Task #31 - Pilot Screw Adjustment - Honda VT750DC ACE Service Interval And Recommended Maintenance Manual

Task #31 - Pilot Screw Adjustment

The carburetors on the ACE have what is called Pilot Screws that set the air/fuel mixture for when the engine
is at idle. These screws are set at the factory and then covered with brass plugs and normally, no adjustment is
necessary on them. However, experience has taught us that a very large number of ACE's were delivered to
customers with these screws incorrectly set and it is highly recommended that every ACE owner does this
procedure to make sure these screws are set correctly. Also, any changes to the exhaust system may require
you to re-adjust the Pilot Screws, such as the Stage 1 mod where the stock baffles are punched or Stage III
where an aftermarket exhaust is used in conjunction with larger main jetting.
The reason why these screws need to be adjusted right is to prevent a condition known as "lean misfire". If
the screws are set too lean (as is often the case for new bikes) the mixture at idle may become too lean and
sometimes it won't completely ignite in the engine. This unburned fuel them collects in the exhaust and ignites
there, causing a backfire. The rider would notice this as rapid "pops" or "bangs" on deceleration, sometimes
called the "Rice Crispy Snap Crackle and Pop". This condition is NOT normal and NOT healthy for the engine. It
creates serious back pressure in the exhaust and can cause damage not only to the exhaust but also the engine
and valves.
Now the service manual has a detailed procedure for setting the Pilot screws that involves making changes to
obtain a specific RPM drop at idle but this requires you to have a shop with an accurate tach and also, you can't
properly adjust the forward cylinder with the air filter housing installed and running the bike without the air
filter is not recommended. So I've created this "simplified" procedure that is more then adequate to meet the
needs of the average ACE owner.
Step 1:
The first step is to remove the air filter housing. We are taking the whole housing off, which is easier then
removing just the filter. Remove the two allen key bolts that secure the back of the housing and then loosen the
screw on the clamp that secures the housing to the air box. Then just pull the housing off.
Caution: After each adjustment, reinstall the air filter before running the bike to test it. The bike will not run
properly under power without the air filter attached.
Service Interval and Recommended Maintenance Manual
Honda VT750CD ACE
65