Rotary engine questions

I have decided to get an old project back out after it had been cast aside for other things in life. I have a 1974 Mazda REPU rotary truck that I am looking to get back on the road but there were some things that bugged me when it was parked years ago. The ignition always seemed to be lacking a bit to be honest. It would be fine if you were just driving around without putting much load on the motor/ignition but if you run it up in the RPM by the time you were trying to run 3rd gear up it would start to stumble. It is on the original points style distributor now, and I was hoping some of the more experienced Rotary people could point me in a direction to help upgrade this ignition. Maybe I am an idiot or maybe I am searching incorrectly but I am having some issues finding information that is more detailed than add an MSD box and new coils. I am sure there is more to it than that. I know the truck was always a challenge due to the low volume produced but I am hoping someone can help me out a bit as the truck has been in the family for 20 years and my grandfather that was helping me with the rotary knowledge has passed.

Thanks for any help

Cool truck, we used to have the 1600 OHC engine in our fleet B1600 Mazdas - great little run-arounds, just shy of 100mph and on cross-ply tyres a lot of fun.

I'm not a rotary guy, but for those that are, it'd help if you gave more info' on the specific engine, whether single or dual distributor, etc?

Ah, 13B so single dissy. Assuming you've done the usual with a full ignition system service - cap, rotor(s?), correctly adjusted points and new leads, it's possible the wrong ignition coil is being used. For that era, i would expect it to be using ballast type coils, that's designed to work with a lower voltage, usually 6-8V, ignition normally with a bypass from the starter to give a cranking 10-11V to help starting - especially as they can easily be flooded from excess throttle pumping when cold cranking. You can check by closing/shorting across the points with the ignition on and checking the voltage to the coil. If a 12V system it will be around battery voltage, if ballast it will be half to two-thirds of battery.

If so, check the bottom of the coils, they should be marked "ballast"or similar, rather than 12V.

That said, are you sure it's ignition and not a carb' problem? A previous owner could have messed it up and/or there could be crap in the system - is the misfire relatively the same at different throttle openings, or significantly worse with more throttle? Oh, don't forget to check/change the fuel filter, I expect there'll be a bunch of crap in the tank after all these years - might be worth stipping and ch4ecking the carbie, anyway, for vrarnish and other issues.

The lowest hanging fruit is to punt on the older points style dizzy and just run an FB distributor/igniter/coil setup. That said I've done a few REPU builds for drivability and they benefit greatly from DFI and EFI - peak power wont change but light load and pulling a loaded up bed is a way nicer experience with a mappable ignition system and since you're already most of the way there running EFI carries those benefits and more.

Sorry for the late reply work got busy and it is haying season where I live. Gord the Truck is till set up with a points style distributor and it has the stock ignition. It has been sitting for a few years so it will be getting the normal flushing of the fluids and cleaning of the carb. When I was driving it years ago, I did have help setting it up with a local rotary engine specialist and he did mention that an ignition upgrade would be the smart thing to do. The motor is street ported with a racing beat intake/Weber 45mm carb and racing beat header. Nothing crazy just was a fun little truck to drive around in with the kids at the time.

I was thinking of doing the FB distributor/igniter/coil setup upgrade that M:EP mentioned but it would stay carbureted as I am trying too also get through the work on my 57 Chevy and this is something to hold me over while we wait on doing the body swap on that. Too much looking at other stuff and the wife said get what you have running.

I appreciate both of your feedback on the truck