Thank you all for taking the time to reply.I bought the wrong one orderd this one hopefully it will do the job.
https://www.ebay.co.uk/itm/Gauge-Ch...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
Andy,
Any unit with a wire that you wrap around the spark plug is designed to be mounted to the engine.
These are difficult to use on hand helds and even harder to use in a workshop due to the nature of the pick up.
You either need to use one that clips over the spark plug lead, like a timing light or is non contact like the one in the video.
Next, the Magic Pudding is a childrens fairy tale.
In the real world, you only get what you pay for.
If you pay nothing, that is what you get.
Click on the see other items for the vendor in your link and look at what else they are selling.
They are a disposal site that have absolutely no idea about anything that they sell apart from the price mark up.
So you could be buying a good one that was wholesale surplus or a faulty one that was rejected by the customer , etc,etc,etc.
Now if you are a gambling man then go ahead, and while you are there, buy 300 spins at an online casino, you have about the same guarantee of coming out ahead.
I use the Fast Tach as seen on this page
https://www.tinytach.com/handheld-tachometers
Note this company sells NOTHING ELSE but service equipment so there is a 99.9% chance everything they sell will be good quality and actually work properly and if it does not they will fix it.
I bought this one because it is small & I am a mobile mechanic so it fits easily into my on site tool box.
The one that came with the business is bulky so is only used in the workshop
https://www.stens.com/751-180-wireless-tachometer
And there is a Strobe/tach I bought decades ago to tune motorcycles with but it is only good to 10,000 rpm ( it was also a months wages ).
Click on the Chainsaw Tools link
https://www.tinytach.com/chainsaw-tools & you will find a lot of very useful tools for working on chainsaws, in particular the vacuum/pressure pump which is an essential piece of kit unless you feel like pulling apart a perfectly functioning carb 30 times for the fun of it before you find the split under the fuel tank gromet.