Ethanol and carb float problems . . .

[mneblett]

I have started doing that too. We'll see how it works on the new white floats I installed today. While I have everyone's attention, I have another question. The specs in the clymer manual say the floats should be 10 grams. The old ones were 14 and 15 grams each and were original bing floats. The new ones are 12 grams each. Should they be shaved down on top to bring them down to 10? Sounds crazy, but I am trying to minimize flooding/leaking and I really need to have these carbs running smoother.

That would be counter-productive.

The idea was to have floats with X grams in Y volume -- i.e., a desired low density so that their bouyancy exerts sufficient force to maintain the float bowl inlet needle against its seat. Shaving the floats lowers their weight, but also their volume -- no net change in density, but lower bouyancy (less volume displaced, less force holding up the needle).

My experience (FWIW) is that two grams is not critical, or even significant. It is far more important to keep the float needle seat free of crud. I'd wager that 90+% of float bowl overflows are caused by crud at the seat -- a reasonably fresh float (one that has not absorbed so much fuel that it is no longer sufficiently bouyant) adjusted anywhere near the proper parallel seating will not overflow in the absense of crud (or the bike laying on its side). A clean tank, intact petcock screens, maybe (strong pro/con opinions on this) in-hose fuel filters of a reliable/proven style, and periodic replacement of the float needle when excessively worn, will address virtually all Bing dribbles.

 

[RACEYDOG]

Geez, what a lot of haggling over nothing!


RELAX. Your bike is ok.

In the first place, float height is NOT THAT CRITICAL. Within reason is fine, no need to beat the thing down to the last .001".

The ethanol problem isn't that severe- I've seen saturated floats, of course, but not on every bike that comes through the door. Fuels vary, some are pretty snotty, most are ok.

Ethanol saturation doesn't become a problem til the float is significantly heavier than a new float, and begins to sit lower in the fuel. New floats weigh, IIRR, 10 grams. Worried? Weigh the floats. Or save your time worry and just replace them every couple years. They're cheap- are you?

Don't gas up at Discount Petrobarf. Don't add every available solvent fuel additive, that's just asking for trouble. Coating the floats with anything will make them heavier a lot faster than ethanol.....and if the stuff flakes/drools off, you have a new problem.

Ethanol-proof floats are great, but you're still gonna be into those carbs every year or so- airhead CV's need o-rings pretty regularly, and diaphragms every couple/3 years too. They're not maintenence free, and they're not gonna be. Live with it. That's why they made the bowls come off so easy.

I've installed the independent Bing floats for others, without any great problems; never used them myself, because it seemed a lot of money for.....well, nothing. I replaced my floats once in a while and never had any problems with them.

It's a smart practice to shut off the gas when you stop. The overflow stand tube in the float bowl is tiny- if you have a major float valve leak, it can still fill the cylinder just fine, while the overflow tube is draining full tilt. The tube isn't big enough to be a 100% solution. Besides, gasoline is....um.....flammable? Do you want a puddle of the stuff under your scoot, waiting for some moron with a cigarette?

I don't recommend shutting the gas off before you stop. (really? you really do that?) What if it stalls right before the semi changes lanes?

I've been draining and re-soldering cracked brass floats for....40 years? I don't see any more of them now than I remember seeing in the past, so it's hard to attribute a sudden rash of them to ethanol. I think they just crack from thermal stress over time- the brass is pretty thin. I mean, it's a float- and brass normally doesn't, so......

Who came up with ethanol? As usual, some well-intentioned, misinformed, smiling bobblehead in DC.
Politicians like it- another smiling baby to kiss, and a chip they can throw to those pesky environmentalists.
Gas retailers like it- they get to sell more gas. Ever check your mileage on gas vs ethanol?
Farmers love it- quadrupled the market price of feed corn overnight. Used to be a trash crop!
Rough on the water, though- corn farming is nitrate-intensive, and most of the nitrates applied wind up as runoff. Fish don't like it much. I hear there's a 600-square-mile dead zone at the mouth of the Mississippi........oh well. It's always something.




Want to haggle over something useful you can do for your Bings? Find a way to keep blow-by oil mist out of your idle circuit. Figure out what to use instead of a cold-start valve cover gasket.

Tune in next week for another episode of "As the Airhead Turns".........


Remember- it's not really rocket science til it gets past the clouds, no matter what they call it.



But if you're a real BMW perfectionist, I've got one last pair of titanium-plated Bing floats that Tom Cutter and I made in his basement back in the '80s, that I could let go for $300.

Each.


YMMV!

wow. just wow.

 

[RACEYDOG]

That would be counter-productive.

The idea was to have floats with X grams in Y volume -- i.e., a desired low density so that their bouyancy exerts sufficient force to maintain the float bowl inlet needle against its seat. Shaving the floats lowers their weight, but also their volume -- no net change in density, but lower bouyancy (less volume displaced, less force holding up the needle).

My experience (FWIW) is that two grams is not critical, or even significant. It is far more important to keep the float needle seat free of crud. I'd wager that 90+% of float bowl overflows are caused by crud at the seat -- a reasonably fresh float (one that has not absorbed so much fuel that it is no longer sufficiently bouyant) adjusted anywhere near the proper parallel seating will not overflow in the absense of crud (or the bike laying on its side). A clean tank, intact petcock screens, maybe (strong pro/con opinions on this) in-hose fuel filters of a reliable/proven style, and periodic replacement of the float needle when excessively worn, will address virtually all Bing dribbles.

I agree with the buoyancy and weight statements totally. I would only shave weight on the part of the floats that didn't sit in fuel anyway which wouldn't affect the volume/displacement As far as the weight difference goes, if the spec for the float weight is supposed to be 10 grams and the new ones are 12 grams, that's 20% heavier. Two grams doesn't sound like much, but 20% does.
As far as a clean carburetor. The bike is a 13k mile bike that sat for 10 years with no fuel in the bowls. They were rebuilt, syncd, cleaned, etc... The left one still leaked. It was the one with the 15g float. That's 50% heavier. I just spent another 350 bucks to have them cleaned again because of a mysterious substance (probably the braided fuel lines being eaten away by ethanol). That sounds like a lot I know. New petcocks and screens. New needles. New gaskets etc.
The left one is still leaking after sitting still overnight. But a lot less than normal. That is why I came to the conclusion that the difference in the weight of the old one and the new one was affecting the buoyancy of the floats and the position of the float valve. I will adjust the tabs tomorrow. I didn't have time to take them off yesterday.
Thank you for your input. A few of the other replies were really negative and unhelpful.

 

[RACEYDOG]

I had some other thoughts about this, but then I see you are running an R50/5. A lot of the info and responses here will be based on the Bing CV's, which you do not have.
So my only suggestions which might be useful for your specific carbs would be;
Clean the carbs
Replace fuel line with something less sensitive to alcohol - found that braided looking fuel line from the dealer really leaches out from the alcohol - leaving black goo in the carbs
Take the bike for a 15 minute ride before attempting carb synchronization. Garage warmup doesn't cut it.

hopefully someone running slide carbs will have some other info for you.....

What type fuel line would you suggest? I had some clear fuel line on it before I took it to the mechanic who put the braided lines on.

 

[RACEYDOG]

+1 on a lot of fuss over nothing really. Shaving your floats to make your carbs run smoother? Ain't gunna happen IMO.

Those specs are akin to a speed limit sign or the line on a shot glass--technically those are the rules, but in reality they are only estimates/guidelines. Your o-rings, jets, cleanliness of the fuel circuit and balancing will help your road tractor run smoother.

I didn't intend to imply that making the float weight match what I read as spec would make them run smoother. I just want to try to eliminate fuel leaking in my garage by possibly making the floats actually shut off fuel flow. My wife is really worried about the gas smell.

 

[RACEYDOG]

I've not heard of this spec...I see no reason to modify brand new floats. Snowbum did some testing on a number of new/used floats:

http://bmwmotorcycletech.info/bingcv.htm

Just clean your carb and passageways, set the carb up properly, and there should be no real problems with leaking. They really do work fine.

I have the Type 53 carbs on a R50/5. Carbs have just been totally gone through again. I found the specs in the large Clymer book. Could be accurate. Maybe not. Thanks for the link.

 

[RACEYDOG]

Some of you guys may think it sounds stupid to suggest shaving the floats to make them match spec (correct spec or not) but until someone tests it, how can anyone be certain. What if it works great and becomes a standard fix in the future. Maybe the process could be named after me.

This thread was about ethanol affecting the floats. It doesn't eat them away apparently, so we must be talking about the weight of them. Otherwise, why are we even discussing it.

Doesn't it make sense to correct the weight of new floats if we are so concerned about the weight/buoyancy of ethanol soaked floats.

 

[jforgo]

What type fuel line would you suggest? I had some clear fuel line on it before I took it to the mechanic who put the braided lines on.

I got some gray stuff from an independent shop here "tridon" I think

 

[jforgo]

I didn't intend to imply that making the float weight match what I read as spec would make them run smoother. I just want to try to eliminate fuel leaking in my garage by possibly making the floats actually shut off fuel flow. My wife is really worried about the gas smell.

I am showing a float needle # 1311 254 767. That is what shuts the fuel from the lines off from the bowl. That may be your problem. I replace these along with the floats on my CV's.
I turn fuel off for my r100's about 3/4 mile away from home. Leaves just a bit in the bowls - I sometimes sputter in. I do this more to spare the floats - but I can see where it keeps crud from settling on the float needle.

 

[RACEYDOG]

I have type 53 carbs. The float needles are new and the carbs were cleaned.

I have been starting to cut the fuel off when I turn onto my street. I live in a neighborhood with plenty of room to get out of the way if I don't make it for some reason. (That last part is for the guys that think it is dangerous and that I might get run over by a big truck or something)

I will check out that fuel line. Thank you.

 

[jforgo]

I have type 53 carbs. The float needles are new and the carbs were cleaned.

I have been starting to cut the fuel off when I turn onto my street. I live in a neighborhood with plenty of room to get out of the way if I don't make it for some reason. (That last part is for the guys that think it is dangerous and that I might get run over by a big truck or something)

I will check out that fuel line. Thank you.

According to Bob's, that needle part # is for the type 53. Do these type 53 have separate needle seats, pressed into the body? ? I have heard these can crack and leak.

 

[Manfred]

Ethanol-proof floats are great, but you're still gonna be into those carbs every year or so- airhead CV's need o-rings pretty regularly, and diaphragms every couple/3 years too. They're not maintenence free, and they're not gonna be. Live with it. That's why they made the bowls come off so easy.

Each.


YMMV!

I've seen a few others on this forum state that diaphragms on Bings need to be replaced every 3 or so years. Really? I recently owned a 1980 Yamaha XS850 with much hated Hitachi CV carbs and the original diaphragms were in them. Once in while a diaphragm will develop pin holes, or it might be torn while removing. But I've never had a Japanese bike that required - or had recommended - replacing diaphragms as a routine matter.

This is curious.

 

[20774]

I don't replace the diaphragms on my /7 in a routine manner, only if a problem develops or it's sufficiently long that I don't remember when last doing it. I keep records so could check that, but generally I only do it only when necessary. Besides getting pinholes, they can harden over time, resulting in poorer performance. So there may be something for replacing them on a bit more routine basis... ...

 

[carlo]

I don't replace the diaphragms on my /7 in a routine manner, only if a problem develops or it's sufficiently long that I don't remember when last doing it. I keep records so could check that, but generally I only do it only when necessary. Besides getting pinholes, they can harden over time, resulting in poorer performance. So there may be something for replacing them on a bit more routine basis... ...

I've replaced one diaphragm on my R100RT in 10 years. It got torn when a slide stuck at the bottom of its travel. The one I haven't yet replaced doesn't appear to have hardened noticeably. Since I purchased a pair of them, I now have a fresh spare to use if I need one.

I don't know how old the diaphragms were when I bought the bike, but given all the work I had to do on the bike when I got it, I'm assuming the PO hadn't looked at them in years.