Confusing float height

[corytburkhart]

looked at my other set of carbs off of the other bike. i have never opened those up and that one ran fine.... they're sittin at an inch and 1/8 upside down and 1 3/8 right side up....
so 1.125 divided by .03934 is 28.5968 mm i think i'm gonna try lowering them back to that

 

[Flexeril]

ethanol sucks ass! whoever approved it, should be bathed on it!

 

[Rambo814]

looked at my other set of carbs off of the other bike. i have never opened those up and that one ran fine.... they're sittin at an inch and 1/8 upside down and 1 3/8 right side up....
so 1.125 divided by .03934 is 28.5968 mm i think i'm gonna try lowering them back to that

Cory, when you go to the garage section of the forums, at the very top of the discussion list is the Yamaha XS400 Manuals. Find the right one for your bike and print it off. I did for my bike the other day and found there are actually a couple different float heights, depending on which model you have. It also tells you HOW to set the float height. For example it says that for mine you are supposed to lift the float and then lower til it just touches the float needle but not does not depress the needle.

 

[Charles]

I would think the correct, and consistent way, would be to measure right side up, with fuel in the bowls. Seems to me both float types would need to keep the fuel level at 2mm below float bowl seam. That way you don't have to worry what float design you have.

Just a reiteration...

 

[corytburkhart]

both set of carbs i have are the same... the difference the ones i'm not using, somebody has cut notches where the mixture screws are to remove the brass plug covering them like the ones i'm currently using... debating on switching them out so i can adjust.....

i did change the float hieght again.. this time down to 1.0625 inches/27 mm.... it ran fairly well... or it would stay running anyway and you could ride it just fine, but i tried to tweek it bc the its out of sync bad and now i can't get it running again....

going to make or buy a manometer right now.. and if that don't work i'll swap to adjust mixture

 

[Denny Scriven]

That is good advice as my 82 SJ model is running well only at high RPM's or at idle.
I set the floats according to the manual, 32mm and had to bend the tangs to a large angle to do it. It looks like I'll have to the carbs off again and again , and again .......

 

[corytburkhart]

after i got the float height right.. i made a manometer out of 2 mason jars,10 ft of 1/4 inch tubing, and 1/4 inch gourmets. cost me about 10$ to make spent about an hour or 2 tuning it.. its never ran better, with headers cut at my toes at that!!

 

[Denny Scriven]

drewpy from the UK suggested placing the carbs in the vise and ensuring it was level to set the float height using a manometer. Speedog from Ontario, CA also suggested the plastic-float height should be 22.5mm. (It is possible I got these mixed up, if so I apologize)
I had set up the floats according to the Haynes manual at 32mm, the bike ran badly and was backfiring, found the right carb was flooding so stripped it all down, cleaned everything, checked the needles and seats with a jeweller's loupe to make sure they were perfect. Set the floats height and checked the level, 2mm below float chamber top and whether there was flooding with manometers.
I also installed a shut-off valve between the petcock and the gas inlet because the petcock drips and I can't fix it.
After all that I started the bike on full choke, it revved high as usual but it won't idle so quit for the day.

 

[arfstrom]

I didnt do that good at math, so I got me a metal ruler with the metric on half, and standard on the other side, and drew a line from one other. I might have used a squared, just to keep precision aspect. I did get a aluminum one, so I could grind it down with sandpaper, or what not, so I can put it in the groove. Goodluck



Seems I am jumping in here late, (sorry) I seen mathmatic's going on, and I hope that doesnt scare others from checking into this! It scared me when it went past the 10's column