Question about GAS Motorcycles
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Posted on Jan 02, 2017
Turn off the gas and remove the water trap bowl at the bottom of the petcock, (gas valve). Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ). Get a set of the stock NGK spark plugs your bike came with. Check for spark on each cylinder before installing the plugs.
Now go to the idle and air screws on the outside of each of the carbs. IMPORTANT > > GENTLY turn both screws all the way in until they LIGHTLY seat. Now turn the screws EXACTLY one and one half turns outward.
SYNCHRONIZE THE CARBS
Remove the air filter and rubber fittings to allow you to see into the throat of both carbs. You may need a mirror to see inside. You need to be able to see the slides go up and down when you twist the throttle. Now turn the fitting where the cable goes into each carb such that there is just a bit of slack in the cable, 1/16" is plenty. Lock ONE of the cable adjusters down tight. All further adjustments will be made on the other carb.
With the motor turned off twist the throttle very slowly while looking at the slides. Both slides need to begin lifting at the exact same moment. If the slides don't raise at the exact same time then slowly twist the throttle until the locked adjuster slide just barely starts to move. Hold the throttle still and turn the adjuster on the other carb so that the slide on that carb just barely starts to move also. Now recheck the slide movement timing. Do this process until the slides on both carbs begin to raise at the EXACT same moment. Lock down the loose adjuster and re-check the slides.
BALANCE THE CARBS
Turn the throttle screw on the LEFT carb one half turn inward. Now start the engine and get it warmed up. With the engine running, remove the RIGHT spark plug wire. Adjust the idle speed on the left carb to the point where the engine just can't quite stay running and dies. Now put the loose spark plug wire back into place.
Now turn the throttle screw on the RIGHT carb one half turn inward. Restart and rev the engine. Next, remove the LEFT spark plug wire. Adjust the idle speed on the right carb to the point where the engine just can't quite stay running and dies. Now put the loose spark plug wire back into place.
Turn the idle screw on each carb EXACTLY ONE QUARTER turn outward and restart the engine. The engine will be probably be idling very fast. Adjust both the idle screws equally from this point to get to the desired idle speed. Congratulations, you have just synchronized and balanced your carbs.
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Posted on Mar 29, 2009
Drain and replace the gas with fresh.
Remove the air cleaner and spray carb cleaner into the inlet. Work your throttle a little then put everything back together and try to start it.
Posted on Jun 02, 2009
SOURCE: back fireing 660 raptor
when its hot and humid you could be having a ignition coil or cable problem.check cables and replace plugs, then take it from there. have your ignition coil tested also. backfiring is a sure sign of an ignition problem
Posted on Jun 15, 2009
a common problem with those, amongst many other yamahas, is the starter clutch gear. if it's not the starter solenoid , most likely it's the starter clutch gear.
Posted on Jan 12, 2010
You will find that there is a problem with the carbie. It runs with the choke on because the choke engages the "enricher" circuit. The idle circuit is different a different circuit inside the carb. When just crack the throttle on, you use the pilot circuit, and then main jet with more twist of the grip. You will need to completely strip the carb, remove all jets, spray carbie cleaner throughout, and blow out all capillary tubes and holes inside the carb with compressed air. Pay particular attention to the fine holes inside the venturi near the butterfly valve. You may need to use a fine piece of wire, like a guitar string to open up any that are clogged.
There is not much else that will cause the symptoms you have. Check for air leaks about the inlet manifold also, spray some carbie cleaner about the manifold connections boots, the revs will change when it sucks up the cleaner through the leak.
Happy to talk to you more about it.
Posted on Jan 24, 2010
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