I have an '85 GSL, runs fine. However I've noticed that if I drive it before is fully warmed up, it seems to have more power, and once it has been running for a while, it seems to loose up to 20% power. I'm far from being a mechanic expert. Anybody knows what could be the cause of this and what can I do to remedy it?

Have you had the motor compression tested?

No. Should I? How's that related to the symptoms? Would I have to go to a Mazda dealer for that?

On Rx7's its nice to know it has good compression.Has the carb been played with?

not since I have it (1 year)

Wierd.You should try posting this thread in the main 1st gen section as well.

https://www.nopistons.com/forums/pub..._DIR#>/dry.png I have no solution, but mine does the same thing. I've always just chalked it up to colder air getting to the motor (lower under-hood temps and the metal on the intake manifold is cold). I'm interested now though, that it might be something wrong.

all i can think is that when the motor warms up, the aluminum and iron are expanding, but if it has overheated, then the seals may be leaking some blowby, just like how piston rings expand and ovalize. Seeing as how it runs great cold (i.e. all metals condensed) that would be a compression issue. If a vacuum wire is crossed, that could be waring the carburetor up, or cooling it down when the air and gas are atomizing, and any extremes there would cause trouble, but likely when cold as well. The only other thing i can think of would be the bearings on the eccentric shaft, when cold, bearings tend to spin and feel smoother, and then warm, the grease inside becomes more like oil, and a worn bearing, or 2, will run rough causing more friction and rob more power. Hope this helps!

I remember my 82 doing the same thing too, but the power loss happened the exact same time the choke turns itself off. Not a gradual thing. It did seem like a 20% power loss to me as well. I used to love driving it until it warmed up, then it was like a light switch, choke went off, and power instantly dropped.,,,,,BB



I am hoping some vacuum leaks I have since addressed will fix it.

dude its your seals. take it down to a machine shop and have em do a compresion test. and most likely it will be the front, its always the front.