How do I adjust seadoo RFI mixture?

fouling plugs means carbon across the electrode gap or carbon build up down the sides of the ceramic insulation allowing the current to short out rather than spark
,If that is what is happening , it is too rich or burning oil or the auto oil injector for the oil/fuel mixture- as in 2 stroke- is allowing excessive oil into the mixture
you have several options
have that mixture properly adjusted using less oil
check the carby float levels
use multipoint plugs ( same as is used on outboard engines and rotary engines)
or overhaul the engine with new rings and bearings

Weak Spark, worn piston rings(Burning oil/compression issues), lack of compression, wrong spark plugs, incorrect spark plug gap, engine not reaching operating temperature (Due to short use), carb. is running rich (May need adjusting), dirty air filter (Causing carb. to choke and run rich). Bad gas
All these symptoms could lead up to fouling plugs.
Hope This Helps.

Fouling of the spark plug makes the exhaust extremely hot due to the burning of the fuel mixture inside the exhaust pipe and the spark plug end turn to black, fouling of the spark plug may be due to too rich fuel mixture check the correct setting of the air valve.

Here's my $.02. Your plugs are getting fouled cause the bike is running rich. Adjust the air/fuel mixture screw to make it run leaner.

Fouled plugs are an indication of a too rich air/fuel mixture. You need either more air (clean air filter) or less gas (adjust main jet needle position lower) or (smaller jet).

If plug is sooty, this is due to mixture being too rich. This can be caused by dirty air filter,
Clean or replace the filter and if this doesn't improve the situation, adjust the carburettor to ensure the mixture isn't too rich.The procedure for this is to turn the adjustment screw (if there is one present) slowly anticlockwise until engine almost cuts out, then turn the screw clockwise until engine almost cuts out. Set the screw halfway between these two positions.
If the plug is black and oily this could be due to engine bore wear and oil getting up by the piston into the cylinder (in the case of a 4 stroke engine) or due to an excess of 2 stroke oil in gas (in the case of a 2 stroke engine) Gas / Oil mix should be in the ratio of 50:1

Hello,

There are four reasons for fouled spark plugs, 1, You have a resticted air flow ( dirty air filter, or partially engaged choke), so the mixture is rich all the time fouling tghe plugs. 2, You have a poor quality fuel ( old, stale ), and it wont combust/burn hot enough, then fouling the plugs. 3, You might have a piston ring failure causing engine oil to be left on the cylinder wall instead of being wiped back down, and then burning as part of the combustion process. Thus burning and causingg a rich condition again, and fouling the plugs. Then finally number 4, low engine compression. This is again caused by worn cylinder walls and worn piston rings, causing compressed air/fuel mixture to leak past the rings into the crankcase, and when the fuel/air mixture is compressed then ignited, some of the air needed to ignite the fuel has escaped, and thus a rich condition again, fouling the plugs.


Determining which of the Four are causing you fouling is your next step.

Hope this helps

If you need further help, I’m available over the phone at https://www.6ya.com/expert/matt_8dbc24bf722649ac

Basics to check:
1) Spark plug - brown or dark brown - OK
a) is it carbon or fuel fouled
b) is there spark

2) Muffler remove for inspection
a) exhaust screen clean or plugged
b) inspect cylinder wall/piston as the flywheel is slowly rotated
3) Check cylinder compression


Overfuel or 'rich' condition
Basics to check:
1) Spark plug - brown or dark brown - OK
a) is it carbon or fuel fouled
b) is there spark

2) Muffler remove for inspection
a) exhaust screen clean or plugged
b) inspect cylinder wall/piston as the flywheel is slowly rotated
3) Check Air filter for fuel saturation
4) Allow engine to run for 5 minutes remove to excess fuel from muffler
5) Fuel mixture ratio: Make sure the oil mix is per your manufactures recommendations
6) If after the above the engine is still smoking and blubbering:
Adjust carb mixture screws to a 'less rich' setting
*NOTE: only move mixture screws 1/8 of a turn at a time,
and try operation before any more adjustment

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae

There are only two adjustments to make on your carburetor; the idle speed, and the idle mixture adjustment. If the spark plug fouls frequently, first make sure you are using the correct spark plug. Your 1997 YZ125 uses an NGKB9EGV. Then be sure you are using the recommended two stroke oil, mixed to the proper ratio, in the fuel. Also make sure the air filter is not excessively soiled.
With all of the above confirmed and corrected, start the bike and run until the engine is up to normal temperature. Adjust the idle mixture screw to attain the fastest idle and best throttle response. Then adjust the idle speed.
If you are still fouling the spark plug, verify that the carburetor has the correct size jets by consulting your owner's manual. Keep in mind that if you are operating your bike at an altitude higher than about 6,000 feet above sea level, the stock jetting may be too rich. Down-size the main jet in small increments until satisfactory operation and the correct spark plug color is obtained.