Question about Yamaha XS 500 Motorcycles
Ok so i got a old 1979 Yamaha xs750 and its been sitting for a long time I cleaned the spark plugs and the carbs and win I got to start it it pops real loud and sometimes shoots a flame out of the exhaust first time it ran for 30 sec and then just started popping after that some help would be nice thanks @
Someone gave me a old motocycle they was taking to the land field..I done everything...but forgot one important thing..Look into the muffler..There were dirt gobblers all in the exhaust keeping it from cranking.. Before I gave up I had my wife pull me around the block....Then I heard a loud pop...The bike backfired them all out...The bike that was going to the land field was rescued.End of story...Just something to check
Posted on Jan 12, 2018
Blimey you really are on the Ball with this request. Do you realise that continuous and repeated deliberate miss firing can and will possibly damage your engine and blow the exhaust system apart?
Why go to all that trouble? When I used to do it I just shut the kill switch off whilst de-cellerating open the throttle a little the turn it back on (Bang/Flames) doesn't do it every time but with practice you can get it most times and the longer you shut off the louder the bang.
This was for OFF ROAD trials only!!!
I DO NOT ACCEPT ANY RESPONSIBLITY FOR THIS REQUEST AT YOUR OWN RISK YOU DO IT!
The reason I have given you the tip above is because it looks a seriously dangerous area you are going into with spark plugs and seperate batteries.
I personally would leave well alone.
Paul 'W' U.K.
Press the Blue button please for rating of my effort!
Posted on Jan 27, 2009
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.
PLEASE RATE THIS SOLUTION. Thanks!
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
clean contacts on points with sandpaper (800 grit). located behind flywheel, will gurantee a fix. you can remove the side cover and get to contacts through holes in flywheel without removing it.
Posted on Nov 16, 2009
Check out this site to find the exact model of your bike from the VIN here. You can get a wiring diagram for your model from the Biker.net website. There is usually a mess in the headlight tub, lots of dodgy previous owner "fixes". Sometimes it pays to strip it all out and work your way through it. Happy to give you advice on the electrics of this bike. I have plenty of experience:)
Posted on Apr 08, 2010
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