Question about 2005 Honda CR 125 R

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Spark keeps fouling but no clue why

The spark blug keeps fouling but the oil mixer is fine just the spark plug gets real oily and only funs for bout 20 then fouls

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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

Posted on Feb 16, 2009

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There is unnecessary noise when the engine is running and hard to start, the spark plug is always wet like an oil


As for the noise in the engine, could be alot of things. If your plug is very oily, then it's probably fouled. That would make it difficult to start & possibly run rough. Pretty common with 2 strokes. Sounds like your mixture on your fuel has too much oil in it when you mix it. Make sure you're mixing your fuel properly then I would check on rebuilding and adjusting your carb if your fuel mix is right. Hope this helps

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If you allow the engine to "warm up" too long with the enricher out, it will foul spark plugs. I usually start the engine and let it run with the enricher out just until I can keep it running with the throttle. At that point, I turn the enricher off. I hope this helps. Good Luck

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Fouling plugs


This can be caused by all sorts of things.There is no real order of probability so I'll just list them.Your oil/fuel ratio could be rich depending on what oil you use,your powervalve could be stuck closed(pop off the plastic cover over the actuator located at the front of the clutch cover,its held in place by 3 screws attached to the barrel,start the bike and give it a big blat on the throttle and see if the lever moves)it could have a blown crank seal(the symptom displayed by this fault is that you will be using gearbox oil),the expansion chamber could be carboned up,or the piston and/or rings could be worn.If all these things check out ok I suggest either raising the clip on the needle(which drops the needle causing the mixture to run slightly leaner) If this does not have enough effect go down one size in the main jet.Adjusting the main jet size will require you initally to very frequently remove the spark plug to check that you haven't gone too lean. The plug should not be wet and oily,the perfect colour is a tan colour and not wet.I must stress that jetting a 2 stroke if you lack experience can be tricky in that if you go too lean you can seize the engine so if you do reduce the size of your main jet frequent initall inspections of the plug is highly recommended.As a final note,if you are using a standard plug and not a racing plug(ie gold paladnium or irridium)thay are inherently more susseptable to fouling & changing to a "racing plug" may help to reduce your plug fouling.Hope this was helpfull

Nov 22, 2009 | Yamaha YZ 125 Motorcycles

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