I have a P-51 that I want to mount a 2 stroke ST G90 inverted, any ideas, suggestions, thoughts, tricks?

Mounting it won't be the problem at all. Once you are ready to fire it up, inverted engines will hydro lock quicker than side or upright mounted engines. It is easier to cool down the glow plug with raw fuel and that makes starting them a little tough sometimes. Good Luck, Dave

It's usually pretty hard to do in a P-51 but try to get your tank centered or lower than the carburetor if possible. You can usually get an inverted engine to run pretty well but use an onboard glow as insurance. I done this several times and never had any problems. I did it with a supertigre 75, os 1.08, and now with an os 1.60.

I would not do it from my own experience. You will have a terrible time getting a reliable idle. alot of headaches. Good luck if you want to try it.

never worked right for me.. one thing that did help was to mount a du-bro fuel valve higher than the tank ..then to the carb
Went to 4 strokes.. no problems

Ron

Inverted 2 strokes take a little extra care and tweaking, but when set-up properly, they can run just as well as any other installation.

As mentioned above, the tank installation needs to be just right...and the carb needs to be adjusted just right...and the starting proceedure is slightly different.

I have several inverted 2 strokes, and always remove the plug before the 1st start of the day...and I leave it out until after filling the tank. Make sure the throttle is all the way closed while fueling...then open the throttle all the way and motor the engine over with the starter to make sure there is no accumulated fuel in the engine. Put the plug in and start it...throttle set a few clicks above idle.

Hey Bob, I've got an inverted ST .75 in my 109, and my pal has an inverted BGX in his Dora. Aside from a learning curve in how the heck to get them started, they run and idle perfectly. It's pretty much impossible to prime the thing w/ a finger on the carb cuz all the fuel comes running out on your finger when you do this. Therefore, we've adapted by filling the tank, flipping the plane over and priming it w/ the cylinder upright, and then flipping it back over on it's feet and starting it. Then, of course it'll burn off the fresh fuel in the cylinder and quit until it gets a constant draw and some heat to it. However, another prime usually gets it done then, and overall, aside from having to flip the plane over to prime it, I haven't had any troubles w/ the arrangements. Also had a ST3000 inverted in my Spit, started and ran awesome too...and i've not used any on-board glow systems---not discrediting the concept of using it, just haven't seen the need for it as the engines are all very reliable runners in existing setups.

Mike

Thanks guys for all the information, you all have brought out some things I have not thought of...

Just a suggestion. You might want to mount the engine inverted in a test stand where your tank height is the same as your bird. See how this works before putting on the plane itself. This could be especially valuable if you have to break in a new engine anyhow - why not do it all on the test stand instead of on the plane where things can get more complicated. You'll certainly see what gyrations you have to go through to start it inverted...

Good luck!

I have a H9 P51 with a 90 super tigre, it works great but it took some tweeking.
It now runs real good inverted.

Good luck

What kind of tweaking did it take?

I have had success running both 2 and 4 strokes inverted. For two strokes try an idlebar plug, that helps alot. Other than that it just takes some time getting used to primming the engine. Too much and you get a hydraulic lock on the piston. Too little fuel and it won't start. Once you get a feel for how much fuel you need to prime the engine, it will be easy. Once the engine is running it doesn't care that it is inverted.

Regards,

Dave

Absolutely no problem.
I have a CMP P-51 with an inverted ASP 1.08.
Easily choke it, then use a "bounce start" to get it started. Idles well too.
I had lots of concerns as I had never mounted an engine inverted, but this combo proved 100%

Does using a fueling system that closes off the carb when fueling help keep from flooding the engine, also what about using an electric starter, does it help or hurt?

I like the Dubro fueler because it does close off fuel to the carb while fueling. Be very carefull with an electric starter. You have to make sure the engine is not flooded. If it turns over easily the starter is no problem, and is the best way to go. If the cylinder is full of fuel and you try to use a starter something is going to give, and it will probably be the conrod.

Regards,

Dave

I use a DuBro fueler and it definitely helps avoiding a flooded engine and also - it's very convenient.

See the pic - it is at the same level as the needle.

I hardly ever use my starter since it can damage a flooded engine, and also it is simply not required.
The "bounce-start" is so easy with that big spinner, that I actually enjoy it and it wows my friends every time.
After fueling I open the throttle, give 2-3 chokes, close to a little above idle, and bounce it casually.
It starts on the first or second bounce every time.

This model has changed my approach and got rid of all my fears from inverted engines.

Also, I have no plug heating, and no idle problems. I believe those who have problems simply may have an incorrectly set carb.

Thanks guys, this is becoming a real education.