Turns but wont start

Hello Anon,
Has the bike been sitting for a while? If yes, then the carb needs a PROFESSIONAL cleaning..there are too many little passages and jets that must be perfectly clean for it to run! NOT to mention the fuel passage into the carb..(Needle and seat)..
If this is the situation... get it cleaned and enjoy the ride...

wear a helmet - even if your state law doesn't require it!!

If your driving and it gets warmed up and shuts off and wont restart it may be a float problem in your carbs. The float needle will get corroded and let gas constantly flow while the bike is on and while you try to start it after it cools you burn the extra gas seeming.like it only starts cold. Ive had personal experience here. New float needles.

check your spark plugs.. try to change your ignition coil.

If it's dying that quick because the battery went dead, it might be a charging problem.

Get a MultiMeter:

http://www.harborfreight.com/7-function-multimeter-98025.html

Make sure the battery is charged, and start the bike.

Put the multimeter leads across the battery terminals (red to +, black to -)
You should be getting 13-14 volts, with the voltage increasing as you rev the motor.

If not, either an alternator or voltage regulator problem.

IF the battery is going flat in that time WITHOUT the motor running, you have a "parasitic" drain somewhere, that is draining the battery when it's off.

Hello mike, first check all the fuses, make sure none are blown. Check the kill & safety switches. Clean the contacts on the starter button. These are the basics.
I hope this helps.

Check the igniter box and make sure its a strong blue spark.

If old gas sat in the carb.s for more than a month it starts to dry up. As it drys up it leaves behind a varnish like film that stops up some very small ports and pin holes inside a motorcycle carburetor. It is also very hard to get out. You can try this before you pull the carb.s for a full cleaning. Use a product called Seafoam, get as much gas out of the carb.s as you can. use a turkey baster and force the seafoam into your carb.s fuel line that you took loose from the fuel tank. Let that set for days 1 or 2. then hook up the fuel tank with a mix of good gas and seafoam, (not a lot but enough to start it up. Move the cycle outside as the seafoam will make a lot of smoke if it does start up. If that does not clear up the problem you may have to pull the carb.s and remove the blows to clean the inside. If you have to do that do not DO NOT MESS with any adjustment screws, DO NoT MeSs with any screws. Just take the carb. bowls off keep each one separate and number them so they do not get mixed up. do not mix up any internal parts. It is best to work on one at the time so nothing goes wrong. Work on a large sheet so if you drop a small part you can find it, you do not want to be missing some tiny spring or screw. Hope this Helps.

you will need to try a new battery, unfortunatly sometimes jumping of a larger battery can spike the regulator, so when the new battery is fitted put a mulimeter across the battery, should read just over 12v engine stopped and rise to 13.5-14v with the engine running.

You have to check the starter motor,prolly the brushes are gone . Also check the connections from battery to the solenoid and from the solenoid to the starter.

Good Luck.
Knight (Yamaha seca XJ750A 1981)

The cutting out is just a coincidence. Go with the correct amount of oil. The piston is splash lubricated. Too much oil kills the splash and the cylinder gets poor lubrication. If your model has a carb, ( as opposed to fuel injection ), then clean the carb and air filter then put in a new stock NGK spark plug. This should take care of the problem.

Please rate this solution. Thanks niknak!