Need help with Mikuni BS34 float height

[Bartolucci]

I spent over an hour on the net looking for some solid examples of where the point of reference is for measuring the float height on my 34s. Very frustrating.

Here's what I've done so far. With the float bowls off, I gently turned the carbs upside down so that the brass float are pointing up. There is a lip on the carb body that the gasket sits in. I am measuring from the actual gasket surface, to the top edge of the floats (from the upside down perspective, it's really the bottom edge). They were something like 33mm measured that way. In order to get to 25mm I would have to do quite a bit of bending of the brass tabs. The problem is, the carbs overflowed before at the higher setting. Unless I'm mistaken, increasing float travel actually is working in the opposite direction.

The other option would be to measure from the lip just above the gasket surface. That gains me 3.5mm.

What is the correct point of reference?

Help is greatly appreciated!

TIA

[psycoreefer]

Are they the late type bs34's or the early type? they need different setttings.

The point your supposed to measure from is the flat, where the gasket would sit, not the lip.

Are you sure your floats float? No holes?

Are you sure the valves are sealing?

Yes you are correct, going from 33 to 25 will raise the fuel level in the bowls.

[ross]

CARBS!!.....hyperdrive is down captain!!

hey there bartolucci....here's how i figured it all out and she runs like butter.....is a pita, but when u get it right, hang the f*ck on!!!....

http://www.xs11.com/forum/showthread.php?t=17116

.....ride hard, ride safe....ross

[rpgoerlich]

Are you still working on those 82 XS400 Carbs?

If so, you'll have to use the clear tube method to get them right.

[Bartolucci]

Yeah, the carbs are off my 82 XS400. I appreciate the advice, but I'm not sure how to proceed. Back to my original question, is the measuring point of reference the distance from the gasket surface to the top edge of the brass float, from the perspective of the carb upside down? If that's the case, 25mm cannot be the correct spec.

[motoman]

Clear tube is the best...with bike idleing. For a static float level setting, do NOT have carb bank upside down! Rock the carbbank on its side so there is NO float weight on the spring! Initial and second option there and a 24-25mm will get ya close for a start, and may run just fine after sync, etc. Gonna vary a bit depending on vacuum draw correlated with ring,cyl. wear, altitude,air filter options,etc.....lot of variables, so what is "perfect" for one bike may or may not be the "perfect" setting for another ones bike. Example to get you started....33mm, idle circuit will be so lean, you'll be lucky if it idles. 22mm, it will be flooding so bad, likely plugs will foul in about a minute or less no matter what rpm....so gotta try and find the sweet spot that works for your particular motor. Book has measured settings for 78-79 carbs.....80carbs...... a RUNNING outside measured down from bottom of carb body setting for 81 and XJ's. The most important factor is whatever setting you choose to use, make sure all four carbs and all eight floats are EXACTLY the same. Will save you alot of frustration!

[rpgoerlich]

25mm was not a spec on the XS400 carbs, just a starting point to get you in the ballpark. I set mine level in a vise on the bench. Used a temporary tank with fuel to measure the fuel levels in the float bowls and adjust the floats as needed before putting them on the bike. Once on, You'll need to re-check fuel levels in the float bowls while running to verify your not going to overflow or be too low.