If you plan on running your engine inverted on a plane , but tune your engine on a test stand , should the engine be in the same position on test stand as it would be in plane or can it be tuned in upright position on test stand , then be set in plane inverted ? Its a saito 1.80 GK engine

I would mount it on the test stand inverted, almost exactly how it will be in the plane. (fuel tank location) That way if there are any hiccups, it will be easier to fix.

It will need to be tuned again if the position of the engine in relation to the fuel tank changes.

Watch your prop mount, Jeff. Make sure that you are really tight with the prop nut. Four strokes can "backfire" or hiccup, which could cause the prop nut to come undone and could launch the prop on you. So, do your tuning while standing behind the engine and make sure the prop nuts (a nut and a checknut) are secure and very tight.

Jeff.. post a picture of your aircraft. Folks, he sent me a PM with a picture of this aircraft. This is one nice job Jeff is doing on this aircraft. This is gonna draw some admirers at the field, for sure!!

CGr.

Thanks for the nice compliment cg , I have had a few issues dealing with this plane , but with the help of the wonderful people on here I have made it almost to the end of it . I think I like building more than anything , even though this is an arf . By the way Dick , I have decided on my next kit that I want to build , but not letting the cat outa the bag yet , . And sorry for late reply on this thread cg.

Jeff

Yeah,dont worry about how it runs on the stand....it will probably run way different in the plane. Stands are great for breaking in and getting to know what your engines capable of(prop sizes,rpms,etc.) and you get a good idea of how your engine will react to the tuning once you get in installed. Nice engine too....just be careful with that thing in a stand!

[X(]The tank position had better not be critical on an engine made in this modern day. Now-a-days there are some hooligans who do outside loops [X(], flat spins [X(] , tumbles [X(], extended vertical climbs [X(], even hovering [X(] with their planes instead of just flying them in a dignified, upright manner [X(].
The tank and or lines should be arranged so that the engine has to work a little to draw fuel and so that you aren't bothered with syphoning. The purpose of bench running an engine is not to derive the final tune in the aircraft, regardless of which way the cylinder is pointed.
Prolonged idling will test your ability to set the low end, raw fuel will snuff out the plug if you are off by too much.