Testing sparkplugs.

[38racing]

Watched a couple videos . guys used ohmmeter. One test was centre core to outer thread body which should have infinite resistance. So my Hyundai 1000 inverter wouldn't start. I concluded it was likely the plug. So I measured the resistance of core to outer. If was really high but not infinite. Got a new plug and now it starts and runs fine. (But another issue now). I bought a pair of the ngk c7hsa plugs from Amazon.ca. I was surprised that they were missing the screw on tip.

[bgsengine]

1) yes plugs should have infinity resistance - any continuity to a ground path is gonna guarantee failure of the plug , if not immediately , at some point down the road depending on how much carbon buildup there gets to be I have never tested a plug - if I suspect it is bad, I put a KNOWN GOOD (not necessarily new) plug in

and 2) NGK plugs, depending on STOCK NUMBER (there may be 2 or 3 stock numbers for C7HSA) may come with no tip (like yours) or removable tip (sometimes the tip unthreads by itself and gets lost, but that would be indicative of how the plugs had been handled in general) and SOLID (tip is not threaded on) - a solid tip is generally preferrable for most 2-high-vibration 2-cycle handhelds - over the years, as you work on more and more, you eventually come across a few (sometimes in bunches) machines where the threaded tip has vibrated itself to oblivion (threads gone and tip stuck in the boot cap terminal) So, just because it is a C7HSA does not always mean it will have the removable tip.. - when I sold plugs on ebay, I always listed by Stock number first - if your vendor cant or won't tell you the stock number of the plug they are selling, I may consider looking elsewhere.. Also , bear in mind there are stock numbers for the "shop-pack" (plugs in bulk foam pack, no individual boxes) , I'd never buy an individual plug known to come from a shop pack, unless it was over the counter.. they are prone to getting damaged when they are shipped. and then there's the special configuration plugs (yet another stock number) but those, usually have a suffix to their number (like BPR7ES-11) showing the plug has a modification made from standard (sometimes they make a longer ground electrode so they can make a plug with a wider standard gap, for example) ... But 'nough ramblin'...

[KE4AVB]

Doesn't hurt to have the NGK non automotive plug catalog either as you can lookup the plug and its images. The C7HSA (STK 4629) only comes without the end nut. Plus it is a non resistor plug.