Question about 2003 Yamaha YZ 250 F

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My son's YZ125 was running great and now we can't get it to kick start. He is new to this bike so I am wondering if the bike ran rich and fouled the plug.

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U fouled your plug ur son cant be a ***** on that bike open it up

Posted on Dec 12, 2011

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Pull the plug and then kick it over if there is a spark then it's not the plug

Posted on Jun 04, 2009

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WHY IS MY SUZUKI RM125 MOTERCROSS BIKE SPITING AND SPUTERING WHILE TRY TO GAIN SPEED THROUGH THE GEARS


I would check your spark plug to see if fouled, if so clean with wire brush and carburetor cleaner or replace plug. You think it is possible the fuel mix got higher than 40 to 1? If mix is too high it can cause the bike to run lean.Usually if mix is off you will have some blueish grey smoke coming out of exhaust.

Sep 22, 2015 | Suzuki Motorcycles

1 Answer

I have a ktm 250 sx 2-stroke. It has a new piston and new cylinder. bike ran great before it needed the repairs. Cranks on first kick. Run good but it leaks the pre-mix everytime i ride it and it won'


Where is it leaking from? If its leaking, that's more than likely why it doesn't run right, the fuel/air mixture is off. Also, I wouldn't continue to run it until the leak is fixed as it may damage the motor from not lubricating properly.

Aug 14, 2013 | Motorcycles

1 Answer

My 04 harley night train keeps fouling plugs left and right i richened the mixture with a 52 pilot jet. ran fine for awhile then fouled again could this be an electrical problem?


A #52 pilot is a bit on the rich side in my opinion. I usually use either a #48 or a #50 but each machine is a bit different and your location effects it as well. I wouldn't think an electical problem is the cause or you'd notice erratic engine performance prior to the plugs fouling such as misfiring, coughing or spitting back through the carb. How long are you running the enricher when cold starting the engine? This is the biggest reason I see for fouling plugs. People will start the engine with the enricher and allow the engine to run while they put their riding gear on, sometimes five minutes at full enrichement. This will foul the plugs quickly. The enricher uses a different fuel circuit than the normal running operation uses. It draws fuel directly from the float bowl and it's a very rich mixture. Try starting the bike with the enricher and once you can keep the engine running with the throttle, turn the enricher off. Use the throttle tension knob underneath the throttle to hold the throttle open enough to keep the engine running until it warms up.

Good Luck
Steve

Sep 03, 2011 | Harley Davidson FXSTB Night Train...

1 Answer

So i was wondering i changed the spark plug on my bike including all oils, also included a costume yamaha fuel filter bike started fine rode it. Than second time i started it i forgot to turn gas line...


hi, the problem is that your bike is running to rich( to much fuel from carb to engine) so its the un-burned fuel mix that your seeing on your plug and thats fouling it out......now this is caused by either to rich of fuel mixture(you should be mixing 32:1) or you need to rejet carb so it delivers less fuel to engine... your carb has a jet in it and the # is stamped on it ( if you take the carb off and remove the bowl( 4 screws) you will see it,it will have an octagon shaped head.) for example if the # on it is 55 then you need to go with a 53 or 54...... also a good sign you need to rejet with a smaller jet is your bike will spooge(leak) a black oily residue from exhaust pipe and muffler( same residue thats fouling the spark plug.)

Sep 27, 2010 | 2003 Yamaha YZ 125

2 Answers

2000 yz125 keeps on fouling out plugs


Fouled plugs are typically caused by jetting that is too rich. This could also be from a dirty air filter which can make the bike run rich. Clean up your filter and see if that is it. If the filter is not too bad, you might want to drop a size on your pilot or main.

Another possibility is poor compression - this can make a 2-stroke run richer than normal as the fuel can not be burned properly. Rings don't last long in these 125s. I used to re-ring each week when I was racing 125s.

You might want to run a B8ES plug, too - this is one step hotter and will help the plug from fouling as often.

Feb 01, 2010 | 2004 Yamaha YZ 125

1 Answer

My yamaha yz 125 is dumping to much fuel and fouling out the plugs but i need to knoew how to adjust my carb its a 1997


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.

Nov 02, 2009 | Yamaha YZ 125 Motorcycles

2 Answers

Bike has a lag when its cold like its something in the motor is in a bid. after 10 miles or so it frees up and runs like its supposed to


What weight oil are you running in your bike? Years ago when we ran the straight 60 weight oil, on a cold morning you had a time kick starting the bike. Another thing is that when your bike is cold, it requires a much richer mixture to run. Whether your bike is fuel injected or carburated, you're running a very rich mixture. The fuel system control or the enricher provides the rich mixture and a rich mixture will make the bike run sluggishly.

Oct 04, 2009 | 2004 Harley Davidson FXST - FXSTI Softail...

2 Answers

YZ125 won't start


yeah something you wanna check next, compression. if you can get your hands on a compression tester.

Aug 09, 2009 | Yamaha YZ 125 Motorcycles

6 Answers

Kawasaki kx 250 fouls spark plug in 30 minutes


You definitely need to change the oil mixture to at least 40:1, use a good grade of 2 stroke oil. You do NOT need to return the bike. I'd highly recommend using an NGK B7EV spark plug. A hotter plug will stop the premature fouling. I would not recommend you decrease the oil to 50:1 because you are essentially robbing the engine from adequate oiling for the piston, KIPPS valves and the bearings. The hotter plug will make a huge difference but remember if he gets to the point where he is able to ride the bike to it's potential he will need to run the cooler plug, B8EV or B9EV. You can also use a cheaper plug in the same heat range, B7ES or B8ES. Those plugs should cost about $1.25 ea. and are an affordable cost of running the bike. It's not uncommon to replace a spark plug frequently, it's the nature of the 2 stroke engine.

Dec 08, 2008 | 2003 kawasaki KX 250

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