CM6 spark plugs

[paul needham]

Hi all, can anybody give me any information about useing CM6 spark plugs in a zenoah 74 twin please. Are they a straight forward exchange for the standard plug or is anything else needed to be done. I'm looking at this so that the engine fits into the cowling without the plugs poking out the sides, or is there any other shorter plugs available that will do the job? thanks in advance, Paul.

[David Brown]

Hi Paul I have converted both of my Z80's to CM6 plugs and RCexcel ignitions, to fit in tight cowls. They are easy to start and very reliable, you need an adaptor for the plug to fit the engine from M14 to M10. I made my own out of stainless but they recon brass ones are better, I didn't have any brass. They are available if you search for them, I only have one left. Hope this helps.

Dave

[David Brown]

Here is the other engine in my Yak.

Dave

[paul needham]

Thanks David, is it possable to keep the engine as a magnito type or does it have to be converted to electronic ignition ?

[Alan Cantwell 1131]

Just engines sell all you need, plug caps, plugs, and the core reducers, cant see why you need to alter to lekky ignition, mine started easy enough with the tony clark booster box supplied with the engine, but i am going to use the rexel unit on my 3W 80, i need it to go into a tight cowl, if the model ever gets to the build stage!!!

[David Brown]

Not sure to be honest, the CM6 plug cap has a resistor in it and the std cap does not so it would have to be changed, I tried fitting a modified top to the CM6 plug to fit the std caps with the magneto but without the resistor it gave massive interference, so I fitted the RCexcel unit, I didn't try with the CM6 caps with the magneto set up. The up side is I don't need the easy start unit and it is so easy to start, flick it on choke til it fires then between 3 & 5 flicks after the choke is off it starts (Just like a 3W). Down side you need another battery unless you do what I am at present with my Yak which is to use one big Lipo 5000mah with a regulator to 5V for the engine and feed the receiver off the same pack at 7.4V. I get no interference and have been using it all year, I use about 250ma - 300ma per flight and only need to charge about once a fortnight.

Dave

[paul needham]

Thanks Alan and David for the replys, things are becoming clearer now, will contact just engines in the week then have the engine bolted to the fence post to see what happens.

[David Brown]

I have looked on Just engines site and could only find the reducers to 1/4 thread to suit the vary small plugs that fit in glow engines, with those plugs it would seriously reduce the width of the engine especially with the 120 degree caps, I might give those a try myself should I need to loose more width.
Let us know how you get on.
Dave

[Phil Clark]

I just bought a conversion kit for a ZG80 (magneto) for CM-6 plugs from here.......plugs, caps, cylinder inserts, resistors, the lot.

http://www.agaperacingandhobby.com/

Phil

[Andy Macqueen]

Hi,
I got my conversion bushings from here

http://www.cncengines.com/orderpage.html

The conversion bushings will convert the typical zenoah plug to cm6,You will then either have to get 2x resistor cap kits and fit them to the rcexl ignition or use a twin dle ignition or rcexl equivilant (for cm6 plug)which already have the resistors in,timing is the same.
you can always try the Ngk BPMR7A plugs which are same type fitting as the standard zenoah plugs but the plug is physically smaller and it is a resistor plug so no modding is required to your current ignition,the rcexl plug caps fit on much better with the ngk plug and will gain you some room but its not huge.
I have done it both ways and both are running great as my gt80's were hit and miss to flick start, but a saving on width did help on my hangar 9 extra.
andy

[Andy Macqueen]

http://www.agaperacingandhobby.com/

Good link phill...!

[Denis Brown]

Message from Paul Needham.

He very much appreciates all the posts re Plugs and thanks you all very much. He is unavailable for a few days but will be in touch as soon as he gets home from delivering a wheelbarrow loaded with sprouts to Yorkshire