912S Hot Starts

[N82HB]

When we have hot weather my 912S acts flooded when I try to restart it hot. The rest of the year it starts like a car. Is there something I should be doing different?

If I start right back up or wait an hour it starts fine. I am thinking it is a heat soak issue, so I immediately open oil door after shut down to disapate heat.

It always starts, but it is hard. Any ideas?

[Av8r3400]

What fuel are you running? Do you have a return line back to tank?

Sounds like vapor lock to me.

[N82HB]

Super Unleaded
Return line from where to where?

[Av8r3400]

The latest and greatest installation information from Rotax says that they want a return line in the fuel system back to the tank. The way this is done is from the area of the "T" where the supply splits to go to the carbs, there is placed an orifice (ø .014") and a fuel line back to the fuel tank (header).

This return line allows for a constant circulation of fuel keeping the fuel in the lines cooler and preventing vapor lock.

[cap01]

Wonder why the return line has to go all the way back to the header? Seems that going back before the gasolator would be far enough besides how much warm gas can there be thru a .014 orifice ?

[Av8r3400]

I would imagine it is as much pressure release as fuel flow. I agree that is a small opening.

I would also think they say tank because not every install has a gascolator.

[Esser]

Wonder why the return line has to go all the way back to the header? Seems that going back before the gasolator would be far enough besides how much warm gas can there be thru a .014 orifice ?

I would imagine it would be to cool the fuel if it is to prevent vapour lock. When talking to Robert Helms of UL Power he told me that my header would haev to be modified to 3 gallons to provide adequate fuel cooling.

[cap01]

i agree with the pressure relief . i dont have the return on my engine and i will see fuel pressure well over 4 lbs after shutdown for a considerable amout of time .

[Dorsal]

I will add a data point that I have a return line (to the header tank) and have had no issue hot starting.

[Wheels]

I had the same symptom a couple summers ago. There were multiple possibilities but the fact of the final fix was the vibration isolators on the engine mounts. Get a little vibration going and ariate the fuel in the bowls and bingo, you have what looks like a hot start. If there is fuel coming out of the bowl vents, I might take a real good look at the rubber in the engine mounts. While the engine is off for the mount replacement, you can modify the firewall with an access door to the starter. It lets you remove, replace the starter without taking off the engine. I did it last week to replace a leaking o ring. Nice and fast, no engine removal required. It was made to be done with a leatherman and a long screwdriver. All good.
Hope that helps.