flyrotary@lancaironline.net Mailing List Archive

Mouse Milk (as sold by Spruce) is also very effective.

Marc

From: Rotary motors in aircraft
Sent: Saturday, December 13, 2025 7:13 AM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Best chemical for stuck apex seals

Finn:

Try some Marvel-Mystery oil. Its should be safer on the rubber corner seals than carb cleaner.

Never used it in a rotary but it did the trick for us when when had sticky valves and ring in the Lycomings and Continentals.

The secret ingredient is Wintergreen Oil (Methyl Salicylate) that's both a solvent and a lubricant.

Additionally, Valvoline Restore and Protect has worked well to free up sticky oil wiper ring issues on late model Volvo engines that have a known problem with overly tight oil ring groves.

"a synthetic motor oil designed to actively clean engines, remove up to 100% of deposits with continuous use, and prevent future buildup"

Mike in Maine

On Fri, Dec 12, 2025 at 5:44 PM Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.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

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