Spark plug gap keeps closing on 2 stroke engine

SPARK PLUG REPLACEMENT
See Figure 9.
This engine uses a Champion RCJ-6Y or NGK BPMR7A spark plug with 0.05 in.
electrode gap. Use an exact model and replace annually.

That gap is too big.... so looked for another and found it in metric.

SPARK PLUG REPLACEMENT See Figure 12. This engine uses a Champion RCJ-6Y or equivalent spark plug with 0.63 mm electrode gap. Use an exact model and replace annually.a


Now 0.63mm is 0.025 inches... that's more reasonable.

Often it's the easiest thing that stump us. Try changing the spark plug first. Sometimes a spark plug just won't fire under load, i.e., while it's in the cylinder but will spark if you have it removed. There are checkers for this, but it's a lot less expensive to just replace the spark plug. Do that first and let me know.

0.024
http://www.globaldenso.com/cgi-bin/global/plug/usa/pw/pw-plug.cgi?filename=pw-14.txt

There is very little to go wrong with a newish spark plug, so it is either getting to hot ans whiskering the plug gap ( the plug will look very white around the electrode and a tiny whisker will bridge the gap ) or the porcelain insulator on the plug electrode has suffered carbon fouling due to the engine running too rich, in which case just clean the plug so as the porcelaine is white again.

I have a flymo 430 petrol strimmer and cannot start it. ive cleaned the filter, put in new plug it went first time and then stopped and wont start again the plug seems to get wet all the time any ideas

two stroke mowers will have a picture of a oil can on the fuel cap,if it doesn't it is most likely a four stroke.
four stroke mowers will have a fuel cap and a oil cap as well.

Hi,
The plug that I have in my 720r is a Champion RDJ7Y. Can I suggest that you pull the old plug out and look to see which one you have? Also when you buy the new replacement it should already be gapped for what you need.
Good luck!

The basic fuel/oil mix is 50 to 1

close your carb adjustment screw a bunch of turns... yours may even be missing.