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Upfront, the car is a '83 FB 12A, with 150.000 km (about 94.000 miles)
This is probably a useless thread, since it is probably an apex seal failure, but I still would like to hear a second opinion.
So I drove the car about 500km (310 miles) home, without having an issue, except a snapped alternator belt. The power seemed fine, it reved freely and startet up nicely cold and warm.
At home I replaced the belt and accidently knocked of the omp-lines while tensioning the belt. I fixed them and also tried to premix with two stroke oil. Trying this the first time, I've totally overdone it with 150 ml on less than 20 litres of fuel (miscalculated it since the tank needle is dead).
Afterwards it struggled to start up cold and I had to keep it alive with the throttle at around 2000rpm, below that it had strong vibrations and died. The strange thing is, that when warmed up a bit, it would start up nicely and would drive as before, although it still wouldn't idle.
I've checked the compression (proper adapter for spark plug holes, sensor goes up to 50 bar can measure up to 4 kHz), there I've got only 3,5 bar at max on both rotors.
Could there be another reason for the compression being so low, despite starting up when warm and seeming to have enough power?
before all else, just for the record ... what was driving the water pump on your trip after the belt broke?
i doubt it's an apex seal based on your description of your test. was this a rotary-specific tester, or a regular tester? if regular, did you remove the Schrader valve?
After the belt snapped, the water pump was still driven by the belt, which drives the air pump - at least it seemed so, do you mean that the second belt hasn't got enough tension to drive it properly? I couldn't really tell if it overheated since the gauge is dead. When starting up, it only smokes faintly blue, if that helps.
The tester by the way, is a self made one with components my dad uses for work, he calibrated it and assured me that it is definitely accurate and I didn't use a Schrader valve.
After the belt snapped, the water pump was still driven by the belt, which drives the air pump - at least it seemed so, do you mean that the second belt hasn't got enough tension to drive it properly? I couldn't really tell if it overheated since the gauge is dead. When starting up, it only smokes faintly blue, if that helps.
The tester by the way, is a self made one with components my dad uses for work, he calibrated it and assured me that it is definitely accurate and I didn't use a Schrader valve.
LOL. brain fart on my part.
i haven't seen an air pump attached to one of these cars for quite some time. yes, it should have been fine as long as all was well (no slipping, etc.). that aside, i'm glad i asked because you never know who you're communicating with on the other side of the keyboard - no offense to you meant.
3.5 bar is roughly 50 psi, correct? so taking that at face value, the engine needs a rebuild, but again, i don't see evidence of a broken apex seal in anything you've presented so far. i suppose you could try soaking it for a while and see if my getting some of the carbon out of it might help get some compression back, but outside of that, it looks like a rebuild is in the near future.
Thanks for the answer and sorry for replying so late.
In the meanwhile Iv'e rebuilt the carb and replaced ignition cables which did the job, so it runs now.
Iv'e also decided to not rebuild the 12A for now, since Iv'e just got a wrecked NA FC S4 on the cheap with a 13B swap in intention, which will be an interesting project to say the least.
07-19-19, 03:47 PM
