2stroke1971

85, 12a....stock nikki, rebuilt....

Since we got the car, its had a stumble off idle...and it idles sort of rough, and if you pull off normally, it sputters just a bit would even cut out..usually at a stop light, I will keep my big toe on the gas pedal and flutter it a bit before letting the clutch out and gassing it....
Runs smoothly once you pull off and all the way up.

When I rebuilt the carb, it seemed to get a little better, and I keep adjusting the accelerator pump to come on sooner, almost maxed out, but still it happens.


Starting to wonder if it could be an ignition issue...does that make sense? Like with the higher RPMs, the spark is adequate but not at or just off idle?

Ive never had a timing light on it.....
Then I wonder if its just a worn out motor, it does have 220,000 miles on it, for all I know original seals, etc....It does start easily though....
When we got it, it was blowing some coolant out the exhaust but some alumaseal in the radiator has kept that gone for over a year now.

Any suggestions on where to look next would be greatly appreciated!

Cookboy

iTrader: (10)

When I rebuilt my carb I had the same issue, I took it apart and sprayed cleaner through every passage I could find. The transition circuit was it, I later found. I don't really know all the nomenclature.
It cleared up the issue. That said, any of the direct fire ignition mods will improve idle noticeably.

2stroke1971

come to think of it, I had an old boat that was behaving the same way, it was a Volvo B21 engine...re did the alternator wires and put a new coil in and it got better. Thought about a pair of accel coils, but I think they are only rates to 5000 rmps or something....

2stroke1971

of course, with the accel, that 5000 rpms is probably assuming 8 cylinders...so it would keep up with the three chambers I bet.

Jeff20B

iTrader: (13)

You're looking in the wrong place for improvement. It's gotta be the carb. What mods are already done to the carb? Is it stripped already? Time to get familar with the Nikki. It's a very rewarding hobby.

2stroke1971

No mods....I rebuilt it about 2 years ago...it was driven every day for about a year after that, since I took it over so to speak, its been driven just a couple times a month, as Ive been working on the car here and there....I had done the mechanical secondaries for a while, but hated the brief woof inbetween, and besides, my diaphragm still works...so I reversed it.

Jeff20B

iTrader: (13)

Ah, I see. I just tested and tuned two hogged out nikkis with mech secs last week that didn't have a flat spot in between. How? I did the Sterling accel pump mod. I let the revs climb to 4k, then floored it and had instant power all the way up to redline. This is how these cars should have been from the factory.

Like I said, a very rewarding hobby. It just takes some more work.

Oh, something else to add. One of the carbs had a very small lean spot right off idle. The accel pump nut just needed a little 180 degree turn. That got rid of most of it. The carbs are about 80% tuned now.

2stroke1971

I was playing with it a bit last night....turned the pump adjusting nut all the way in...seemed to help....in any case, looking down the throat of the carb, the accel pump is certainly working.....

You know what else...the distributor it all the way clockwise....I turned it the other way and the idle slowed down, and the woof that happens right when you open the throttle got worse...progressively so across the range to the left, and then better to the right.

Seems to me if I could get the thing a little further clockwise it, the flame out might be gone. I know the previous owner had replaced the distributor, after having trouble with the ignitors...wonder if he missed a tooth. I gotta get a light on it.

2stroke1971

Really though, it idles sort of rough...if I get anywhere near low enough as far as where its supposed to idle, it would just cut out. hovers around 12-1300 now....and the lower the idle, the more dramatic the woof is when applying some throttle.

2000 and above is smooth as silk though....if you feather the clutch and light it up from a stop, the thing will burn the tires off. I wonder if it does not have a bad seal or two, or its just hurting from having so many miles....what really sucks is that the rebuild parts cost so much....Ive seen much nicer FBs go by on craigslist for just a tad more than the rebuild kits....

Jeff20B

iTrader: (13)

My first setup was a rotary truck and it could barely get out of its own way. Now I have a hogged out Nikki ready to go in, or a Camden. More testing of the actual intake manifold I'll be using with the nikki is needed before anything else is decided on. The point is your first setup is supposed to suck. It's the best teacher.

Sounds like your setup has an overlooked vacuum leak or something. Also learn how to static time the engine. It's easy to be one tooth off.