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Discussion Starter · #1 ·
Hey all,

Latest challenge in getting my bike running right: fueling! On a shakedown ride last week, it started and ran well, but seemed to run progressively richer at light load during the ride (soft/sluggish response at light acceleration or when blipping the throttle on downshifts, etc.), and eventually flamed out at a stop light, at which time gas started dribbling out of the vents on the front carb. I figured the float level was too high (or something stuck keeping the float needle open), so I pulled the bowl and was surprised to find the float (both chambers) filled with gas. So it was not a float anymore at all. I've never seen anything like it.

A few minutes of searching online showed a lot of people complaining about the same leaking Dellorto floats that fill with gas, but most of those posts were in the 2010-2015 range, and nobody seems to be talking about this anymore. The carbs on my bike were purchased new around that same time period, in 2014. So, questions: has anyone else here had the same problem with the white plastic Dellorto floats in the past few years, and does anyone know if Dellorto revised the floats sometime since 2015 to eliminate the problem? I can't think of any other reason why all of the comments on this problem are concentrated around 6-7 years ago.

I guess my basic question is if I purchase new floats, do they still potentially have the same issue?

-R
 

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I bought a new set of PHBH 30’s for my Guzzi a couple years ago, and within a year, both floats had filled with fuel. No telling how long the carbs had been sitting on the shelf before I ended up with them, nor is there any kind of date code on the boxes. The floats themselves look just like the opaque white ones that are available online now, so I suspect they’re same-same.

I ended up putting the 35 year old floats from the original carbs into the new ones, and they’ve been fine since.
 

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I have put a set of later plastic floats in both my bevel 900SS (PHM) and my race Pantah (PHF). No issues after a year plus in either so far. Increasingly difficult to buy original floats and after they have been bent a few times to adjust them I worry about them being fragile. Heard stories about the plastic floats filling a few years ago but not recently. The plastic floats are not adjustable but seem bang on 17.5mm float height when fitted to both carb models.
 

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Discussion Starter · #4 ·
I reached out to a fair number of places in the US and EU that sell the modern plastic Dellorto floats and asked for feedback. The responses ranged from "I've never had a problem, I don't know what you are talking about" to "the problem is not the floats, it's the gas you are using". And just about everything in between.

In short, disappointingly inconclusive. Nobody is aware of the material or the molding process of the floats changing anytime in the recent past, but it is curious that complaints of this happening have dropped off for the past several years. It would not surprise me if there is some regional sensitivity to this problem, as ethanol content and other emissions related additives of pump gas do vary quite a bit and could impact how the gas interacts with the plastic.

Anyway, there's no other practical option, so I guess I'll order up some new plastic floats and keep an eye on things.
 

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This could well be ethanol related, as the Italians do not have a good track record when it comes to mixing plastic with fuel (see sport Classic melting tanks).
 

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Discussion Starter · #7 ·
Yeah, of course ethanol free gas is best, but depending on where you live in the world, that can be hard or impossible, practically speaking. Here in California, your only ethanol free option is race gas, which unless you happen to live close to where there is such available at a pump (there are only a handful in the state, so for most people this does not apply), your only option is buying it by the drum (at a cost/gallon of at least 4x that of normal gas), fueling in your garage, and never riding further than a tank will take you. So yeah, impractical unfortunately in my case. Like others here, I've also experienced the frustrations of ethanol's effect on plastic tanks on modern bikes. Even worse in the case of bikes where the plastic tank itself is painted rather than having a cover (i.e. Aprilia RSV4/Tuono, etc.). My only real option may be to run the float bowls dry after each ride, and just keep an eye on the floats periodically.
 

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Discussion Starter · #8 ·
Finally got around to pulling off the rear carb, and found the float in that one was perfectly fine. So, two carbs of the same age (6 years or so since new) subjected to the same conditions (virtually no use in those 6 years until recently, and only a few hours total run time), and one float is filled with gas while the other is fine. Ethanol or other additives in the gas might be a cause, but clearly there is some variability in the production of the floats themselves that causes some to ingest gas while others don't. Guess I'll keep a spare on hand in addition to replacing the flooded one.
 

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Discussion Starter · #9 ·
Small update for anyone that is curious. For context, the carbs/floats have very few hours in total, but are about 6-7 years old since new; most of that time the bike was stored and the carbs were dry. Also, I added the old style float bowls just a few months ago, and the carbs have literally just 1-2 hours run time since then. The flooding of the one float has happened since the bowls were replaced.

The plastic on the float that is flooded has obviously discolored, and the bowl on that carb has white powdery deposits inside that can be rubbed off. The plastic on the float that is not flooded is pure white, and there were no such deposits on the bowl on that carb. Obviously both bowls started off clean a few months ago. It seems clear that the fuel is actually permeating and absorbing into the plastic, rather than getting into the float via a tiny crack or hole along the seam, and it further seems clear that the plastic on the flooded float has partially dissolved into the fuel leaving deposits on the walls of the float bowl. Pics below.

Bottom line here: the variability observed in my two floats seems to be attributable to differences in the material (plastic) itself rather than due to any differences in the manufacturing of the part (molding quality or fusion of the seam between the upper and lower halves of the float). Fingers crossed the new floats are made of the better plastic...

1012873
1012874
 

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It does look as if fuel has reacted with the plastic on one of the floats. Are the floats definitely genuine Dell'Orto? There are a lot of pattern Dell'Orto parts out there.
 

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They must have made the floats out of the same plastic they made the expanding fuel tanks with. Are they leaking at the seams ? Could be ethanol eating the adhesive.
 

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Discussion Starter · #12 ·
Are the floats definitely genuine Dell'Orto?
This is a very good question, and to be honest I cannot be sure. According to my records and conversations with the shop that did the restoration originally (for a prior owner), the carbs were purchased new as a pair. Since that time, the bike had only been run once after the resto, and had been on display since and until my purchase, so there is no obvious reason to think the floats would have been exchanged from whatever they came with during that time. However, I will point out that the float which has filled with gas has the green paint blob (inspection mark) on one chamber, while the float which is fine in the other carb has no paint mark at all. From that alone, it seems the floats in the two carbs may not be the same. The two new ones I have just purchased, which were represented by the shop I purchased them from as genuine Dell'Orto parts, both have the green inspection paint blobs on one chamber...

Any obvious way to visually confirm which floats are genuine?

1012940
 

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If the seam leaks, do you think plastic welding the seam may seal the float ?
 

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Discussion Starter · #14 ·
If the seam leaks, do you think plastic welding the seam may seal the float ?
Perhaps. But based on the discoloration of the plastic on the entire part, it looks to me like the gas has absorbed into and through the plastic itself, rather than entering through a gap at the seam. In any case, that float is going in the trash and a new one will replace it. Since one of my floats was fine, it's not obvious if there is a need to do anything to the float until you figure out if it actually leaks or fills with gas. That's why I bought an extra...
 
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