Setting float heights

[LAB3]

Am still not quite sure I'm getting the most power out of my 82 GS450 and have a couple of items on order as of this morning. One of my needles has lost it's springiness and I have a pair of 117.5 jets to replace my 115's along with a new petcock. These items in of themselves may give me what I'm looking for, the question is setting the floats right. I'm thinking of getting a bowl plug and drilling it out to put a fitting into since that seems to make the most sense. Anyone out there have a better method?

 

[Nessism]

Measuring fuel level is the best method. Setting float height is just an approximation.

 

[850 Combat]

How do you know where to set the height visually?

I haven't personally had a problem after using my Motion Pro tool for float setting, but I'm open to doing it some other way.

Measuring fuel level is the best method. Setting float height is just an approximation.

 

[Nessism]

How do you know where to set the height visually?

I haven't personally had a problem after using my Motion Pro tool for float setting, but I'm open to doing it some other way.

If the fuel level is high lift the float, and visa versa. It's a trial and error process...which is why so few people like to mess with it. With old carbs it's worth doing though. When the float needles are new (OEM Mikuni needles anyway) they will support the weight of the float. With aged parts, they typically won't. So the fuel level may increase with old parts.

 

[LAB3]

Mine where set 3mm different from each other, on a bike with 7500 miles I don't think anyone has ever gone through them before to make a mistake. Can't hardly believe the float would have ever had enough force to bend the tab.

 

[londonboards]

You are correct sir. There is never enough force in that float chamber to bend a tang.

I can't say I have ever seen one straight out of the factory to see how they are new (all mine are 35 year plus old) but they have probably been subject to all sorts of POs adjustments over the years.

As has been said, the little springs in those needle valves get weak over time and even if you adjust the float height so they are just resting on the snib, the fact that they will compress so easily, means they will not be holding the fuel back so efficiently.

Float heights are given in the manual with a plus or minus 1mm. So it isn't exactly super critical. And just imagine how that fuel looks in the bowl when the bike is under way, revving and vibrating hard and going over bumpy roads. It's a veritable prefect storm in those float bowls.

More importantly, I might suggest, is ensuring the valve seat O rings are not letting fuel through and that the valves themselves are seating and sealing. If in doubt, replace the valves and seats completely. They are not too expensive. Then adjust your float heights to the new valves. Doing this has provided me with the best improvements in my carb operation over the years.

Also ensure that the float bowl breather pipes are clear and correctly routed. Some people remove these pipes completely but I am not sure how that might affect the air pressure within the bowls so I prefer to keep the pipes.

And these days, with the crap gas we have and the few miles we drive, your carbs will be best if they are ultrasonically cleaned every year.

 

[LAB3]

You are correct sir. There is never enough force in that float chamber to bend a tang.

I can't say I have ever seen one straight out of the factory to see how they are new (all mine are 35 year plus old) but they have probably been subject to all sorts of POs adjustments over the years.

As has been said, the little springs in those needle valves get weak over time and even if you adjust the float height so they are just resting on the snib, the fact that they will compress so easily, means they will not be holding the fuel back so efficiently.

Float heights are given in the manual with a plus or minus 1mm. So it isn't exactly super critical. And just imagine how that fuel looks in the bowl when the bike is under way, revving and vibrating hard and going over bumpy roads. It's a veritable prefect storm in those float bowls.

More importantly, I might suggest, is ensuring the valve seat O rings are not letting fuel through and that the valves themselves are seating and sealing. If in doubt, replace the valves and seats completely. They are not too expensive. Then adjust your float heights to the new valves. Doing this has provided me with the best improvements in my carb operation over the years.

Also ensure that the float bowl breather pipes are clear and correctly routed. Some people remove these pipes completely but I am not sure how that might affect the air pressure within the bowls so I prefer to keep the pipes.

And these days, with the crap gas we have and the few miles we drive, your carbs will be best if they are ultrasonically cleaned every year.

Mine where cleaned in March of this year but I'm sure I'll at least shoot some cleaner in it as I'm hoping to not take them apart again. The vent tubes are original and in good condition, they where put back in their place upon reassembly. Both plugs are off-white and I'm getting 55-59 mpg at highway speeds, the engine starts to die out at 6500 rpm and rarely reaches 7000. Now that I'm living in twisty country it'd be nice to have the revs higher for engine braking.