Brass floats, plastic floats, and the facts about fuel height

[81xsproject]

I just wanted to pass this one on to save others the trouble I went through. This process involved setting up my carbs with an old brass float, setting a specific float height, then installing the carbs and using a clear tube to read the actual fuel height. I then pulled the carbs, installed a newer plastic float set to the same float height, then installing and reading the actual fuel height. Great care was taken in setting the float heights using my calipers and made sure that both sides of the floats were the same. Both fuel level tests were done with the bike running, on the same carb, without ever moving the bike. Also not that the float heights on the plastic floats were measured as instructed in the supplementary section in the back of the Clymers that has 80's models specific info.

The final results were... that they both yield the same fuel height.

So, the fact is that float heights should be set according to the year/model spec not the difference in float type.

[ross]

81xsproject....i just went thru this and still am doing some final "tweaks"...i found it was not that hard as long as you stay consistent...not that i know everything about carbs, but many hours of trial and error out in a cold garage and you learn how 2 fix the problem real quick.....but very interesting information and research....thanx....ross

[79XS11F]

That's good information to know but an actual fuel level test is the only sure way to be on the money. I have 4 plastic floats that I will install the next time I have the carbs off the bike.
Rob

[TopCatGr58]

Hey Jessie,

Great info, will have to add it to the Carbs tech tips!
T.C.

[81xsproject]

Rob, the problem with the fuel level test is that it needs to be done on the bike, with it running, and the bike perfectly level, or you get inconsistent fuel levels. I built my own little carb stand and aux fuel tank about a year ago to set my floats with after checking fuel levels. It was a big waist of time because the bike needs to be running to keep consistent fuel levels. (and no, my float valves don't leak ). Fuel height is the 'best' way to go, but the results are barely noticeable at best. Totally not worth the PITA of doing it.(IMHO)

[skids]

It is absolutely good research! I take it that you did not change out the float spring in the valve, right? You used stock pin (non-vitron) for each comparison? Any problems with bending the tang excessively?

[81xsproject]

Especially since the plastics are available form mikes and seem to have a way better life span than the brass. Sure the brass can be repaired by re-soldering. However, I have yet to come across a leaking plastic float. The other thing I like about the plastics over the old brass, is that the tang and mount piece is a more rigid metal. While it makes it harder to adjust, they are also harder to screw up while doing other carb work.

[81xsproject]

Skids, none of the tangs needed XSive bending. The tests were done on my 81 carbs for the shear convenience of having the pre nippled drains. The results were used to set the floats on LVTom's '79 carbs. He wanted to upgrade to the plastic floats. He also opted to do the Viton float valve upgrade.

[79XS11F]

what is the Viton float valve upgrade?
Rob

[81xsproject]

Can be found with a search for 'viton.' But HERE it is anyway.

[GNEPIG]

If I put the plastic floats and new viton tipped needles in my 79 carbs, do I set the float height to the 80 and up specs? Or to the 79 float height specs?

[81xsproject]

That is exactly the scenario I was dealing with that forced me to do all this testing. Set them to stock 25.7mm and make any fine adjustments from there as needed.

[skids]

All of this info should be in the tech tip, TC.