Carb rebuilding questions


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Hi guys,

I have been reading some threads about rebuilding carbs and decided to make one for any questions that I didn't really see answered that I have since I am in the process of rebuilding the carbs right now. I was advised that maybe my float valve would be stuck but when I opened the bowls everything seemed fine. Any help would be appreciated! I was looking at the picture of the stock carb settings and saw someone mentioned to make sure that the float height is set correctly. I see that it says it should be set around 25mm but how would I check the height?

The nice thing about the BS38s is there's no jet tower protruding up in between the two float "bulbs". This allows you to place your ruler on the far side and sight over the tops of both float "bulbs". And speaking of rulers, I use a 6" steel rule graduated in MM on one side. It is very thin and that allows me to stick it down in between the gasket and outer lip on the carb body to reach the gasket surface. Saves me the trouble of having to remove the gasket if it happens to be stuck onto the carb body. Here's a float set to 25mm .....

38 Correct.jpg

Be sure to sight directly from the side, with the tops of both float "bulbs" in line. If you look at it from too low or too high of an angle, your reading will be off. Here's the same float looking at those wrong angles, too high .....

38 Low.jpg

..... and too low .....

38 High.jpg

Also, you need to measure from both sides. Often, the floats are twisted or "tweaked" on the mount, one "bulb" sitting higher or lower than the other. You won't catch this unless you check them from both sides.
Dip floats in a cup of hot water for a few seconds, bubble trail = fail, and you need new floats.
When doing 5 twins float setting above be sure the little spring pin in the needle is not depressed, getting pushed in, that will mess up you height setting.
It's best to confirm fuel height with the clear tube method.
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