Spark Plug - wrong model fitted to trimmer - could it cause problems?

[DIYNotIan]

Hi all

I had some problems with my Tanaka trimmer last year and had it fixed (and serviced) by the local repair shop. It's not behaving too well now either so I have cleaned the air filter, and ordered some replacements. I will also replace the spark plug, but was going to try giving it a clean up as well (and check the gap). It was replaced when the machine was serviced.

Upon checking I see they put in a NGK BMR6A. The manual calls for a NGK BMR7A. I *think* the only difference is the Heat Range.

It's all new to me, so I wondered whether this difference in heat range is important or not? Should I be asking the repair shop why they fitted the wrong one? Could it have caused damage to the machine?

Many thanks

 

[Burnerman]

You are correct it is the heat range the number refers to - you won't notice the difference!
John

 

[DIYNotIan]

OK, thank you. So they can be used interchangeably?

I've got to give it a good clean in the morning as it is quite black. I run 50:1 - or thereabouts. Only recently discovered how inaccurate the mixing bottle is!

Cheers

EDIT - well, I say quite black, but I don't really know what I'm talking about so here's a pic instead:

 

[Burnerman]

It looks like that plug has done a fair bit of work really - looking at the carbon deposits inside.
Anyway, you can interchange the plugs at your leisure and the strimmer will be fine on 50:1 mix - so long as you are using a genuine two stroke mixing oil such as Oregon or whatever.
You can increase the oil content slightly if you wish but you'll get some smoke appearing.
Just for (useless) info.....the higher the plug number the hotter it runs, which is fine for a two stroke and its oil burning. Basically, its the exposure of the centre electrode from the insulator that makes the difference.
John

 

[Keithmac]

With NGK the Higher the Number the Colder the plug, Champion and probably everyone else do it the other way.

A Grade 7 would be even darker if that's possible!.

Looks a bit rich BUT that's safer for the engine, harder on the plug.

 

[Burnerman]

Aha cheers for that Keith - after cutting my teeth on the Champion N9Y I forgot that some manufacturers go the other way!
John

 

[Keithmac]

Think NGK only did it to be awkward!.