Question about Motorcycles
Just put new rings and piston in and seems to not be getting enough fuel thru the carb
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Posted on Jan 02, 2017
SOURCE: timing Adjustment issues!
If the bike runs then Top Dead Center (TDC) is not an issue. But to check piston stroke position, Remove the valve cap cover on the intake of the front cylinder. Remove both the spark plugs. Rotate the crank shaft untill the rocker arm starts to move. The piston is now starting down on the intake stroke. Rotate the crank further and the rocker arm moves in the opposite direction. The piston is now going upward on the compression stroke. Look at the marks on the flywheel. Rotate the crank untill the TDC mark lines up with the timing index mark. The front piston is now at TDC.
If your model has carbs then the backfire fix requires you to syncronize and balance the carbs.
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 balanced and synchronized your carbs.
Please rate this solution. Thanks sgtswampdonk!
Posted on Apr 02, 2009
open up the ignition cover plate and check the backing plate. it may have come loose and threw the bike out of time.
make sure your plug wires are plugged on tight and the coil wires are secure.
It is most definitely a timing problem.
Posted on Jun 06, 2009
SOURCE: fresh rebuild now no spark
If it ran before, I would double check your electrical connections. Its more likely you didn't get a connector pushed all the way together or left off a ground wire. The ignition coil specs are generally 1 ohm or less on the primary (small Wire) side, and 5K-10K ohms on the secondary (spark plug) side. Each side should be tested to ground. Pick-up coils are typically open or really large ohm reading in Megaohms normally and around 100 ohms when the magnet on the flywheel passes by. there is no way to test the CDI box other than putting it on a know running bike or getting a known good CDI and putting it on your bike. Double check that the spark plug cap is secured to the high tension lead as well. Testing the stator is a little more complicated, but a quick way is to close the gap on an old spark plug to about 0.010" and see if there is a week spark. If so, the stator will need to be replaced.
Posted on Jun 16, 2009
I had a simular problem with my 88 xr. It started out just running bad at higher speeds which had me thinking it was a carb or plug problem. I started changing plugs and had varing results which still had me guessing. So I started adjusting and jetting the carb. Still the same varing results. I suspected the CDI box so I tried to get one. (I live in Thailand, not the easiest thing.) The parts places produced several boxes that plugger in but gave me the results you just described. Good spark but no start, I also got one box that started the bike real good but would not accelerate. There is a built in timing in those CDI boxes. Just thought you might check this, By the way the original box of mine eventually failed completely and I was correct in my suspicions. I found a used one and it runs great.
Posted on Jul 09, 2009
hi mate you need to adjust the float if theres to much fuel going through you need to take the float out and adjust it to the manual specifications but remember slot the pin out and take the float out but watch the little valve which stops the fuel where the little valve is hanging from that is the part you need to adjust
Posted on Jul 23, 2009
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