help with getting spark on M75

[whoha]

Hi Guys,

ok update on my M75

rebuilt the carb Thanks Karl
rebuilt engine thanks all who helped with parts
bought brand new magneto's and ignition harness
NOW the small issue I have and I think its small. we have fuel working no problem BUT I cannot get any spark. OK I need to figure out when I should have spark and should I have power to 11 12 or 13 all the time to make spark or I'm I missing how the Mag's work. when I hit the boost button on the mags I can get power going to the booster. so is it a bad booster?
any one have some ideas they could throw my way as I stumped.

Thanks again for any help.

Mark

 

[rdixiemiller]

Not sure on an armor application, but the old Vertex magnetos on drag cars used a grounding wire to kill the ignition. Opening the kill circuit would allow the mag to fire. All the mags I worked on did not require any external voltage source to make spark.

 

[vtdeucedriver]

what engine does the M75 have?????

 

[vtdeucedriver]

did a quick brouse on the web (books are packed) finding a continental engine, 6 cylinder????? assuming aircraft type with dual or single mag. What dixie said is exact. mags create there own spark, The ignition switch will create a open in the circut and that mag will be hot or should create a spark. Say for example, twin mags. Mag switch off, both grounded, run, both open. Dont know what type of mag it is. Maybe Bendix..............there should be a wire, would be shielded to the mag. Disconnect that and do a contunity check. check and see if its open with the swich in run or whatever it might be. then off, it should be grounded. I should go to my local museum this week and see if they can open up there M75 for me to look at........then maybe I can help more. post pics of the beast!!

 

[ARMYMAN30YearsPlus]

I know I had a fault without spark for a long while and traced it down to a bad ground in the distributor. Simple little cleaning got the engine working again. I don't know if this applys to your engine but thought it might help.

 

[littlebob]

Not knowing what you've already tried all I can tell You what I found on the magneto on my genrator for the shelter trailer. I was told to check the points and they were a little crusty. I cleaned the points and checked for shorts with an ohmeter before putting back on. I spent more time trying to find the TM telling how to put it back in time than I did actually working on it I know its a different motor, but sure other mags work the same. Good Luck,
littlebob

 

[whoha]

thanks all

Thanks all,

yes its an CONT 895 with dual mags.

I think I get the grash of making spark now. the unit has a booster button for the mags...so I assume and only assume that when I hit the starter its not turning over fast enough to make spark and this would be were the mag booster comes into play and boosts the mags to get it firing and running faster to create spark.

does that all make sence?? and yes bendix mags.

Regards,

mark

 

[TacticalTruck]

RE: thanks all

yes mark, you need the boost for starting. chance wolf was correct on "the list"
i am still suppose to get a core motor from the guy i bought my tank from. it may have the boosters on it.
jeff

 

[whoha]

yup

YES I'm so close to having my mean machine running is just crazy.

always that one more piece LOL


I opened the booster and well its just looks dirty so will try to clean up.

mark