Spark Knock

The_Proletariat wrote:

missionkz wrote: Are you using a fuel filter set up after the tank selector ..... Before the carbs?

Yes, a sintered bronze filter meant for lawnmowers and such. I know the pleated paper style ones filter better but they won't flow without a pump in my experience.

I was shocked to see so much crap in the carb bowls. Strangly enough only carbs 3 and 4 were affected. 1 and 2 were very clean.

Where did you source this filter material?

I would suspect a fuel line decomposing.
I used a couple layers of fiborus air cleaner material for forced air furnaces. It catches 95% of all the crud the passes through it.

I am thinking my bogging problem is because of poor fuel supply.

I've seen the clear or translucent blue fuel lines disintegrate and clog up carbs. Some of the black urethane lines do that as well. I only use fuel lines for cars. They hold up well, but because they are meant for fuel-pump pressure, they are heavier and stiffer, which makes them harder to work with.

Maybe urethane was ok with gas, but I suspect it can't handle alcohol.

I use Gates 1/4" EFI hose and I replace it every spring.

I believe this started in the gas tank with all the debris in there, and somehow passed through the tank strainer and my inline filter. Maybe when I painted the tank I got paint inside and the gasoline somewhat dissolved the paint.

All the jets were clear but two bowls and two emulsifier tubes were nearly clogged. As long as my throttle position was in the pilot jet range it ran fine but would bog in the main jet range. The idle kept getting lower and lower as well to the point where I had to use the throttle to maintain idle. I did not have these symptoms with a full(er) tank but as the fuel level dropped the bogging got worse which makes sense looking at the debris on the tank strainer.

I guess when I receive my tensioner I will find out if my diagnosis is correct. Severely disappointed I have no transportation this week but I was chasing my tail working on this thing. I never thought with an inline filter I would have fuel supply problems.

Well after cleaning the carbs and tank out no more bogging in the last two days.

Check your tank strainers!