Question about 2003 Yamaha WR 250 F
Hi, William_s83 ouch!!!! I feel your pain you may have what is called "PRE-IGNITION" and the usual suspects are:
1. Spark plug heat range too high.
2. Spark plug loose in the cylinder head.
3. Broken spark plug porcelain with carbon buildup.
4. Foreign particle embedded in the combustion chamber.
5. Excessive carbon deposits on the piston head or in the combustion chamber.
6. Points ignition timing too far advanced due to improper timing plate position.
7. Faulty electronic ignition sensor inputs from the MAP, CKP, CMP to ICM/ECM.
8. Engine overheating due to lack of lubrication or coolant.
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Posted on May 08, 2017
Using the wrong grade of fuel can cause that. Octane too low causing pre ignition.
Posted on May 08, 2017
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Posted on Jan 02, 2017
SOURCE: yamaha FZ 750 FM
It sounds like the idle screw is not set right., but if your going to clean the carbs anywyas. Clean them, sync them and see how she runs, if still doing the same thing the idle screw needs to be adjusted. The RPMs should be between 800 to 1200 while idling. If your bike is an older on it will most likely sit around the 1200 rpm at idle.
Posted on Nov 10, 2008
Are you loosing transmission gear oil? I seem to remember an older bike I had with a crank seal issue. Gummed up plug is usually only 2 things:
1) Carb too rich. Check jetting or sticky float needle valve that will dump fuel into the intake manifold.
2) Too much oil (check mixture ratio or crank seals that is mixing crankcase oil with the fuel mixture). Either of these two oil issues should produce a massive amount of tailpipe smoking and a noticable drop in power.
Posted on Apr 29, 2009
I suspect poor fuel delivery or starvation. At those rpms your bike requires a lot of fuel.Replace any and all fuel filters, check fuel lines for any kinks. Drain tank (petcock on pri ) then remove and clean petcock , replace. Run a bottle of techroline thru your next couple tanks of gas....Good Luck to you my friend...Tim
Posted on May 10, 2009
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