Scintilla magneto,

[Talltee44]

I have two Scintilla magnetos ( VMN7DF ) fitted to a 7-cylinder Continental W670A Radial Engine. No problem on tick-over(800 rpm). Severe missing from 1200 to 1500 rpm, then perfect up to 2100 rpm. Same situation going up the revs as coming down. Any help would be useful, where do I search next, please ?

[ListerDiesel]

Sounds more like mixture than sparks.

You could also check that you haven't got a worn part that vibrates/oscillates at a certain speed.

Peter

[K D Redd]

I am with Peter. I would not think both mags would show the same failure. That is one of the reasons why airchraft engine have dual ignition. Does it run the same when running left mag only, right mag only, and then both?

Kent

[Talltee44]

Peter, Bonjour.
Thanks for replying, we will check the mixture, but the engine gives full revs without any misfiring. If you are ever in France for holidays, please call by and see us on the airfield in La Baule.
Terry

[Andrew Mackey]

You might want to check out the condensers - they may be getting tired, especially if they are getting old. Sounds more like a mid-range transition problem with the carb though - pay special attention to the float level, and the fuel ports by the throttle plate. Is your miss a stumble on accelleration or a steady miss? Miss on accelleration is an indication of insulation breakdown in the secondary wiring (spark plug wires).
Andrew

[bbeci85]

Hy!
I have a scintilla magneto,type NAB1 R1K.I like,to know which engine or motorcycle used these type?

[Andrew Mackey]

Talltee44, have you resolved the engine miss?
Andrew

[Talltee44]

Andrew, yes ..... and no !
We bought a new magneto from the States, seemed OK at first then the engine "coughed" a couple of times on base leg. Have since changed the SCINTILLA Condenser, seems OK for the moment, but we find the engine very temperature sensitive. Thanks for your helpfull comments. Talltee44