Hi all, I recently bought a '85 rx7 with the OE nikki carb that sat for roughly 5 years with gas in the tank and Carb. After running 2 cans of seafoam through an almost empty tank I got her to idle well and smooth for the most part. I replaced the fuel pump because the original one was dead. I bought a Carter oe replacement but only got 2psi from it. I couldn't Rev the engine past 3 grand so I bought a higher pressure pump, 8 psi to be exact and two filters, one of which is clear to check to sediment. I have a valve and pressure gauge just before the Carb to regulate it at 3.5psi. The problem is the only thing I can do is WOT to close to red line and idle. Part throttle from 10% to about 85% throttle is nothing but sputtering and that's even from 2psi to 8psi. Please help me. This is driving me crazy.



Thanks in advance

Jeff

 

The early carbs had a return line just past the inlet that took fuel back to the tank. The carb just needed a pound or so to work. The rubber tipped needle had a spring inside and a plunger, so when the car bounced over rough streets the carb would not overflow because the spring gave it a broad range where it could shut off the fuel.



In an Imsa Racing Stock car we installed a piece of center tube (the ink tube) from a Bic pen instead of the spring. If the carb has an internal filter, discard it.



Is there a good accelerator pump stream? The engine should rev up so long as the stream is maintained. If there is none, then you need a rebuild. When you shake the carb you should hear a rattle of the check ***** in the accelerator pump. The piston may have shrunk and be useless.



If there is a nice stream and the engine dies when the stream ends, then transition holes are blocked. Idle and transition holes are beside the down edge of the butterfly, and appear microscopic in size. The idle is good news.



If it runs at high RPM, then it is running on the auxillary (booster) venturis. The tubes that hang down into the chokes (the smallest part of the carb tube).



You need a full rebuild on the carb. A long soak in carb cleaner, and if the transition circuits cannot be cleared out perhaps a new or functioning used carb.



Lynn E. Hanover

 

Thanks for the quick reply Lynn. the accel pump appers to work ok. There's a decent stream from it. I figured it was a blockage in the carb. I just wanted to make sure i was headed in the right direction and it wasn't the rats nest. I will keep posted as soon as i get this carb off and apart.



Jeff

 

Since you can go WOT, but not much else, it might be as simple as clogged jets. This is fairly easy to check, and is probably where I would start.



You can remove the brass plugs on the front/back of the carb, then loosen the jets with the appropriately sized screw driver (just loosen them). Then, take a wooden toothpick and jam that into the jet, and use that to unscrew and remove them. To replace them, just do the reverse. This saves you from having to remove the carb, or pull the top off of it.



If that isn't the problem, then rebuild the carb.

 

I removed one of the brass plugs and there was so much slide in there that I decided to disassemble the Carb. I found about 1/4 to 1/2" of sludge in both float bowls. I cleaned every jet, tube and gally that I could find. Just waiting on gasket kit now.

 

Sounds like you're on the right track. While you're waiting for that gasket kit you can read up on the carb, and the rebuild process. There's a butt load of info at Sterling's site: www.sterlingmetalworks.com There is also a section for tuning the idle, which you'll probably be needing once you get the carby put back together.



Best of luck....

 

Thanx guys for the hep/guidence. She runs great. Only issue now is the fuel tank has a LOT of rust in it. Like cleaning the fuel filter every trip I make. I live in Annapolis MD an have no idea who can clean this thing. Any ideas on places to go?



Jeff

 

if it's that bad then i'd be worried about holes rotting through and get another tank if you can find one.

 

Hey, I live in Baltimore. WE should meet up sometime. I do know for a fact that Crazy rays off rout one north of Laurel has a 85 12A sittin there. Ive pulled off a couple of parts from it. You could grab that tank

 

if the car's been sitting for quite awhile (especially in new england) the tank is probably going to be just as bad. he can keep his current tank in there though so he can still drive it while he gets the other one cleaned if it's not in too bad of shape