Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Jett 90LXT inverted

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Old 11-19-2005, 12:01 AM
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Airnondas
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Default Jett 90LXT inverted

I would like to hear from anyone who has the Jett 90LXT engine running inverted and if so what muffler they used.

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Old 11-19-2005, 12:45 PM
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rmenke
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Default RE: Jett 90LXT inverted

My 90L runs in a inverted position with no problems. Starts are easy with no unusual problems. Do not over prime the engine or as with any invented engine, you will come to come grief in starting. You are going to have to get used to the open throttle start recommended by Jett. I go to about 3/4 as a sort of compromise (in my mind) and bump the muffler end and off we go. I use a starter on everything as I like my fingers and in the case of a 90, my arm. Our club has a number of metal starting stands that lets us start these things unassisted in complete safety. Enjoy the monster, its a great engine.
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Old 11-19-2005, 05:59 PM
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Default RE: Jett 90LXT inverted

Thanks Rmenke for your info.

The Jett 90 LX is the engine you recommended for the Cermark Alley Cat racer.

Now I can't wait to receive it.
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Old 11-20-2005, 09:17 AM
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Cyclic Hardover
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Default RE: Jett 90LXT inverted

Well if you like that, The compression is so high that I have seen one guy start his (try) and took the whole firewall and engine clean off! He was using a electric starter. After I saw that, I used a chicken stick a few times until it loosend up a bit and then went to the electric starter. On another, I have seen the front end of the plane covering "honeycomb effect" when it was going full rpms. Last but not least on my 90L, I shut it off and it was off for about 5 seconds or so and it started right back up again. Has happened to me a few times.

I have been running mine about 4 years now and still strong. Also own a Sport .50 too. I blew a connecting rod last year on the 90L when it threw a prop in flight and had an overspeed. Installed a new one and been fine ever since. They are as easy to dial in as any OS or Super Tigers. Like they say, "you get what you pay for."


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Old 11-20-2005, 09:53 AM
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Default RE: Jett 90LXT inverted

I shut it off and it was off for about 5 seconds or so and it started right back up again. Has happened to me a few times.
How possible ??? Without gow plug ingniter ?
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Old 11-20-2005, 09:08 PM
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Default RE: Jett 90LXT inverted

I dunno. I'm sure "Dar Zeelon" can explain it but I darn near lost a finger a couple times. I think it might have been still in some compression stage or something. Now everytime I shut it off i hit it with a chicken stick or kick the prop with my boot to make sure its loose if ya know what I mean?
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Old 11-20-2005, 09:17 PM
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Default RE: Jett 90LXT inverted

There is a catalytic reaction between the methanol in the fuel and the platinum in the glow plug. Got bit like this once or twice when playing with C/L combat engines years ago.
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Old 11-20-2005, 11:53 PM
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Default RE: Jett 90LXT inverted

When you ask, you gotta read closely or?

Ok guys, back a ways, I told you how to start a Sport Jett 90L. Go back and read! If you dont have a starter, get one. Note the do not over prime. When you have unburned fuel around the head and glow plug, in a inverted engine or just wet, the only lacking requirement is compression. Of course it will backfire, the compression will ignite the glow fuel well before the piston gets to near TDC, so back it goes. Got it! Sure you can tear a engine off the firewall, engine stand or about anything. Have seen it done with .25s to 150 CC twins. Hydraulic lock! Lets start out doing this right with a little more direct info. Befor hooking up the glow plug to the igniter, give the motor a little kiss on the head! Turn the prop a little to be sure the works is well lubericated. Apply igniter. With the throttle 3/4 or more, apply starter to a starter cone or spinner, at the same time place a finger over the exhaust port of the muffler. Turn the motor over with the finger in place no more than a moment. She should come to life immediately and just scare the heck out of everyone in the area. Be sure to take good safety care with the motor on a stand or the plane being held by a experienced pilot. The thrust is going to be a lot more than anticipated. To be honest, I turn the motor over with the starter a moment before I prime with the finger-muffler thing. Unless well lubed, and mine are, you have a moment of metal to metal wear and you don't want to let Bob know you are not taking great care to the engine. You should see the starter for my 150 DA, could start a car with it. We are not talking a cut finger here, talking a whole arm! Not talking a cut finger with the 90s either. Use a darn starter, much cheaper than one trip to the Dr. You guys that thought the kiss was just a joke, think again. Ok its a luck thing, but again? Have had engines start when I attached the plug igniter on many occasions, the piston is up in compression, you add heat-bango. Note the guys that use their thumb and forefinger on a spinner, and flick the spinner backward, and it starts in the right direction. Yess a starter can push the crankshaft into the backplate on a cheepe. Rethink things here, this is a high dollar, high quality Jett. Don't ram the starter in, after the kiss, applygently to the starter cone or spinner with enough push to turn it over. Learn the light toutch! Go back and read the Jett recommendations for break in. He wants the throttle wide open at start. Can't quite make myself to this but about 3/4 seems a gentle compromise that I may pay for in the long run.

Stupidity has a price that is always paid. Bro #119
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Old 11-21-2005, 06:19 AM
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Default RE: Jett 90LXT inverted

Since this is a 90 thread, I've got a quick question. I have a 90L that has been in my Great Planes F-15 for a few years.

I'm thinking about pulling it out and putting it in a Shrike 40 ARF. I know the plane should be extremely fast, but will the airframe handle the speed?

Ken
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Old 11-21-2005, 11:09 AM
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Default RE: Jett 90LXT inverted

And they think I overpower things!

Think the total weight of the Shrike will be bad, gonna have to buy some lead to CG. No doubt it will go up, getting down in on piece may be something else. If you do it, let us know how it comes out. A 90L in one of the larger deltas like the Delta Fighter would be ok?

Stupidity has a price that will be always paid!
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Old 11-21-2005, 12:26 PM
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Default RE: Jett 90LXT inverted


ORIGINAL: kennyandannie

I have a 90L that ............I'm thinking about pulling it out and putting it in a Shrike 40 ARF.
Ken
The Shrike 40 comes out nose heavy with a 40 so a 90 would be a real problem. Expecially an ARF that can't easily be modified to move the CG back. I have seen large engines on a Shrike 40 but the firewall was moved back and a few other mods.
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Old 11-21-2005, 11:30 PM
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Default RE: Jett 90LXT inverted

I have heard of the 90 being installed in the 40 size Patriot and DC F20. They shorten the nose a bit and was suppose to be a heck of a flyer. I think there is still a picture of the Patriot on Jetts page in the Hall of Fame
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Old 11-22-2005, 05:52 AM
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Default RE: Jett 90LXT inverted

Well the CG thing will probably cause me to change directions. I hate adding lead, especially on a speed plane.

The only thing stopping me from getting a Patriot XL is the fact that it's a kit. I just don't have the time to build a kit.

I'll keep searching for the right plane for my motor.

Thanks for the comments.

Ken

P.S. What I'm looking for is a 150 mph plane that will work woth the Jett 90L
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