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Small engine compression tester adapter

theoldwizard1

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Feb 22, 2011
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So a couple of months ago I did the "buy once, cry once" and bough the Mityvac MV5530 Compression Tester Kit. Lots of adapters !
Screenshot 2025-06-29 104439.png

But wouldn't you know, not one for this teeny, tiny spark plug out of a Craftsman 32cc backpack blower ! No brand on the plug but the number is 794-00082.

IMG_0834.JPG

It APPPEARS to be either an 8mm or 10mm "fine" thread, but the M10 adapter in the kit does not fit !

Where can I get an adapter to work with my Mityvac Kit ?
 
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ToolFanGeoff

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Jul 19, 2017
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Old Wiz, I had the same issue - and could not find an adapter that matched. I took the old spark plug, broke the ceramic, and center electrode out. I brazed a fitting to the steel spark plug shell that adapted to hose if the compression tester. Worked great. It took less time to make the fitting then I spent looking to buy one.
 

Sumboodie

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That's an MTD part number. Crosses to a RDZ4H plug which is 10x1.0 thread.

Same size as 6.2 and 6.5L diesel glow plugs which Mityvac has an aye-dapter for.

Or MVA5501 is the actual adapter I think.
 
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ericg

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Nov 14, 2009
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879
Could this be it
 

KnurledNut

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That plug is a M10x1.00 as Sumboodie mentioned.
I have the rebranded Craftsman version of your kit and the adaptor is the same, M10x1.00.
Cant say why its not cooperating.
 

Sumboodie

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That plug is a M10x1.00 as Sumboodie mentioned.
I have the rebranded Craftsman version of your kit and the adaptor is the same, M10x1.00.
Cant say why its not cooperating.
Same, I know I've done small engines, but can't remember if I ever bothered with very small small engines so wasn't sure what the kit had.
I bought mine probably near 25 years ago at Sears.

Normally easy to tell if it's got decent compression or not just from the pull cord.
 
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