I need a "hotter" Plug for my Briggs & Stratton lawnmower engine...

[Batpig]

Dear Folks,

The short way of asking my question is: Has anyone got a late model Briggs & Stratton-powered Mower, with the non-adjustable type of Carburettor, and your Spark Plug is burning the correct and healthy Light Tan colour (rather than the unhealthy Black)?. If yes (ie. your Plug's burning Light Tan), what is the Brand and Model No. of your Spark Plug?..

The long way of asking the same question is as follows: The Champion RJ19LM is the factory fitted Spark Plug on most Briggs & Stratton Lawnmower engines. Mine is burning black, and since the mower is still newish and chock-full of compression, and since I've given the Carby a good clean and tested the Float, the problem has got to be either an excessively-rich Air-Fuel Mixture (which I can't do anything about, since the Carby is all "preset" and non-adjustable), or a Spark Plug that isn't "hot" enough...

So... Do any of you perhaps know of another Plug (of any brand) that is physically equivalent to the RJ19LM (which has a 14mm Thread, 9.5mm Reach, 20.6mm Hex, and a Gasket-type Seat), but with a Heat Range slightly hotter than the Champion's 19 out of their own 25-stage Heat Scale?

Just by the by, the "R" at the start of the Model Designation stands for "Resistor" (but I don't think it would make much of a difference whether or not the Plug had one...), and the "LM" at the end refers to it being a special LawnMower Plug (but I can't see much difference between it and the end of one of the Plugs out of my car...). The "19" in the middle of the designation refers to its Heat Range...

Unfortunately, there's no such Plug by Champion as an RJ20LM....

NGK do an equivalent (the BR2-LM), as do Bosch (the WR11EO), but if they both just have only about the same Heat Range as the Champion, then I'll probably just end up with another Plug that ends up black again, from not burning hot enough...

Complicating the whole question is the fact that the different Plug manufacturers all use different Heat Scales. Some have more stages in their Scales than others, and some Scales go up numerically with increasing heat, while others come down...

Any takers, oh Small Engine and/or Spark Plug Aficianados?...

Many Thanks,
Batpig.

[RETIRED]

Have a look here. Bit of reading but about 3/4 down the page.

http://ww.honestjohn.co.uk/forum/post/index.htm?t=33119

[Burnsy]

Batpig you have to much time on your hands if you are worrying about this on a Briggs and Stratton lawnmower engine

By the way Holden grey motor plugs fit my B&S weed basher.

[Batpig]

Dear Burnsy,

Batpig you have to much time on your hands if you are worrying about this on a Briggs and Stratton lawnmower engine

Ha Ha... Yeah, if only...

Burnsy - the sad truth is that I'm looking after four lawns every two weeks with the thing, and it's pinging me off that I used to be able to do any two of them on one tank with the old Suzy 2-stroke Rover, but now have to refill halfway through the second lawn with the Briggs & Stratton - especially since the Head-Honcho at B&S Australia told me that their 4-stroke would make my Suzy 2-stroke look like a "Greedy Guts!". And before you go thinking that the Suzy's got a bigger tank, it hasn't . I kept careful figures on the fuel consumption of both mowers for a couple of months after I bought the B&S, and the Suzy was using 0.45L per lawn, while the B&S was using 0.67L per lawn...

Anyway, I pulled the carby down on the thing late last year and gave it all a good clean - including the Needle and Seat - and put a new Plug in it to see what would happen. Fast-forward to earlier this week, and I was in the Power-Gardening aisle at the BigB having a gander at the new OHV-engined Rovers, when I fell into a conversation with one of the staff chaps in the aisle (a very friendly fellow, I might add ) and it turns out that he's got a late model B&S Rover with the non-adjustable Carby too. And guess what?... His Plug is black too! So I went home and pulled the new Plug in mine out for a look, and... (you guessed it...) Black again.... Bugger!

The BigB chap also happened to mention that he has to refuel his after only half an hour or so of mowing! So in light of another B&S having exactly the same problem, it can't really be anything but the Mixture (which I can't do anything about since the Carb is non-adjustable), or the Plug temperature (which is what we're talking about now...). The only other thing I can do is start thinking about putting a 2nd-hand tuneable Carby on the thing (but that will probably be the next thread...)

50% extra fuel consumption adds up over four lawns every fortnight up-and-over here in muggy-old Brisbania, Burnsy! (besides, a Black Plug is a Black Plug! It's an Internal Combustion Apostasy! )

Best Wishes,
Batpig.

[marker]

Batpig
The brass bolt that holds the carbie bowl on is the main jet. It should have a number or letter stamped on it to indicate the jet size, you may be able to get a smaller one to lean out the mixture rather than replacing the whole carby. I don't know what colour the plug on mine rans at , just greatful when it does.
Mark

[Batpig]

Dear Mark,

Yes, that's not too shabby an idea! I might give Supercheap a call and see whether any of their suppliers do some sort of a range of various Carby Jets... (or, just maybe a Honda one would go straight in to the Briggsy Carb...)

Still interested in hearing from anyone else regarding a nice hot Plug for these things, though...

Many Thanks,
Batpig.

[rrich]

Before anything else I would try cleaning the air filter.