Oh God! Float height adjustment

[gearjammer]

So I decided to clean up and balance the carbs on my B12 which has been sitting through a long winter here in MI. I got the carbs out fine, laid them out on a table and washed them with carb cleaner. The factory manual says the float valves need adjustment to 14.6mm+/- 1mm with respect to the line that divides the float bowl and carb body in the inverted position. The readings I got were between 11-12mm. The bike however ran fine before I started this job, although rough between 7-8k.

I then went ahead and bent the float arm to set the position to approx 14 mm on all carbs and hooked it back to the bike. Now she starts idles very rough and dies as soon as the throttle is lifted. Is there a different way to check the float height?
I reset the float heights and will test it tomorrow. Im assuming I went over on the height and the carbs are flooding. Any help is appreciated.

[Fordtech]

Inverted means only so much that the floats make closing contact with the float needle. You do not want the floats pressing down on the spring portion of the float valves. Best way is to tilt the carbs at a 45 degree angle, just so the valves are closed and that is all.
I have done this a few times....and now at 97,000 km's it is sorta routine.
Would suggest you take out the idle jets....right beside mains....and be careful they tend to be bloody tight! Clean them while you are at it!

[txbanditrydr]

I assume your's is a first gen 1200????   Otherwise the float height is 13mm.

Float height is tricky to adjust because the weight of the float itself will put pressure on the adjustment tab.  The float height has to be checked with the carbs on their side and carefully allow the float to swing close before taking the measurement - gravity should not be part of the measurement.  

[gyrogearcrunch]

So I decided to clean up and balance the carbs on my B12 which has been sitting through a long winter here in MI. I got the carbs out fine, laid them out on a table and washed them with carb cleaner. The factory manual says the float valves need adjustment to 14.6mm+/- 1mm with respect to the line that divides the float bowl and carb body in the inverted position. The readings I got were between 11-12mm. The bike however ran fine before I started this job, although rough between 7-8k.

I then went ahead and bent the float arm to set the position to approx 14 mm on all carbs and hooked it back to the bike. Now she starts idles very rough and dies as soon as the throttle is lifted. Is there a different way to check the float height?
I reset the float heights and will test it tomorrow. Im assuming I went over on the height and the carbs are flooding. Any help is appreciated. /unquote

Holeshot makes a float valve setting tool that may help you with setting the float height. But another poster is sure right about experience being a factor when it comes to making the work easier. I learned the hard way how to set float levels on an old Yamaha 850 when I had to install a stick of Mikunis from a 750 because parts for the Hitachi carbs became unobtainable. Not only was the jetting way off, but the float levels used on the 750 had been messed with. The Mikunis also had a cute little hairspring on the left side that closed off the enrichment circuit when the choke lever was knocked off. Needless to say, said spring was missing on the used carbs I had on hand, so I had a head-scratcher trying to figure out why the engine always ran rich!! Thank god for exploded-view diagrams of the mikuni carbs on line that showed this "insignificant" little spring. In fact, that's one of the better features of Mikunis - PRODUCT SUPPORT BY THE COMPANY THAT MADE 'EM! A handful of jets (cheap!) allowed me to fine-tune these carbs to take account of even the different running temps between the inner cylinder and the outer cylinders. The result was like-new power and 47 mpg on a bike that had given only 32-35 mpg before. All this took 3 removals and installs of the carbs, but it was sure worth it. Patience and a good set of notes are recommended when doing a tune or rebuild on your carbs.

/unquote

[gearjammer]

Thanks for the info guys!  :thumb:I heard that holding it at a 45 deg angle and then measuring is the way to do it. I reset the float arms and if I invert it upside down with gravity pulling down on the float, I get about ~11mm. If I hold the carb at a 45 deg angle, I see that the float arm just about touches the valve needle. At this point the float height is closer to 13~15mm. I checked and rechecked the values, and the carbs are now back on the bike. Im heading to a buddy's place (40 miles) to sync the carbs. Yeah, I cant afford to store a merc manometer here in my apartment. Think Ill make it to him if I bench sync the throttle bodies? I recorded the turns on the sync screws before dismantling and then checked the angle of the throttle bodies visually.

Im not going to run her today, MI is a bit too wet for a carb sync day!

[Robertbarr]

Let me hijack your thread for a moment... with two extra inquiries on this topic.

On the carbs on my '01 B12, in each bowl, the two floats are at different heights.  If measured at the same location on the float, one will be perhaps 2mm (!) lower than the other.  Which should I measure from, or should I average them out? 

And... in the Dynojet ket, there's a photo of the measurement.  They want the height set at the molding / parting line at the center of the carb body.  I've been measuring from the highest point of the float, the greatest perpendicular distance from the carb bowl o-ring surface to the highest point of the float.  (A picture is worth a thousand, etc...).  In the Suzuki manual, they simply show the highest point (like I've been using) and there is no reference to the center of the carb body.

This gets frustrating, since it makes a big difference where you measure from / to (obviously).  Comments?  Rude suggestions?

[gyrogearcrunch]

Let me hijack your thread for a moment... with two extra inquiries on this topic.

On the carbs on my '01 B12, in each bowl, the two floats are at different heights.  If measured at the same location on the float, one will be perhaps 2mm (!) lower than the other.  Which should I measure from, or should I average them out? 

And... in the Dynojet ket, there's a photo of the measurement.  They want the height set at the molding / parting line at the center of the carb body.  I've been measuring from the highest point of the float, the greatest perpendicular distance from the carb bowl o-ring surface to the highest point of the float.  (A picture is worth a thousand, etc...).  In the Suzuki manual, they simply show the highest point (like I've been using) and there is no reference to the center of the carb body.

This gets frustrating, since it makes a big difference where you measure from / to (obviously).  Comments?  Rude suggestions?

Try the "Bandits R US" website (if they're still "up", that is). There's a chart on p.13 of their Bandit FAQ that lists all the carb specs for your bike. But for your immediate reference, the float height is 13mm. By comparison, the '96-2000 Bandits have a 14.7mm float height.

I understand that the floats ought to be adjusted without gravity forcing the floats down, so it's suggested that the carb be held at an angle that takes all the gravity load off the float needle before a measurement is made. Also make sure that none of your floats have fuel in them (are not "waterlogged"). Obviously, this will affect mainly the older hollow brass ones, but even the foam plastic ones can get waterlogged. You can weigh them on a digital kitchen scale to find the ones that weigh more, then replace them.

Your measuring instrument can be the simple 6" machinist's ruler with a sliding "T" on it set to 13mm (very close to 1/2"). Yes, you measure from the highest part of the float to the carb's parting line. You must measure each carb. There's no "averaging " involved. Don't quit adjusting until you're 13mm on each carb, "dead nuts".

You can also go to Mikuni's web site. They have (had?) a really good website packed with good and useful information.

Luck!

Herb

[gyrogearcrunch]

Thanks for the info guys!  :thumb:I heard that holding it at a 45 deg angle and then measuring is the way to do it. I reset the float arms and if I invert it upside down with gravity pulling down on the float, I get about ~11mm. If I hold the carb at a 45 deg angle, I see that the float arm just about touches the valve needle. At this point the float height is closer to 13~15mm. I checked and rechecked the values, and the carbs are now back on the bike. Im heading to a buddy's place (40 miles) to sync the carbs. Yeah, I cant afford to store a merc manometer here in my apartment. Think Ill make it to him if I bench sync the throttle bodies? I recorded the turns on the sync screws before dismantling and then checked the angle of the throttle bodies visually.

Im not going to run her today, MI is a bit too wet for a carb sync day!

A neat way to sync your carbs without the mercury or air gauges is to use a slip of paper between the butterfly and the carb body. all you need to do is adjust them like valves - making sure they all have the same amount of drag when you pull the paper out. This kind of static adjustment has always worked well for me.

[gearjammer]

Robertbarr I hear you man. The suzi manual isnt very effective at delivering the message. Since my reply is so late, Im probably rambling here. If you hold the carb body upside down at an angle of 45 deg, you should get the measure from the float top to the surface at about 14mm. In this orientation, you can see the float arm just about touching the needle valve.   Its a bit painful but easy after a bit