VENOM VEN-1827, Instruction Manual

Tuning Guide

Tuning Guide

There are three basic areas of adjustment on a gasoline 2 stroke engine:

1.  Carburetor
2.  Spark Plug
3.  Gasoline to Oil Ratio

Carburetor Tuning 

While the engine is running at idle speed you can adjust the Low Speed Needle to set a steady low 
RPM idle. When the engine speed is at its maximum RPM the High Speed Needle is used to adjust 
the optimum top speed performance. The goal is to try to tune the engine until there is smooth transi-
tion from low to high speed and back to idle with out any interruptions. 
To set the High Speed Needle while the engine is running there are two steps.
 

1. 

Once the engine is warmed up set the engine to full open throttle and adjust  

the High Speed Needle until the engine sound is clear and smooth. Now place the  

needle setting to 1/8th to 1/4th turn rich (Counter Clockwise, CCW). Do this within 30  

seconds and allow the engine to return to idle. Monitor the engine temperature during  

this step.

2. 

Step 1 above is done without a load on the engine to get an initial setting. Now run the  

engine in the model and set the throttle to full open. The engine should run smooth and  

with full power. If not, readjust the High Speed Needle until you hear a smooth crisp  

exhaust note. This will be the maximum performance setting for that particular day and  

will require fine tuning depending on climate and location from day to day.

NOTE: Always pay close attention to the engine temperature when tuning on the bench and in normal use.

Maximum Operating Temperature - 250F
Optimal Engine Head Temperature Range - 210-230F max
Maximum Engine Head Water Temperature - 212F

Pro Tuner Tip

Use a small aquarium water pump, extra silicone tubing and a bucket 
of cold tap water to keep the engine and exhaust pipe cool while 
testing and breaking in a new engine. 

The Idle Screw will set the mechanical travel of the carburetor butterfly valve which controls engine 
speed and response. Setting the Idle Screw and the Low Speed Needle together will control the low 
speed idle range of the engine. In a boat application when a clutch is not installed on the engine a 
higher Idle Screw setting is required and it is common for this to be adjusted to the maximum setting. 
Use the Low Speed Needle to make idle speed adjustments in this case.

Factory Needle Settings

High Speed Needle - 1 5/8 turns from closed   

Low Speed Needle - 1 turn from closed

CCW (Counter Clockwise) = Richer mixture 

CW (Clockwise) = Leaner mixture

(Does not apply to the Idle Screw)

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