THOR single mixing valve/carb questions

[munimula]

My old THOR has bright blue spark and 60psi compression.  Is that compression reading too low to suck gas into the mixing valve?  And, while I’m at it, how many turns out for the adjustment needle, would be a good starting place?   I’ve never messed with a mixing valve before this one.

[Buccaneer]

It’s the crankcase pressure needed to get the poppet valve working.
On can have decent compression, but poor crankcase pressure.
You should be able to hear the valve operation when pulling
the engine over.

 

Prepare to be boarded!

[munimula]

Yeah – I knew that….smack my head.

[munimula]

https://www.youtube.com/shorts/-7ra30UB8aY

Got it!

[Buccaneer]

It’s alive!

Prepare to be boarded!

[PM T2]

60 lbs of compression is pretty good for one of those. Make sure you oil it heavy, I’d suggest mix at least 8:1. Those motors use  plain bearings to support the crankshaft and they are known to wear under the stress of running if they don’t get enough oil. You’re dependent on crankcase compression to accomplish two things here – first is to compress the fuel mix well enough to force it into the combustion chamber, and secondly to also force the fuel mix into the bearings so they get lubed well enough. Have a rag handy to clean up the fuel residue that drips from the carburetor, those things tend to spit out of the mixer quite a bit. The earlier motors with the mixer valve opening completely uncovered were the worst ones.

PM T2

He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...

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munimula

[munimula]

This old thing is leaking just about everywhere!  I sealed the tank that was leaking at the seams.  I need to make a new fuel line and it’s leaking around the adjustment needle to boot!  The threads for the neeedle’s compression nut are buggered up a little, so I need to parse out what the thread count and pitch is there on the mixing valve.  The packing around the needle, in said compression nut is also shot…any suggestions for a replacement?  I was thinking of trying to make a new one out of a thin chunk of leather…

[RICHARD A. WHITE]

Take some yellow thread tape, it is for fuel.
About 3 inches long and roll it so that you end up with a 3 inch long piece, then lay it in the packing nut, cut it o the length you need.

http://www.richardsoutboardtools.com
classicomctools@gmail.com

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munimula

[munimula]

I tried making a washer, out of a little twisted yellow teflon tape, but the thickness of the tape – which wasn’t very much –  and the backing steel washer, put the compression nut right in the middle of the buggered up threads around the adjustment needle.  Retapping the 7/16-24 threads didn’t help.  So, I did away with both washers and wrapped a little of the teflon around the threads of the needle itself.   The tape holds the needle from vibrating loose and now the compression nut can reach some better threads farther up the way.  Best part is there wasn’t a giant puddle of gas underneath the old THOR this morning!  Seemed to run okay too, for a few seconds.  I’ll dunk it in some water, when the glacier recedes!

Thanks for the help!

[Author]

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