Idle Speed Adjustment

Another small Pictorial from me

Pictorial - Idle Speed Adjustment.

[ADMIN EDIT: Somehow this pictorial file is no longer available]

Do you have to remove rubber piece to adjust?

No, you don't have to remove anything

If you don't want to spend a lot of money on a vacuum gauge, you can construct this manometer for about $10.

The 1" x 2" lumber and the clear 1/8" or 3/16" tubing from a home improvement store. I got the 3/16" vacuum restrictors from Advance Auto Parts. I used 3 wire ties to hold the tubing to the lumber.

Any oil will work for the fluid. I used red automatic transmission fluid. You want to add just enough to get the fluid to fill the tubing up to the center wire tie.

You follow the procedure that Blackfly has detailed to connect this manometer. The fluid will be pulled higher on the side with the higher vacuum. Adjust the two air screws until the level is the same on both sides of the manometer. The restrictors slow the movement of the oil.

I might add that you always adjust the higher cylinder vacuum reading down to the lower vacuum reading. Don't try to bring the lower reading up to the higher. The reason is that the idle speed will drop if you adjust to a higher vacuum and your readings aren't as accurate if the idle is below spec. The more the throttle is closed, the lower the idle, and the higher the vacuum.

Thank you for the DIY manometer pictorial Mr Doles.

I didn't see any manometer info on Blackfly's link, only info regarding the idle adjustment screw. But maybe I missed something somewhere.

Is it that the two vacuum lines are directly connected to the Throttle Body vacuum ports? And if so, do you then plug up the disconnected vacuum lines?

How would you adjust the two Air Screws if you only have access to one vacuum gauge?

Tim

The vacuum line from each cylinder is connected to a tee fitting. The third hose connected to the tee is from the fuel injection manifold pressure sensor. Blackfly disconnected a vacuum line from one of the cylinders instead of using the vacuum ports. It doesn't matter which vacuum line you disconnect. He cautioned that you must leave the vacuum line to the fuel injection connected. You would connect the two ends of this manometer in series with whichever vacuum line that you disconnected.

In other words, when you pull one of the cylinder vacuum lines off, push one end of the manometer tubing onto that barb fitting. You would then connect the other end of the manometer to the vacuum hose that you removed using a tubing or the vacuum restrictor.

After removal and cleaning of the throttle body, I believe the service manual suggests turning both the air screws all the way in and then back them out 1 and 1/2 turn for a starting point.

If the engine is running OK and you just want to check the balance you can just hook up the manometer and see how close to balanced they are without disturbing the air screws.

Both air screws will affect the vacuum balance. You just want to turn one or the other just a bit to get the liquid in the manometer to be the same level on both sides of the column.

The difference in liquid height on my Honda Shadow was about 3 inches of liquid to start and after the adjustment, it was less than one inch difference. The throttle response was better and the idle was smoother after the synchronize adjustment.

I apologize for linking the manometer threads to the idle adjustment presentation that Blackfly posted. It was meant for the air screw adjustment presentation that Blackfly also posted in this category.

It doesn't pay to get in a hurry.