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.46AX sleeve in .40FX

Old 04-20-2007, 05:27 AM
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PlagueWielder
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Default .46AX sleeve in .40FX

Hey,

I have an old 0.40FX thats on its way out.
I had a 0.46AX sleeve and piston laying around so I put that into the .40FX.

Will it work? When I turn the prop there is a "jump" in the top part of the piston movement. Is this because its brand new?

Thanks, Eliraz
Old 04-20-2007, 06:24 AM
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w8ye
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Default RE: .46AX sleeve in .40FX

The catch or jump at the top would be characteristic of a ABC/ABN type cylinder-piston combination.

To my knowledge, there is some difference between the AX and FX cylinders. Enough that they are not interchangeable. The locating pin to orient the cylinder has been moved to a different position and the design of the lip at the top of the sleeve is different. The locating pin for the sleeve orientation on an AX is over the exhaust port whereas the locating pin for the 40FX sleeve orientation is in the rear of the engine.

In your case, it is highly likely that your intake-exhaust port timing will be off? Not because of the stroke (that is the same) but because of the lip on the sleeve?
Old 04-20-2007, 06:39 AM
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Default RE: .46AX sleeve in .40FX

I installed it so the exhaust port match to the muffler and didn't pay attention to the location pin.

I know that the 40FX the 46FX are interchangable so do you think this will work? Should I try?
Old 04-20-2007, 08:53 AM
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DarZeelon
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Default RE: .46AX sleeve in .40FX

Eliraz,


Please read [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]this break-in thread[/link] that I began several years ago...

It explains why ABC/ABN engines have a pinch at the top of the piston's range of movement.

This, however, discusses engines that have their own standard parts...

I am not completely sure the piston+sleeve from the OS.46AX are 'drop-in' replacements in the OS.40FX engine.

The .46AX and .46FX do have the same bore diameter (22 mm) and their stroke is identical to that of the .40FX (19.6 mm).

But do look closely into the engine, to make sure no direct metal-to-metal contact occurs.


There could be a matter of different con-rod lengths that could cause the piston to actually contact the cylinder head.
This will surely make a bump on the top...

But all ball bearing OS .40-.46 engines, from the SF on, use [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCF43&P=Z]the same con-rod[/link]...
So it looks like you have 'upgraded' your .40FX (20.5 mm bore) to a .46FX, with a better quality ABL nickel plating.
Old 04-20-2007, 11:41 AM
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PlagueWielder
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Default RE: .46AX sleeve in .40FX

Hey Dar,

Thanks for the reply.

I went ahead and tried to start it. The pinch at the top went away after it worked for a few seconds and came back while it cooled down.
It also won't run at more than half throttle and for more than a few seconds.
It seems as the engine cant overcome that "jump" - it is pretty hard even by hand.

Anyway, I looked inside before closing the head and backplate to check that nothing is touching but now that I think about it, the piston probably touches the head.

Any ideas how I could make this work? Maybe add another one of those rings under the head?

Another thing, the engine had a very hard time getting fuel. Any ideas why? As I said, I aligned the cylinder so the exhaust port matches with disregard to that notch. Maybe its different from that?

Thanks, Eliraz

Also, forgot to ask you, do you know anyone in Israel that has an 9x8 or an 8x8 prop? Or something else that the 46 will run for pure speed?
Old 04-20-2007, 12:46 PM
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Default RE: .46AX sleeve in .40FX

Eliraz,


The fact that you can still feel the pinch when the engine is cold, signifies it still has plenty of life in it...

If you know where Rosh-HaAyin is, I can take a look and even get your engine started.
I have a yard around my home and it wouldn't cost you any.


I also have APC pylon racing props, in 8.75 and 8.5 inch diameters and pitches from 7 through 8 inches, and maybe head shims that can fit.

Using such a prop on the OS.46 will have the engine spinning over 16K... the P-Box muffler (.46AX) repeatedly disintegrates at that RPM...
I don't know how your older #783 muffler will behave.
The bearings may not hold up for very long either, but this can be solved for less than OEM replacement cost.

Call (052-2588489), or E-mail me if you want to co-ordinate something.
Old 04-20-2007, 01:02 PM
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Default RE: .46AX sleeve in .40FX

Thanks for the help, Ill probably call within the next couple of days or after yom hazikaron.

Thanks again.

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