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Old 12-27-2008, 07:00 PM   #1
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Default mgt 3.0 help!

Went to break in my MGT 3.0 today, and had the engine seize about 30 seconds into break in. Thought it was flooded at first, but it wasn't.
It ran, then when it seized the pull start wouldn't budge.
I ended up taking the head off, and freeing the piston manually. After moving it with the head off, I noticed the piston would get stuck inside the sleeve at the very top of the stroke. Happened every time, at the top of the stroke it would get stuck, and I would have to turn the crank with pliers instead of the pull start.
Any one else had this problem? And is there a remedy that doesn't involve buying a new piston/sleeve kit?
Emailed Team associated about warrantying it, but they don't open until monday. Am hoping to get a fix that doesn't involve sending in the engine/truck.
Any help would be appreciated!
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Old 12-27-2008, 08:06 PM   #2
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Yetiak,

Few questions: have you broken in a nitro engine before? how many turns out was the needle when you ran the engine? Were you using a car specific fuel or aircraft fuel?

I've broken in some engines before that were very tight. Here's what you do...

Pull the plug, drip some after run oil (I personally like to use STP engine treatment for the car) in the plug hole and rock the piston over TDC while you watch TV (or your fav DVD; & keep a towl handy to keep your hands clean). It will slowly begin to loosen up. The sooner you can get the engine to run on it's own the better, because you need the heat to properly lap and anneal the P&S. Once you can turn the engine over by pull-cord with the plug removed (even if it's stiff) you're ready to add the igniter. Put the plug in, turn it down fingert tight, then back it off 1/2 turn or so. This will allow some blow-bye on the plug and ease getting the engine started. once the engine is going you can finger tighen again (don't go snug yet). It shouldn't be long before you can start the engine with the plug fully seated.

These engines are known as ABC (Aluminum, Brass, Chrome) engines. There are designed with a taper to the sleeve that is narrow at the top and pinches the piston at/near TDC (some pinch more than others) The top of the sleeve is where the heat is and this will cause the sleeve to swell and loosen up. On the really tight engines, heat cycling is very important. Set the needle rich (too rich) and cover the cooling fins. You want to run the engine for 60 seconds with the temp above 250 and below 300; after 60 kill the engine and let it come down to cool-to-the-touch. Do this for two tanks. I know I'm going to catch an earfull from other posters for this but hear me out. Fuel adds cooling, a lot of fuel (really rich) adds a lot of cooling to the sleeve and you have to have a lot of oil on the piston when breaking in a super tight motor. The problem is this excess oil is going to hold the temp down. Though the HEAD may read 240, a super rich setting (a burbbling sounding idle w/a lot of smoke) is actully pulling the sleeve temp down 15-20 F below the head reading. To properly anneal the sleeve and hone the fit between the P&S, the temp has to come up above 250. If you do this, you'll get a perfect honeymoon fit with the P&S.

The last thing you want to do is hone or ream the sleeve. This will take a way the plating and greatly shorten your engine's life.


chunk
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Last edited by chunk t; 12-27-2008 at 08:31 PM.
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Old 12-27-2008, 09:04 PM   #3
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I have never broken one in. This was an xmas gift since I wanted to get into the hobby.

I had the high speed mixture about a 1/4 turn richer for break in.
I am using 20% nitro from Trinity. Only stuff my lhs sells.

I ran some after oil in, and the piston freed up enough to make the pullstart work again. Can't really try it out again until tomorrow though, since it's 12:00am.

I was also told to put it on a stand, and just let the tires spin initially to build up engine temps, makes it easier to manage. I will do that as well.

Hopefully I can get through the first tank in the morning without any problems. I will do the finger tight plug, and all that, and see if it helps!

Will let you know tomorrow how it turned out
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Old 12-27-2008, 10:02 PM   #4
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Since this is your first nitro break-in, I'll assume you do not have a temp gauge to check temps. With that said, start your next attempt with the high speed needle (long one) at 4.5 turns out from closed (turn in until it stops, don't force it then back it out). Try to get the engine to start and run at this rich setting (I recommend driving the car, idling there is no load on the engine and it will naturally lean out; not what we want). You should get some healthy smoke out of the engine. If it wants to run with the glow on but won't w/out it, turn the needle in 1/4 at a time until it will run. A simple temp test you can do is a water test. It should sizzle when a drop lands on the head next to the plug. If it burns off in a flash, your too hot.

FYI if you did not know, to stop the engine, pinch the fuel line with your thumb and finger until the engine quits. Pay attention to how the engine reacts when the line is pinched. this will be important later when you refine the engine's tune.
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Old 12-29-2008, 06:08 AM   #5
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I went out and got a temp gauge. But unfortunately the temperature here went from 55, to 25... so I will have to wait to break it in :/
But I am hoping now I can get it to run without seizing!
thanks for all the info
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Old 12-29-2008, 05:16 PM   #6
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I wish you the best. There's always a level of frustration when learning something new. Just keep reminding yourself this is going to be really fun once you get past the learning curve.

chunk
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