Alright, i just bought a 12a out of a yard i used to work at for 100 bucks. there were supposedly <100k on the engine and it was running beautifully. I was told its been sitting indoors for 15-20 years now. What steps should i take to revitalize this treasure?

Any and all ideas welcome, I need this engine to get my 79 running again

 

pull it apart, clean everything, replace the rubber bits, and anything else that looks bad, and put it back together.

sitting for 20 years, there is a good chance the rotor oil seals, and or water seals are just toast

 

Rebuilt it and either port it to a larger than stock port or just clean the casting flaws it will help with giving better power and flow

 

Yeah, like J9 says you'll have to take it apart clean everything up and see what's useable and what is worn beyond tolerance. I guarantee that the rubber water seals are gonna be brittle and break.

Nice find tho - old 12As that have good irons and housings are getting harder and harder to find. Good luck to you - I hope it's gently used and can be rebuilt.

 

Step one, replace all the fluids & hoses. Unless you're going to pull the engine & do a rebuild, of course.

 

When i got to looking at it, rotor 1 looked clean through the exhaust port, but rotor 2 looked kind of rusty, so i pulled just the rear iron and cleaned the rust out as best i could. I then sprayed everything down with wd40, closed it, and poured in some 20-50. and it spun really nice!
--I will replace the rubbers, i guessed that had to be done.
Next. I still have the all the parts from the 79 12a that was in it, so should i just put the 79 distributor on the new engine or should i wire in the '85 distributor to the 79 harness? And Same with the carbs?

 

Why i ask is because i'm replacing my blownish 79 12a with an 85 12a. i want everything to go smooth, but im defintely willing do some custom work to make the best engine out of both. Any suggestions are great.
--So should i replace the beehive with the frontmount cooler from the 79 or leave it as is? And is this even the right section for build questions?

 

Definately ditch the beehive. It doesn't do much as far as cooling. As far as the other stuff, if you like points you could keep the dizzy from the 79 iirc but I would just upgrade to the electronic dizzy from the 85. Reason being is I hate messing with points...

 

will the coils from the 79 be compatible with the 85? the have less then 1k miles on them so id like to keep them.

again, any criticism will gladly be taken, i really want this engine to turn out well.

 

Nope - 80-85 electronic ignition specify a diff coil than 79.
Engine: if still sealed up - and you plan to leave it that way, I'd drizzle some seafoam in thru a port on each chamber, give her a few spins and let it sit till you get around to either a restart or re-build. Great stuff to eek out any carbon build-up, esp around the apex seals. Not needed if you plan to completely disassemble it tho, since cleaning all that stuff out manually is part of the procedure....

unles you have done a rebuild before, I highly recommend Mazdatrix 13B rebuild DVD as an assistant. Tons of great tips and technique, virtually all applicable to the 12A... saved my bacon on my rebuild!

Stu Aull
80GS
Alaska