Topic: Where to measure float height on '78 F2?

[Teach]

I'm troubleshooting my carbs (won't idle) and I'm gonna try to do several thing while the carbs are off the bike, one of which is check the float heights.  My clymer manual shows the earlier model round float carbs in the illustration, but my 78 750F has flat bottom (top?) floats.  So, do I measure from the middle of the float (when the hinge is to the side) or from the end of the float opposite the hinge?  Do I measure from the edge of the chamber or from down inside the chamber.  Is the 14-15mm float height listed in the manual (if I remember correctly) correct for this model?  It sounds like I need some hand-holding-- I REALLY DO, and I'm not ashamed to admit it.

Thanks in advance!

[theunrulychef]

You should download all of the applicable manuals listed in the FAQs.  I printed them out at work & bound them to use in the garage.  Here's the one that tells you what you need to know right now - http://www.mctangen.dk/cb750-k8-f3.pdf page 53.

Also, you'll want to make sure that your float valve is set, but isn't compressing the pin (kinda hard to explain - much easier to show).  A good way to do this is to turn the carbs float side up & slowly roll them over until the metal tang (attached to the float itself) is just barley touching the pin.  Move the carbs around gently while watching the float action & you'll see where it's supposed to be.

Good luck,
Jay in Philly

[jtb]

Hi Teach,

Make sure that your slow jets are clear.  Even with that, my F2 didn't really settle down to idle until I got new carb mounting rubbers.  I got them from Service Honda, they were about $16.00 each a year ago.

John

[eldar]

Measure from the edge of the carb body at about the middle point of the float. The height is 14.5mm +- .5mm so in otherwords 14 - 15mm.

[Lumbee]

...so is the 14-15mm with the carbs actually upside down and the pin in the closed position?

[eldar]

float valve closed but pin not pressed in.

[Lumbee]

ahh...yes, what does that pin do anyway???  the rubber on the end of the valve is what stops the gas to the bowls right?  So what does the little pin do?

[Bob Wessner]

It's spring loaded. It assists, I think, in keeping the pin/valve from bouncing open and closed with every little jarring motion while riding.

[byidesign]

The spring loaded end on the needle takes up all the jarring that the bike makes.
   actually with fuel in the bowl, the float rides a little up, using that play as the cushion.
     If you want a little experiment take a short drinking glass,wider than the float bowl
     {do this outside } fill it up to @ 3/16 from the top ,and set one carb with the float in place slowly down into it. Then you will see how they actually sit.
         in setting levels I turn them {carbs}about 10 degrees back from vertical {pivot pins up} just enough to rest on the needle .and then
    block them in place, then adjust,the floats so they are the right spec, and
    ALL 4 are the SAME.... that is most important in tuning them later on....
       Hope it helps
             Bruce