My 85 GS has been having some issues, and I am trying to narrow down what it might be. It’s had a rats nest delete, and has a weber 48 IDA on it.

The main issues:

1# It doesn’t really want to idle below 1200 rpm, I have messed with the idle speed screw and it just wants to die if it goes any lower than that. (Supposedly the timing was done before I bought it but who knows if it’s right) I also put a brand new set of NKG spark plugs in it but I haven’t checked the wires to see if they are good (they look relatively new and are nkg also) It also has a new fuel filter.

2# Once you get rolling she drives pretty good, until you hit 3000 rpm, then it hesitates and sputters like it’s not getting fuel or is going way too lean until you give it a little more gas and get over 3000 then it starts acting normal again.

Any help would be appreciated.

 

welcome to the board.

first, you'll want to verify the timing is where it should be.
next, check for vacuum leaks. they can be tricky so be thorough.

your second problem sounds like something going squirrely with the transition from idle to main circuit. when the vacuum leak is fixed and its idling properly, if it's still acting weird on transition then you'll have to start tuning. you're probably going to want to get a notebook and pull the carburetor off at some point to see what you have right now to document a starting point.

some links:
https://www.rx7club.com/1st-generati...t-12a-1160848/

https://www.rx7club.com/1st-gen-gene...paper-1145099/

 

I’m back, I noticed that the omp vacuum lines were worse for wear and I know the omp was rough too so I have been running a 1 oz to gallon premix ratio. So I just decided to block off the omp until I can rebuild it or something and cap the vacuum ports.

(I don’t know if I mentioned that after driving it and letting it warm up, it wouldn’t wanna idle at all.)

But now it idles, and it even will idle down to 1k rpm. I still haven’t checked the timing, but I drove it and the 3k rpm sputter seemed to drastically improve. It still seems to have a slight issue with that, but it’s slight. It probably needs me to go over it for a good tune. So it’s doing a lot better.

I’ll update when I have time to work on it some more, but my time is being consumed by the fact I had jury duty yesterday, work, my miata which I am doing a clutch on, and a vacation next week (which I can hopefully relax on lol).

 

It sounds like a fuel issue to me. How new is the fuel filter? It may be worth removing and cutting open to see how much, if any sediment is in the filter. The tank could have gunk in it that's causing a reduction in fuel pressure. As the gunk gets sucked up, it works it's way into the fuel filter and ultimately into the carb, plugging the jets and settling in the float bowls. It's at least a good starting point.

 

The fuel filter is replaced very regularly and I use clear ones so I can see if there’s any gunk and there isn’t any I can see. I was thinking it nay be an issue with the emulsion tubes.

 

I though I had replied to this before but just in case, I wanted to say thanks for the advice. I think I solved a vacuum leak and I appreciated the links on the carb you sent me as well. I have been doing lots more research on the tuning, but that white page was very helpful.

 

no problem. glad to help and happy to hear that you're working through it.