The new slant plug version of the MT70 twin comes with M8 plugs. What's an M8 plug? What is the thread size and is it shorter than a CM6? Are they 1/4-32 glow plug size?

The M8 plug is the NGK version of a 1/4-32 spark plug...They are overpriced and don't work as well as the Rimfire plug sold by C&H....Best thing tomy could do is change to CM6 spark plugs...The Chinese version of the 1/4-32 plug works well, better than the M8, but not as good as the Rimfire....
One of my customers has thousands of hours on small 4 stroke gassers using these plugs, we KNOW what we're talking about...
The Rimfire is the world's BEST 1/4-32 spark plug....
If tomy is using the M8 he's making a big mistake...

Hi Ralph,

Thank you for the reply.

The regular straight plug version 70 twin uses CM6 plugs. To narrow the engine they angled the plugs down and use the smaller plugs. I'm hopeful it will fit in my 50cc Aeroworks Extra 300.

I guess if the 1/4-32 plugs don't work out the cylinders could be drilled and tapped for the cm6.

After searching I found NGK ME8 plugs. Why are the rimfires better?

the M8 PLUG mean M8 SIZE plug . made by RCEXL . also can use Rimfire plug good luck

Don't know why the Rimfire is better, it just is...
The manufacturer of the Rimfire plug is Paul Knapp...Paul is a perfectionist who owns a large machine shop in Arizona...He builds miniature gas engines as a hobby...He made a model Bentley radial...The NGK plugs didn't last very long in his engine...He appreached Champion for permission to make an exact copy of the 1/4-32 plugs they quit making when glow plugs came out...They declinded...He made a close copy...Myself and a few others were around and got involved in the testing of prototypes...One was a surface gap, no side electrode, but was apparently too cold so it was dropped...The current Rimfire was the best, and still is...
He makes many different sizes of VERY small spark plugs, now marketed by another company, Marvin and Morrison(I think)....
The Chinese version of the 1/4-32 plug is quite good, just doesn't last as long as a Rimfire.
One of the problems in the past was a good shielded cap for the ignition..Bill at C&H makes the best one but it's a labor intensive thing...RC EXL has come up with a pretty good cap, not as good as Bill's but adequate....And less $$$.
If you get an engine with 1/4-32 plugs be sure to take some spares along when you go flying....
FWIW, Dennis Crooks used 8.8 Husky Challenger inline twin engines in his 195 mph scale P38 unlimited race plane...Each engine had two C&H ignitions and four 1/4-32 Rimfires in it...I think they changed each plug and the end of a heat race..8 plugs at a time, $$$

Great info Ralph, it is nice to hear the background on something.