Idle and Synch Puzzle

[MisterCinders]

Clean and re-oil the pods, clean the plugs, and follow my screw setting suggestions for the pilot circuit. Test and let us know what the plugs say. Remember that the pilot fuel screws (underneath) can be backed out to approx' 3 turns before they are no longer effective. If you still feel the pilot circuit is lean and the less than 1/4 throttle position plug reads indicate the same then it will be necessary to use 17.5 pilot jets and turn the screws back in to something close to factory (3/4 turn) to start.
Re-reading your post #17 it does indicate you're lean. But with the pods oiled properly will be a better test. Let us know what your tests show. Be careful testing the jet needle and mains as this obviously requires some high speed testing.

Is 3/4 turns the factory fuel screw setting? I could not find that spec because of the whole 1978 EPA issue. The only spec I saw was the 1977 which called for 1.75 turns. Ofc, that bike also had different main jets, but that should not matter for the idle circuit.

I'll take a crack at Air Screw 1.75, but where should I start the Fuel Screw - 0.75 or 1.5?

Recall this post:

Fuel Screw - 1.25 turns out (a little higher than the basic 1 turn)
Air screw - 1.5 turns out

I would think with these setting that you are way too rich. The air screw should be about 2x the fuel screw settings.

I'm too rich. I'm too lean. I'm too rich. Too lean.

IT'S CHINATOWN!

[KEITH KRAUSE]

There is no specific setting for the pilot fuel screws.
Generally, they come from the factory about 3/4 to 1 turn out. That's the most common amount. They are set using an emissions analyzer. Sometimes they aren't set the same for each cylinder. It can vary some such as: 3/4, 5/8, 1, 3/4 for example. They may be all the same or different. Why? Because these screws are the fine tuning for the pilot circuit. The pilot jet regulates flow through a hole and the pilot fuel screws adds a little more fuel through a separate hole. Because of differences in each cylinder you need the pilot fuel screw to fine tune. When I say "3/4" it's an approx' amount commonly used. On an old bike that's had the screws disturbed all we can do is pick a starting point that's fairly common.
You test and adjust accordingly. Without a Dyno all we can do is test ride, using the throttle position that's regulated by the jet we're trying to use.
As for the side air screws, they SHOULD have an effect that you can hear if the carbs are operating correctly. They are to be set using the highest rpm method, just like carbs on older cars have a mixture screw. Since you can't hear an rpm difference I'm suggesting that you set them to 1 3/4 as an approx' setting that's also common.
As for rich or lean on your pilot circuit, all I can say is that pipe and pods effect the pilot circuit greatly. They WILL lean it out significantly. If you have a motor that's tuned correctly and has no compression issues then a bike so equipped and using the stock pilot jets is certain to be lean. It's possible that richer pilot fuel screw adjustments MAY be enough to assist the stock pilots so it's worth a try. Test and find out. If not, then you'll need 17.5 pilots and set the screws back to something closer to stock. Again, test and do what the plugs/performance say.
What signs do you look for regarding rich/lean? Depends on the weather, temp, etc. Generally, a cold motor should need moderate choke to start. Warm up about 1 1/2 to 2 minutes at about 2,000 rpm's should allow you to take off. In a few minutes it should be running decent. The idle may pick up 100 to 200 rpm's from stone cold rpm's but hold that after full warm up. You should be able to let the bike idle a minute or so at 1,000 rpm's and then moderately blip the throttle without seeing a puff of dark exhaust. The idle should return without hanging up. It should idle well. Reasonably smooth. When you decelerate the "popping" shouldn't be too much. Decel' from higher rpm's will result in some popping though it's difficult to tell you over the web how much is acceptable. Popping is a lean condition but you have to remember that the carbs are under the leanest condition when the slides are basically closed (very little fuel entering) but the motor is still buzzing. Also, header pipe leaks will cause more popping.
To go on, the pods shouldn't "spit" out. That's a lean condition. But again remember, running the stock jet needle and/or a too small pilot jet can have that effect. Sometimes, you can get a bike jetted fairly well but something minor like a spit now and then may happen. You may find that trying to richen things a bit can lead to worse problems and you just accept minor problems. Whenever you add parts that make more power and change flow, you have to re-tune and sometimes things aren't perfect.
But you should be able to get the bike running well and the plugs running a decent color. That's why you do all the other tuning first and then the jetting last. If you have trouble at least you know it's caused by the jetting.

[MisterCinders]

Here is the latest.

Good news - I managed to get the vacuum port screws out with a little penetrating oil. w00t!

OK news - Compression tests on cylinders 1, 2 and 4 came out at about 110 psi dry. Low, but not terrible.

Not so OK news - Couldn't fit the tester into cylinder 3 because of that PO's botched spark plug insert. The larger compression test fitting would not thread into the expanded hole. So not sure what compression for that cylinder looks like. Will pull the head this winter to sort out that plug hole. Probably do a little valve and ring inspection too.

Bad news - Hooked up the vacuum synch gauge (the MotionPro not Carbtune) and cannot calibrate the damn thing. No matter how far I back out the gauge screws, the liquid shoots out of the thing, preventing calibration. I know the CarbTune is better, but did not learn that until after dropping $100 on the MotionPro. So no vacuum synch for me until I pick up or borrow a better gauge tool, or come up with a solution to make this SynchPro work.

Cleaned and re-oiled the pods.

Upped the main jets to 122.5 and the pilot jets to 17.5.

Set the fuel screws to 1 turn and the air screws to about 1.5 turns. Fiddled with them at idle, but still cannot really detect the RPM changes via sound or tach. Best efforts got me to about 1.75 - 2 turns out on the air screws, but I am not really sure of that.

Will take her out to do some plug tests. Should also have a ColorTune in hand soon. Between the two, I will conquer this bloody pilot circuit mix.

[KEITH KRAUSE]

Sounds good. Let us know how she runs.

[MisterCinders]

Took bike out for short trip. Idle is climbing a bit. Need to dial back the air.

In this colder weather, it's pretty hard to diagnose things or even tell when the bike is warm enough to set the idle.

At the dentist now, but will fine tune air and fuel in the lot and chop plugs when I get home.

[MisterCinders]

Ugh. Got the idle tamed. Did some plug tests. They are all over the.map. Including one that is black and oily. FML.

[KEITH KRAUSE]

Ugh. Got the idle tamed. Did some plug tests. They are all over the.map. Including one that is black and oily. FML.

Oil on the plug isn't good. You can't get good combustion when oil's involved so plug reads (for jetting purposes) are useless. You'll have to repair the oil problem as much as I hate to say it. Sounds like you've been busting it trying to get the bike running well but that's how it is with old bikes. Maybe a valve guide seal but I guess you can get to it when you take the motor apart as you were intending. If you still want to ride as is you may be able to get away with it. If that cylinder completely fouls then you'll have to stop or keep cleaning/replacing that plug to squeeze more miles out of it.
Which plug test result is this? At minimal throttle/putting around (pilot circuit)?

[MisterCinders]

Yes. Just putting around town.

[MisterCinders]

I only have a couple more rides until snow. Then I'll tear into the top end.

[KEITH KRAUSE]

Ugh. Got the idle tamed. Did some plug tests. They are all over the.map. Including one that is black and oily. FML.

I read your latest posts too.
You read my opinion on the oily plug/cylinder. As for the other plug reads being all over the map, the pilot circuit is VERY sensitive to mixture changes and vacuum issues. More so than the jet needle/main circuits. Just hook up a vacuum gauge and watch the vacuum levels move at factory idle and you'll see what I mean. So relatively minor adjustments at the pilot fuel screws may be all you need.
As for final tuning, you need to vacuum synch to get accurate reads about the jetting and THEN fine tune the jetting. You CAN bench synch and test to get a basic idea of how each carb is mixing. If you have the wrong jetting installed then a vacuum synch won't result in good performance. If you believe you're close (no excessively rich or lean readings) after initial testing then vacuum synch and test again. With reasonably uniform vacuum at all cylinders you can fine tune the jetting.
In your case I would also test the performance at 1/3 to 1/2 throttle to be sure the jet needle positions look good. If they should be too light or dark then you'll have to make jet needle adjustments and that requires a new bench/vacuum tool synch each time you disturb the needles on VM carbs.

[KEITH KRAUSE]

And I'm not sure what's going on that's making your carb gauge shoot out mercury. Mercury gauges will spill if you back off the throttle too quickly. If you weren't backing of too quickly then I don't know what's up with your gauge.

[OldVet66]

I never seem to catch up with you Keith. I just wanted you to know that I finally got my carbs dialed in. Nice idle, good power off idle, great low speed manners and a bit of a beast wide opened. Thanks for your initial help. We all know what George can do, but I won't say it in an opened forum.

[MisterCinders]

And I'm not sure what's going on that's making your carb gauge shoot out mercury. Mercury gauges will spill if you back off the throttle too quickly. If you weren't backing of too quickly then I don't know what's up with your gauge.

These aren't mercury gauges. They use some liquid instead. I have a call in to the mfc to get that sorted out.

[MisterCinders]

After some more putting around, I did another plug check.

This beast is running richer than Daddy Warbucks. Plugs are black and sooty, and she was backfiring heartily. She also chugged gas like it was 1972.

Of course, the No. 3 cylinder is a complete mystery, oily and suspect. So I will have to tear into the top end.

As for the other mixture results, I am not that bummed out, because richness I can tackle.

So far, I pulled the carbs and reset the fuel screws to about 3/4 turn. Will try to fine tune that mix for one more ride before the weather craps out on me.

For those keeping score at home, the current specs are:

V&H 4-1 Pipes
K&N Pods
Main Jets 122.5
Pilot Jet 17.5
Fuel Screws 3/4 turn
Air Screws 1.5-1.7 turn (factory says 1.6)

Now I will put together a shopping and task list for the top end work. Time to wreak havoc in the 4-Cylinder Engine Forum with another "Noob" thread.

[Coady]

Hey that 1.6 you've got for the air screws isn't the number of turns out. That's the number of the "air jet". The air screw is often referred to as the Mixture screw" and the number of turns varies depending on the engine number.