Idle and Synch Puzzle

[MisterCinders]

As covered in other threads, I have changed intake o-rings, set the valves, totally rebuilt and bench-synched the carbs, switched to K&N Pods, upped the main jets and am wrestling now with tuning the pilot circuits.

With bike reassembled and a long fuel line to the separated tank, I am struggling with getting the pilot circuit right.

Before I shed that %&^$*ing air box, she was waffling between rich and lean. Now that I have pods in place and the VH 4:1 pipes, I understand the need to compensate for the additional air flow.

Present settings are:

Main Jets - 110s (stock are 100/102.5, and I will likely increase to 120s per earlier suggestions)
Pilot Jets - 15s (stock)
Fuel Screw - 1.25 turns out (a little higher than the basic 1 turn)
Air screw - 1.5 turns out
Needle Clips - one step down (richer) from center slot

Here are the current issues and questions:

Choke

The bike starts with little or no choke. Indeed, it is sensitive to choke. Have I gone too far with my lean worry?

Idle Screw

Screwed all the way in, the bike only idles at about 1,000 RPM. It had a lot more play in the idle screw before. I think I may have bench-synched the throttles too tightly. Will redoing the bench synch bring back more idle screw range? Or do I need to shorten the idle screw spring?

Plugs

With all the back and forth on the carbs, I have not been able to do a real plug chop yet. Three of the plugs are new (recall that the fourth plug works but cannot be changed because of a bad thread expander). Currently, they look pretty dark, but not oily. I think that is from riding it last weekend before these new changes. I am trying to clean the plugs up a bit, so I can get better readings. Can I just use a wire brush and carb cleaner to do this?

Air Screws

I have tried to follow the process on BassCliff's site for setting the air screws, namely, setting the idle low and adjusting the air screw to best idle RPM. I suck at this. The instructions indicate that very slight turns (within 1/4 turn or so) should yield results. I have gone up to about 1 turn and detect no change in RPM. Have I started them too far in perhaps?

Smoke

Previously, I was seeing light wisps of smoke off the cylinder head. They were sporadic but more prevalent when she was running a bit lean. I see them far less now, but the smoke does return occasionally. Inspecting the cylinder head, I found some oil residue, but it was not near any of the seals/gaskets. Not convinced that it is a leak, but I think it is just slop from other work I was doing (e.g., oil splash when a valve shim dropped into place). I have gone over it with a rag to clean off the residue and will look out for any new residue/smoke. What is a good cleanser to use for that?


Tonight, absent other/better ideas ITT, I plan to:

1. Pull carbs and re-synch them to get more idle play;
2. Reconsider putting my air/fuel screw settings back to 1/1.25 (very open to other ideas here);
3. Cleaning the hell out of the plugs to get better readings;
4. Cleaning the cylinder block more to trap any leaks, new residue;
5. Dial in the air screw/idle settings (hopefully);
6. Vacuum synch; and
7. Go get some plug chops.

What did I miss?

[almarconi]

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.

If you can't hear the rpm change, consider getting a colortune to set the idle mixture. You'll be able to see the color in the combustion chamber and make adjustment.

Stock pilots should be fine with your setup. Just make sure the pilot circuit is clean and the fuel level in the bowls is within spec.

Carbs need to be vacuum synced.

[MisterCinders]

I checked the float levels (dry and wet tests). They check out fine.

I have the vacuum synch tool, but need to get the idle sorted before synching the carbs. Without a helping hand on the throttle, I need to set the idle at 2,500 (with a fan over the engine). Can't do that with the current bench synch.

I thought that might be too rich and will reset those screws to lean out the mixture a bit.

[OldVet66]

You are wasting your time. Get a Dynojet stage three kit that has a needle tapered for your setup. Keep in mind that the Dynojet jets are marked a little higher than a Mikuni jet (DJ 132 jets = Mikuni 130's). Z1 lists this set under your year model, but I would double check that. http://www.z1enterprises.com/detail.aspx?ID=4061

[MisterCinders]

There is no Dynojet kit for my bike.

[almarconi]

I have the vacuum synch tool, but need to get the idle sorted before synching the carbs. Without a helping hand on the throttle, I need to set the idle at 2,500 (with a fan over the engine). Can't do that with the current bench synch.

2500 rpm is a bit high, I try to shoot for 1500-1800 rpm. Adjust your baseline idle with the idle adjustment knob, no need to have anyone working the throttle.

Perhaps you could find a more knowledgeable member to help you. I'm sure there are some in the Chicago area that would lend a hand.

[rapidray]

His carbs COME with adjustable needles. You need to start by setting the air screws back to stock. Then tune the mixture screws in or out to get the fastest idle. After that, go after the needle & main tuning. That's where I would start. I do the carb sync with the engine at 2000 rpm so you should be able to go ahead with that. If the carbs are WAY out of sync it can make tuning a nightmare. Sync the carbs and then go back to the mixture screws. After you get it to idle good, check the sync one more time & continue on. Ray.

[almarconi]

You are wasting your time. Get a Dynojet stage three kit that has a needle tapered for your setup. Keep in mind that the Dynojet jets are marked a little higher than a Mikuni jet (DJ 132 jets = Mikuni 130's). Z1 lists this set under your year model, but I would double check that. http://www.z1enterprises.com/detail.aspx?ID=4061

The one you referenced is for CV carbs, his are VM. He can get the carbs dialed in with a main jet change it will just take some patience.

[MisterCinders]

Ugh. I still cannot detect the RPM changes for these airscrews. Sod it, I am getting a ColorTune.

Also found a small oil leak off the valve cover. That probably explains the wisps of smoke I was seeing - oil drips on the exhaust and cylinder heating up and burning off. Guess I will pull the valve cover and check the seals. I put a new gasket on there, but it may need some grease or sealant. v0v

Re-synched (bench) carbs and reset the fuel/air screws to 1 and 2 turns. Idles OK with more range in the idle screw. Hopefully tightening up that valve cover leak will sort out the smoke wisps.

Also noticed a slight pop from the No. 4 pod filter when the bike was warming up. Looked like the pop was air going into that pod. It seemed to occur only once or twice when I first started the bike. Cause for concern?

[OldVet66]

Do it with two people, one watching the tach at idle, and the one doing the adjustments, having a good ear. You will see some very small changes, just go from one carb to the next until you get them as high as possible, waiting a bit between adjustments. When it's right, your idle should sound really nice without any loping, and the pipe temps. real close. The changes might not be more than a needle width. the person watching the tach can tell you which direction is increasing the idle. When I adjusted mine, a Harley mechanic with an excellent ear was adjusting, and he was actually listening to me when I corrected the direction he was going in, watching the tach. It's that close with some carbs. Drive it for a day, and then see how the low speed manners are. If it is not very smooth at 25 to 30MPH, turn the pilot jets a tad counter clockwise maybe 1/8 of a turn. Drive it for several more days and adjust if necessary. It should not affect the idle. I started with my pilot fuel screws at 1 turn out, and ended up between 1 1/8 and 1 1/4 turns out. I'll refine those by putting around at slow speed and adjusting for color when I have time. The Color Tune will not do as well as the above method, but might get you in the ball park. Sorry about the stage three kit, Z1 listed it for your model year, and I didn't check it further. You will get some lean pops at random from the carbs, especially when starting cold, but it's not a concern unless it's consistent.

[MisterCinders]

Cleaned up the valve gasket and sealed it up nice and tight.

Idles well, but I have no ear for the air screws. Will try the ColorTune and OldVet66 method.

Downside is that even with the valve gasket tight, there is still a hint of smoke coming from the head. It trickles out of the No. 2 exhaust head. Not sure what is causing it. Could be the mixture. Could be some other horrific disaster inside?

[Coady]

Downside is that even with the valve gasket tight, there is still a hint of smoke coming from the head. It trickles out of the No. 2 exhaust head. Not sure what is causing it. Could be the mixture. Could be some other horrific disaster inside?

Do you mean the exhaust header pipe?

Could be residual oil from the leaking gasket which will stop after a bit of a run? Or maybe leaky exhaust gasket - but then you would also have smoke out the muffler too.

Don't think it's got anything to do with the mixture.

[MisterCinders]

Do you mean the exhaust header pipe?

Could be residual oil from the leaking gasket which will stop after a bit of a run? Or maybe leaky exhaust gasket - but then you would also have smoke out the muffler too.

Don't think it's got anything to do with the mixture.

The smoke is from the exhaust header pipe, and there is a tiiny amount of smoke in the exhaust as well. Not steady or heavy though. Too dark out to detect the color, but it is not black.

[tkent02]

Idles well, but I have no ear for the air screws.

You don't need an ear, look at the tachometer. You can see tiny changes if you look closely.

[OldVet66]

With my header, I used two gaskets on each pipe, it seems to seal better that way with the stock bolts. I don't know about the 750, but on my 1000, Suzuki put tabs and an extra bolt on the head between 2 and 3 in '79. My '78 leaked there but the '79 motor does not. I expect it is more or less normal.