Topic: float valve/float question

[kyre]

I'm rebuilding my 75 cb400f carbs and bought 2 new Honda float valves. I put them on and measured the float height on all. I then turned the carbs upside down and the 2 new float valves (1st which is closest and 3rd) floats are very soft compared to the old ones I thought were good. The old floats/valves spring back up where the new ones just bottom out. I know they're upside down (first set of sohc4 carbs I've rebuilt completely) but I want to know if they're supposed to bottom out like this when new? Should I replace the other 2 valves as well? They're really expensive so I hope not. thanks.

[Xnavylfr]

Did you follow a manual to set the levels???
The floats are supposed to be set with the carbs bottom up so when the level of gas fills the bowl it floats up and closes the needle valve. I know on CB750 the float is set at 26mm from the carb body to the top of the float with the carbs UPSIDE down. Are you sure you have the float with the needle tang on bottom (with carbs upside down).


Xnavylfr(CHUCK)

[kyre]

Yes, I know how to set float levels and they're set to the correct height when the floats are barely touching the needles. The carbs shouldn't be totally bottom up when setting the levels, but at an angle so the floats just touch the needles.

The pictures below are the carbs completely bottom up showing the fact the new needles are compressed completely while the old float valves seem to have a bit stronger spring. I'm just wondering if this may be a problem? All 4 float valves move smoothly.

[flybox1]

Time to get 2 more float valves so they all work the same. When it comes to carbs, if you have to replace one part in one carb, replace all others as well, just so you don't get results like you just did. 

[kyre]

thanks that's what I was thinking, 2 new float valves to get them all even...

BUT I still want to know from someone who's rebuilt a lot of vintage honda carbs, are new float valves supposed to be so easy to compress? Seems like you'd want a nice, smooth movement but they don't have "spring" like the old float valves, not that you need spring.

[City Boy]

Hi Kyre.I have done my share of carbs and this has been my experience.When the carbs are inverted just enough for gravity to bring the floats into contact with the valve tip,the tip spring should not compress, though your  replacemments may not be as stiff as original. Set float level at this position. Other's experiences may be different.

[bollingball]

Did you follow a manual to set the levels???
The floats are supposed to be set with the carbs bottom up.

No X they are not set when upside down.

Yes, I know how to set float levels and they're set to the correct height when the floats are barely touching the needles. The carbs shouldn't be totally bottom up when setting the levels, but at an angle so the floats just touch the needles.
kyre this is correct

Time to get 2 more float valves so they all work the same. When it comes to carbs, if you have to replace one part in one carb, replace all others as well, just so you don't get results like you just did.
I think I would do this. Make them even.

Did you follow a manual to set the levels???
The floats are supposed to be set with the carbs bottom up so when the level of gas fills the bowl it floats up and closes the needle valve. I know on CB750 the float is set at 26mm from the carb body to the top of the float with the carbs UPSIDE down. Are you sure you have the float with the needle tang on bottom (with carbs upside down).

Show me where the manual or any one says the carbs are to be UPSIDE DOWNkyre make sure you get them from the same place (manufacture).
Ken

[kyre]

Thanks ken. I bought oem float valves from service Honda.  Will buy 2 more. I just can't believe how expensive oem from Honda are! $24 each! Best to do it right the first time..