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First post - SJ50

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Old 08-16-2008, 05:57 PM
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kenhiraihnl
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Default First post - SJ50

my friend gave me a nib sj50 (red needle-in-carb, and red tuned muffler) which he bought in 1998...i ran it this morning with a 9x7apc using wildcat15%nitro18%syn...i'm very impressed...the needles were set for around 15,500 wot...needle adjustments were very precise, and i leaned it to 16,500, and ran about 4 tankfuls through it...it's still a little tight at tdc, but it starts easily with a backflip, and idles and accelerates like some of my best os engines with performance specialties abc piston/sleeves...i have an almost-completed arf .40kaos, which was going to take an os.46diesel just for fun, but i'll mount the sj50 instead (same motor bolt spacing)...it should be an interesting 'sleeper'...just wanted to commend jett engineering for a great product...ken
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Old 08-16-2008, 06:06 PM
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Default RE: First post - SJ50

Hi Ken....

Thanks for writing, and I am please tohear it is running well.

Tight is GOOD.... it should not loosen up a great deal. When running, the piston/sleeve fit is perfect.

Performance sounds ok. Put a 9x6 on it if you have one.. take it up over 17K rpm. Should get their easily. Two tanks like that preferabely.

The engine should be propped to run at 16,500 or higher peak ground rpm. 9x7, 9x8, 10x6 typically gets there. Find peak rpm briefly, back off from there 500-800 rpm for flight.

Let me know how things go!

Bob
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Old 08-17-2008, 03:56 PM
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Default RE: First post - SJ50

Ken:

Please do not compair the Jett with the OS in any manner, they are just not in the same ballpark as to quality, rpms, idle, transition or longivity. Yes, am a rabid Jett fan.
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Old 08-18-2008, 09:58 PM
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Default RE: First post - SJ50

ORIGINAL: rmenke

Ken:

Please do not compair the Jett with the OS in any manner, they are just not in the same ballpark as to quality, rpms, idle, transition or longivity. Yes, am a rabid Jett fan.
you're absolutely right...my os engines (.46 and .61) w/ piston/sleeves from dave shadel were the best for easy starting, idling, and accelerating to high rpm (14.5k or so)...this morning, i ran my sj50 again on coolpower15% and a 9x7apc...i adjusted the needle to 17,000 wot and stepped away to observe the beast from a more comfortable distance...when i went back to tach it again, it was running smoothly at 17,400...i backed it down to 17,040 for the remainder of the run...the guys at the flying field were impressed...after refueling, the second run started on the first backflip, and i varied the rpms between 17,100 and 16,850, occasionally bringing it down to savor the smooth idle, then going back to wot...it's still tight at tdc when cold, but i have no concerns about that any more...wow...now i'm a rabid jett fan too...ken
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Old 08-19-2008, 11:17 AM
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Default RE: First post - SJ50

Hi Ken......

Pleased to hear it is running well. Sounds like you are enjoying the new toy

Be sure to send me a photo or two of your aircraft after you have a bit of time to enjoy it a bit !

Bob
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Old 08-20-2008, 03:56 PM
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Default RE: First post - SJ50

Ken:

There is lots of information on the Jett engines at Jett's web site. Follow their break-in and running instructions and you will have a outstanding engine that will run for years. Go to that 9x6 as Bob recommends. You want the rpm's without the heat of the 7 pitch prop for breakin. My first one, a 35L is still going strong after 7 years and lots of running and racing. I still take it out as a backup to the 60LX as I can almost fly it in my sleep at this point. Remember, the specs given on the Jett web site are minimums. As the engine ages, occasionally stick the recommended prop back on and see if it still performs to the minimum. If not look for a loose head, bad plug, air leak. Don't think you can wear one of these things out. Last year out of towner came to out club race with a 10 year old pylon 40 Jett with the new carb added, cramed in a LR-1. OMG, he outflew me (not so heard these days) but the 60LX was actually faster in my homebrew "thingy". It did (LR-1) not come back for heat 2 due to a rough landing in the first heat, but sure shocked me. Did not expect the wing to stay on, or be able to turn without skidding way out, but it sure did. My ear said that raced out 10 year old engine was turning over 20,000. Don't know the prop size. I honestly expect my Jett engines to outlive me. ENJOY
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Old 08-20-2008, 05:50 PM
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Default RE: First post - SJ50

thanks for your advice and stories...i'll remember that too much load will result in too much heat...btw, my lhs was selling 15% omega (30%castor/70%synthetic, 17% total lube) for $15 a gallon...i picked up a gallon for my sj50...i had to order some servos from servocity...i'll post a report of my first flight - hopefully sooner than later...lol...ken
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Old 08-21-2008, 07:49 AM
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Default RE: First post - SJ50

just of note.....

the engine will run just fine with 5% or 10% fuel .... will drop a few rpms, but most folks never notice.
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Old 09-02-2008, 11:07 PM
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Default RE: First post - SJ50

here's a pic of my kaos40 jett...i couldn't isolate the 10oz fuel tank w/ foam, so i'll just have to fly 1/2 tank to preclude fuel foaming...the engine is broken-in fine (18,300 on 9x6)...i'll fly it w/ 10x6 zinger...should be a blast...ken
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Old 09-03-2008, 07:22 AM
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Default RE: First post - SJ50

Nice......

should be a blast to fly !!
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Old 09-09-2008, 03:41 AM
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Default RE: First post - SJ50

my final post in this thread...bob, it WAS a blast...the 10x6 zinger was too much, so i used a 9x7apc...17,450 on the ground...the guys were impressed by the flat-out speed, rolling verticals, and humongous loops...one of the jet turbine guys came over to see my engine (he owns 3 nelsons)...i'll still fly the kaos from time to time, but i'm starting a build of a venus2 arf pattern plank w/ os1.08fsr rebuilt w/ perfspec piston/sleeve, etc...thanks for your help and encouragement...ken
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Old 09-09-2008, 10:57 AM
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Default RE: First post - SJ50

Outstanding....

Always good to bring the pit crowd to their feet [&:]

Bob
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