Mazda12AGS

I have an 84 with a 12A. It has a racing beat header and presilencer. I also removed the rats nest and rebuilt the carb a week ago. I have replaced the fuel filter. It still dies off in higher RPM's. It seems quick up untill then, but then it nose dives. I got beat by my brothers 94 1.5 civic the other day. I am running the stock muffler right now and it has an exhaust leak about mid way back. Could these be part of the problem. I also think it is running a little rich. Does anyone have any suggestions of what the problem might be. I have searched and searched and found nothing.




Thanks,
Chris

cdrad51

do a fuel pump volume and pressure test.

Kentetsu

Yep, that's the place to start. If that checks out, you might have to rebuild the carb. If your secondary jets are clogged, you won't be able to get enough fuel into the carb at higher rpms to maintain power.

YapaKanichi

I wouldn't think he would have to rebuild the whole carb to clean out the jets would he?

Kentetsu

Probably not, but as long as he's in there....

andre sinclair

iTrader: (36)

Time for a upgrade...13B

Mazda12AGS

thanks i will perform the fuel pump volume test today and get back with the results. I thought the carb was the problem, but i rebuilt it a week ago and it still does it.

skrewloose78

have you checked your timing?

cdrad51

and how would timing problems cause those symptoms?

boostedHULK

iTrader: (1)

it's a fuel problem. any results on that pump test yet?

boostedHULK

iTrader: (1)

where did you get the rebuild kit? just curious.

Kentetsu

Good point, and easy enough to check. You aren't hearing any weird noises at high rpms, are you? Either way, throw a light on there and see where you're at.

Mazda12AGS

I didn't get a chance to check the pump today. It is not making any noises at high RPMs. I will also check the timing. I got the carb rebuild kit at advance.

Kentetsu

When you rebuilt the carb, did you remove the jets (the ones where you go through the sight window to remove them)? That's where my blockage was, resulting in high rpm power loss.

cdrad51

Also make sure your secondaries are working.

Mazda12AGS

Does anyone have any comments on switching the mechcanical secondaries. I have been thinking about switching it but i was wondering if it helped out that much.

YapaKanichi

is your vacuum advance hooked up?

Sterling

I put money on you accidently having swapped your primary and secondary fuel jets.

Mazda12AGS

i only took the jets out one at a time and put them back in as soon as i was done cleaning them, so i wouldn't do that

cdrad51

You can switch them. That's one way to make sure they work, as you can see them open , as opposed to the vacuum secundaries, which you can't see open.