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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> SJ50 Toledo buy
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SJ50 Toledo buy - 4/20/2007 3:31:04 PM   
BillO


 

Posts: 9
Joined: 7/25/2006
From: London, ON, CANADA
Status: offline 		Hi Bob,
Good meeting both you and Dubb in Toledo.
I might have a chance to run in my SJ50 this weekend. In the instructions, it says to run it for 15-30 minutes. My test stand tank will not support a near peak run of that duration. (11-12 minutes??) If I run 3 tankfulls, do all 3 at the same needle settings - i.e. - a bit off peak? All 3 tanks with the APC 9x7? Let engine cool completely between starts?
Are these ideas correct?

Thanks.
Bill

_____________________________

BillO
       Post #: 1

RE: SJ50 Toledo buy - 4/20/2007 4:47:50 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Yeah, you are on the right track there...

Basically you want about 20-30 minutes of total bench time. Does not have to be continuous. Just fuel up a few times. Cooling down between is not critical, but it will give you a break to look over things.

If you have a standard tank on the test stand, do not let the engine run the tank dry.... shut it down before any air bubbles appear and before the engine starts going lean on its own.

Put the 9x7 on it, start it so it is a bit rich, then slowly lean it to find peak rpm..... once it no longer increases, quickly back it off about 800-1000 rpm from there. Just let it run. Should be running around 17,000 rpm in this condition while being just a bit rich.

On the last tank (last 4-5 minutes) lean it out a bit --- find the peak, back off just about 300-400 rpm.

If for some reason at any point you go past peak, the engine gets hot and sags..... don't try to continue ..... richen up 1/2 a turn, then shut it down and let the engine cool. Then refuel and try again.

Then before you remove it from the bench, run it again, this time with the prop you plan to fly with. (flying with the 9x7 is ok too if you choose to start there). If you are going to move to a 9x8 or 10x6 or similar, now is the time. Find out the peak rpm, back off a bit see approximatly where the needle setting is for 600-800 rpm down.

You can also use this time to verify the throttle response and low/mid mixture. Learn how the engine runs, and what to expect. Although the low end should not require any adjustment.... Later on as the engine continues to work itself in or if you change to larger props, if any low end tweeking is needed, never move more than about 1/8 of a turn in either direction from the location it is now.

When you remove the engine from the test stand, verify that every head and crankcase bolt is tight (sometimes helps to do this with the engine slightly warm).

Bob


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to BillO)
       Post #: 2

RE: SJ50 Toledo buy - 4/20/2007 5:17:58 PM   
BillO


 

Posts: 9
Joined: 7/25/2006
From: London, ON, CANADA
Status: offline 		Thanks for the tips Bob! It's great to have an expert giving advise.
I sure hope to get out & run this engine this weekend, break it in, and install it soon.

Bill

_____________________________

BillO

(in reply to bob27s)
       Post #: 3

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> SJ50 Toledo buy
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