Explanation and Fix with PICS
I have seen several post but no real answer. I have the Robin Suburu 33cc four stroke on a friction drive. Whenever I apply full throttle under load the engine will quit. First time it happened I was trying to pull a 10% grade and had to coast back to the bottom. I have figured out that it is "fuel starvation" because if I let up on the throttle about 1/4" before it dies then it will regain power. I have seen some post about this so I know others are having the same problem. Anyone found a fix?
YES! The fix is easy. And you're right about the fuel starvation; that is EXACTLY what is
happening. Here's what's causing it.
The Subaru Robin was made to run in just about any orientation; even upside down, albeit for a short time. Think about that for a moment. It can actually be turned upside down while running and: A) keep running. and B) not spill any fuel. AH HA! There's the tip off.
These little engines suck... so hard (as in vacuum) that they will actually pull more fuel out of the tank (and faster) than the VENT can let air INTO the tank! Voila! Vacuum equilibrium; hence--Fuel starvation!
I too had the same experience going up hills WOT and losing power. I too drew the same conclusion of fuel starvation. Then one day when it occurred, I reached down and loosened the gas cap and INSTANT power restoration!--The AH HA moment.
The Fix: Remove the baffle (duckbill) in the fuel cap. That will be $45 US please. JK
Here's how:
Unscrew the cap from the tank DUH. and pry off the tether retainer.
The fuel cap is built in a couple of pieces. Pry off the inner vent retainer and remove the foam
diffuser. Yes, I'm making these names up as I go along. They aren't in any manual.
Under the foam diffuser you will see the duck bill one-way valve that lets air in but won't let the fuel out. It is made of rubber and will pry out with a tooth pick or similar. (I used an old spoke here)
Reinstall the foam, inner lid, and tether and replace the cap on the tank.
DONE and never to be bothered by this problem again!
If you are unsure about this fix, try loosening the fuel cap next time you're on that hill and if the power returns try my fix and send me your check or money order!
Look, hopefully none of you will be riding upside down so you really don't need the check valve in the lid. And you won't leak any fuel either. Just look at the many layers of baffles the fuel would have to splash through and the wee tiny holes in the tether retainer.
Good Luck!
WC
Well! 5 pic limit...continued next post.