description).
though, I think TR4 & MG floats did come up.

 

[Geo Hahn]

I have seen them drilled to drain and 'repaired' with a sheet metal screw to plug the hole.

A drain of the fuel in it should last for some time (enough for a day anyway). The fuel is not under any significant pressure to get inside the float. What happens (my theory) is that a drop in atmospheric pressure cause air inside the float (and below the 'water-line') to come out and then when air pressure is higher fuel goes back in. Takes a while if it is just normal variation in air pressure - happens much faster if you are driving up & down mountains (which is how I discovered this).

 

[CJD]

Interesting idea. If it has a leak, you might be able to set the float over a steam kettle and let the gasoline "boil" out. It should boil, create pressure, and vent out of the crack. No need to drill a larger hole to drain it.

 

[Geo Hahn]

... I have drilled those floats and used a heat gun to dry the gasoline out...

But use the heat gun sparingly. I found that the melting point of the solder is quite a bit lower that what my heat gun can produce.

Another way to get the fuel out is to submerge (by force) the float into a pan of near-boiling water. You watch for the bubbles that indicate a hole & mark that spot with a Sharpie. Cool the float and submerge it again with the hole on the bottom side this time and fuel will be forced out. Cool & repeat as needed.

 

[TR3driver]

Randall,

just curious, how'd you find that part # at TRF?
Nothing came up on there data base search ( by description).
though, I think TR4 & MG floats did come up.

Well, I first looked up the Stanpart number in the spare parts catalogue (SPC), which is usually the best starting point when dealing with TRF. I keep a PDF of the SPC on my toolbar for easy access, even on this lame laptop. Then I searched on that number (108336) on TRF's site, which gave the cross reference to the SU number.
https://drive.google.com/file/d/0B2...YmE2LWFiN2UtZWYzMjNjNGFiYzY4/view?usp=sharing

As a double-check, I also looked it up using "float" as the keyword and with "TR3" in the "Limit To" field. That brought up the same number, 3rd line from the top.

FWIW, early TR4 did use the same float (and carb), so don't let that fool you.