Why Bing Carbs Leak

[SJRoome]

Hi

I am a bit of a fanatic about adjusting and cleaning the 40mm Bing carbs on my 1989 R100GS. After I had just stripped, cleaned, tuned and synchronised my carbs I went on a short test ride, ran out of fuel and switched to reserve. As my tank was rusting inside this promptly dumped a load of rubbish into my inline fuel filters and I limped home.

The story of how I tackled sorting out the rusty tank can be read here http://www.ukgser.com/forums/showthread.php?p=1861086.

After I had sorted out the tank I refilled with petrol and yes, one of the Bing carbs leaked fuel. Bing carbs are very prone to this. Enough very fine debris had got through the inline fuel filters to get onto the float needle to make the carb leak.

Here is an image of the float needle exactly as extracted from the carb. You will see there is a faint ring of debris on the tip, and that is what is causing the leak.

This debris may not look much, but under a microscope you can see it totally transforms the surface of the float needle.

All that is needed is a spray of carb cleaner and a quick wipe with a lint free cloth and the needle is as good as new. Alternatively rub the needle tip on a piece of clean cardboard. But of course I had to clean the rest of the carb too.

Steve

 

[electric_monk]

Microscopes...!!!! what next?
You need to ride that bike a bit more...

 

[cookie]

before going to all that trouble next time, try hitting the carb with the microscope

 

[Rob Farmer]

There's a fine line between a hobby and a mental illness

 

[SJRoome]

Hi

This from a guy who used a thermal imaging camera on his cylinder heads!

Steve

 

[Kenny]

You have a valid point there Steve !!

 

[Rob Farmer]

I don't deny it

 

[Rugged Path]

Has anyone ever done a write up on setting the float bowls on the Bing's?

If they are not set level, they cause flooding.

 

[SJRoome]

Hi

Setting up the float height on the Bings is really easy. You remove the float bowl, put a container under the carb, open the petcock and use your finger to find the height that just shuts off the petrol flow. The top of the float should be parallel with the bottom of the carb body. Carefully bend the brass tang on the float with a small screwdriver to correct any error. If you dont want to smell of petrol afterwards you can omit opening the petcock and find the height at which the small inner rod starts to move into the main body of the float needle. After doing both carbs put the bowls back on, turn on the petcocks, let the float bowls fill then turn off the petcocks and remove the float bowls. You should have the same amount of fuel in each.

I described how to test the float valves in my contribution to this post http://www.ukgser.com/forums/showthread.php?t=185594

As well as incorrect float height you can get dripping carbs from heavy floats, the floats sticking on a damaged pivot pin and a damaged float valve seat. The last two will cause very heavy dripping.

The point I was making with the photographs was that Bings are very susceptible to dripping and even incredibly fine dust on a known good float valve will cause a problem.

Steve

 

[BillN]

Steve

as usual "top class" replies

keep them up - they ARE very good

ignore Cookie - he is really a Guzzi man!!!

Cheers

 

[bmwrich58]

If they are not set level, they cause flooding.

..............to HIGH or to LO of a level,... can create a Rich or Lean condition....