I can see the fuel in the tank bubbling like mad and there's a constant stream of air bubbles going to the carb.

The manual advises that the tank should be wrapped in foam but the holes in the formers are not large enough to allow this. I put foam when I could but the tank will still be touching the formers. I suspect that this is causing the problem.

It's not easy to take out the tank and install an anti-foaming clunk. Are there any other options ?

Thanks

I may be over-stating the obvious, but it's
prop/spinner that will cause the vibration,
that is if you don't have a bent crank.

I balance all of my props. Some people have
told me that different brands don't need balancing.
That's simply not true. I rarely find any props that don't
need some balance adjustments.

Next, don't use any plastic spinners. Use only
the solid aluminum spinners, like Dubro.

Now, if you have done what you can to address
the prop & spinner, I have had good luck with
a squirt or two of Armor All per gallon of fuel.
Or if you don't trust this, pour some fuel in a
smaller container & shake to see the amount
of foam that you generate. Add a small amout
of AA & shake it again. No foam.

I add it to every gallon I buy as a precaution.

I have great luck with my 1/2A's using it. They
run at such high RPM's, it is difficult to get the prop
balanced good enough for them...

Good Luck!

Johnny C!

Couple of things, is the bung on thetank screwed in tightly enough and if you check your fuel lines maybe there is a small hole in one of them that is allowingair to get into the line, sometimes the fuel linesget minute holes in them. Maybe you just need to check the lines and the bung, replace all the lineswith new tubing and see what happens

Armour All will stop foaming, but not air leaks obviously. Try Armour All in the fuel first - if there's still bubbles then you have a leak for sure.

Cam