Spark keeps fouling out

SOURCE: 1994 yamaha fzr 600 spark plugs foul after about

Really...strange what you need to do is see if the bike is running too fat. So...warm her up witha fresh set of NGK! spark plugs. After the bike is warm take it down the street and back. When your on the way back get on the throttle and accelerate then shut er down and coast it into the garage. This will give an acuurate read on the spark plugs at operating temperature and under a load. Pull all the plugs. If they are brown like coffee with cream that means carbs are adjusted correctly. If they are black and wet too rich and if they are white or very light brown too lean. Other problems may be oil soaked plugs from loose top end parts. Maybe valves or guides.

SOURCE: loss of power and back firing. misses out like

check your plugs all of them. after that and you still have a problem you will want to do a compression test on your cylinders. you may have a valve problem. if that is not the case the only thing after that would be the timing.

SOURCE: my 02 yamaha yzf 426

I have had the same problem with my bike, but found out that the jets were wrong and had to down size two times and now i have had no problems starting up or if i have stalled the bike it only takes about kicks to get it running again.

SOURCE: We keep fouling spark plugs.

Several ways to try. Be sure the air filter is clean and without any tears or punctures, install an in-line fuel filter, gap the spark plug at .030, be sure the stock spark plug is used ( NGK CR7HSA ), be sure the muffler not plugged up at all, increase the idle speed, and change the gearbox oil every 2 or 3 months. The only other thing would be to de-carbon the piston and head but that requires the head to be removed. Taking the head off isn't hard but you must be sure to have the valve cam timed properly when reassembled. If not installed properly, you can bend a valve the first time you try to kickstart. Please rate my answer.

SOURCE: 1982 yamaha maxim xj650 running

it could be your carb