M_D_H

Recently rebuilt my carb. Ya'll know what's coming. 1985 12a S nikki bone stock, all emissions currently present. (Except gutted cats)

I've got a bit of a strange one, didn't see anyone exactly replicating this issue with brief searches.

I've got my idle dialed in perfect. 7-800 rpm steady idle, choke mechanism works properly but is barely needed even in the chilly morning.
AP works well, and gets me accelerating very steady and smoothly.
Up to about 2000 rpm everything is good, but from about 1800-4000 rpm she spits and sputters and I lose the majority of my power. Have to really mash the throttle to about 50% to keep the car running at 40mph.
With the throttle past 50%, and the vacuum secondaries opening up, after 4000 rpm everything clears up and she shoots past 7500 rpm no problem lickity split.
Full throttle works great, good power, and the idle is perfect all the time.
Also on cold starts first thing in the morning, with no warmup time other than to build oil pressure, everything works perfectly for about 30 seconds-2 minutes. Smooth power from 700-5000 rpm, no hesitations or stumbles. After that short time, the stumbles come back.

Coils are new msd high vibration. Cap and rotor are new, wires are new, plugs are 100 miles old.

Plugs are VERY fouled out, after only 100 miles. After a plug cleaning, the hesitations do not clear up.

My exhaust is stock, but I have hollowed out the cats until I get a new exhaust made up.


My interpretation is thus- Idle mixture is great, but primaries are flooding badly. More throttle input allows in more air and brings the a/f ratio closer, and thats why it runs a bit better with more throttle. 50%-100% throttle works better because after the secondaries open, the extra air coming in further improves the a/f ratio.
Does this sound right? Are my primaries incredibly rich?

Possibly something to do with the richer solenoid?

New carb rebuilt kit on the way, and an intake gasket/orings/freeze plugs to fix the intake coolant leak. I'll be digging into this in about 3 or 4 days when the parts arrive, but wanted to get all the input I could beforehand.

GSLSEforme

How about year,kind of carb,what did you do to the carb...

M_D_H

Oh my god I've been so wrapped up in this I momentarily forgot that everyone else doesn't know all the details.

1985 12a S Nikki. Completely 100% bone stock. All emissions equipment present.

Carburetor was completely disassembled, cleaned thoroughly, all lines and passages cleared. Float levels normalized, all new gaskets. Floats needles and seats all original. All check ***** and weights are replaced to their factory locations. Fuel system tested, fresh gas, fresh filter.

GSLSEforme

What is float level in windows? Are you sure all jets back in original positions? Original reason for attacking the carb?

M_D_H

Float levels are smack in the middle of the view windows. Probably had to take the carb hat off 10 times to get them just right, but it's perfect now. Jets are all back in the correct positions.
used an organizer with labeled slots and copious pictures. Missed a check ball originally but found it and replaced it before everything was together.

M_D_H

Original reason for the rebuild was the heavy buildup of scale. Secondaries were completely clogged. 180k miles unopened motor, unopened carb

GSLSEforme

Can you take video of engine running with air cleaner lid off? Do you have any fuel dribbling into either set of venturies? Does the bowl vent solenoid work,can you hear it click when you turn the key on,have you tried removing it?
What plugs are you running,condition?
Have you checked for good quality leading/trailing spark?
Is your ignition timing set properly,do both vacuum advance canisters work?
What is battery voltage with car running,what is voltage at both ignition coil primary positive terminals with engine running?

You may have a weak spark condition and you're thinking problem is fuel related?

M_D_H

That's some great suggestions. I'll pull out the multimeter tomorrow and check some voltages. I'll get some video too, been meaning to do that.

ray green

iTrader: (14)

It sounds like it might be flooding.

I'd watch the fuel levels in the bowls very carefully, the float valve needles may be leaking.

Sometimes they leak, sometimes they don't, or maybe only one leaks at a time causing temporary flooding.

Mike's suggestion of taking the top off the air cleaner and watching for excess fuel in the venturis is a good way to check on this.

t_g_farrell

iTrader: (1)

If you used the new needles and seats put the old ones back in. New ones are crap and cause issues like this.

M_D_H

Original needles and seats. Read that new ones are crap, so didn't use them.

Here's some videos.

Idling:
Overview of both primaries and secondaries, idling and accel, completely cold start in the morning:
View of primaries, idling and accel:
Secondaries, idling and accel:
Tach view, various rpms:
Gonna check my ignition system and recheck my float levels now.

M_D_H

This is my first carb to work on, and I've never had the pleasure of driving another rotary, other than a gsl-se test drive one time for about 5 minutes, so it's hard to know what is normal, and what I should be looking for.

Really thankful to have so many people here that have so much knowledge and suggestions while I work through this. Rebuilding the carb was pretty amazing, I was scared of losing parts or doing something wrong for a while, but once I got into it it helped me learn more about how the whole system works and why, and it's pretty great.

GSLSEforme

Ignition timing sounds retarded. Check basic Leading/trailing ignition timing. Check centrifugal advance. Check vacuum advance.
What kind/condition spark plugs?
What is happening with float levels while revving,do they stay constant?

M_D_H

Alright. Checked and adjusted timing, checked centrifugal and vacuum advance. Timing was a little off, but adjustment didn't fix the problem. Centrifugal and vacuum advance seem to be working as intended.

I don't trust my cheapo timing light though, think I'll pick up a digital one next week and check my adjustments again.

Also planning to yank the distributor and check the internals just in case, and test the ignitors. Changing oil and plugs tomorrow.

Here's a driving video after the timing changes. In the video, I hold a constant throttle input of approximately 50% from 1000-7500 rpm, so its easy to see the areas where the issue is occurring.

When the rebuild parts arrive, I'll be proceeding with another carb rebuild and a new intake gasket just as a precautionary measure. Not sure if I'm dealing with a fueling or ignition issue anymore.

rxtasy3

iTrader: (2)

is it only running on one rotor?

M_D_H

Doesn't feel like running on one rotor, but I'll be going to a rotary shop soon to have a proper compression test done.

KansasCityREPU

iTrader: (9)

I see GSLSEforme asked about spark but don't see a reply from OP.

M_D_H

Ah yes. Testing spark quality and changing plugs tomorrow

Benjamin4456

I haven't had a chance to watch the videos but it sounds like you're making good progress, or at least narrowing down what it could be. I'm still wondering about a possible accidental jet swap by the symptoms - perhaps the main fuel jets were switched accidentally? Just a thought. How many turns out is the mixture adjustment screw?

M_D_H

I'm not so sure it's rich anymore as much an ignition issue or.. Shudder, low compression. However, I'll be pulling the carb apart to ease my mind as soon as the rebuild kit arrives wednesday. Gotta do the intake gasket anyway.
Compression test scheduled for next monday at the local rotary shop.

Idle mixture screw is about 4 ish turns out, I think? Might go check later, but I hesistate to mess with the mixture too much anymore now that its mostly dialed in.

Also had a suggestion that my secondaries might not be closing fully, so that's on the list to get checked during the rebuild.

Benjamin4456

Hmm, ok. Interested to see what it ends up being.

About 4 turns is fine, I was just wondering if it was closer to 2 as that may have been indicative of a jet flip. ~3.5 is considered the starting point for a factory carb iirc.

If your secondaries were not closing fully, one, you'd have a hard time getting it to idle nicely, and two, I'm fairly certain that wouldn't cause it to run rich. Although, if like you now think, it's not running rich and has some other issue, perhaps they are, though I doubt it. Idle would have more problems than it seems to (still haven't watched the videos though).

Edit: I'll try and what the videos when I get home today.

M_D_H

Well guys, mystery is solved.

For future reference, the jets inside the float bowl, 92 and 160, were flipped. Led to an extremely rich primary circuit, but rather lean secondary circuit, but the numbers balanced out well enough that it idled with a lope and ran well when the secondaries kicked in.

I had the compression tested and everything checked out. One side seal leaking a little bit of pressure but otherwise pretty decent numbers all the way around, especially for 179k miles on an unopened motor.

I ended up rebuilding my OMP, carb, replacing most of the remainder of vacuum lines, and replacing the leaking intake gasket and orings.

Rebuilt the carb and took what I thought was extreme care in labeling and sorting all the parts, but I ended up swapping some of the only parts in the entire carburetor that CAN be swapped.

On the bright side, I could rebuild this carb in my sleep now, so there's that.

Anyway, I got everything sorted, and spent about 20 minutes dialing in the idle speed and mixture, and took her on a 50 mile cruise around the city... I have no words. So much fun, I was grinning from ear to ear blasting around town. No more panicking accelerating from stop lights, or horrible vibrations from the shaking engine, and no more 4 miles per gallon, and best of all I can cruise in any gear now! Smooth and strong from idle to redline. Everything I hope it would be.

Thanks to everyone that helped and gave advice.

I may try to write up some tutorials while its fresh in my mind with some notated pictures, eventually. It would have helped me a few months ago to have some really dead nuts clear pictures to follow. I've got to get some video of driving the 7, too.

Edit: I'd like to point out, the reason I didn't catch these jets being flipped earlier, is that I seriously forgot they existed... I had the carb hat off many times and quadruple checked the locations of everything and was sure I had it right... But forgot aaaaaallllll about the little jets hiding in the float bowls. Plus they look nearly identical to each other, unlike the jets on top that all are either different shapes of colors. All's well that ends well. Not too terrible for my first carb job, honestly. Could have been worse in many ways. And the next ones will be easier.