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Before guessing a vacuum leak for lean symptoms, consider a bad ACV.
Stock 1985 carb'd 12A RX7 GS. Cherry, no mods and completely stock.
Works OK when warming up, once choke goes in most power is lost. Can hardly go up a hill at highway speed. Can hardly press in the accelerator without losing power. All the signs of going lean. Vacuum leak most will say.
Thanks to Sgt Fox for posting the tech service bulletin that mentioned the issue. Notably, when an unusual issue arises, check the service bulletins. This was my first hunch and it proved to be rewarding.
Will say now, before when the choke is engaged, it had far less power than it does engaged now. It merely had more power than when it was disengaged simply because of the extra fuel.
I made a bypass plate for the ACV. Worked like a charm.
Altitude compensator valve.
ACV block-off plate.
ACV block-off plate on the Nikki.
Last edited by phixer; 06-07-18 at 10:13 PM.
Reason: Update title
Hmm, I've never heard the altitude compensator referred to as an ACV. I thought you were talking about the air control and check valve, which we all call the ACV for short.
But yes the alt comp is intimately linked to the primary circuit and any little vacuum leak or other problem leads to a really big running problem. Air bleeds are the number one most overlooked and yet most important part of these carbs, considering that they came form the factory with oversized ones (in my opinion, but it was for the rats nest and vacuum secondaries to work, among other things). Thus any additional unwanted air introduced through a vacuum leak will wreak havoc.
Hmm, I've never heard the altitude compensator referred to as an ACV. I thought you were talking about the air control and check valve, which we all call the ACV for short.
But yes the alt comp is intimately linked to the primary circuit and any little vacuum leak or other problem leads to a really big running problem. Air bleeds are the number one most overlooked and yet most important part of these carbs, considering that they came form the factory with oversized ones (in my opinion, but it was for the rats nest and vacuum secondaries to work, among other things). Thus any additional unwanted air introduced through a vacuum leak will wreak havoc.
I don't seem to have the option to change the title of this thread to a more obvious title. I can see how, A-ltitude C-ompensator V-alve, might not be enough for searching. I made a mistake by using common sense, didn't know the lingo here.
In most forums I've been in, an "air control and check valve" is called an ACCV.
I thought I had the full set of plates but of course the always one missing.
Would you know if someone out there makes them.
Or would you consider making me one ....
I will pay all cost.
Thanks
Elliott Rodriguez
Cell 863-210-1097 abbarod@gmail.com
06-07-18, 10:11 PM
