How can I set gas/air mix screw? - Motorcycles

Carb?
Each barrel will have its own mixture screw.
with engine running, slowly back out. Rpm should drop. Slowly screw in. Rpm should increase, then drop. Back out to peak rpm then another 1/3 turn. Do screw for each barrel.

Overheating is usually caused by too lean fuel mix (too much air, not enough gas). Check the low and high speed mix screws. Normally about 1 1/2 turns in from bottom. But you should check the manual to be exact. See diagram part #31. Also could be float set too low.

try closing the idle mix screw on your carb.

Hi
General advice aplicable for all gas powered chain saws;
Clean air filter regularly.
-Adjust spark plug gap (very important). A faulty gap will either cause poor spark or a overloaded and damaged spark plug coil.
-Use correct good quality spark plug
-Use correct oil/fuel mix ratio and correct oil.
-Do not use old premixed fuel if you can avoid it.

Carburator adjustment;
-idle speed setting screw should be set so that the saw idles well, without engaging the chain. If you normally have to press the gas lever to be able to start it coul indicate a to low seting. Clockwise will increase idle speed. This screw is found near the carburator and is slightly larger the the two adjusment screws.
- fuel-air mixture screws can be set to standard factory setting as a start. Normally there are 2 screws labeled L and H, for Hi and Low rpm band adjustments. Factory setting are usually 3/4 turn out(anti clockwise) from fully closed setting for both (clockwise to closed position).
Experiment with adjustments by 1/8 increments at the time. Anti clockwise turning will increase fuel to air ratio and opposite. Warm weather will require a slightly leaner mix and cold weather will reqire a slightly richer mix(more fuel). Low rpm setting only serves the idling performance. The Hi rpm setting can be evaluated by removing the spark imediately after running at full load for a period. The spark plug should be dry, and be lightly brownish at the electrodes. White-ish color indicates low fuel to air mix, and this causes too high combustion temperature. A black colour indicates a too high fuel to air mix ratio, and it causes carbon build up on the plug.

If you still have starting problems, cylinder/piston compression is the next to check for. This is a more extensive job and should best be left to professionals, unless you are very skilled and have access to special tools required. Compression on modern saws are very delicately balance, so the slightest damage to either the rings, piston or cylinder can cause problems. Is is not alwas worth to replace the cylinder and piston kit, so compare prices and ask for advice at your dealer.

I hope this helps you.

Lightly seat both screws then open each of them one and one half turns. This is the factory setting for Japanese bikes. Clean the air filter, install a new spark plug, I assume the Sym has a two stroke engine, mix the gas ans oil 32 to 1. That equals 4 ounces of two stroke engine oil per gallon of gas. NEVER use motor oil, only two stroke engine oil. Also, tighten all carb fittings such as mount bolts and clamps. Replace any rubber fittings if you see cracks. A cracked manifold will let air into the mixture which leans the mix and makes the idle rev upward.

what gas mix are ya running 40:1 or 50:1

Hello there:
Please follow these very easy steps and this should help you
Instructions Things You'll Need:

• Gas Ranges
• Screwdriver Sets

1. Step 1 Find the tube that feeds the burner. There's a burner air adjustment on it that mixes the air and gas.
   
2. Step 2 Look to see what type of burner air adjustment you have: It will either be a barrel-shaped chamber or triangle-shaped with a cover plate.
   
3. Step 3 Loosen the air-shutter screw on the barrel-shaped type. This screw is on the end of the barrel closest to the burner.
   
4. Step 4 Open the shutter on the barrel-shaped type by turning it counterclockwise; close it by turning it clockwise. Opening it will add more air, which will make the flame higher; closing it will reduce the air in the mix and lower the flame.
   
5. Step 5 Loosen the screw holding the plate on the triangle-shaped burner air adjustment. Don't remove the screw - it just needs to be loose enough to move the plate.
   
6. Step 6 Move the plate so that the opening is either more open or more closed. More open will make the flame higher whereas more closed will lower the flame.
   
7. Hope this is very helpful for you
   
8. Best regards Michael
   

Only use premium unleaded gas. No Ethanol blends.
LIGHTLY seat the air screw and the throttle screw. Now open up each of them one and one half turns. This is the stock setting.

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