General Engine Tech Talk

[iceman1]

At a loss--Just purchased Fox 29R "Bathtub" needle valve frozen-triedf soaking-what else can I try without destroying it---THIS ENGINE IS RARE
iceman1 It's been fixed,used heat---Thanks for all the help.

[gossie]

Very nice engine, that one.

Needle is still up the back I guess?

You say you have only just got it, so how about soaking it in lacquer thinner or acetone, in a screw top jar.
Make sure it's fully covered and put the lid on tight, then leave it soak for a month or more. Don't mess with it, just leave it soak.

It's probably 'gunked' up with old castor, and the thinner will slowly soak it away and soften it.

Good luck, and let us know how it went at the end of November.

[ffkiwi]

A good way of shifting siezed engines is with heat-I find this far more effective than soaking in thinners methanol or kerosene. Put the engine in a domestic oven at about 150C at leave it for about 15-20 mins. Remove,(using an oven mitt) and fit a prop to the hot engine, tighten up in the normal way, and turn the engine over (slowly) using the prop as leverage. Once you have the engine moving, generously hit it with afterrun oil and keep turning it over-several dozen times until freed up. Then whilst still warm-and while any congealed castor gunk has been softened by the heat-start dismantling to whatever level you require. I've never known this approach to fail with an engine that is simply stuck solid with old fuel residues. [If there is a mechanical problem and/or damage-then this approach may not work] The reason for turning the engine over slowly the first time is simply insurance against there being a mechanical problem-you should be able to feel this while turning it over slowly, and not make matters worse.
If the needle is only stuck in the housing, the heat aproach should work-if it is broken off flush in the housing, the only option would be to machine off some off the spraybar to expose a portion of the needle shank and then carefully unscrew this using small gripping pliers or the like