It carb cleaning time again....

[Semper Gumby]

So the bike is running a little lean with the throttle closed (soft back firing).  So I put the colortune plug on hte RH cylinder (the one that flooded over Christmas) and suprise.  It behaving badly at idle.  At Idle the mixture cycles from lean to rich and back again like the float is sticking open and then suddenly closing.

So tomorrow before I go off to work I think I will pull of the RH float bowl and remove the float and clean the needle valve and look for stupid stuff (sinking float? trash in the bowl etc.)

At 96,000 miles it may be time to replace all the bits (needle, needle jets, main jet, all the rubber bits.)  I hate doing this.  If I do I understand that its diaphrams from Bing/BMW and bits from ? to keep the cost down on my old flat tops.

TTFN,

[Yikes]

I just replaced my new Motobins hydrin diaphragms that I couldn't get to work right with some Bing replacements that I got from EUBMW.  The new ones from EU are much more supple than the hydrin ones and do pass Lucky Lou's quarter test. Haven't road tested them yet due to the foot of snow we got last weekend, but fully expect them to do fine.

The diaphragms from EUBMW came in a kit that does both carbs and includes the replacement gaskets and o-rings.  Less than $30 for the kit including shipping - best price I could find.  I got my jets, floats and needles from Chicago for the usual decent price and long wait.  Even with the stiff hydrin diaphragms, the carb rebuild made a very noticable difference in the performance.

[Semper Gumby]

These guys?

http://www.eubmw.com/

[Yikes]

Yep.  First item on the Carb Parts page.  

[Bob_Roller]

That's a great deal on  the carb kits, that's less than the cost of 2 diaphragms !!!!!!

[Yikes]

Less than the cost of one diaphragm from the dealers.

[Semper Gumby]

Hey yikes. Is that for the Flat top carbs or the dome top?

(Good luck with the snow)

[Yikes]

For the dome top.  They went perfectly into my '82's carbs.  Looking at the parts fiche, it appears that the diaphragm in the flat top is (expensively) replaced as part of a piston assembly.

And it has just finished snowing here.  We've got about 9" on the ground right now.  Looks like another week of caging it into work.  

[Barry]

Looking at the parts fiche, it appears that the diaphragm in the flat top is (expensively) replaced as part of a piston assembly.
 

Many flat top Bing owners have been able to remove and re-use the white securing ring with the aid of a little heat and just replace the diaphragm.

Flat top bings are bad enough (apparently) without been held to ransom on spares prices. Anyone know in what way Flat tops are supposed to be inferior to the other bing CV's ?  That they are seems likely as they were only used for a couple of years and must have been cheaper to produce so they will have been repaced for a reason.

As a flat topper I'd just like to know what Im missing out on.

[Semper Gumby]

100 watt light bulb works best for removing the nylon ring.  Although I would put the ring in the oven inorder to put it back on.  

Now if I could just remember the up and the down side of the ring...it's got a kind of "L" cross section shape.  

(thinks)

[Yikes]

ey yikes. Is that for the Flat top carbs or the dome top?

Checked the Bing manual and there is only one 32 mm diaphragm for the CV carbs, so looks like they're the same.

[Semper Gumby]

After replacing a cheepo fuel filter with a FF2314 from Autozone, I tore into the RH carb this morning at 30'F OAT and found the float bowl remarkably clean.  There was a rough edge on the pivot of the float so I filed/sanded it down.  I also twisted the fuel shutoff needle a few degrees in case it was wearing three groves in the tube below the needle seat.  This seemed to stop the rich lean cycling for todays trip. But it is apparent that I need to replace the slide needle and needle jet if the is that kind of wear on the shut off needle.

I'll put the Colourtune plug on the cylinder to be sure about the rich-lean cycling thing later this week.

TTFN,

[Barry]

Bill

The needle and needle jet have surely been replaced one or more times at your mileage.  If not they must be badly worn. By most accounts 30,000 is the recommended interval.

It's hard to assess wear on the needle without knowing the dimensions but a 2.66 needle jet for example just has a 2.66mm hole in it so with care it is possible to get some idea of wear by making up a 2.66mm test piece. I polished up the shank of a 7/64" drill bit until it measured 2.66mm and convinced myself the the jet was very close to the correct size and not worn oval.

[Semper Gumby]

It was replaced once by me years ago at somewhere near 45,000 miles I think.  

Where is  my excel file.

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