From: "Finn Lassen finn.lassen@verizon.net" <flyrotary@lancaironline.net>
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Date: Tue, 23 Dec 2025 14:55:46 -0500
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Subject: Re: [FlyRotary] Best chemical for stuck apex seals
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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After working on it through sparkplug holes I had all six apex seals moving.
However, only compression on one of the six rotor faces, confirmed with 
only firing on one of the six.
(Have checked fuel injectors, sparks, tried starter fluid, heavy oil.)

Took off exhaust. Turbo housings, so no splitters and good view of 
rotors, housing and sides.

Tried with MMO, through 5W30, through 80W90 gear oil and still only 
compression enough to fire on one camber.

Can a stuck side or corner seal lower compression enough (<30 psi) to 
prevent firing, even when everything is coated in heavy oil?

I assume that stuck corner or side seals can only be dislodged with side 
motion of the rotor, but any way of doing that through exhaust port?

Any other suggestions before I pull the engine, disassemble, clean and 
reassemble?

Finn

On 12/12/2025 5:43 PM, Finn Lassen finn.lassen@verizon.net wrote:
> I'm finally getting around to getting my RV-3B with its 13B flying 
> again. Hasn't flown for 4 years or more.
>
> I can turn the engine by hand but several of the apex seals are stuck 
> -- won't move (back out) when pushing with a wood rod through leading 
> sparkplug holes.
>
> What's the best to spray in there to loosen them up/? WD-40?
>
> I'm reluctant to use carb or brake cleaner -- might they degrade the 
> rubber corner seals or maybe o-rings?
>
> Finn
>
>
>
> -- 
> Homepage:  http://www.flyrotary.com/
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