Super Tigre engine not drawing fuel

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Super Tigre engine not drawing fuel

Postby rcr22b » Wed Nov 21, 2007 10:01 am

I have a ST G15 control line glow engine with the square venturi that will start and run if I prime it from my squirt bottle but will not suck fuel from the fuel tank.

The tank and location works with two other engines so I know the problem is with the G15.

I have checked the spraybar and it is not obstructed.

And I've tried using an initial needle setting of 1 1/2 turns out to 3 turns but the engine does not respond.

Can anyone help with this problem?
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Joined: Sat Oct 06, 2007 3:47 pm

Postby gossie » Wed Nov 21, 2007 9:45 pm

Does the fuel suck through when you choke it?
ie. put your finger over the carb. and turn it over.

Are the holes or hole in the spraybar set correctly?
Opposite across the carb. for two holes, and pointing downwards on a 45% angle for a single.
You can put a single hole straight down, but sometimes the engine sucks better on the angle.

Is there crankcase compression? If the backplate for example was leaking then as the piston goes up to reduce atmospheric in the 'case it would not pull fuel in.

Good luck. :)
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Location: Gold Coast Australia

Postby rcr22b » Fri Nov 23, 2007 11:23 am

The engine will start by priming and if I continue to prime it runs very well.

Or, if I elevate the fuel tank it will feed by gravity and the engine runs very strong.

So I don't think I'm losing crankcase compression or have air leaks in the fuel line.

Super Tigre experts elsewhere have pointed out that the square red plastic venturi on the G15 is designed for pressure fuel delivery only.

Either a pacifer bulb or using a pressure fitting from the crankcase.

Apparently the venturi is just too large to create enough suction and needs positive fuel delivery.

I've since found an original G15 booklet that confirms that.

So I will have to use pressure or try to fit a smaller venturi.
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