Float Bowl Check

[boyat68]

The sticking floats that I had caused me to doubt the MacGyver gene that I thought I had. After many dismantles and bench test, I finally thought of a method to test if the floats were sticking on the edge of the bowls. They were, all four of them with new floats. I also put the old floats back in just to test the method, and they also showed that they were sticking at the same place. Note: that the old floats were put in by a Yamaha dealer that the P O had paid to do. Conclusion is that floats right out of the box may stick and probably will. I suggest that many of the float problems can be resolved by the following method.




Mark Float Edges: I used pastel white but any color will do.


Thread a piece of Dental Floss around float to make a loop to pull through drain


Pull ends of loop through drain hole


Bolt the bowl back on the base as the positioning is critical. Jiggle the float up and down so as to try to make the float stick.


If float sticks, then remove bowl to see if any marks are left. I found the mark on the lower edges of the support casting of the bowl corners on all four floats. Pay close attention as the mark is hard to see. If you can jiggle the float several times with out it sticking, then let loose of one string and pull the string out through the drain hole, Then check the fuel height by using the sight gauge method. Note that the bowl depth fall is not straight down but has a slight Vee taper inward that caused the problem

I think I still have the gene, but very weak.

[TopCatGr58]

Hey MacGyver....,

SO...are you saying that the new plastic replacement floats may be just a tad too big for the float bowls?? Which way do we need to bend/adjust the float "balloons" to clear the float bowl, bending them inwards like Toe-In while looking directly DOWN at them, or do we need to bend the pontoons inward like looking at them level with the carb...like
___
\.../
Had to put the .... to keep the spacing right?
T.C.

[Ken Talbot]

Re: Float Bowl Check

Originally posted by boyat68
I think I still have the gene, but very weak.

I dunno, sounds to me like you've got it bad. In all the years I've been hanging around here, I've never heard of anybody else think up a scheme like this to check for interference between floats and gaskets.

[egsols]

Been having problems with intermittent leaks. I've been thinking it was bad float valves/seats. I'm gonna try your method and see. I know the po had problems no mech could solve. Maybe mine are hanging. Will let you know the outcome.

Sure wish we had glass bowls, would make life easier.

[boyat68]

TopCatGr58:

It may be a tad too big or it could be the slop fit of the swing pin to the hinge plate of the float or it could be that the floats were designed for another carb but made to fit by Yamaha. In any event the swing arc of the forward edge of the floats catches about 1/4 to 1/2 inch above the bottom on those two support edges. Bending the floats down a tad (trial and error), then using the dental floss to test the fit will bring them in line and best of all will prove if the floats are sticking anywhere.

It also may be that the metal float hinge plate has elongated over the years and allowed the floats to thrust forward a bit causing hang ups.

It also could be that Yamaha changed the float bowl design from the 79-80s and made the bowls a little different. I only have the 80 bowls so I could not compare. Perhaps some one with both types could measure the insides and compare.