0-2000 RPM

[bigbore2]

So this engine [84-1100]  runs poorly in that RPM range. as soon as it hits the stock needle, it is fine.  I have gone up one in the pilot from stock, as i believe it is too lean. Spits, pops, will kill when idling, bogs with the throttle rev test. Tries to spit , pop on takeoff unless the revs are higher.  Adj. screw is backed out 4 turns for more fuel. Altitude is 5200 ft.
4 into 1 exhaust,  Unipods.

I am wondering if I go richer on the pilot 2 steps, is there enough adjustment in the screws to adjust it properly if I have gone one step too rich? trying to avoid going one step richer just to find out I needed to go 2 steps.

[copper]

Sounds too me like the pilot circuit is not clean. I presume those have the flat bottom slides in them. Which I don't have much experience with so maybe someone else can chime in. Also if it has 160 airbleed jets a 42.5 pilot would put you in the range of the idle screw adjustment, or a 155 airbleed with 40 pilot.

[Flynt]

my '84 has the 42.5/160 pilot setup at about 1.5 turns out with 15 mains and the aftermarket needles (RPM kits) two steps out.  Stock motor with unipods and RPM 4-1, so that should work for both of us.  I was just on an altitude adventure for the WCR and went up to ~10,000 ft with no issues.

Sounds to me like you're fat down low in general and maybe really badly in the range you mention.  Are the carbs clean and balanced well?

Frank

[bigbore2]

My how time flies. I started this June 1.

Well, after trying 3 different pilot jets and not getting any results on the idle circuit, I finally gave up and took it to my local guy for a diagnosis.  He is telling me the vacuum advance on the CDI box is leaking and is the problem.  Can anyone comment on that?

[oldktmdude]

Disconnect it and plug the vacuum nipple on the intake tube.
                                                                                       Pete.   

[movenon]

I think the vacuum advance is for emissions only.  I am under the impression that it only advances when you let off the throttle. My suggestion is just cap the vacuum port at the manifold and test it.
George

[bigbore2]

Yea, I was thinking if that would work.    If it works like I need it to, perfect solution.

I see no CDI box available anywhere.

[bigbore2]

and that would cause a lean condition?

But only on 1 carb, correct?

[movenon]

Yes a vacuum leak will cause a lean condition in the cylinder that the tap is in.   It is something to correct but I doubt it is causing your problem.  Best guess the problem is in your carbs.  But before you tear into them are they balanced correctly ? Also check your valve clearances.
George

[Firehawk068]

If it bogs when you do the blip/rev test, you are too RICH.
going up a pilot size plus 4-turns out on the mixture screws is way too rich for your altitude.

You need to lean it back out closer to normal.

[bigbore2]

Firehawk- how is yours set up? We are a similiar altitude here as you.

[Firehawk068]

Firehawk- how is yours set up? We are a similiar altitude here as you.

I have the stock 155 air bleed.
I was attempting to run a #40 pilot jet, but I found it too rich. I just recently switched back to the stock #37.5 pilot.
I have my mixture screws 2-1/2 turns out, and it runs perfectly in the lower rpm range.