Bings, any differences??

[MR.E]

Hope you're all well.

Can anyone tell me the differences between the bing carbs, I've a flat top set and a nipple topped set.
Is one betters than the other, does one give better/ more fuel flow?

Thanks

[Barry]

You asked a big question !

Having a set of flat tops I've often wondered the same thing and after a lot of research I'm fairly confident you won't find a definitive answer anywhere.  We know the flat tops were a very brief experiment on Bings part and yet they seem to work just fine. Perhaps the only exception being the enrichers which are not as progressive as later carbs but that feature is nothing to do with the flat top and is also shared with the early non-flat top Bings.

Differences:-

The method of mounting the diaphragms is different and there is no spring fitted above the piston but again some of the other carbs had no spring either.

If you try out both sets of carbs and notice any difference I suspect you'll know as much as anyone about flat top Bings.

[nhmaf]

There are s number of parts which are specific to the flat top Bings not on the domed top models - I don't think that the flat tops are necessarily inferior, as some would claim, but they are a bit different in getting setup properly.   I suspect that the absence of the return spring above the piston might make them a little more susceptible to vacuum/diaphragm sealing issues, but this is only personal speculation.

If you contact the Bing agency in the US they can sell you a parts catalog with exploded diagrams of all the Bing carbs, repair kits, etc.    When I bought the catalog it was $10 - probably a bit more now, but has some very useful information.

[MR.E]

thanks for the comments, think i'll run the flat tops for a few weeks then maybe change them round if i can be bothered!

Elliott

[Bob_Roller]

One of the few differences between the flat top and dome top, is the rubber diaphragms .

Now, I don't  have any flat top carbs, members here that do have them say if you can't the diaphragm alone, you have to get the diaphragm and slide as one piece, costly .

Apparently the diaphragm is held onto the slide with some sort of white plastic ring .

I guess it can be problematic getting the diaphragm onto the slide properly, if you can just get a diaphragm separately .

Hopefully someone that is well versed in this can add their personal experience to this .

[NC Steve]

I recall that Rob Valdez had an issue with the flat tops on his '79 model a few years back, related to a torn diaphragm in one carb as he was making his way South for a Airhead get together. Seems like the big problem he had was related to the plastic ring too, and trying to find the correct part.

He could be a good resource to discuss the differences between flat vs. round top Bings. Again, if I recollect correctly, he had a fairly indepth posting on the merits of the cone vs. flat toppers.  :-/

[Barry]

BMW would have you believe that the flat top diaphragms and pistons should be replaced as a unit however lots of people with the aid of a little heat have managed to remove and replace the plastic securing ring without trouble. In fact I never heard of anyone that didn't.

[Armen]

My '79 came with the flat tops stock. Totally hateful devices. I did everything I could to get the bike to run well with them, and finally sold them and tried other carbs. The R65s I've ridden with dome tops were much happier bikes.
YMMV
-Armen

[steve hawkins]

Conversely my flat tops have more than 110,000 miles on them and work fine.

I had no issue replacing the diaphrams on mine either.

No telling what a PO might have done to them though.

Cheers

Rev. Light

[MR.E]

I've not had them to pieces yet, but i'll service them ones the engines rebuilt.

As it's going on the project bike, would i be better buying a pair of different carbs, minkunis or similar??

[steve hawkins]

It all depends on how deep your pockets are.  Can the money be better spent elsewhere in the short term?

It might be better getting the bike running in the initially with what you have and then deciding whether to splurge out on mikunis at a later date.

We are told the is a performance advantage to be gained, but by how much it is, is only annecdotal.  No evidence other than "my bike pulls much better than it did".  I have absolutely no doubt that it does, but by how many multiples of £100.......i.e. was the gain worth the expense.

Let us know what you decide, and no, we don't expect you to dyno the bike before and after you fit them!

Cheers

Rev. Light (too tight to fit Mikunis)

[nhmaf]

As this topic is more of a BMW/R65 bike-related discussion than a General Announcement, I am moving this discussion over to there to tidy up.

[nhmaf]

[movedhere] General Announcements [move by] nhmaf.

[Luca]

We are told the is a performance advantage to be gained, but by how much it is, is only annecdotal.  No evidence other than "my bike pulls much better than it did".  I have absolutely no doubt that it does, but by how many multiples of £100.......i.e. was the gain worth the expense.

IIRC there was a post within the last year in which somebody talked about their new Mikuni sliders.  In addition to having a snappier throttle response, he said the bike warmed up more quickly.  Yes, anecdotal... but if you know your bike well enough I think you can safely make such claims.

And those Mikunis never have torn diaphragm issues  [smiley=wink.gif]
Plus, with the price of Bing rubber (which our CV's have a lot of), do you think in the long run you could help offset the cost of Mikunis by saving on rebuild kits, etc.?

One thing about slide carbs though, that I don't hear people talk about, is that although you get a snappier throttle, you also can put a lot more hurt on the engine.  The real destructive forces in an engine are impact forces, and when you put in a wrist-full of throttle and wait for the rocket, your con-rods and bearings take a beating (just like when you lug an engine).

[Barry]

My '79 came with the flat tops stock. Totally hateful devices. I did everything I could to get the bike to run well with them,

Not doubting you had problems with your carbs but that's the first time I've ever read a specific criticism of the way flat tops perform.

I have no running or balancing problems at all with Flat Tops. Logically the only way they differ in operation is that fact that piston closing is reliant on gravity instead of gravity and a return spring.  An obvious thing to do is to check for stiction.  If the piston is raised with a finger it should fall smoothly and fully. If they do that, there is no reason for them to perform worse than any other CV carb... provided they are jetted correctly.  Whether or not BMW managed that is another question.