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Anonymous Posted on May 25, 2012

97 yamaha yz250 excessive oil in exhaust keeps fouling plug

After 2-3 rides fouled plug. Excessive oil leaking from exhaust.

4 Related Answers

Anonymous

  • 46 Answers
  • Posted on Feb 16, 2009

SOURCE: spark keeps fouling but no clue why

Are you losing gear oil.
When the crankshaft seal leaks, oil from the gearbox is sucked into the crankcase, and this can foul the plug.
Also check the plug gap, most guys set the gap too small. It should be 0,7mmto 0,8mm. The plug should be a B9 EG, or equivilant.
Now, you can also change the plug cap to a type that has a built in resistor, this also helps with plug life.
Note that 2 strokes use plugs way more than 4 strokes, and you should replace the plug every 15-20 hours to keep your riding pleasant.
Good Bike you have there
Cheers
Jon

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tombones

  • 3567 Answers
  • Posted on Apr 04, 2009

SOURCE: wondering what the carb settings are for a 1983

The header says it is a 2004 YZ250F. That's a four stroke and gets no oil in the gas. Your 83 model is a two stroke. As far as the oil and gas mix, 32/1 is the proper mix. That's 4 ounces of two stroke oil per gallon of gas.
DO NOT USE STANDARD MOTOR OIL IN THE GAS.

Remove the water trap bowl at the bottom of the petcock, (gas valve). Any water or trash in the bowl? Drain a cup of gas from the tank. Any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).

Drain the carburetor. There should be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Install a new stock NGK spark plug and try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the two screws on the outside throat of the carb and spray into the screw holes as well.
< < READ CLOSELY > >
Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Be sure the bolts are tight. Let the float bowl fill then start the engine. Set the idle speed with the idle screw. This process should get you back on the road.


Please rate this solution. Thanks macnevind!

Anonymous

  • 22 Answers
  • Posted on Apr 05, 2009

SOURCE: i keep fouling my plug on my 03 rm85. oil/fuel mix is right

what color is the spark plug when you take it out? All black too rich, a chalky white look is way too lean which is far worse than a rich mixture. I blew up my CR-80 when I was a kid from an improper fuel mixture. You really have to get that correct and the dealer can give you the numbers on that. Also you might wanna get a measuring cup from a local dollar store or discount store to help you add the correct mix into the gas. You said its boggy in 1st and 2nd....how is it from 3rd up? Has the carb been jetted for possibly a different exhaust pipe or filter that aren't on the bike anymore? Or did you change those components and not jet correctly? I'm going to log this as a solution, but its borderline a clarification request....

Michael Green

  • 3799 Answers
  • Posted on Mar 17, 2012

SOURCE: 1979 yamaha enduro 50cc 2 stroke fouls plug quickly. I am not using proper jet needle. Can't find one. Is this one reason plug is fouling?

More than likely, a 2 stroke engine is very picky about the fuel mixture. Try and find a new one. there is a DT owners club and most club trials riders will be able to tell you where to find one. Or try "Wemoto" on the web. they may have the bit you are looking for.

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Excessive oil consumption

First of all, it would be helpful to define what you mean by excessive. How much oil is it using? Do you still have most or all of your power? Is it smoking? Is there oil on the ground under the car after you park for a while?
High mileage engines often have leaky gaskets (oil on the ground), but they also tend to burn oil. Valve guides wear out, and oil leaks into the firing chamber because of that. Usually, when this happens, you will have a problem with fouling spark plugs and lack of power. The piston rings also wear out, letting oil get by and into the firing chamber. Excessive crankcase pressure due to "blow-by," where combustion pressure is released by worn out rings into the crankcase, which pushes oil into the air intake. This doesn't foul the spark plugs as severely, but also causes smoke out the exhaust.
Finally, if the engine has not been serviced for a long time, there are many things that can cause or allow oil to go where it shouldn't, usually into the combustion chamber and out the exhaust.
There is an excellent product available from Rislone that can help in some cases, and with amazing results. However, if your engine is worn out, it may need to be rebuilt or replaced.
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I bought a 92 fzr 600 ride it for a month no problem. But now it keeps popping the resistor in the spark plugs. 3 sets of plugs in the last 2 weeks. Last set lasted 2 days. All have been ngk.

NGK plugs dont stop, especially all at once, so there is another problem.
There are some resisters in the plug caps that can fail.
Are the plugs carbon fouling?(dry black) if so make sure the air filter is new, and oil is changed.
Does the enginge blow smoke or use oil?(wet black)oil fouled may mean rings.
Fuel fouled may mean the jettting is wrong or choke stuck open
Its the battery good(new) and charging ,put a multi meter across the terminals 12v stopped, 14v running approx.
it always helps to drain the carb bowls every few weeks
If exhaust is not standard, the jetting may be wrong.
does the fuel tap work correctly? only use the run or res positions never pri
A short in the kill switch or a worn ignition switch can cause a miss or backfire
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What is causing the fouling? Engine oil? On a two cycle dirt bike, the fouling can be caused by excessive oil in fuel mix. I believe 50 to 1 is the correct ratio yet you may want to cut back, a little at a time, on the oil or run hotter fuel. The exhaust system will also accumulate enough oil sludge to impede the exhaust flow causing poor performance and plug fouling. A two cycle must breath freely to keep itself internally clean. Air cleaner to exhaust. Proper fuel mix should have little , very little. Good Luckand hopefully this helps you.
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Fouling occurs when the spark plugs' firing tip becomes coated with excessive fuel, oil, or combustion deposits so that it is unable to produce a spark. A plug can become fouled from continuous low speed driving, improper spark plug heat range (too cold), improper timing (over-retarded), too rich an air/fuel ratio or an oil leak into the combustion chamber. A variety of self-cleaning features are designed into most plugs to reduce fouling.
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Spark keeps fouling but no clue why

Are you losing gear oil.
When the crankshaft seal leaks, oil from the gearbox is sucked into the crankcase, and this can foul the plug.
Also check the plug gap, most guys set the gap too small. It should be 0,7mmto 0,8mm. The plug should be a B9 EG, or equivilant.
Now, you can also change the plug cap to a type that has a built in resistor, this also helps with plug life.
Note that 2 strokes use plugs way more than 4 strokes, and you should replace the plug every 15-20 hours to keep your riding pleasant.
Good Bike you have there
Cheers
Jon
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